Photocell question...

Merry Christmas
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I was trying to be funny. What I was trying to say is that the photocell is a controller, not the required disconnect, and therefore, it doesn't need to disconnect all ungrounded conductors. In fact, you even see warnings inside the package units that say that voltage is present when the unit is off.

I think the photocell on one leg is not a violation.

Mark
 
If you do use it on 208 you are assuming that the solid state electronics can handle the 208 volts. Granted the photo cell will see 120 but when it closes it will still see 208 across the triac . In any event the current rating will at least be cut @in half.
 
Maintenance Man?

Maintenance Man?

480sparky said:
It will work, but it's a bad design, since you're only turning off one of the ungrounded conductors. Some poor, uneducated and unlicened maintainence man could get zapped if the photocell shut them off, but the power was still on.
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Why did you have to go and say that? Some of us maintenance men are Master Electricians and have electrical cards in many states.
I'm just picking on you.
I do think that you will get someone hurt or killed by this practice and if it was not made and tested to do this, you should not ever do it.
Spend the money and do it right.

Michael Hester
Master Electrician and yes, Maintenance Electrician
Campus Crusade for Christ
 
480sparky said:
So how does that apply to post 21?
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It doesn't apply at all. Look at the context of article 410 - Luminaires.

As I said earlier, the NEC does not apply at all to manufactured AC units. One look inside any of them should be enough proof of that.
 
chevyx92 said:
Had a co-worker ask me this this morning and I couldn't come up with the answer. If you have some 208v volt wall packs and want to use a photocell to control them why can't you use a 120v photocell? Why does it HAVE to be rated 208v when all you are doing is breaking one leg of the 208.
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Back to the original question. A 120 V photocell used to control 208 V lighting.

Answer: Use photo cell to control 120 V coil of two pole lighting contactor. End of story. ;)


Edit: turn off breaker and lock out when working on lights. You'll live longer.
 
growler said:
Back to the original question. A 120 V photocell used to control 208 V lighting.

Answer: Use photo cell to control 120 V coil of two pole lighting contactor. End of story. ;)
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Exactly. :)

By the way, I did not see it mentioned but switching just one leg of 208 puts 208 volt across the switch, not 120.
 
chevyx92 said:
. If you have some 208v volt wall packs and want to use a photocell to control them why can't you use a 120v photocell?
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Or, we could forget about contactors for a minute, get even simpler and just say that the reason you can't use a 120 volt photocell is because the code doesn't allow it.

(I agree, a contactor is the best solution)

Sometimes we miss the forest for the trees in these threads. :)
 
peter d said:
just say that the reason you can't use a 120 volt photocell is because the code doesn't allow it.
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And the 208 applied across the 120 photo cells contacts might be a problem.

Kind of like using a 120 volt SP on a 277 circuit, it might work, or it might go 'poof' spectacularly. :grin:
 
Its very common to only break one leg of a 208 or 240 volt luminaire. Many photocells are multivoltage rated, IE 120-208 120-240.
 
tom baker said:
Its very common to only break one leg
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Are you saying it's legal, or just that it's common? I thought we'd already determined that it isn't legal for luiminaries, per codes mentioned above.
 
I bet Tom is thinking of these photo cells which go on 'Cobra Head' street lighting fixtures.

They are part of the factory wiring which puts them outside the NEC.

Sell_Twist_lock_Photocontrol_Photo_Control_Photocell.jpg

Twist lock photocells

0167200_large.jpg

Cobra Head
 
tom baker said:
Its very common to only break one leg of a 208 or 240 volt luminaire. Many photocells are multivoltage rated, IE 120-208 120-240.
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Do you have a link for these photocells. I'm not finding them, only fixtures with photocells ( they contain a multi-tap transformer ).

I noticed one with a operating volting of 208 through 277 but it didn't mention only breaking one leg. I don't think that's legal.

I went to the van to look at the photo cells I have in stock and they are all only rated for 120 volt. I really think it's going to zap like a flash bulb when you hit it with 208.

I'm not kidding folks I have never seen only one leg broken useing a 120 V photo cell.

Learn me sumpthen...:grin: :grin: I revert to a hill billy when trying to grasp something new.
 
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