# Why two neutral camlok inputs?



## McCready00

On many dimmer/distro racks, there's two neutral camlok inputs. I read somewhere that the second camlok was used when you had dimmers. Actually, I am not quiet sure of what I am talking about. 


Finally, I was just wondering why there was a second neutral camlok and where do you connect this one back to the main power distribution. 

thanks


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## derekleffew

*Re: why two neutral camlok inputs*

McCready00, promoting your post to a "Question of the Day." STEVETERRY and others are not eligible to answer.http://www.controlbooth.com/forums/members/mccready00.html


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## LekoBoy

Serves no purpose at all, other than to sell more CamLoks and allow manufacturers to charge more for the racks. No one ever uses the second one, because as you said, there's no place to connect it back at the service panel.


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## soundman

Not sure if I am one of the others or not but it has to do with how three phase dimmers work. In a perfect world anytime you use 3 phase power (for 120 V operation) you draw on each phase equally and they cancel out giving you a draw of 0 amps on the neutral leg. (it has to do with the phases being out of phase from each other) When you use SCR dimmers you chop up the waves and do all sorts of horrible things to them. I am not in the math mood right now but if one phase is fully loaded and on at 100% and another phase is fully loaded but only on at 33% you could end up with 133% on the neutral leg depending on the circumstances. going over 100% means you are going to have some issues so they distribute the load amount 2 cables to be sure.


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## porkchop

I've never seen this but I have to guess that soundman is correct. There is definitely a chance that you could run more than 100% of the allowed load down that neutral line if you have very very poor balancing of phases. That would be the only reason that I could see you having to have the second neutral. If I really remember my EE classes this would only effect Y pattern three phase hookups as Delta Hookups use their ground a there effective neutral (admittedly theres a good chance of me having the switched)


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## dramatech

It is because of the SCR/triac/SSR dimmers switching into the phase after the "0" crossing. The exact effect has been explained to me several times, but I can't repeat the exact technical explanation. As best I remember, it creates some sort of back load on the neutral that is slightly out of phase with the hot line. In any case, Dimmer manufactures post instructions in their permanent rack installations, to increase the size of the neutral wire. If I am not mistaken, different manufactures post different values. In my EDI rack it states 110% of the hot. In the Teatronics rack it states 115% of the hot lines. Camloks being for portable installation, and most feeders already being 4/0, which is the largest wire to fit into a standard camlok connector, it would be impossible to install a larger wire, and so the need to run the second neutral.
Yes, I am aware that there are camloks larger than the 400 amp units, but the larger ones are rarely seen in in locations other than carnivals, where they are used for running amusement rides such as roller coasters.


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## Footer

Just to tack onto this... say you are running 4 sets of feeders for "the big rock show", how do you run them? All neutrals together, grounds together, phases together or do you do ABCNG? 

And... the final question.... when you run the feeder and have some left over, what should you do with the excess.


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## Sean

Footer4321 said:


> Just to tack onto this... say you are running 4 sets of feeders for "the big rock show", how do you run them? All neutrals together, grounds together, phases together or do you do ABCNG?
> 
> And... the final question.... when you run the feeder and have some left over, what should you do with the excess.



The 5 (or6) wires should stay together next to one-another. Through the same hole in the wall, hole in the floor, etc.

Figure-eight the cable. Do not make a big round coil of feeder.

--Sean


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## philhaney

McCready00 said:


> On many dimmer/distro racks, there's two neutral camlok inputs... I was just wondering why there was a second neutral camlok and where do you connect this one back to the main power distribution.



It doesn't go back to main power distribution, on a dimmer rack it goes to the lighting control board/panel (the old analog ones) to prevent ghosting.

(OK, that's my semi-informed guess.  )


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## ship

Its called a six wire feeder and at times used and will more so hopefully in the future especially with 120v loads due to as above the unbalanced loading conditions where by like 2/3 or more you see at times a load on a neutral over that of a power conductor. Even these days now seeing beyond GFCI breakers, four pole breakers, the fourth pole being at 50% loading for the neutral to shut it down if the neutral is over normal even half way acceptable amperage. But the two conductor neutral is a sort of ESTA standard these days and even if rare anyone uses the six wire system, it's still standard.

No, not some way to make more money... sorry but really not the answer. Six wire.. were it my choice I would be using it.


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## LekoBoy

ship said:


> ... Six wire.. were it my choice I would be using it.


The questions remains as to what to do with that extra neutral back at the service panel which is fed with a neutral conductor the same size as the hot legs.

Upgrading every company switch, or even requiring a double neutral for new construction, would be more than a little cost-prohibitive, now wouldn't it? Incredulously, if adding a useless extra connector on road dimmer racks helps some sleep better at night, more power to them.


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## derekleffew

ship said:


> ... But the two conductor neutral is a sort of ESTA standard these days and even if rare anyone uses the six wire system, it's still standard. ...


Um, ship, I see nothing in the ESTA TSP documents addressing this issue. _

Applying Demand Factor for the Neutral_ is discussed in NEC 220.22.

The magic factor is 1.33.


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## David Ashton

I think it's time for one of "the others" to get some facts on to this thread.
It is the fact that a perfectly balanced dimmer load will run a current of 130% of the full load/phase current when the dimmers are in the 40-60% range.
While there may be the same load on each phase they are switched on at different times because of the phase difference so there is no phase cancellation in the first 60 degrees of wave chopping and limited cancellation in the next 60 and only in the last 60 degrees does the phase cancellation down to near zero happen.
The important point is that load balancing has no importance in this issue.
If you have problems think about us poor Australians, our "standard" 3 phase plug has neutral pins half the size of the actives, but it's "too hard" to change.


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## derekleffew

allthingstheatre said:


> ...It is the fact that a perfectly balanced dimmer load will run a current of 130% of the full load/phase current when the dimmers are in the 40-60% range. ...


Are you saying that a dimmer rack with a full load of 200A per phase will show a load of 260A on the neutral when all dimmers are at 40-60%?


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## David Ashton

Absolutely, that is what you will get, but please do not believe what I say, get a reasonable rms meter and see for yourself, of course its easier to do at 10a on a little dimmer to experiment, but the result is the same.


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## derekleffew

allthingstheatre said:


> Absolutely, that is what you will get, but please do not believe what I say, get a reasonable rms meter and see for yourself, of course its easier to do at 10a on a little dimmer to experiment, but the result is the same.


Please see the documents attached to this post: http://www.controlbooth.com/forums/lighting/6582-clamp-meters-3.html#post80618. At the time, the focus was on non-RMS vs. true-RMS meters, but the data appear to dispute your statement.

With dimmers at 50% the neutral current is ~133% of the least loaded phase, but is NOT close to 133% of the "dimmers at 100%" load, (in fact, always less).


