# 115 volt AC to 220 volt AC



## byrnebox (May 16, 2010)

So this might be a stupid question. But I am going to ask it non the less. I have done some searching around and can not find an answer to this. Any help is appreciated. Thanks in advance.

Can you take 2 115 VAC circuits and turn them into 220 by just connecting the neutral and the grounds and using the 2 hot leads for each side of the 220?

If so you get the amperage of the 115 V circuits right? Here is what I am thinking about doing. Get 2 115 VAC circuits at 20A and make them 1 220VAC circuit at 20A. Let me know if that will work.

Thanks again.


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## avkid (May 16, 2010)

If you're asking this question you should be calling an electrician.
Purely for educational purposes I will supply this diagram.


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## derekleffew (May 16, 2010)

If the two 120V circuits are on the *same* phase, the potential difference between the hots is zero volts, so that's a no.

If the two 120V circuits are on *different* phases, the potential difference between the hots is 208 volts, so this _might_ work. However, it is forbidden by the NEC. [Citation needed.]

Essentially, you'd be making this, with all genders reversed:

PowerFLEX Cable Assemblies: 3Phase 3Fer | Lex Products

I've seen some companies use these type of "cheater" cords to power 3Ø chain hoists, but they're illegal. The only approved method is to use a Rotary Phase Converter.

EDIT: See this device: Voltage Converter: 220 230 240 Volt Power from 110 115 120 Volt Outlets


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## zmb (May 16, 2010)

This also depends where you are at. Large commercial buildings are likely to have 120/208Y 3ph power while very small buildings and homes will have 120/240 power.


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## zuixro (May 16, 2010)

I've heard a cable that does this called a "Suicide Cable". 

So...


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## dcollins (May 16, 2010)

A suicide cable is the sort that has two male ends that are wired together. This would only be exciting if there was a hot/neutral fault somewhere. One hot netural fault and you've shorted a hot to a neutral, depending on the order you plug them in, it's 50/50 you make a suicide cable or pop the breaker, two hot neutral faults and you've shorted two hots, which is just not a fun time, /and/ you're powering your 220V device with two neutrals. Either way not so good.


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## Chris15 (May 16, 2010)

dcollins said:


> This would only be exciting if there was a hot/neutral fault somewhere.



Sorry, wrong.
If you have a load connected phase to phase, let's say for the sake of this example it's a boring incandescent lamp. The average lamp has a few ohms of impedance when cold.

With the load connected, plug one plug of this "adapter" in. Now go and grab the active pin on the other connector. You WILL get a shock (assuming that the first circuit is energised). You'll be presented with basically the same situation as sticking your finger in the original socket...

It would be possible to make a device that takes 3 single phase inputs and renders a three phase output (given relevant sources) and was safe. You could do it with interlocks so that nothing energises until all inputs are connected and also disconnecting everything if one of the inputs is lost. I doubt it would pass code compliance, but it would be safe.

As to what the OP wanted, IF and only IF the supply is a split single phase will there be any chance of getting 230 out of the arrangement.

Involve transformers or isolated supplies and all this goes out the window, 2 115V sources can be made into a 230V source easily, safety issues would still be relevant...


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## dcollins (May 16, 2010)

Hah, you're right, if the load was connected then yes, you'd get a nice little shock. Suicide adapter it is!

Funny because just earlier today I was working on the exact same sort of thing: an outlet connected to a switch where the hot and neutral were reversed. The neutral metered 120V to ground, but the hot only read anything with a load connected - I should have made that connection.


> With the load connected, plug one plug of this "adapter" in. Now go and grab the active pin on the other connector. You WILL get a shock (assuming that the first circuit is energised). You'll be presented with basically the same situation as sticking your finger in the original socket...


But hey, it would work, right? The lamp would light up? I think we have a solution here - now we just need a few sacrificial conductive actors.


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## derekleffew (May 16, 2010)

Chris15 said:


> ... It would be possible to make a device that takes 3 single phase inputs and renders a three phase output (given relevant sources) and was safe. You could do it with interlocks so that nothing energises until all inputs are connected and also disconnecting everything if one of the inputs is lost. I doubt it would pass code compliance, but it would be safe. ...



