# Fully Rated Breakers



## zuixro (Jan 26, 2010)

It's been said before that breakers installed in buildings should are not meant to be run at 100% (for very long anyway). So if I had a 4 channel dimmer pack at 6amps per channel plugged into a 20amp breaker, I couldn't put 4 Source 4's @ 575watts on it. You could step up to a 30amp breaker, but then, as I understand it, you couldn't use Edison plugs (because the breaker has to be rated for the lowest rated piece in the chain, in this case the 20amp Edison outlet).

All that to say, is it possible to get breakers for a building that are made to carry 100% of their rated load?


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## DuckJordan (Jan 26, 2010)

your use of breakers pluss dimmers concerns me, Dimmers are not breakers. the power leaving a dimmer is diffrent than going in. this would mean that when you installed a 30 amp breaker your weakest link would lie in between the dimmer rack and the breaker. not between the dimmers and the source 4's


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## zuixro (Jan 26, 2010)

I meant plugging the dimmer pack into an outlet connected to the breaker. I know the difference between a dimmer and a breaker.


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## Lotos (Jan 26, 2010)

zuixro said:


> It's been said before that breakers installed in buildings should are not meant to be run at 100% (for very long anyway). So if I had a 4 channel dimmer pack at 6amps per channel plugged into a 20amp breaker, I couldn't put 4 Source 4's @ 575watts on it. You could step up to a 30amp breaker, but then, as I understand it, you couldn't use Edison plugs (because the breaker has to be rated for the lowest rated piece in the chain, in this case the 20amp Edison outlet).
> 
> All that to say, is it possible to get breakers for a building that are made to carry 100% of their rated load?


 
The NEC contains very informative information on this topic, I'm told... As I'm in Canada, anything I could dig up in my local codes, while probably being close, would be inaccurate for your needs...

As for the pack itself... A 4 channel pack will also have a rating... Something to the tune of: "400w per channel, not to exceed 1200w total" or "600w per channel, not to exceed 1800w total" or possibly a similar rating in Amps...

Basically, assuming the NEC says you can put in a 20Amp breaker, rated at 100% load... You're still breaking code if you put over 1800w on the pack... So you're still capped out at 3x 575w fixtures anyhow.


Edit to note: Edison plugs are only rated for a maximum 15 Amps, as it is... So 80% of that is 12Amps sustained... or 1440Watts @ 120v not even enough to run three 575w fixtures for an extended period of time.


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## zuixro (Jan 26, 2010)

Lotos said:


> As for the pack itself... A 4 channel pack will also have a rating... Something to the tune of: "400w per channel, not to exceed 1200w total" or "600w per channel, not to exceed 1800w total" or possibly a similar rating in Amps...



Specifically I was looking at the ETC SmartBar:
Lighting solutions for Theatre, Film & Television Studios and Architectural spaces : ETC

All the datasheet says is:
"Total load can not exceed capacity of main power connection
(wall outlet, 15a, 20a)"

This was mostly hypothetical, if it ever did come to fruition, all work would be done by a licensed electrician. 

After running the numbers and some more research, I think it's a better idea to just go with 375w lamps.


> Edit to note: Edison plugs are only rated for a maximum 15 Amps, as it is... So 80% of that is 12Amps sustained... or 1440Watts @ 120v not even enough to run three 575w fixtures for an extended period of time.



That's been debated so much here, I don't even know what to believe anymore. I believe it's been said that there are 20amp rated Edison plugs, but they are expensive.


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## epimetheus (Jan 26, 2010)

Lotos said:


> The NEC contains very informative information on this topic, I'm told... As I'm in Canada, anything I could dig up in my local codes, while probably being close, would be inaccurate for your needs...
> 
> As for the pack itself... A 4 channel pack will also have a rating... Something to the tune of: "400w per channel, not to exceed 1200w total" or "600w per channel, not to exceed 1800w total" or possibly a similar rating in Amps...
> 
> ...