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## David Ashton

In my shed I have a 3 phase box with 4 meters on it 3ph and neutral, as you bring up a balanced load the currents on each phase sum as there is no cancellation and continues to rise until around 50% when they are well in excess of the peak/phase current.
This is a simple fact which is clearly demonstrable, unless the laws of physics are different in te US you will get the same result.
This is a basic simple experiment and you do not need expensive meters, simple moving iron meters work perfectly well, make up a rig to show students, this is of fundamental importance.I will bet that any data which seems to disprove the fact of high neutral currents is wrong.
This is not rocket science.


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## STEVETERRY

*Re: why two neutral camlok inputs*


derekleffew said:


> McCready00, promoting your post to a "Question of the Day." STEVETERRY and others are not eligible to answer.http://www.controlbooth.com/forums/members/mccready00.html



The Code calls for the neutral terminal and neutral feeder of a portable 3-phase *phase-control* dimmer rack to be sized at 130% or 200% of the phase conductors See below for more discussion of 130% vs. 200%). This is because of the non-linear nature of a phase-control dimmer rack that produces neutral overcurrents.

On a 400A feed, there is no readily available portable conductor above 400A, since table 400.5(B) gives 4/0 in free air a rating of 405A. In addition, an E1016 Cam-Lok is only rated at 400A.

So, a second parallel neutral conductor is required, hence the second Cam-Lok. Generally, electricians just add another 4/0 neutral, which is more conductor than is needed, but helps if the two neutrals are not of exactly the same length.

Why isn't a second neutral required in the conduit feeding the 400A company switch? Because those conductors have a lower ampacity to begin with (and are therefore larger) and in addition are de-rated to 80% ampacity because there are four current-carrying conductors in the pipe. The neutral is always considered a current carrying conductor when feeding a non-linear load. The four wires in the conduit heat _as a system,_ and the neutral experiences overcurrent only when the phase conductors _are at less that full current _(when the system is dimmed and the current waveform is most non-sinusoidal).

On the other hand, the portable single conductor feeders are pushed to their free-air rating, are not in a pipe, and are not in contact with each other, so they _heat as individual conductors_. The neutral conductor therefore has no overhead to deal with neutral overcurrents. So, we add a neutral.

Note that a three-phase dimmer rack without internal conversion to single phase (240/120V 3W+G) requires a double size neutral terminal. Why? The assumption is that when the road electrician is faced with only a single phase 3 wire +G service, he or she is going to connect two phases of the rack to one phase of the company switch. This means that the neutral could be loaded to 2X the phase current.

BTW, sine wave dimmers do not require oversize neutrals because they are not non-linear loads.

Clear as mud?


ST


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## Franklights

as many have mentioned it is to make up for an unbalanced load on the neutral. California code began this trend and many dimmer rack manufacturers are implementing it to be compliant and safe. it is a matter of time before the rest of the states start to implement it as well. As always, most production companies are behind the trend due to a lack of national support for it, the expense on the extra cabling, connectors, labor, etc. every dimmer I have bought recently has the double neutral although we haven't been using it.


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## STEVETERRY

derekleffew said:


> Please see the documents attached to this post: http://www.controlbooth.com/forums/lighting/6582-clamp-meters-3.html#post80618. At the time, the focus was on non-RMS vs. true-RMS meters, but the data appear to dispute your statement.
> 
> With dimmers at 50% the neutral current is ~133% of the least loaded phase, but is NOT close to 133% of the "dimmers at 100%" load, (in fact, always less).



Err...when the right combination of phase currents and waveforms occurs, the neutral will get to about 130% of the phase load when all is at full. That may not occur, however, when fading the whole system on the grand master. To hit the worst case, patch 3 subs for the A phase, B phase, and C phase dimmers. Then play with them. You'll get to around 130%.



ST


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## derekleffew

It will be a while before I can set up this experiment. My hypothesis is that the most neutral current will be seen when one phase's sub is at Full, another at 50%, and the third at zero. I'll let you know.


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## porkchop

derekleffew said:


> It will be a while before I can set up this experiment. My hypothesis is that the most neutral current will be seen when one phase's sub is at Full, another at 50%, and the third at zero. I'll let you know.



That will depend highly on what kind of dimmers you're using, but I'll be very interested in your results. For the traditional wave chopping type dimmers I would not be surprised if you are correct.


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## David Ashton

derekleffew said:


> It will be a while before I can set up this experiment. My hypothesis is that the most neutral current will be seen when one phase's sub is at Full, another at 50%, and the third at zero. I'll let you know.


I just put those settings in my demo rig and you are precisely correct.I will post some photos of various settings soon.


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## STEVETERRY

allthingstheatre said:


> I just put those settings in my demo rig and you are precisely correct.I will post some photos of various settings soon.



I have some interesting scope photos (yes, photos, not files--actually taken with a Tektronix Polaroid scope camera!) of this experiment when I performed it first in 1982. When I get back to my office next week, I will scan them in and post them.

ST


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## ship

Draft BSR E1.18
Standard for the Selection, Installation, and Use of Single-Conductor Portable Power Feeder Cable Systems for Use at Less than 601 Volts Nominal for the Distribution of Electrical Energy in the Entertainment and Live-Event Industries
Ep/2002-7003r10.2
For 2006 ESTA Spring (USITT) Meeting

© 2006 Accredited Standards Committe E1, Safety and Compatibility of Entertainment Technical Equipment and Practices, and its secretariat, the Entertainment Services and Technology Association. All Rights Reserved.


Suppose it did not get adopted but I did read it well and took many notes on problems and compliance issues with it were I work. I view it as a rule even if not yet and something to strive towards.

But simpler than that... suppose nobody has seen a neutral CamLoc type connector with serious melting issues. Sure one could say the roadies didn't properly balance there load and that's valid but not always realistic to the extent possible during real conditions.

Yea.. neutral in the common system won't be overloaded and also one never has to deal with choosing a 400A three Phase main breaker that will deal with six HonguroFlash fixtures for a show that while none use neutral, it will at times stobe and cause pandimonium with a main breaker by like 150% or more even if for a few seconds. 

Six wire just as proper safety cables, that's a goal of the industry. Sorry if it offends and or one might get worried about compliance or how some day in the future they might have to replace a panel. ETC on the other hand is there... won't have to replace those panels - those outlets used or not. On the other hand if given unbalanced loads that second neutral outlet needing a cover for it could be a good discussion in idiot proofing or Darwin proofing that second outlet/imput. This given the concept of a six wire system is assumed it won't hurt even if doubtful on the math or conditions of always balancing the load.

