277volts AC line I need to find the breaker

[mramos1]

I have an exit light that runs on 277 volts. I can not find the breaker, not labeled. I have a 120volt Sperry AC tracer, that works like on the 120volt line.

Does anyone have a clever way to hook the 120volt toner to the 277?

I thought about a step down 277 to 120 and caps primary to secondary to jump the toner (frequency) over the transformer.

Any other ideas. The electric was here and he did not know where the breaker was and his tracer had been stolen so he could not help.

 

[Andy1845c]

How many breakers do you have to sort through?
It seems like alot of work to step down to 120v to use the circuit tracer. Wouldn't you have to work on it hot in order to get the transformer hooked up anyway?

Is there anyway to do it trial and error style? The 277v breakers are likely in there own panel. Is there a time of day when you could flip them on and off, and have a buddy watch,to find the right one? It seems to me somtimes emergency lighting is on its own circuit. I have also seen it tied into diesel generators in some large stores/building.

If your not 100% sure you know what your doing, I would hire a pro. 277v line current is nothing to mess around with.

 

[Hayato]

And if the 277V line is "biphasic"? Then you'll have a bipolar breaker.

 

[mramos1]

Andy1845*:

If I had a front end to the 120vac curcuit, I clip on hot and go find the signal. I have one I have to find (mine). And it is hot.

But the Building Engineer will have many more, he was lucky to get a 10 story building and breakers with labels I would trust.

I have a hot 277 and want to clip on and go fine a signal at my breaker. I thought about ordering a UK version and hope 240 and 277 is close enough. And low watts (4-8 range) to drop an R in there and all is good.

Or drop in a transformer the BE had that did 277 to 120 and bridge it with a couple caps to send the signal over.

Nigel (UK, oz and US guys included):

You might peek in here. What do you think? I have some 250+volt non polarized caps. Pushing the line on them I am sure, tring to feed the signal back across the transformer. Old telco stuff.. There must be a better way to hook to it with a 120VAC device with no isolation.

Hayto:

The panels have big breakers and small.. But I imagine it is straight 277.. And the electric guy said it is much more effcient to feed 277 down to 12 volts. And I looked at the light inside and saw a step down and a balast and think. Maybe in the old days..

 

[ClydeCrashKop]

You might have half that voltage from either leg to ground which probably wouldn’t overload your tester but use your own discretion.

 

[giaosucan]

it is to difficult to understand what you say .Anyone tell me more detail

 

[awright]

Is your tone generator POWERED by the 120 volt line, or just safe to connect to it? Does your tone generator use batteries? If so, it must just be protected against damage from the 120 VAC line. If that is the case, you should be able to safely reduce the voltage seen by the toner with a capacitive/resistive voltage divider and use the capacitor to couple the low RF from the toner into the line.

The capacitive reactance of a 0.001 uF capacitor is about 2.6 megohms at 60 Hz, but is probably very adequate for coupling the RF from the toner into the line. (Bear in mind that I don't know the impedance of the toner or the frequency of the toner.) A 47K resistor shunting the output leads of the toner will assure that the line voltage is attenuated to a very safe voltage for your toner no matter what its terminal impedance is.

So I would suggest connecting a 0.001 uF, 500 volt or more capacitor in series with a 47K, 1/2 watt resistor from the 277 volt hot line to ground at the light fixture. Connect the toner ground, then clip the toner hot lead to the junction of the resistor and the capacitor (very carefully). This sequence minimizes the likelihood of coupling a transient voltage spike to the toner via the capacitor suddenly connected to the line at the peak of the voltage waveform. Check that the tone is present on the wire several feet from the toner. If it is, go find the breaker with your sniffer.

Be aware that I am not an EE, just a hobbyist. You take responsibility to make the connection to the hot line safely.

Careful!

awright

 

[Nigel Goodwin]

Just stick a bulb on the output, and go round turning breakers off until the bulb goes out - or use a radio - but obviously you need something that works off that voltage, or a transformer to drop it.

 

[Hayato]

You know that "phase-testers" screw drivers? The ones that have a Neon Bulb + Resistor inside the handle.

If the 277V line is straight, the Neon Bulb with be brighter in that line than in the 120V ones.

So you could test the wires which come out from the breakers.

 

[ClydeCrashKop]

Florida Power & light doesn’t make 277 volts so that exit light is probably something special with its own transformer like sodium bulbs with a 15000 hour life span. The supply voltage inside the fixture is probably 120v. But (hehehe) anyone will tell you to turn off the breaker before opening the unit.

"If the 277V line is straight, the Neon Bulb with be brighter in that line than in the 120V ones."
Neon signs have their own transformer too.