To correct a couple of things:

The 80% does not apply to the plug/receptacle, only to the breaker.

You can get 20A receptacles. (NEMA 5-20R and L5-20R)

I don't have my NEC here at home, but I think there's a branch circuit rule that allows 15A receptacles on 20A circuits. I'd have to look this one up to be sure, somebody please correct me if I'm wrong.


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## DuckJordan (Jan 26, 2010)

I would go with your idea of dropping bulbs down to 375w if you really need 4 fixtures per dimmer pack, otherwise are you sure you would use all 4 at the same time? this would mean making sure anyone using the system knows not to bring all 4 of those channels up to 100% but it would mean you could have 4 fixtures at 575w and just use 3 of them. also may i ask why they need to be portable?


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## zuixro (Jan 26, 2010)

DuckJordan said:


> I would go with your idea of dropping bulbs down to 375w if you really need 4 fixtures per dimmer pack, otherwise are you sure you would use all 4 at the same time? this would mean making sure anyone using the system knows not to bring all 4 of those channels up to 100% but it would mean you could have 4 fixtures at 575w and just use 3 of them. also may i ask why they need to be portable?



Right now it's a "pie in the sky" setup for my former high school. Right now they own no lighting equipment. None. Well, none besides a few clip lights and colored party bulbs. If they did get a system, it would need to be portable so it could be used in the drama room (used as a black box space a lot) and in the gymatorium. It would also be great during graduation, outdoor events, dances, etc. Anyway, this is content for another topic.

I was thinking that we would have to add some 20amp circuits in order to use the system, but with 375w lamps, they could probably share with circuits already in place.


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## DuckJordan (Jan 27, 2010)

that would probably be the cheapest solution as the wiring in the walls may not be rated fro 20 amps also i would check with the other spaces you are planning on using to make sure they have either the same amp rating or higher. But as far as using the 375s they shouldn't need to be brighter than that for the distance they will be used at. as we have four source fours in a catwalk throwing about 100' and they are running 375s while our colortrans 20* is running 575s and the source four is brighter.


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## SHARYNF (Jan 27, 2010)

The typical dimmer installation never supports all instruments on at full rated power, the NEC allows for the power supplied to be at the anticipated usage
Other wise we would have massive power feeds to large dimmer racks

I would suggest a few things

One you could just not use one of the channels on the dimmer or put a lower rated lamp on one of the channels

If this is for the future you could look at led solutions


you could just remember that you cannot put all the instruments on at full power on all dimmer channels


It is less of a practical problem and more of a theoretical one

Sharyn


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## cdub260 (Jan 27, 2010)

SHARYNF said:


> you could just remember that you cannot put all the instruments on at full power on all dimmer channels



I can in my venue. I have a 600 amp, 3 phase feed for my dimmers. If I were to power up every piece of lighting and effects equipment in my inventory, I could pull a bit more than half of that. Now, If I were to load it all onto 1 phase, then I'd be in trouble.

Of course, I may have expanded my inventory a bit since I did those calculations.


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## SHARYNF (Jan 27, 2010)

The point I was trying to make was that say you have 196 channels of 20 amp dimming it does not mean that you need a 1300 amp three phase supply

So you must have been one of the guys that made CA buy all that extra power from Enron back in the day ;-)))))


Sharyn


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## cdub260 (Jan 27, 2010)

SHARYNF said:


> The point I was trying to make was that say you have 196 channels of 20 amp dimming it does not mean that you need a 1300 amp three phase supply



I know. I just couldn't resist the impulse to make a post that had little bearing on the topic at hand.