I'm over that concept of balancing the load by those applying the concept. My opinion and answer in why ETC is doing a second neutral - it's not for cost its for their own safety in if nothing else those that don't as well balance their load. Yea, you pay at the store for the shop lifter factor just as you pay for the ETC liability in those that don't perhaps balance a load. Take a pole on the website on balancing load and you might get a concept of how many in percentage even know what such a thing is, this much less can balance a load for reality of the show verses what's plugged in but perhaps not used at the same time. 

ETC ain't out for charging more as my answer, it's normal industry demand or code or ESTA standard these days used yet or not. This just as feed thru outlets on many of their racks - ability to feed something else by way of the CamLoc plugs as opposed to it being the end of the chain of power supply or needing twofers to feed it and something else. Yep, more useful when a second set of CamLocs male/female on one rack than it only the male end of them where you have no abilty to tap those outlets in managing your power above always done by way of balanced load.

Not just six wire panel mounts but also feed thru ability... pay a bit more but use or not is what most in the world most want out of the rack. Don't want such a thing... see if you can buy older used or without for a few bucks like $150.00 at best cheaper. That verses the price of rare earth metals for the price of the rack is nominal I'm sure.


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## ship

Draft BSR E1.18
Standard for the Selection, Installation, and Use of Single-Conductor Portable Power Feeder Cable Systems for Use at Less than 601 Volts Nominal for the Distribution of Electrical Energy in the Entertainment and Live-Event Industries
Ep/2002-7003r10.2
For 2006 ESTA Spring (USITT) Meeting

© 2006 Accredited Standards Committe E1, Safety and Compatibility of Entertainment Technical Equipment and Practices, and its secretariat, the Entertainment Services and Technology Association. All Rights Reserved.

Crucial End User Reader Notes & Questions on the proposed changes: - Brian Ship....,.

1.4 Definitions
p.17 Proximity Effect: Increased conductor impedance caused by a conductor being in close proximity to another conductor while both are carrying current.
p.18 Transient Connector Assemblies (tails): A short length (usually between 5 and 10 feet long) of feeder cable with a connector on only one end, which is temporarily connected to the supply equipment (commonly called “female tails set” or to utilization equipment (commonly called “male tails set”).
(FPN) 1 A female tails set may have male or female grounded circuit conductor (Neutral) connectors(s). It may also have male or female grounding circuit conductor connector(s).
(FPN) 2 A male tails set may have male or female grounded circuit conductor (neutral) connector(s). It may also have male or female grounding circuit conductor connector(s).
p.19 Triped: A method of bundling cables together. 
(FPN) Triping invariably requires derating of the ampacity of single-conductor feeder cables.

p.20 Part 2 Component Selection for single-conductor portable power feeder cable systems
p.21 2.1.2.2 Internal Wiring of Distribution Devices and Distribution part of Utilization Equipment: All Internal wiring shall utilize copper busbars with a current density of 1000 amperes per square inch or listed switch board wire that has a temperature rating of 90̊C or greater.
(???) What grade of copper has that current density, what’s it’s cubic area for each amperage rating? 
(???) Type MTW , THHN and other types of wire are not suitable when appropriate in gauge and rating? As per below, specification: Type SC cable under 24" in length is suitable for use also.
(Note) Switchboard wire is type XLP - Switchboard. 600 Volt, 90̊C, stranded tinned copper, suitable separator cross-linked polyethylene insulation, UL listed. Stock color gray; others available. SIS/VW-1 
Cole #	Size AWG Cond. Strand Nom. Wall	Nom. O.D.	Amps *	WT Lbs/M
01-5110	14	41 str	.031	.135	42	24
01-5111	12	65 str	.031	.157	55	33
01-5112	10	105 str	.031	.192	72	47
01-5113	8	133 str	.045	.290	97	81
01-5114	6	133 str	.060	.330	131	115
01-5115	4	133 str	.060	.390	172	172
01-5116	2	133 str	.060	.480	232	263
01-5117	1	133 str	.080	.570	266	347
01-5118	1/0	133 str	.080	.620	309	423
01-5119	2/0	259 str	.080	.680	355	520
01-5120	3/0	259 str	.080	.730	410	640
01-5121	4/0	259 str	.080	.810	481	770

* Ampacity based on a conductor temperature of 90̊C and an ambient air temperature of 40̊C. 
For 18 AWG & 16 AWG; see UL 3173 above. (Type XLP hookup)
(Cole Wire & Cable., Inc. Catalog p.A.6)

p.22 2.1.6.1 Cable Size: Cable Size Shall be Number 2, 2/0, or 4/0 AWG. Number 6 AWG shall be permitted to be used as a grounding conductor when the overcurrent device associated with the ungrounded (hot) conductors is rated at 200A or less.
(Note) #4 AWG feeder cable is no longer acceptable.
p.22 2.1.6.1 Acceptable Materials and Construction: Conductors shall be made of annealed copper wires in accordance with the elongation, finish, and coating requirements of ASTM B 3 or ATSM B 33. Portable feeder cables shall utilize flexible copper conductors with a fine strand Class K or M, maximum strand size 30 AWG. (Note) Type SC cable is Class K.
p.23 2.2.4 Outdoor Use: When used outdoors, single-pole separable connectors shall be NEMA 3R “Rain Tight” or protected from the weather.
(???) What is considered to be suitable protection?
(Note) CamLoc style connectors are not NEMA 3R and plastic bags covering or around them is not suitable. 
p.23 2.2.5.2 Panel Mount Connector Termination to Flexible Conductors: Single Pole Panel Mount connectors shall be terminated to flexible conductors via direct crimp, double setscrew, listed compression ring terminals or listed mechanical compression connectors (lugs) affixed to the threaded stud of the connector. Panel mount connectors utilizing single setscrew termination methods shall not be used.
(???) This would include single lug compression ring terminals?
p.24 2.2.7 Cable Size: Connectors shall be used with a cable size that they are rated for.
(Note) #4 & #6 feeder cable is not acceptable for use with a CamLoc type plug.

