Voltage drop in whole home

I am sure someone mentioned this already but the neutral impedance is included in your voltage drop calculation.

You mentioned having a multiwire branch circuit which could mean at the neutral conductor could be longer than the phase conductor.

More than likely it is a poor connection on the neutral or phase conductor increasing the impedance of the circuit. If we start by using the heat gun photo, having 114V and 1200W heat gun we can say the current is 10.53A.

So the simple circuit with KVL would be

0=-120+(10.53*ZL1)+(114)+(10.53*ZN)

120-114 =10.53(ZL1+ZN)

6/10.53 = (ZL1+ZN)

(ZL1+ZN) = 0.570

Now if we substitute the impedance for the voltage drop of each portion.

Z = length x (conductor resistance * cos(theta) +conductor reactance * sin(theta)))

For #14 Cu - we have a resistance of 3.1 ohms/1000ft and 0.058 ohms/1000ft.

I will assume a power factor of 0.98, at least initially.

cos-1(0.98) = 11.48°

Z#14 =[ L * (3.1*0.98 + 0.058 *sin(11.48))] / 1000

Z#14 =[ L * (3.038 + 0.0115)] / 1000

Z#14 =[ L * (3.05)] / 1000

Now for some assumptions, I will assume the length of both the neutral and the phase conductor are equal lengths.

(ZL1+ZN) = 0.570 = [ L * (3.05)] / 1000 ] + [ L * (3.05)] / 1000 ]

570 = 3.05L+3.05L

570 = 6.10L

L= 93ft

So that Romex length, from the panel to the receptacle is 93ft. The length of the phase + neutral is 187ft from the source and back.

If they are unequal lengths, for this particular circuit, you can start with,

186.89 = ( L Hot1 ) + ( L Neutral ) , where L is the length of each conductor.
 
ccoop said:
The cable is a 12 gauge 50ft cable. The circuit that it is connected to is a 14 gauge circuit.
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tortuga said:
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.
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That's 50' of existing #12 to 200' of #14 remodel wiring, with electrical tape flying splices, and cut off EGC.
 
FYI,

You could use the same method above (slightly tweaked) to measure the feeder's impedance at the load of the panel. You would just need to amp clamp the lines and neutral and get the wire sizes.

The only way to know which portion is really impacting the circuit is by checking it all under a controlled load amount when you are noticing the 90V at the receptacle.
 
I cant think of all the times people had me put in a outdoor plug and I never asked what its for.
Funny you mention the sprinter van, one customer wanted a outdoor receptacle installed on a old house right behind a existing bedroom receptacle. Seemed like a easy job just tap off the bedroom receptacle and that was my plan until
I went back to do the job I saw this fully decked out sprinter camper RV conversion van parked right by where the recept was going.

I had to talk to the customer, confirmed it was for grandpa's van and after revising the estimate I ran a 12/2 to the panel so it was on a dedicated 20A.
It was a well done DIY conversion van, grandpa was proud of his work. It had a 120V AC/heat unit, 120V convection oven, lithium battery bank the works. The bedroom circuit I was going to use probably had the back half of the house on it.
 
Impulsive load like garbage disposal or a vacuum cleaner is the best for checking abnormal voltage drop.

Place the said load from L1 to N at the panel. Have basic light bulbs fed from different breakers, one each on L1 N, and L2 N.
Cycle the test load on and off and watch for abnormal flicker/flash. You should setup two identical light bulbs, then watch for "push/pull" where one would dim and other would brighten. If it's noticeable and the sides switch depending on which side the test load is placed, it's a neutral issue.
The effect should not be noticeable, or at the worst, very barely noticeable.

The test load and lights should not be on the same branch, because, at this point, you're looking for issues before branch level issues.
 
ccoop said:
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.
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My suggestion would be to stop using that cheap Klein circuit tester to measure voltage, and repeat your testing using the RMS meter for both measurements, at the breaker end and at the receptacle end. Also, measure the actual current draw of the heat gun, so that can be compared to a calculated drop with an assumed conductor length. You may find the voltage drop is normal once you have accurate measurements, especially if the branch circuits were installed with 14awg conductors.
 
115' of wire is not hard to envision in a 2000sq ft home. A 10 amp resistive load results in about 113 volts at the load end. VD at devices and junctions should be nil or they will show elevated temperature. Use of a thermal scanner will show it. A 4 volt difference @ 10 amps means 40 watts being dissipated somewhere. 40 watts at a single point is significant. Think soldering iron.

I didn't notice if you took an actual current measurement at the breaker. 15 amps easily results in 109 volts.
 
winnie said:
@kwired , would you really expect 9V of drop with a 50 foot 12ga cord and a 10A load?

I would expect some voltage drop, but less than 2V.

-Jonathan
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No, but what is making up the other mentioned 175 feet of run. Part of the total run apparently is 14 AWG NM cable between the panel that shows no significant VD and a receptacle somewhere that has this 50 foot cord and possibly even more cord from what I get out of his information.

