Voltage drop in whole home

[ccoop]

Hello, I have been trying to figure out this issue for a few days now and can't seem to pin down a reason.

The issue that's occurring is voltage drop at all receptacles in a home. The home has a 150A panel single phase. Normally I would assume a loose or improper connection of a neutral at the panel but this doesn't seem like the case. When measuring the circuit, when there is no load on the circuit the voltage is ~120V at breaker and receptacle. Under load the receptacle voltage will drop as low as ~99V i have measured. This is the case with every receptacle in the home on many different circuits. The interesting part for me is that at the receptacle I will measure ~109V under load but at the breaker I will measure ~120V. The wiring for each circuit is correct gauge for the correlating wired breakers 14 or 12 gauge. Some circuits in the home do have shared neutrals due to running a 3 wire and sharing the neutral but splitting the Black and red on separate breakers. This from my experience shouldn't be affecting anything but is something to note. Also circuits without shared neutrals still experience the same issue. I have measured 0-ohm resistance from the SE cable coming into the lugs on the main breaker and neutral to the correlating bus bars. It also seems the further distance the circuit is from the panel the larger the voltage drop and normally in a standard 2000sqft home voltage drop should be minimal on a circuit. I am just stuck on how I can get normal voltage leaving the breaker under load but at the device the voltage is significantly less. I have not opened my meter enclosure yet due to the weather but I am not sure if those connections could be contributing to the issue. Any tips or experience with diagnosing this issue would be amazing. Thanks.

 

[tom baker]

Are there more than one house on the transformer? Can you check voltage at those houses?

 

[ccoop]

Are there more than one house on the transformer? Can you check voltage at those houses?

I do believe there are other houses on the same transformer. I don't think I will beable to test there voltage but i can inquire. Would a bad transformer cause that voltage drop off. I would assume if it was the transformer I would be seeing the drop at the panel aswell in that case. I. Only see the drop off at the receptacles and not at the panel.

 

[kwired]

A bad neutral would cause voltage rise on one leg and drop on the other if load isn't balanced.

What are you using for a load are you using when doing this testing?

some those receptacle testers don't put real full loading on the circuit but rather draw a test sample that may only draw a bit from the rising peak of the AC wave and then do some calculating based on what it sees. In order for it to actually draw a real test current of say 10 amps - that would mean on 120 volts it would have to have ability of dissipating 1200 watts of heat, which non of those testers do that so they have to take some other sort of limited sample and make some assumptions from that.

 

[ccoop]

A bad neutral would cause voltage rise on one leg and drop on the other if load isn't balanced.

What are you using for a load are you using when doing this testing?

some those receptacle testers don't put real full loading on the circuit but rather draw a test sample that may only draw a bit from the rising peak of the AC wave and then do some calculating based on what it sees. In order for it to actually draw a real test current of say 10 amps - that would mean on 120 volts it would have to have ability of dissipating 1200 watts of heat, which non of those testers do that so they have to take some other sort of limited sample and make some assumptions from that.

When testing for load i used a heat gun that would draw 1300 watts. There is no voltage fluctuations from one leg measured at the panel than the other. That is what's not making sense. When I put a load of 1300 watts on the circuit the voltage reading at the same receptacle will be 110Volts ( no load is 120Volts), but back at the panel during the load the circuit will read 120Volts. Also the further the distance the circuit seems to be from the panel the larger the drop. And let's say at approximately 30ft from the panel i will get 5-8volts of drop. At 100ft I will get 20volts of drop, all while the reading at the panel remain the same. No increase of voltage on the opposite leg of the service either that would equal out the difference you would expect of a loose neutral.

 

[TwoBlocked]

I think of two things when hearing about a problem that seems inexplicable. First, I'd have to see it for myself. Second, if this is all true, then some basic assumption is probably wrong. Like maybe (and maybe not...) the meter is not a RMS meter and the blower motor in the heat gun is doing something weird with the voltage waveform.

Then I also wonder, why was the voltage drop being checked to begin with?

 

[winnie]

At _every_ receptacle in the home you measure a large voltage drop under load, but at the panel you get minimal voltage drop when load is applied?