From Voltage Converter: 220 230 240 Volt Power from 110 115 120 Volt Outlets, cited above:

> Meets UL Standard 1012
> Tested and Listed by Intertek, a laboratory approved by OSHA to test products for workplace safety.
> Patented safety circuit checks and automatically locks out power circuits until connections and voltages are correct.
> Interlock immediately and simultaneously electrically disconnects all input and output power lines if one of the 110/120 volt cords becomes disconnected or loses power.


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## Chris15 (May 16, 2010)

So now I'm expected to read the writing rather than just looking at the picture?

The fact that the safety circuit is patented does worry me though...


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## mrb (May 16, 2010)

hubbell actually makes a device that does this and has safety interlocks to keep the output from being energized if the inputs are not correct. Its made for marine use, i dont know offhand if its listed.


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## JD (May 17, 2010)

Here's the thing- Unless the breakers feeding the circuits are common trip (same handle for both circuits), you set the stage for a dangerous situation. For instance, if circuit "A" trips, circuit "B" would then be able to back-feed power into circuit "A" by way of the 240 volt device bridging the circuits. This may put someone at risk who is trying to repair circuit "A" as they would believe that it should be a dead circuit because the breaker is off. The whole concept is a big no-no. 

Just a semantic correction on the title- On single phase, voltages would be 110 / 220 or 115 / 230 or 120 / 240 depending on what your local utility feels like giving you. On three phase it would be 120 / 208 (or any similar ratio) due to the phase lag.


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## mrb (May 17, 2010)

JD said:


> Here's the thing- Unless the breakers feeding the circuits are common trip (same handle for both circuits), you set the stage for a dangerous situation. For instance, if circuit "A" trips, circuit "B" would then be able to back-feed power into circuit "A" by way of the 240 volt device bridging the circuits. This may put someone at risk who is trying to repair circuit "A" as they would believe that it should be a dead circuit because the breaker is off. The whole concept is a big no-no.
> 
> Just a semantic correction on the title- On single phase, voltages would be 110 / 220 or 115 / 230 or 120 / 240 depending on what your local utility feels like giving you. On three phase it would be 120 / 208 (or any similar ratio) due to the phase lag.



the interlocked devices shown disconnect the load if one phase is lost.


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## Chris15 (May 17, 2010)

JD said:


> Here's the thing- Unless the breakers feeding the circuits are common trip (same handle for both circuits), you set the stage for a dangerous situation. For instance, if circuit "A" trips, circuit "B" would then be able to back-feed power into circuit "A" by way of the 240 volt device bridging the circuits. This may put someone at risk who is trying to repair circuit "A" as they would believe that it should be a dead circuit because the breaker is off. The whole concept is a big no-no.



Not on something that is interlocked.
Basically how I'd set it up, and the commercial product will have a similar concept is a relay fed from each incoming supply. NO contacts of each supply's relay are looped together so that all supply's relay contacts are in series and that circuit would feed the coil of a contactor to connect the incomings to the outgoing and any commoning.


JD said:


> Just a semantic correction on the title- On single phase, voltages would be 110 / 220 or 115 / 230 or 120 / 240 depending on what your local utility feels like giving you. On three phase it would be 120 / 208 (or any similar ratio) due to the phase lag.



Perhaps we could stick to IEC standard voltages, 115/230 and 115/200...


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## JD (May 17, 2010)

I will defer to Steve Terry should he drop by, but I do not know of any code application that allows two independent 20 amp ~120 volt circuits, with no common trip, to be recombined to form a single ~208/240 circuit, especially post outlet.


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## zmb (May 17, 2010)

Justing wondering, what do you need to have 220 VAC for?


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## FMEng (May 17, 2010)

Chris15 said:


> Not on something that is interlocked.
> Basically how I'd set it up, and the commercial product will have a similar concept is a relay fed from each incoming supply. NO contacts of each supply's relay are looped together so that all supply's relay contacts are in series and that circuit would feed the coil of a contactor to connect the incomings to the outgoing and any commoning.
> 
> 
> ...



Your relay scheme still would not prevent an accidental backfeed of the supply circuits. Why? Because any control circuit has to draw current, unless it has an infinitely high input impedance. Basically, that is impossible. There is no way to do what you describe without creating a hazard and violating the NEC.