Not only do you have VD in conductors themselves but if you have a mix of wiring types, receptacles, cord caps, etc. in the path you may have poor connection here or there that adds to the problem.
 
ccoop said:
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.
Click to expand...
Here is an update for everyone, I went and cleaning the main feed coming into the panel because it had alot of extra old anti-oxident on the wires and i mean alot. Then wired a receptacle directly to the panel on a 15 amp breaker 1ft of 14 gauge from breaker to receptacle. I have then attached a brand new 14 gauge 100ft extension cord from the receptacle to the van. I am reading 120volts at the panel and 114.3 volts at the van under load of 6 amps. This now does look closer to normal voltage drop but still is a little lower than expected. Is this just other normal factors in play along with voltage drop. A ~2 volt difference from calculated to actual seems normal.
 
ccoop said:
Here is an update for everyone, I went and cleaning the main feed coming into the panel because it had alot of extra old anti-oxident on the wires and i mean alot. Then wired a receptacle directly to the panel on a 15 amp breaker 1ft of 14 gauge from breaker to receptacle. I have then attached a brand new 14 gauge 100ft extension cord from the receptacle to the van. I am reading 120volts at the panel and 114.3 volts at the van under load of 6 amps. This now does look closer to normal voltage drop but still is a little lower than expected. Is this just other normal factors in play along with voltage drop. A ~2 volt difference from calculated to actual seems normal.
Click to expand...

That sounds like normal voltage drop to me. The ~2V difference from calculated could be a combination of real world factors like the socket, meter error, load changes, etc.
 
Where are you measuring at the panel? How did the voltage 1' away at the new receptacle compare to the voltage at the main lugs? Voltage drop here should be minimal, but if it isn't there could be problems with the bus or breaker.
 
Problems at the bus or breaker or even meter socket should drop the voltage at the breaker output terminal but OP isn't seeing any drop there.

The drop he is seeing is in the extension cord segment of the circuit. The last example he explained does have a short length of NM cable between the breaker and a receptacle. short enough it shouldn't really contribute any significant drop other than possibly because of poor contact/connections, but if they are poor enough they should warm up to at least an amount that likely is measurable with an infrared thermometer within a short time as well.

Quality of the extension cord could come into play as well. He says it is 14 AWG. Poor grade copper, maybe even little undersized to cheapen it? Poor connections to the end connectors? All such things will be additive.
 
Do you have access to a good 4 lead ohm meter to check the resistance of the 14 ga wire?
 
I haven’t followed all the posts.

Have you for instance taken 150’ of 12-2 NM cable , installed a receptacle ( side wired vs push in) , and then plugged in a Verified given load and checked the VD with a good quality meter.

If you come up with a value that’s very close to what the actual calculation should be I’d say there’s no issue.

Branch circuit lengths in houses can be hard to ascertain.

The way some travel from A to B can and usually are considerably longer than one thinks.

Add into that the fact that circuit is traveling through several j boxes and receptacles only adds to the decrease in Voltage.
 
2023 NEC

Here's one of the formulas for voltage drop, single phase.

VD = 2 x K x D x I / CM 2 is for single phase....K is the factor for resistance usually 12.9 for copper......D is the one way distance.....I is for amps
I is for intensity (amps) Note: D is for 2 conductors, for single phase. For three phase, drop the "2" and replace it with 1.732.

The CM is circular mils. See Chapter 9 T.8 Circular mils Column.

Thus, multiply the top row then divide it by the CM size

TX+MASTER#4544
 
kwired said:
Problems at the bus or breaker or even meter socket should drop the voltage at the breaker output terminal but OP isn't seeing any drop there.

The drop he is seeing is in the extension cord segment of the circuit. The last example he explained does have a short length of NM cable between the breaker and a receptacle. short enough it shouldn't really contribute any significant drop other than possibly because of poor contact/connections, but if they are poor enough they should warm up to at least an amount that likely is measurable with an infrared thermometer within a short time as well.

Quality of the extension cord could come into play as well. He says it is 14 AWG. Poor grade copper, maybe even little undersized to cheapen it? Poor connections to the end connectors? All such things will be additive.
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And all very noticeable. Even to touch.
 
ccoop said:
Here is an update for everyone, I went and cleaning the main feed coming into the panel because it had alot of extra old anti-oxident on the wires and i mean alot. Then wired a receptacle directly to the panel on a 15 amp breaker 1ft of 14 gauge from breaker to receptacle. I have then attached a brand new 14 gauge 100ft extension cord from the receptacle to the van. I am reading 120volts at the panel and 114.3 volts at the van under load of 6 amps. This now does look closer to normal voltage drop but still is a little lower than expected. Is this just other normal factors in play along with voltage drop. A ~2 volt difference from calculated to actual seems normal.
Click to expand...
You are describing a series circuit.
One of the rules of a series circuit is that the voltage is additive.
Which means if you have different voltages at different outlets, they will all add up to you source voltage,120 V.
You may have an "open neutral".
Did you use a multi wire circuit?

TX+MASTER#4544
 
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