My first thought is to double check this particular point. Is it possible that you applied the load to one leg of the service, but measured the 120V on the other leg? Excessive voltage drop on _every_ receptacle requires something common to _every_ receptacle, and usually this means the service, not the individual receptacle circuit.

My second thought: is this new construction where severely undersized wire was used?

Some voltage drop is always expected, but you are seeing excessive voltage drop on _all_ circuits. If a criminal did something such as wiring the entire house with 18ga 'bell wire', then you would see excessive voltage drop everywhere.

My third thought: is there some sort of common issue that is causing problems at _all_ of the conductor terminations. I'm thinking of the 'Chinese drywall' issue from several years back, where a defect in the drywall was causing copper wires to discolor. Perhaps something similar is damaging _every_ wire termination and adding a bit of extra resistance.

-Jonathan

 

[winnie]

Then I also wonder, why was the voltage drop being checked to begin with?

This is a very good point. What symptoms are the reason for checking for voltage drop?

 

[Fred B]

Poor connections. Under load will start to drop off voltage, the bigger the load the bigger the drop off, seen this with a bad underground, was bad enough that a load would render all the way down to 15V, then after a few moment without load it would bounce back.
Load testing for bad neutral: applying a large load to L1 and meter both L1 and L2 with load applied. L1 would drop and L2 would rise a corresponding amount with a poor neutral.

I have measured 0-ohm resistance from the SE cable coming into the lugs on the main breaker and neutral to the correlating bus bars.

How are you getting the ohm reading with power on?

If it is indeed not a neutral issue megering will give you an idea if it is a wiring or connection issue.

 

[ccoop]

I think of two things when hearing about a problem that seems inexplicable. First, I'd have to see it for myself. Second, if this is all true, then some basic assumption is probably wrong. Like maybe (and maybe not...) the meter is not a RMS meter and the blower motor in the heat gun is doing something weird with the voltage waveform.

Then I also wonder, why was the voltage drop being checked to begin with?

This is a very good point. What symptoms are the reason for checking for voltage drop?

Voltage drop was being checked because I was charger my sprinter van ( basically a camper van electrical setup). And on my inverter I can read incoming voltage level. At the van I was reading. 100Volts. At the receptacle the 50ft extension cable is plugged into i was ready 109volts. And at the electrical panel I was reading 120volts. I started experiencing issues with the van charging to to the voltage drop. Under normal loads on the home I don't see the voltage drop below 110 volts which is why I never noticed the issues and devices aren't affected. Only at extendanded distances I experience the issue becoming a problem. I have provide pictures with and without load on circuit. Also I am using a klein tools clamp meter that is a rms meter.

 

[zbang]

How many meters have you used? If I was seeing 10 volt drop on 50' cable (under ???? load), I'd start by swapping that cable, since it's probably undersized - Mr Southwire says that 10 amps on a 14g copper 50 cable should only show 2.3% drop (so call it 5v).

Is it possible that the entire house is 14g and the runs are long? At this point, a lot more info would be useful

 

[ccoop]

How many meters have you used? If I was seeing 10 volt drop on 50' cable (under ???? load), I'd start by swapping that cable, since it's probably undersized - Mr Southwire says that 10 amps on a 14g copper 50 cable should only show 2.3% drop (so call it 5v).

Is it possible that the entire house is 14g and the runs are long? At this point, a lot more info would be useful

The cable is a 12 gauge 50ft cable. The circuit that it is connected to is a 14 gauge circuit. The load from the van is 650watts. I have used different extension cables with the same result. For me it seems like there excessive voltage drop based on the distance. The closer I am to the panel at about 25ft of circuit the drop is ~5 Volts at 1200watts. But at approximately 175ft from the panel to the van I see 20volt drop at 650watt load.

It feels like to me that I am somehow having increase is voltage drop due to distance but the drop is being exaggerated by some other factor that I can't seem to locate almost like there is increased resistance in the circuits.

 

[winnie]

Voltage drop was being checked because I was charger my sprinter van ( basically a camper van electrical setup). And on my inverter I can read incoming voltage level. At the van I was reading. 100Volts. At the receptacle the 50ft extension cable is plugged into i was ready 109volts. And at the electrical panel I was reading 120volts. I started experiencing issues with the van charging to to the voltage drop. Under normal loads on the home I don't see the voltage drop below 110 volts which is why I never noticed the issues and devices aren't affected. Only at extendanded distances I experience the issue becoming a problem. I have provide pictures with and without load on circuit. Also I am using a klein tools clamp meter that is a rms meter.