p.25 Part 3 Selection of Single-conductor Portable Power Feeder Cable Assemblies
p.25 General: Single-Conductor portable power feeder cable assemblies shall be protected by an overcurrent protection device at their supply point and any location in the portable system where the wire size is reduced. Overcurrent devices shall not be required at points of conductor size reduction if the assembly is protected by an upstream overcurrent protection device with an ampacity equal to or less than the ampacity of the reduced conductor.
Cables used in single-conductor portable power feeder cable assemblies shall meet the requirements of 2.1
Connectors used in single-conductors portable power feeder cable assemblies shall meet the requirements of 2.2.
p.25 Ampacity: Ampacity of a cable or a connector shall be limited to a value which will prevent the cable or connector from reaching a temperature higher than its temperature rating or the temperature rating of the equipment it is attached to.
Current in a single-conductor portable power feeder cable assembly shall be limited by the use of an overcurrent device at the supply point to a value not greater than that listed in sections 3.3 or 3.4. Under no circumstances shall the overcurrent device protecting the cable have an ampacity greater than the ampacity of the cable unless the tap rules of sections 3.4(A), (B) or ( C) apply.
Conductor sizes and ampacities of single-conductor portable feeder cable assemblies shall be limited to those described in sections 3.31 through 3.3.5.1.
All single-conductor portable power feeder cable assemblies shall have a temperature rating of at least 90̊C. This temperature rating shall apply to all cables, connectors and terminations that are part of the assembly.









p.26 Ampacity of single-conductor portable power feeder cable assembly: Single-conductor portable power feeder cable that meets all of the conditions in (A) through (E) below shall be protected by an overcurrent device not greater than the value listed in table 3.3.1 at the supply point, and at any point the wire size is reduced and shall have an ampacity as listed in table 3.3.1
(A) The cable shall not be installed in a raceway, conduit, nipple, or enclosure for more than 24" of its length.
(B) The cable shall not be bundled, triped, harnessed, triplexed, or in a triangular or square configuration.
( C) The cable shall not be stacked, and must be installed in a single layer.
(D) The cable must be installed with no more than a single point of its circumference (that is less than 15% of its circumference) in contact with anything besides air or less than one cable diameter from any other adjacent object or cable(s).
(E) The cable must be used in an ambient temperature of 30̊C (86̊F) or less.
Table 3.3.1 Ampacity of Cable

Wire Size	Ampacity Maximum Overcurrent Protection
#2	190	100
2/0	300	200
4/0	405	400


(Note) All cable in a distribution system must be rated for the specified overcurrent protection, there is no stepping down cable size for it’s protected load by the gear fed by this cable or use of distribution equipment without it’s own overcurrent protection when stepping down the conductor size.
(Note) By the above specifications (D) & (C), no more than two conductors at any point can touch. This is unless as appropriate as per Triped de-rating of cable above where it enters a service entrance, is loomed or bundled in a cable pick up point. See table 3.3.3 below
(Note) 24" A specified maximum length inside a switchboard, panelboard, switch or other piece of equipment (down line of the overcurrent protection) unless derated in ampacity as per table 3.3.2 below at both supply point and inside the device or cable size stepped up at the device to compensate for downrating.
(Note) Very specific de-rating of conductor ampacities per table 3.3.1.

p.27 3.3.3 Ampacity of a single-conductor portable power feeder cable assembly bundled, triped, harnessed triplexed, or in a triangular or square configuration or stacked, or less than one cable diameter from any othe adjacent object or cable(s)
Single-conductor poertable power feeder cable that is:
Not installed for more than a total of 24" in a raceway, conduit, nipple, or enclosure and;
used in an ambient temperature of 30̊C (86̊F) or less.
Shall have an overcurrent protection device not greater than the value given in table 3.3.3 at the supply point and at any point the wire size is reduced and a shall have an ampacity as listed in table 3.3.3.

When single-conductor portable power feeder cable assemblies are bundled, triped, harnessed; triplexed or in a triangular or square configuration; or stacked; or less than one cable diameter from any other adjacent object or cable(s) all of the conductors that are bundled, triped, harnessed; triplexed or in a triangular or square configuration; or stacked; or less than one cable diameter from any other adjacent object or cable(s) shall be counted in the ampacity calculation of table 3.3.3.

Table 3.3.3 Ampacity of a single, single-conductor portable power feeder cable assembly bundled, triped, harnessed; triplexed, or in a triangular or square configuration; or stacked; or less than one cable diameter from any other adjacent object or cable(s).

2 
Conductors	3 
Conductors	4-6 Conductors	7-9 Conductors	10-20 Conductors	21-30 Conductors

Ampacity Maximum
Overcurrent
Protection	Ampacity Maximum
Overcurrent
Protection	Ampacity Maximum
Overcurrent
Protection	Ampacity Maximum
Overcurrent
Protection	Ampacity Maximum
Overcurrent
Protection	Ampacity Maximum
Overcurrent
Protection
#2	174	100	152	100	122	100	106	100	76	75	68	60
2/0	271	200	237	200	190	175	166	150	118	110	107	100
4/0	361	350	300	253	250	221	200	158	150	150	142	125