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## byrnebox (May 17, 2010)

Thanks all, I see what you are saying now. It makes sense. Thanks for the advice I appreciate it.

James


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## Chris15 (May 18, 2010)

FMEng said:


> Your relay scheme still would not prevent an accidental backfeed of the supply circuits. Why? Because any control circuit has to draw current, unless it has an infinitely high input impedance. Basically, that is impossible. There is no way to do what you describe without creating a hazard and violating the NEC.



The NEC is moot, I said earlier that this won't make code. Oh and it's not applicable here...

I've done a schematic so there's no confusion what I mean. I can't see how that can backfeed with a supply absent. While everything's live, sure and any RCD on those feeding circuits will trip.


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## 00AVD (May 18, 2010)

Chris, from a quick glance it appears that the top-left relay is redundant. The top-right relay can't energise if there's no voltage on the top incoming line anyway.


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## Chris15 (May 18, 2010)

00AVD said:


> Chris, from a quick glance it appears that the top-left relay is redundant. The top-right relay can't energise if there's no voltage on the top incoming line anyway.



This would probably be true, I did a rough design and neglected the system optimisation phase...

Depending on how you built this in terms of perhaps involving low voltage in the control systems, there may still be advantage in involving the dual step relays if there is a supply cap that would hold a charge and not disconnect quickly enough...

You could also expand the design for a three phase system, but all of this relies on being able to get the relevant phases of supply in the space you need them...

Oh and to solve the issue in a safe and compliant manner, use either a step up transformer (bearing in mind the reduced amount of current) or to have a qualified electrician install the relevant circuit for your needs.


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## JD (May 18, 2010)

Bridging the neutrals is not cool either. There is no guarantee that two random outlets will be fed by the same load panel. In this case, you would be bonding two panels with a piece of #12 or #14 wire. In the case of our building, there are 5 load panels. Although voltages on neutrals due to drop tend to be small, the current can be massive. Need to keep distribution in a "Star" topography.


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## Chris15 (May 18, 2010)

JD said:


> Bridging the neutrals is not cool either. There is no guarantee that two random outlets will be fed by the same load panel. In this case, you would be bonding two panels with a piece of #12 or #14 wire. In the case of our building, there are 5 load panels. Although voltages on neutrals due to drop tend to be small, the current can be massive. Need to keep distribution in a "Star" topography.



Neglect to bridge them and you can easily kill your gear because of those very neutral currents...

I hope by now people have worked out that this discussion is purely academic. The compliant method I mentioned at the end of my last post...


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## CBR372 (Jul 20, 2010)

*Getting 200-240VAC with 120VAC Pigtails.*

So I have a question. This is all hypothetical as my theatre's don't have access to any movers that require 200-240VAC or any constant or relay dimmer modules. 

Lets say I want to run some 200-240VAC moving lights on my 120vac 3-phase dimmer system. If I put a relay module lets say dimmer 1 which is on Phase A and then another relay in dimmer 2 which is on Phase B. Then I built a reverse 2fer (2 males, one female) and that took those two circuits at the pigtail end and took both hot leads from the 2 circuits and only one neutral and both grounds, would that create 200-240vac? I've been really confused reading other posts about how the difference between phases is 208 or 240 as it doesn't really explain how to make 200-240vac.

Thanks guys!

Again I just want to know this so i can stop trying to wrap my head around it!!!


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## Sean (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

Well....

First of all this is a bad idea from a safety standpoint: you'd have a hot MALE connector.

Electrically you'd have two hots, and a ground. Voltage between the two hots would be ~208v.

The way you really do this is to get a Power Distro (PD) that is "tied-in" to the building's power, usually at a company switch.

Again, DO NOT do what you're suggesting. It's a really bad idea.


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## tyler.martin (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

That would not "make" 240V. potentially very dangerous. Get an electrician in to see if there are any 208 lines in your building

Splitting a fixture across phases is bad IIRC.


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## ajb (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*


martinty said:


> Splitting a fixture across phases is bad IIRC.


 
Any 208V fixture connected to a 120/208 Y system is "split" across phases. . .phase-to-phase is the only way to get 208V in such a system. 