SHARYNF said:


> So you must have been one of the guys that made CA buy all that extra power from Enron back in the day ;-)))))


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## billn (Jan 27, 2010)

> Basically, assuming the NEC says you can put in a 20Amp breaker, rated at 100% load... You're still breaking code if you put over 1800w on the pack... So you're still capped out at 3x 575w fixtures anyhow. ------ This is totally incorrect. The NEC BREAKER derating applies to permanent loads, ones that may be left on continuously. I have many portable packs, and use them frequently. Some are rated 15A maximum and are marked 600W/channel 1800W max. Some are rated 20A and simply state 600W/channel. A few are rated 20A and say 1200W/channel 2400W maximum - in this case, the dimmer has the potential of drawing 4800 watts on a 20A circuit (until the circuit breaker trips). ALL of these packs are supplied with 15A plugs. The 1200W/channel pack has two power cords. > Edit to note: Edison plugs are only rated for a maximum 15 Amps, as it is... So 80% of that is 12Amps sustained... or 1440Watts @ 120v not even enough to run three 575w fixtures for an extended period of time. Again, incorrect. 15A plugs/outlets may be used with 15A loads, continuously. If your feed circuit to the dimmer pack is 20A, you may run four 575W fixtures, even for long periods of time. There was a reason why ETC chose that wattage for their lamps. If you divide 575 watts by 115 volts, you get exactly 5 amps. That comes to a total of 20 amps for four 115 volt lamps, less for 120 volt lamps. Bill


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## Tracyu (Jan 27, 2010)

From my NEC news letter:
"Question:

[FONT=Arial, Helvetica, sans-serif]If a thermal breaker claims 100 percent duty in its data sheet, does this satisfy the 210.20(A) exception stating, "Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load"?
[/FONT]
Answer:
Circuit breakers evaluated in accordance with Underwriters Laboratories Standard 489 are suitable for providing the overcurrent protection of branch-circuit conductors required by 210.20. Circuit breakers that are evaluated in accordance with this standard and are listed for operation at 100 percent of their continuous current rating can be used at that rating, provided the assembly in which the circuit breaker is installed is also listed for 100 percent operation. The fact that the circuit breaker itself is listed for 100 percent operation does not satisfy the conditions of the exception to 210.20(A). The equipment in which the circuit breaker is installed also has to be listed for use with protective devices operating at 100 percent of their continuous current rating."

In a distributed dimmer system, if your breaker panel is designed and listed to carry %100 load, your circuit wiring is sized to carry it AND the dimmer you are plugging into is designed and listed to carry %100 load you would be fine. HOWEVER, it does not mean you will not get nuisance tripping of the circuit breaker if loaded to full. Your power is never perfect all the time. The Lamps in your fixtures are not perfect throughout there rated life. Your breakers are not perfect after a few years of use.
20 amp edisions are very common in commerical construction like schools. At EDI we build the Scrimmer Stick and all of them leave the factory with 20 amp plugs on the power feed because that's the only way U.L. will let us do it. That's not to say I've not retofitted a 15 amp plug on them in the field, but if you do, that's now your total limit for your dimmer.
Hope this helps,
Tracy


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## tjrobb (Jan 27, 2010)

The "answer" to the 100% loading is related to the operation of the breaker. Thermal-magnetic breakers heat up in use and are thusly only rated to 80% of the load (12A @ 15, [email protected]); electronic trip breakers have a sensor to read the amperage and thus are (usually) 100% rated.
The issue you would run into in this scenario is that most electronic breakers are found in the incoming switchboard (your mains power). They are too expensive / bulky to be used for "common" loads. (I think Lex Products uses them for shore power, though).

As for the wiring, most places it seems run no less than 12AWG, simply as a precaution against later upgrades and/or voltage drop (that and commercial buildings tend to run mostly 20A circuits). In fact, if your wire run gets long enough you may find 10g, or even 8g, on a 20A circuit.