Ok, so your first symptom was running a 650 W charger. Normally I'd call that a 5.4A load, but it might be more if the thing is adjusting for voltage drop.

The resistance of 12ga copper is 1.6 ohms per 1000 feet, so in the 100 feet of extension cord conductor I'd expect 0.16 ohms of resistance and a voltage drop of 0.9V, not the 9V you are actually measuring. This suggests to me either a metering issue or a problem with either the cord of the receptacle.

One thing I noticed in the picture of your voltage measurements at the panel is that you have the meter probes stuck into the lugs where the wires come in. If those wires are loose, then the voltage drop might be from the wires to the lugs. A useful diagnostic is to load your circuit, and then make measurements at the panel from L-N, first just as you did, then lug to lug, then breaker terminal to neutral bar.

-Jonathan

 

[Fred B]

How far from utility transformer? That distance will add to the VD underload.

 

[TwoBlocked]

The specs for the Klein RT250 do not indicate that it is RMS. Not saying that there is definitely an instrumentation error, though.

What others have mentioned is poor connections on the receptacles. Easy enough to check.

When confounded, I like to check the easy stuff. Lets my head clear, too.

 

[ptonsparky]

A 1200 watt load should easily show warm connections after a few minutes. Use a thermal scanner at each device and junction. A 10 volt drop with a 10 amp load shows 100 watt connection(s) somewhere.

Next would be to do a FOP across the hot. Then neutral.

Plug a 100' cord in where the load is. Stretch it back to the panel. What is the VD breaker load side to hot of cord? Neutral buss to neutral of cord?

 

[Eddie702]

I would find 1 easy circuit with a short run. Shut off all the breakers except one and find one circuit then check all the connections keeping the load at the far end of the circuit. There has to be a problem somewhere. Time consuming, I know

 

[suemarkp]

When you measure at the panel are you only measuring at the lugs or at the output of a breaker? If the breaker stabs are corroded or the breakers fit poorly, you could get voltage drop there. Also check the torque on the breakers where the branch circuit connects and all the neutrals on the neutral bar.

 

[tortuga]

When testing for load i used a heat gun that would draw 1300 watts. There is no voltage fluctuations from one leg measured at the panel than the other.

and normally in a standard 2000sqft home voltage drop should be minimal on a circuit.

It would not surprise me if a 1300W (10.8A) test load showed 7-10% voltage drop in a typical home wired with 14AWG wire.
I bet you can have runs of 14 AWG that are 250' of wire before they reach the panel.

 

[kwired]

The cable is a 12 gauge 50ft cable. The circuit that it is connected to is a 14 gauge circuit. The load from the van is 650watts. I have used different extension cables with the same result. For me it seems like there excessive voltage drop based on the distance. The closer I am to the panel at about 25ft of circuit the drop is ~5 Volts at 1200watts. But at approximately 175ft from the panel to the van I see 20volt drop at 650watt load.

It feels like to me that I am somehow having increase is voltage drop due to distance but the drop is being exaggerated by some other factor that I can't seem to locate almost like there is increased resistance in the circuits.

I wouldn't call it excessive as much as I'd call it expected. When you have long circuit lengths you need to increase conductor size to counter voltage drop. Voltage drop is dependent on current drawn and resistance. The more current you draw the more voltage drop you will have in any given conductor. You are seeing little or no drop at the panel because of the size of the service/feeder conductors. After 175 feet of length with 14 or 12 AWG conductor in the run I expect to see a fairly noticeable voltage drop with a 650 watt load on a 120 volt circuit before even doing any calculating. One that would definitely make even an incandescent light connected on same setup dim when the heavy load is switched on.

Bottom line is if you can not tolerate the voltage drop encountered you need larger conductors to lessen the drop. Other possible solution is increase voltage and then transform it back to 120 volts near the load being supplied. depending on circumstances this might be less cost effective than simply running larger circuit conductors.