To the OP: What you describe would, in fact, do what you're after, but doing it safely is a bit more complicated than you've described. For one thing, you'd need a very specific interlock arrangement to ensure that with a load plugged into the female and one male plugged into a live receptacle that the other male did not wind up at line voltage, and that the load only gets either both phases or none. For another, the NEC requires that any multiwire branch circuit (which is what you're creating by combining those two separate 120V circuits) be equipped with an overcurrent protection device that simultaneuously interrupts all line conductors--in other words, a single two-pole common trip breaker, or two single pole breakers with the handles mechanically tied together. This is not something that is easily accomplished in an off-the-shelf dimming system. It may be possible to place an OPD somewhere within the device that joins the two circuits that will satisfy your AHJ, but that would require some close reading of the NEC and/or local codes--and more importantly, you'd have to convince an inspector that it's safe and compliant, which would possibly be the hardest part.


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## mrb (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

Hubbell and one or two other manufacturers make a device that does this safely with necessary interlocks. Theyre used in marine applications. Too costly for it to make sense for this application, just have an electrician install the circuits you need, or get the proper distro if you have a company switch to connect to. 

as others have said, DO NOT do what you propose. It is very dangerous.


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## derekleffew (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

Furthering what's been said, note that products exist to go from one 3Ø to three 1Ø outlets:
(one example)


PowerFLEX™ Cable Assemblies: 3Phase 3Fer | Lex Products

but NOT the reverse (not legally, at least). 

If one were so inclined, one could likely find pictures at various "wall of shame" sites. Pictures depicting bad, illegal, or unsafe practices are frowned upon here at ControlBooth.


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## CBR372 (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

Thanks guys! I'm just trying to understand how 208 is made from 120v. our building doesn't have a company switch, so "legally" the only way to do this whould be to have an electrician install a few 208-240 circuits around the grid? (these would be a black box application).


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## derekleffew (Jul 20, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

For explanation of single-phase and three-phase circuits, see Single-phase power systems : POLYPHASE AC CIRCUITS and the pages that follow. 

Correct, the only way to obtain 220V or 208V circuits is to have a licensed electrician install them.


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## n1ist (Jul 21, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

One other way would be to use a 110V non-dim circuit feeding a step-up transformer. It may be a cheaper solution for a 1-off rental. For permanent use, I'd get the correct circuit installed.
/mike


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## jjkool (Jul 21, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*

I bet if you were to get a proper rating on your system it isnt @ 120v its more then likely @ 208v


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## ajb (Jul 21, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*


jjkool said:


> I bet if you were to get a proper rating on your system it isnt @ 120v its more then likely @ 208v



huh? 

If the OP's nominally 120V circuits are actually running at 208V, then there's something seriously wrong. . . and they'd probably have noticed issues already. 

If you're suggesting that the OP's building infrastructure is wired with 3Ø 120/208V Y distribution. . . well, that was a given in the opening post, and the resulting discussion was entirely based on that fact.


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## derekleffew (Aug 2, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*


mrb said:


> Hubbell and one or two other manufacturers make a device that does this safely with necessary interlocks. ....


A post on SML has reminded me of this device: Voltage Converter: 220 230 240 Volt Power from 110 115 120 Volt Outlets, which we discussed here: http://www.controlbooth.com/forums/lighting/19720-115-volt-ac-220-volt-ac.html.


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## kicknargel (Aug 3, 2010)

*Re: Getting 200-240VAC with 120VAC Pigtails.*


ajb said:


> huh?
> 
> If the OP's nominally 120V circuits are actually running at 208V, then there's something seriously wrong. . . and they'd probably have noticed issues already.
> 
> If you're suggesting that the OP's building infrastructure is wired with 3Ø 120/208V Y distribution. . . well, that was a given in the opening post, and the resulting discussion was entirely based on that fact.


 
I think what he's getting at is the 208V can probably be installed with no new wiring, just modifications at the breaker and a new outlet. By a licensed electrician of course, but maybe not too expensive.