(Note) By NEC standards, the grounded conductor (Neutral) is considered a current carrying conductor, this makes in the above list five wire feeder cable looms 4-conductor for appropriate ampacities. Six wire (double neutral) dual loom cable assemblies as a standard in many cases, would comply with the above two and three conductor ampacities for a higher rating as long as dual bundled cable assembly run parallel with each other and given qualified supervision over. Neither loomed cable assembly now comply with the below niceties for feeding applications such as a 96 way dimmer. (Appropriate specific and allowable ampacities of this specific distribution/dimmer rack feeder cable below covered in specification of allowances for down rating the feeder for maximum load of switchboard mounted maximum overcurrent protected equipment given a 640 Amp per phase maximum draw of specified dimmers before considering feed thru, convince, supplemental and hard patch devices or outlets installed both “main breakered” and feed thru).
(Note) Closed Loop installations (below) in specification could compensate for this ampacity as long as inspected and supervised by qualified technicians but is not normal policy and has it’s own ball of wax in policies as it were in not being a good solution for keeping feeder cable loomed in ease of use. Dual parallel conductors given potential back feed situations is also an option but necessitating qualified technicians using it. This is highly dangerous in back feed and looses any use of the feed thru of other equipment design intent of normal distribution equipment. It also adds to safety problems of in dual / parallel conductors feeding gear having potentially very exposed male ends on the female side of the feeder cable. Dual runs even if very equal in cable length is not recommended. It would seem by way of this specification in normal temporary distribution equipment installations, feeder cable from Tails, to jumper to feeder, should no longer be loomed and now individually laid out.
(???) By way of specification, even if not bundled, should more than one conductor touch in a cable pick or layout, it is derated. This includes all feeder cables that touch naturally by way of gravity even if not loomed in being lifted or laid out and not specifically grouped by means of bundling to be a banded together tripple or quad pairing unless spaced apart in prevention from touching also against specification for derating. eeg. On a cable pick, cables that should touch must be derated. There must be no more than two cables touching at any point in the layout. This is difficult in definition by way of strain relief required by the NEC at a service entrance or other equipment unless separated or exception in dual conductors by way also of proximity and number of cable separators. There might be some leanancy or implied necessity for conductors to a point to touch at specified or necessary and or normal binding of the conductor points given the rest of the cable is separated. Such a waver for all pinch points is difficult to define say as a two screw strain relief tensioning device as the norm but otherwise in definition of a cable pick, what will de-rate the ampacities of the cable given even one point of contact.
(Note) This derating of feeder cable by way of surface contact also includes while not specified all other current carrying conductors or cables in an assembly. Socapex cable for instance would also count against the rating of a feeder cable when more than one conductor touching a feeder cable line.
(Note) This specification by normal current carrying conductor defination also includes the (Neutral) current carrying conductor(s) for all intent of touching and de-rating intent.
(Note) This specification for the most part does not at this time does not address the need, derating or necessity at times for oversizing or dual parallel runs of the grounded conductor (Neutral) in gaining acceptance in the industry. At some point this might become an addition to these specifications.
p.28 Other than 30̊C (86̊F) Ambient Temperature: When the ambient temperature is other tnan 30̊C (86̊F) the ampacity in tables 3.3.1, 3.3.2, and 3.3.3 shall be adjusted by the correction factors in table 3.3.4 (A), and the Maximum Overcurrent Protection listed in the table shall be changed to the values in table 3.3.4(B)
(Note) This ambient temperature is going to become another very specific factor in de-rating for outdoor applications for more than 86̊F temperatures given loadings. This 86̊F design factor for most gear is problematic in losing say 9% of a conductor or distribution equipment gear’s ampacity rating once it becomes say 90̊F instead of 86̊F. Given heating from stage lighting gear, audience factor heating loads on air conditioning and/or just the temperature of the day, once the show starts, this might become a important table to consider for an expected say 0.82 derating for a 120̊F day or other conditions, or say in the shop 96% of expected ampacity derating during a 90̊F day. Such a dynamic temperature shift might be necessary to rate all Ampacities for a maximum expected temperature rather than average one.
(Note) The norm of a 20% safety factor in amperage of system calculated load can soak up some of this derating necessity due to temperature but this reduces it’s intent of being a safety factor instead of design factor. For say a show in the summer where the temperatures about the stage or feeder might become over 86̊F as potential, in selection of AWG and it’s rating, potentially that feeder should become a factor.
(Note) Table 3.3.4(B) becomes the governing factor for all general tour or show use feeder cable in further laminating amperage of feeder cable but load applied in formatting the formula. This table 3.3.4(B) in pre-designed show and current draw than would seem to be the most important table for cable sizing, and should be the primary table used assuming the loomed or picked cable does not also factor in.


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## STEVETERRY

ETC supplies the second neutral Cam-Lok because a 200% neutral is required by the NEC (520.53 (O)(1), and thus by the UL Listing.

For a general view as to why more neutrals have not burned up, see the ETC Load Survey. There is huge diversity in these systems. Over 70% of the 119,000 dimmers surveyed had 1150W or less connected to a 2400W dimmer.

ST


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## SHARYNF

Steve T is definitely the expert here. I have a Lex Pagoda and after talking with Lex they send me a new neutral harness so I could rewire the internals of the distro.

One thing to keep in mind, I would be surprised if the neutral service through out the building from the service entrance to the panel and company switch has a double rated neutral, so in the extreme situation, you might have double neutral or double rated neutral, but back up the line IMHO it is unlkely that the building wiring will be done that way. Interestingly here granted not in the most up to date electrical power company, no one looks at having a double rated neutral on the power distrobution to the city, even though the on occasion the loads can be severely unbalanced.

Sharyn


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## Sean

SHARYNF said:


> Steve T is definitely the expert here. I have a Lex Pagoda and after talking with Lex they send me a new neutral harness so I could rewire the internals of the distro.
> 
> One thing to keep in mind, I would be surprised if the neutral service through out the building from the service entrance to the panel and company switch has a double rated neutral, so in the extreme situation, you might have double neutral or double rated neutral, but back up the line IMHO it is unlkely that the building wiring will be done that way. Interestingly here granted not in the most up to date electrical power company, no one looks at having a double rated neutral on the power distrobution to the city, even though the on occasion the loads can be severely unbalanced.
> 
> Sharyn



Sharyn,

Read Steve's post from September 14th, 2008, (Post#18). He explains why building wiring does NOT have to have doubled neutrals. It's all about whether the netral is treated as an individual chunk of copper, or as part of a system. There is a need for additional neutral capacity in portable cable, but not in conduit.

--Sean


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## TimMiller

Double neutrals are used in massive data rooms, in which there is a lot of "junk" being fed up the neutral from switching power supplies used in computers. Also, my dimmer rack actually has double cam in's due to it has a 600A main (this is a portable rack), I do not load past 375A a leg, so i end up running two sets of 4/0. Or if i have it available and it is a short run i run 2 sets of 3/0. When running double conductors you have to make sure that both sets of double conductors are the exact same size, or you can have a 50+A imbalance between your two runs of each conductor.


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## derekleffew

Sean said:


> ... There is a need for additional neutral capacity in portable cable, but not in conduit.


Actually Mr. Terry stated: 
"Why isn't a second neutral required in the conduit feeding the 400A company switch? Because those conductors have a lower ampacity to begin with (and are therefore larger) and in addition are de-rated to 80% ampacity because there are four current-carrying conductors in the pipe. The neutral is always considered a current carrying conductor when feeding a non-linear load. The four wires in the conduit heat _as a system,_ and the neutral experiences overcurrent only when the phase conductors _are at less that full current _(when the system is dimmed and the current waveform is most non-sinusoidal)."


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## SHARYNF

I am aware of what Steve wrote but if you look at it:

the cables in the conduit are derated to 80 percent, and treated as a whole system. 

Now if there is a need for 50& derating on the portable and this same identical unbalanced load is being feed via conduit derated to 80 percent you still are not operating as derated to 50 percent

The NEC points are assuming that the 3 phase lines are running reasonably balanced loades, and my point was that it is possible in a theater setup that these assumptions might not be correct

For instance, three phase supply switch, one phase for AV, second phase for half dimmer and third phase for other half of the dimmers. It would be possible to have the full half off situation in a conduit installed situation.

Since the de rating to 80 percent works for in conduit I wonder if de rating the switch by 80 percent would be a safe alternative so instead of 400 amps go to 300 or 320

Is the alternative that you add a second neutral to the company switch camlok's to the existing neutral bar and leave the wire feeding the switch alone?


Sharyn


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## derekleffew

SHARYNF said:


> ...For instance, three phase supply switch, one phase for AV, second phase for half dimmer and third phase for other half of the dimmers. ...


I can think of no better way to ensure humbars on the video and sixty cycle in the audio.


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## SHARYNF

derekleffew said:


> I can think of no better way to ensure humbars on the video and sixty cycle in the audio.