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## SteveB (Jan 27, 2010)

zuixro said:


> It's been said before that breakers installed in buildings should are not meant to be run at 100% (for very long anyway). So if I had a 4 channel dimmer pack at 6amps per channel plugged into a 20amp breaker, I couldn't put 4 Source 4's @ 575watts on it. You could step up to a 30amp breaker, but then, as I understand it, you couldn't use Edison plugs (because the breaker has to be rated for the lowest rated piece in the chain, in this case the 20amp Edison outlet).
> 
> All that to say, is it possible to get breakers for a building that are made to carry 100% of their rated load?



This is actually a topic that is somewhat esoteric and at the same time crucial to consider when you are trying to choose between a distributed "SmartBar" type system and a collected dimming system such as Sensor. 

The code limitation is usually that you can't power an incandescent lighting load for more then 3 continuous hours, and must downrate the feed and load breakers(s) 20%, or you must use a breaker designed for 100% loading. Circuit breakers that are 100% rated are very expensive for industrial/commercial breaker panels, and usually not used, thus this kind of loading issue rears it's ugly head a lot. Sensor dimmers (and others of this type) ARE rated for continuous loading, so the only limitation in use is the size of the main feeders and breakers. 

Note that it's not uncommon to find distributed dimming systems that have built in breakers that are 100% rated, which does you no good if the feed branch circuit at the same rating is not rated for 100%. 

So you are correct that you have to be aware of the expected demand load when pricing out and specifying a distributed system as you often find yourself needing additional dimmers and branch circuits to feed them. Or as others have stated, you can go to power feed system using higher capacity breakers and feed cabling. The Lex Anaconda dimmers is one of the distributed systems we found that has 3 feed cables for 6x1200w dimmers, that would be capable of full loading, if you specify the feed cables as 10/3 SOOW and use appropriate connectors, with associated branch circuits rated at 30 amps. That gives you some loading headroom.


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## derekleffew (Jan 27, 2010)

As has been stated, the rated ampacity of the supply connector(s) is the primary limiting factor and is not subject to any derating.


epimetheus said:


> ...I don't have my NEC here at home, but I think there's a branch circuit rule that allows 15A receptacles on 20A circuits. I'd have to look this one up to be sure, somebody please correct me if I'm wrong.



You are not wrong. The duplex receptacles in your home are most-likely protected by a 20A OPD. I believe code allows for a maximum of thirteen of these devices on a single branch circuit. A 20A breaker cannot feed a single 15A receptacle, but may feed multiple ones. Plugging in the desk lamp wired with 18g. zip cord is acceptable, as the load is limited to the "100W bulb maximum" as stated on the fixture.


SHARYNF said:


> The typical dimmer installation never supports all instruments on at full rated power, the NEC allows for the power supplied to be at the anticipated usage
> Other wise we would have massive power feeds to large dimmer racks
> ...



While more-or-less accurate, the above is ambiguous and can be misconstrued. A dimmer rack need not be fed its faceplate rating (see Dimmer feeds--How much power is enough?) but no mention is made of connecting more lights than available power, knowing not all of them will be used at once or at less than 100%. For the purpose of theoretical CB discussions, we accept as a given that all connected fixtures will run at full at some point.


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## SteveB (Jan 27, 2010)

derekleffew said:


> As has been stated, the rated ampacity of the supply connector(s) is the primary limiting factor and is not subject to any derating.



I believe that the primary main breaker feeding a dimmer rack is subject to de-rating though, which is one of the reasons the typical ETC Sensor SR48 with a typical capacity of 96x2.4kw dimmers, is bussed at 800 amp per phase, so that if you take into account the de-rating of an 800 amp breaker, you end up at 640 amps per phase, which is the theoretical connected load of the rack (96 dimmers times 20 amps per dimmer, divided by 3 phases). Not sure if using fuses as primary feed protection means the fuses are de-rated though. 


> For the purpose of theoretical CB discussions, we accept as a given that all connected fixtures will run at full at some point.



Yup. Typical is 3 hrs. being continuous. It's VERY easy to run your system full on for 3 hrs, as you may well be sitting in a film or TV shoot ALL day, or a looong rehearsal period.


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