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## SalvatoreDelorean (Jan 5, 2013)

*Pulling 240v from two 120v circuits*

I'm lighting a small corporate event in an office building, and I have a few Mac 575s I was hoping to use. They run on 200-240v, but there aren't any accessible 240v circuits in the building. I was talking to the building electrician, however, and he told me it would be possible to pull from the hots of two normal 20a 120v circuits, make an adaptor, and wind up with 208/240v. I've heard of things like this, and it makes sense to me in theory, but seems incredibly sketchy. Is this safe, and if so, how would I go about doing this? 

My first instinct would be to do something like wire up a twofer in reverse with two male edisons to plug into the 120v wall circuits, and a female L6-20 on the other end, but that just seems like a bad idea. In my experience, jury-rigged solutions like this rarely end up working well, so I'm wondering if this is a more common practice than I'm aware, or if this building electrician happens to be an idiot.

It also doesn't seem like it can be that simple. Would drawing from two 20a 120v circuits give you 40 amps of 120v, or 20 amps of 240v? Would a transformer of some kind be needed to step up the voltage?


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## LavaASU (Jan 5, 2013)

*Re: Pulling 240v from two 120v circuits*

Ok, not quite. An actual electrician should be able to get you 208 or 240V (depending on if the building is single or 3 phase), but it needs to be run through a panel with appropriate double pole breakers. 2 20A circuits on the same phase would get you 40A of 120V. 2 20A circuits of a different phase would get you 20A of 208/240. You would not need a transformer in this case.


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## ProgrammerInTraining (Jan 5, 2013)

*Re: Pulling 240v from two 120v circuits*


like this?


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## derekleffew (Jan 5, 2013)

*Re: Pulling 240v from two 120v circuits*


ProgrammerInTraining said:


> View attachment 8444
> 
> like this?


I thought we had set you straight when you originally posted that picture in this thread: http://www.controlbooth.com/forums/lighting-electrics/27159-120-208-240v-questions.html .
.


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## TimMiller (Jan 6, 2013)

*Re: Pulling 240v from two 120v circuits*

If you are going to run 240/208 at least use a rated connector. Most movers can run on 120 check with the shop and see if they can be ran on 120 and they will typically swap the connectors and voltage for you. I was always happy to do this as a free service to prevent and strange wiring just like I would loan out non dim modules. I wanted to protect my equipment and help prevent any liabilities. If you have 120 and need 240 the best way is by using a transformer. They are the most safest and easiest way of fixing this problem besides changing the voltage taps on the fixture if 240 is not avaliable.


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## danTt (Jan 6, 2013)

*Re: Pulling 240v from two 120v circuits*


SalvatoreDelorean said:


> I'm lighting a small corporate event in an office building, and I have a few Mac 575s I was hoping to use. They run on 200-240v, but there aren't any accessible 240v circuits in the building. I was talking to the building electrician, however, and he told me it would be possible to pull from the hots of two normal 20a 120v circuits, make an adaptor, and wind up with 208/240v. I've heard of things like this, and it makes sense to me in theory, but seems incredibly sketchy. Is this safe, and if so, how would I go about doing this?
> 
> My first instinct would be to do something like wire up a twofer in reverse with two male edisons to plug into the 120v wall circuits, and a female L6-20 on the other end, but that just seems like a bad idea. In my experience, jury-rigged solutions like this rarely end up working well, so I'm wondering if this is a more common practice than I'm aware, or if this building electrician happens to be an idiot.
> 
> It also doesn't seem like it can be that simple. Would drawing from two 20a 120v circuits give you 40 amps of 120v, or 20 amps of 240v? Would a transformer of some kind be needed to step up the voltage?



You should have the building electrician install a service capable of powering these. Whether it's a disconnect of some sort that you can connect your own 208v PD to, or simply an L6-20 plug or two in a helpful location is up to you (Actually, an L21-30 plug might make the most sense, and then you can use a variety of breakouts to get the power you need. The fact that the Building Electrician suggested the solution he did scares the poop out of me, honestly. And he's a licencensed electrician? If that is the solution he gives you, make sure he does all of the power connections, and you go nowhere near any of it. 

I'm surprised that the mac575 can't run on 120, but based on the manual it looks like the magnetic ballast is the issue, just make sure you flip the wires around based on whether he gives you 208 or 240, whenever a solution is made.


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