So you have never seen a situation where a production uses one distro, for audio video and lights?i
Perhaps in Vegas the land of endless electrical power

I've seen the above in lots of smaller productions, typically using single phase dimmers
Lots of people used Lex Pagoda distro's and set up the connections that way 

As long as the grounds are fine, never seen a problem


Sharyn


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## STEVETERRY

SHARYNF said:


> I am aware of what Steve wrote but if you look at it:
> 
> the cables in the conduit are derated to 80 percent, and treated as a whole system.
> 
> Now if there is a need for 50& derating on the portable and this same identical unbalanced load is being feed via conduit derated to 80 percent you still are not operating as derated to 50 percent
> 
> The NEC points are assuming that the 3 phase lines are running reasonably balanced loades, and my point was that it is possible in a theater setup that these assumptions might not be correct
> 
> For instance, three phase supply switch, one phase for AV, second phase for half dimmer and third phase for other half of the dimmers. It would be possible to have the full half off situation in a conduit installed situation.
> 
> Since the de rating to 80 percent works for in conduit I wonder if de rating the switch by 80 percent would be a safe alternative so instead of 400 amps go to 300 or 320
> 
> Is the alternative that you add a second neutral to the company switch camlok's to the existing neutral bar and leave the wire feeding the switch alone?
> 
> 
> Sharyn



400A/.8= 500A This is the derated ampacity we need for each of four current-carrying conductors in a pipe (A,B,C, N).

90 degree copper conductor with an ampacity of at least 500A from table 310.16 = 700 kcmil. That's the effective size of the derated phase and neutral conductors in the pipe feeding our 400A Company switch.

The 4/0 AWG 90 degree conductor we use for portable feeder in free air has a cross sectional area of 211.6 kcmil. Thus, you can see that putting 4 current-carrying conductors in a pipe and derating accordingly requires a conductor with 3.3 times as much copper to match the free air rating of our 90 degree 4/0 portable cable.

That's why oversize neutrals are not a code requirement for the wires in the conduit, but are required for the portable cable. Also, the Code leaves open the possibility that oversize neutrals may actually be needed in the pipe with some types of loads. See the FPN from 210.4 (A):

_FPN: A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic currents on the neutral conductor._

BTW, the whole concept of balanced load across the three phases becomes much less of an issue when the primary contributor to neutral overcurrent is the non-linear load, not the phase imbalance. We _assume_ a completely unbalanced load in the safe design of our systems, simply because it is possible. We never derate the neutral below 100% as is allowed in some other types of installations.

Finally, a second neutral on the output of the company switch is a Good Thing.

ST


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## SHARYNF

So Steve what you are saying if I can interpret is that going into the company switch and simply tying another camlok on the neutral bar will work fine since the in pipe cable will handle it. 

Am I correct that the camlok connector for the neutral will not support the double rating so that simply making up a neutral y cable would not work? Are most of the company switches wired up with the high rated pipe cable to the neutral bar and then use 4/0 from there ot the camlok?
Sharyn


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## Sean

SHARYNF said:


> So Steve what you are saying if I can interpret is that going into the company switch and simply tying another camlok on the neutral bar will work fine since the in pipe cable will handle it.
> 
> Am I correct that the camlok connector for the neutral will not support the double rating so that simply making up a neutral y cable would not work? Are most of the company switches wired up with the high rated pipe cable to the neutral bar and then use 4/0 from there ot the camlok?
> Sharyn



A camlok connector is rated for 400amps, so you cannot make a "cam twofer" to add a neutral. The 4/0 cable also cannot carry more than 400 (or was it 405amps?) amps, so no part of a "y" cable is rated to carry the additional amperage.

--Sean


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## STEVETERRY

Sean said:


> A camlok connector is rated for 400amps, so you cannot make a "cam twofer" to add a neutral. The 4/0 cable also cannot carry more than 400 (or was it 405amps?) amps, so no part of a "y" cable is rated to carry the additional amperage.
> 
> --Sean



Correct. You need to add a second Cam-Lok (and short cable if necessary) to the Neutral bus of the switch.

ST


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## SHARYNF

Here is a link for a double neutral distro box
these are becoming more common

Associated Mobile Power - Your Portable Power Solution!

Sharyn


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## derekleffew

A shameless plug for one of my favorite distribution device companies, largely due to the name: the  Dadco Super Cam Thru Spider, aka "Duzz-All".

Note the two neutral Cam-loks in Lex Products' Company Switch:


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## STEVETERRY

derekleffew said:


> It will be a while before I can set up this experiment. My hypothesis is that the most neutral current will be seen when one phase's sub is at Full, another at 50%, and the third at zero. I'll let you know.



Here is some real Neutral History in the attached file. I did this around 1981. We were having weekly Code revision meetings at See Factor (boy, were we young and full of piss-and-vinegar!). Mitch Hefter said to me: "SCR dimmers can generate neutral currents in excess of the maximum phase current." "Impossible!" said I, and then went back to my shop to prove it. Oops! I proved Mitch's statement, and the gory details are attached.

This was the start of the work we did in the 1987 Code to require upsized neutrals on phase-control dimmers. I don't think many people in the electrical community were even aware of "harmonics" or "non-linear loads" at that point.

Note the Courier typeface generated by my Diablo 630 printer driven by an Altair 8800 computer running Wordstar!

Enjoy!

ST


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## David Ashton

In Feb 88 one little Australian was painfully aware of the problem but could not convince the supply authorities or anyone else, oh for the internet.
"what went wrong" "neutral problems"

edit: Direct link: http://www.controlbooth.com/forums/what-went-wrong/7842-neutral-problems.html


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## ship

Need to make a CamLoc to 24way Edison AC distro for a show leaving in about two or three weeks. Either going to build it myself or if the only supplier that has not walked out of the bid given short notice can get my specifications for it according to what I specified actually on the drawing and quote instead of what artistic licence they feel like it in quoting it out, either I'll build it if cost effective or they will. Should know in the morning, in the mean time suppliers for the components I would put in it are also taking their own sweat time in me asking to know all info by the end of today about pricing etc.