 

[Hayato]

Florida Power & light doesn’t make 277 volts so that exit light is probably something special with its own transformer like sodium bulbs with a 15000 hour life span. The supply voltage inside the fixture is probably 120v. But (hehehe) anyone will tell you to turn off the breaker before opening the unit.

"If the 277V line is straight, the Neon Bulb with be brighter in that line than in the 120V ones."
Neon signs have their own transformer too.

It's not Neon Signs that I'm talking about. It's test-phase screw drivers, that have a small neon bulb inside.

 

[Hero999]

Those screwdrivers are normally rated from 100V to 500V.

One side of small neon lamp inside is connected to the tip and the other is connected to the screw on the back via a high voltage high value resistor (typically 1kV 2M2). You form the earth return part of the circuit, but you don't get shocked because the current is so small you can't feel it.

 

[Hayato]

Those screwdrivers are normally rated from 100V to 500V.

One side of small neon lamp inside is connected to the tip and the other is connected to the screw on the back via a high voltage high value resistor (typically 1kV 2M2). You form the earth return part of the circuit, but you don't get shocked because the current is so small you can't feel it.

Exactly, I have a couple of those screw drives, they are very handy sometimes.

But I modify them, I put a 5M resistor instead of a 2M2.

 

[Hero999]

Is that to provide an extra level protection?

I was probably wrong earlier when I said the resistor's rated to 1kV, it's probably rated to 2kV (or at least a 2kV transient) - the minimum withstand voltage between you and an insulator connected to the mains. Yes I know the resistor isn't an insulator but I think 150:mu:A is an acceptable leakage to earth via you.

What voltage rating resistors do you replace them with? I certainly wouldn't replace them with anything rated to less than 2kV. I'd rather have 150:mu:A passing through me than 100mA when there's a surge and the resistor breaks down.

 

[Hayato]

Is that to provide an extra level protection?

I was probably wrong earlier when I said the resistor's rated to 1kV, it's probably rated to 2kV (or at least a 2kV transient) - the minimum withstand voltage between you and an insulator connected to the mains. Yes I know the resistor isn't an insulator but I think 150:mu:A is an acceptable leakage to earth via you.

What voltage rating resistors do you replace them with? I certainly wouldn't replace them with anything rated to less than 2kV. I'd rather have 150:mu:A passing through me than 100mA when there's a surge and the resistor breaks down.

Yes to provide some extra protection. Sometimes when my hands are sweat I can feel a weak shock, with the 2M2 resistor.

I use standart resistors, because I use that for 220V maximum. But it's a very good idea to use >1kV rated resistors, even if the circuit (R+NEON+Body) does not form a significant inductive load.

 

[ClydeCrashKop]

Sorry Hayato, you are right. You reminded me about neon signs just as I posted but that’s not what you were talking about.

 

[Hayato]

Sorry Hayato, you are right. You reminded me about neon signs just as I posted but that’s not what you were talking about.

lol, no problem. I was scared when you said "NST", I wondered that moment "from where did he get that NST from my post!?!" lol!!!

 

[Hero999]

Yes to provide some extra protection. Sometimes when my hands are sweat I can feel a weak shock, with the 2M2 resistor.

Wow, you must be very sensitive. I can put it in my mouth without feeling anything!

Are you sure it's a 2M2 resistor and not a 1M, what voltage do you have in your country, is it 110V, 230V higher?

I use standart resistors, because I use that for 220V maximum. But it's a very good idea to use >1kV rated resistors, even if the circuit (R+NEON+Body) does not form a significant inductive load.

If your mains is 220V then it will be 311V peak and it's got nothing to do the inductance, it's about safety. I don't know what the laws are in your location but the British safety standards say you should design your insulation so it won't breakdown when exposed to 2kV spikes on the mains. This prevents anyone from getting zapped when lighting strikes the overhead cables.

 

[Hayato]

Wow, you must be very sensitive. I can put it in my mouth without feeling anything!

Are you sure it's a 2M2 resistor and not a 1M, what voltage do you have in your country, is it 110V, 230V higher?
.

Yes, it's a ~2M2 resistor.
Here we have 110Vac and 220Vac, 60Hz, for residential distribution. Where I live it's 220Vac.

If your mains is 220V then it will be 311V peak and it's got nothing to do the inductance, it's about safety. I don't know what the laws are in your location but the British safety standards say you should design your insulation so it won't breakdown when exposed to 2kV spikes on the mains. This prevents anyone from getting zapped when lighting strikes the overhead cables.

Yes, here it's almost the same. But the insulation capabilities are differents for each groups of application.

 

[Hero999]

What basic, single and reinforced insulation?

I have a feeling it's international.

Yes, it's a ~2M2 resistor.
Here we have 110Vac and 220Vac, 60Hz, for residential distribution. Where I live it's 220Vac.

Perhaps the resistance drops when it's overvoltaged so you're passing more than 320:mu:A.