Today at the job someone came to me with a concern. It seems that one of the vinyl flooring guys were using a torch of some kind that drew about 14 amps at 120v one the same outlet another carpenter was using a halogen light that took 4 amps. The outlet is about 100 ft from the panel and the vinyl tool was on another 50ft (at least) extension cord. When the carpenter turned on his light you could see it pulsate. My initial thought was voltage drop. Putting my meter into the circuit I found it fluctuating between 112 and 118 volts. Is this a voltage drop situation, is this what is normally experienced with them??
fluctuating voltage
- Thread starter nathan1
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bphgravity
Senior Member
- Location
- Florida
Re: fluctuating voltage
Sounds like voltage drop to me!
Its possible that the fluctuating between the 112-volts and 118-volts is where you were getting the pulsing effect. Voltage drop tends to slow motors down and cause lights to dim. 18-ampere on either a 15-ampere or 20-ampere is enough to allow voltage drop, especially at those distances.
Sounds like voltage drop to me!
Its possible that the fluctuating between the 112-volts and 118-volts is where you were getting the pulsing effect. Voltage drop tends to slow motors down and cause lights to dim. 18-ampere on either a 15-ampere or 20-ampere is enough to allow voltage drop, especially at those distances.
- Location
- Massachusetts
Re: fluctuating voltage
There is a chance that the heat gun was cycling to maintain temperature, that would explain the voltage changing.
Voltage drop on a 12 AWG 100' 120 volt circuit with 14 amps on it comes out to a little over 5 volts, add the 4 amp light and you get a little over 7 volts 'lost'.
There is a chance that the heat gun was cycling to maintain temperature, that would explain the voltage changing.
Voltage drop on a 12 AWG 100' 120 volt circuit with 14 amps on it comes out to a little over 5 volts, add the 4 amp light and you get a little over 7 volts 'lost'.
Re: fluctuating voltage
If we assume the open circuit voltage was 120V, taking the 7 volts lost when both are on gives 113 volts. Very close to your measured 112 volts.
If the heat gun cycles off, and just the light is on, I calculate about 1.5 volts. Take that away from the 120V, and we get 118.5 volts. Very close to the measured 118 volts.
I think Iwire hit the nail on the head.
Steve
If we assume the open circuit voltage was 120V, taking the 7 volts lost when both are on gives 113 volts. Very close to your measured 112 volts.
If the heat gun cycles off, and just the light is on, I calculate about 1.5 volts. Take that away from the 120V, and we get 118.5 volts. Very close to the measured 118 volts.
I think Iwire hit the nail on the head.
Steve
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: fluctuating voltage
It shouldn't make a difference if the only thing on the extension cord was the heat gun as if anything it eliminated some of the current on the circuit. now if both the light and the heat gun is on the cord then it will make a difference. But if the flooring guy plugged into another outlet that is on another circuit then it should not cause the light to dim as much.
It shouldn't make a difference if the only thing on the extension cord was the heat gun as if anything it eliminated some of the current on the circuit. now if both the light and the heat gun is on the cord then it will make a difference. But if the flooring guy plugged into another outlet that is on another circuit then it should not cause the light to dim as much.
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