In my case the four phase breaker with 60% neutral sensing with GFCI, adjustable loading amperage trip ratios and in-breaker amperage sensor as with trouble shooting diagnostics is in my concepept for main breaker as compliant with a sort of feeling for how things are going these days. Ok, such a thing would cost at least $5K and not in price but in lead time I scaled down from that a bit but not by much in still pressing for what neutral sensing and GFCI is a good idea for something I'm building. The other place that can get it done in time... they are UL listed but won't supply a fan for the rack in if I do so they say it than voids warranty. This much less only supplying normal three phase breakers and its' a fight to supply on the drawing a six wire system for feeding it amongst other design changes that one just has to ask where did these changes come from in me specifying part numbers and only wanted a quote on what I specified not something totally different. Days wasted... almost two weeks now in me just finding a supplier, getting a quote and getting it defined how I asked for it and still not done yet. The guys making it will no doubt be cursing me for requesting such a thing on such short notice yet it their own sales people that took their own sweet time before either deciding after waiting a while they couldn't supply or still refining their design to my specifications that down to the part number were correct they just took artistic licence with them. Stuff like five wire instead of six wire supplies.... If I specified a six wire supply with specific part number, why on the quote would a five wire suddenly become what's quoted? That lost at least a day in changing that and other artistic licence stuff - at least.

Not a discussion on "you should contact these guys" they have always done well by me, more a concept of current UL listings of gear and or easy plug in type done before thus is former or current code compliant plus easy to do and it's going to be a while until things change makes gear hard to make proper according to the latest concepts in what should be done code or not. If I'm offering to pay an extera $K in money for a new fangled proper breaker be it GFCI, neutral sensing four wire or both... only been told so far... nope, can't do that even if better or safer. This at best above pre-made component based power supplies that can't be done on a two week notice... Suppliers and experts heck... they respond back normally this is what we are listed for and what has always worked in the past. Breaker manufacturers are more concerned about legal stances about... if they specify a proper breaker for say the Hunguro Flash strobe light, they might be liable for it than... than in wasting a week doing anything to help. Industry just wasting my time with compliance of the past set ways and legal problems in helping me get my job done. Stand in my way you get stepped on and I don't normally travel back down those stairs.



Certain other panels I need and bidded out I sent photos of. Similar questions on how to, it's not how we do it, this is how we do it for about double as much as it costs you to do it. Yet nobody was able to make a panel from scratch given a limited lead time cost effective to my specifications and that's all falling back to me. A lot of electrical panels to wire up in the coming weeks including possibly the above.


Big challenges for me: given the options in commercial grade breakers - well beyond QO or QOU types we get into trip ratios for voltages the breaker won't see etc. in headackes of not so well defined tables. Choosing the main breaker - big problems in getting leading edge in technology simply from the education standpoint.

Second, getting a quote for what you want even if you specify the part numbers for the components in the rack you want - still often takes at least a day or more for a price quote. This much less even if specifying part numbers, getting the quote for what you asked for can be challenging in wasting days that could have been spent building the thing in either in the end it can or most often is not enough time left to build it.

Next and while I have a GreenLee punch that will punch say an Edison outlet, and even have a jig for that punch made up, my time is valuable and it's a pain in the rear to punch Edison outlets. Such panels pre-made need to be more available and no doubt are. Takes time to even quote out such things.

Pain in the rear to make a AC distro rack, this much less one that can travel the world. Not sufficiently trained for circuit breaker technology and the suppliers of such gear need longer lead times than is often available or reasonable no matter the cost, pre-punched gear even if listed in catalogs is not persay available on short notice, sales people take their own sweat time in quoting prices no matter if breaker or panel, breakers especially if high tech take weeks to construct and cost thousands of dollars each etc.

Welcome to my world, but my current goals are first to supply feed thru CamLocs, next to supply six wire for anything 120v, next to get into the GFCI and neutral sensing breaker world. Next to asside from Middle Atlantic's component base rack system, get pre-punched panel suppliers that can just ship them on limited notice because if in the catalog, that means it's something pre-designed and easy to supply. After that, it's a few $K in rack, if I want something special which makes sense to have you don't say you cannot do that.

Yep, the last week or so I have been working with the issues of this discussion in rack panels, six wire and breaker types a lot. Spent the entire morning reading various Cutler Hammer catalogs on their breakers to say the least. Wound up with a headache instead of answers as to which specific circuit breaker was the one I wanted by part number. Neither did my sales rep. for them end up with any different. Still waiting on her tech support to reply a day or two later.

Welcome to my world. While for sure harder to do what's proper and the way the trends are going it's still my intent for very valid reasons. Little steps perhaps in the end.


----------



## STEVETERRY

ship said:


> Need to make a CamLoc to 24way Edison AC distro for a show leaving in about two or three weeks. Either going to build it myself or if the only supplier that has not walked out of the bid given short notice can get my specifications for it according to what I specified actually on the drawing and quote instead of what artistic licence they feel like it in quoting it out, either I'll build it if cost effective or they will. Should know in the morning, in the mean time suppliers for the components I would put in it are also taking their own sweat time in me asking to know all info by the end of today about pricing etc.
> 
> In my case the four phase breaker with 60% neutral sensing with GFCI, adjustable loading amperage trip ratios and in-breaker amperage sensor as with trouble shooting diagnostics is in my concepept for main breaker as compliant with a sort of feeling for how things are going these days. Ok, such a thing would cost at least $5K and not in price but in lead time I scaled down from that a bit but not by much in still pressing for what neutral sensing and GFCI is a good idea for something I'm building. The other place that can get it done in time... they are UL listed but won't supply a fan for the rack in if I do so they say it than voids warranty. This much less only supplying normal three phase breakers and its' a fight to supply on the drawing a six wire system for feeding it amongst other design changes that one just has to ask where did these changes come from in me specifying part numbers and only wanted a quote on what I specified not something totally different. Days wasted... almost two weeks now in me just finding a supplier, getting a quote and getting it defined how I asked for it and still not done yet. The guys making it will no doubt be cursing me for requesting such a thing on such short notice yet it their own sales people that took their own sweet time before either deciding after waiting a while they couldn't supply or still refining their design to my specifications that down to the part number were correct they just took artistic licence with them. Stuff like five wire instead of six wire supplies.... If I specified a six wire supply with specific part number, why on the quote would a five wire suddenly become what's quoted? That lost at least a day in changing that and other artistic licence stuff - at least.
> 
> Not a discussion on "you should contact these guys" they have always done well by me, more a concept of current UL listings of gear and or easy plug in type done before thus is former or current code compliant plus easy to do and it's going to be a while until things change makes gear hard to make proper according to the latest concepts in what should be done code or not. If I'm offering to pay an extera $K in money for a new fangled proper breaker be it GFCI, neutral sensing four wire or both... only been told so far... nope, can't do that even if better or safer. This at best above pre-made component based power supplies that can't be done on a two week notice... Suppliers and experts heck... they respond back normally this is what we are listed for and what has always worked in the past. Breaker manufacturers are more concerned about legal stances about... if they specify a proper breaker for say the Hunguro Flash strobe light, they might be liable for it than... than in wasting a week doing anything to help. Industry just wasting my time with compliance of the past set ways and legal problems in helping me get my job done. Stand in my way you get stepped on and I don't normally travel back down those stairs.
> 
> 
> 
> Certain other panels I need and bidded out I sent photos of. Similar questions on how to, it's not how we do it, this is how we do it for about double as much as it costs you to do it. Yet nobody was able to make a panel from scratch given a limited lead time cost effective to my specifications and that's all falling back to me. A lot of electrical panels to wire up in the coming weeks including possibly the above.
> 
> 
> Big challenges for me: given the options in commercial grade breakers - well beyond QO or QOU types we get into trip ratios for voltages the breaker won't see etc. in headackes of not so well defined tables. Choosing the main breaker - big problems in getting leading edge in technology simply from the education standpoint.
> 
> Second, getting a quote for what you want even if you specify the part numbers for the components in the rack you want - still often takes at least a day or more for a price quote. This much less even if specifying part numbers, getting the quote for what you asked for can be challenging in wasting days that could have been spent building the thing in either in the end it can or most often is not enough time left to build it.
> 
> Next and while I have a GreenLee punch that will punch say an Edison outlet, and even have a jig for that punch made up, my time is valuable and it's a pain in the rear to punch Edison outlets. Such panels pre-made need to be more available and no doubt are. Takes time to even quote out such things.
> 
> Pain in the rear to make a AC distro rack, this much less one that can travel the world. Not sufficiently trained for circuit breaker technology and the suppliers of such gear need longer lead times than is often available or reasonable no matter the cost, pre-punched gear even if listed in catalogs is not persay available on short notice, sales people take their own sweat time in quoting prices no matter if breaker or panel, breakers especially if high tech take weeks to construct and cost thousands of dollars each etc.
> 
> Welcome to my world, but my current goals are first to supply feed thru CamLocs, next to supply six wire for anything 120v, next to get into the GFCI and neutral sensing breaker world. Next to asside from Middle Atlantic's component base rack system, get pre-punched panel suppliers that can just ship them on limited notice because if in the catalog, that means it's something pre-designed and easy to supply. After that, it's a few $K in rack, if I want something special which makes sense to have you don't say you cannot do that.
> 
> Yep, the last week or so I have been working with the issues of this discussion in rack panels, six wire and breaker types a lot. Spent the entire morning reading various Cutler Hammer catalogs on their breakers to say the least. Wound up with a headache instead of answers as to which specific circuit breaker was the one I wanted by part number. Neither did my sales rep. for them end up with any different. Still waiting on her tech support to reply a day or two later.
> 
> Welcome to my world. While for sure harder to do what's proper and the way the trends are going it's still my intent for very valid reasons. Little steps perhaps in the end.



A few thoughts:

1.For the kind of money you will spend, I would want a UL1640-listed distro. That leaves out making it yourself, unless your shop is a Listed Assembler.

2. Why do you want neutral overcurrent sensing on the main breaker? If the distro is designed for any overcurrent, it should not be needed. The feeder to the company switch certainly will not have it.

3. I am not clear if you are thinking about GFCI protection on the main breaker, but if so, I would be cautious. Not all GFCI mains work with non-linear loads (talk to Bender or K-Tec about ones that will), and adjustable GFP (ground fault protection for equipment only) main breakers (30ma to 300ma or so) do not provide personnel protection.

4. If you need high-inrush breakers to deal with the strobes, I suggest a fully magnetic type from Airpax or Carling that has a specific high inrush curve.

ST


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## TimMiller

Check out The best way to buy industrial controls--low prices, fast shipping and superior service. Look at their little breakers, they have different breakers with different trip curves, they also have breakers that will trip if the voltage drops below x amount.


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## ship

Still have a lot to learn on distros and modern technologies available these days. For the money to spend I invested it in the end in a supplier that could get it done on short notice, within less budget and with UL listing for what gear I specified. Gonna spend more time on doing that specifying while I learn more into breaker types to match my wishes and or what I think most appropriate especially in this case for a at random load under uncertain show conditions in use. I was covering the basics in what I was wanting but in the end went for experience more than I have. Still the initial merits I'll study into.

The strobes were a different AC distro I also in the end farmed out in not being ready to do the work on. Getting closer.





STEVETERRY said:


> A few thoughts:
> 
> 1.For the kind of money you will spend, I would want a UL1640-listed distro. That leaves out making it yourself, unless your shop is a Listed Assembler.
> 
> 2. Why do you want neutral overcurrent sensing on the main breaker? If the distro is designed for any overcurrent, it should not be needed. The feeder to the company switch certainly will not have it.
> 
> 3. I am not clear if you are thinking about GFCI protection on the main breaker, but if so, I would be cautious. Not all GFCI mains work with non-linear loads (talk to Bender or K-Tec about ones that will), and adjustable GFP (ground fault protection for equipment only) main breakers (30ma to 300ma or so) do not provide personnel protection.
> 
> 4. If you need high-inrush breakers to deal with the strobes, I suggest a fully magnetic type from Airpax or Carling that has a specific high inrush curve.
> 
> ST


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## Edrick

My understanding from the brief coverage I got about this subject was in the Theater industry or touring where you're using dimming systems. 

So the issue with these types of systems and being 3 Phase is they all need to be in balance within 30 AMPs. Now when you're working on a Film set for example (which is what I'm going to be doing). Everything is balanced out within that 30 AMP margin and for the most part it doesn't change and there's no excessive difference. If there was you'd blow the genny or transformer not only that but you could also fry the cabling on the neutral as it's only rated for 200 AMPs. Phase 1 - 200 AMP Phase 2 - 200 Amp Phase 3 - 200 AMP (600 AMP). Neutral as close to balance but if all of the sudden it goes out of balance and you're sending 250 AMPs down that neutral you'll fry it. 

So in the case of going back to theater where at one moment you might have a few lights on then the very next moment you'll have the whole stage lit. You're constantly going in and out of balance. Thus you need two neutrals to cover the unbalanced amount.


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## SHARYNF

remember that this only applies IF you are running at the full capacity of the cable system ie a full 200 amps say. Usually this is not the case. same as the Generator or transformer most of the genorators are rated way beyond the full capacity demand. 
Sharyn


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## David Ashton

Please try to grasp this concept, I apologize for the capitals it is important
BALANCING YOUR LOAD WILL NOT SOLVE YOUR NEUTRAL PROBLEMS, WITH DIMMERS, WITH A TOTALLY BALANCED LOAD, YOUR NEUTRAL CURRENT WILL GO WELL OVER 120% OF PHASE CURRENT AT 50% DIMMER LEVELS.
An imbalance will raise the neutral up to 130% or so but you cannot, it is impossible to avoid these high neutral currents.Steve has mentioned this often but the point has been missed.


----------

