Is this voltage drop normal?

[dragonballz]

2 different circuits. All new wiring, new 15 amp circuit breakers. Both 14 gauge. Resting voltage is 123 volts measured with digital multimeter.

Receptacle on circuit 1 is 5 feet (5 ft of conductors) from the panel. With a heavy load (shop vac) running, the initial voltage drop on start-up is about 1 volt, from 123 volts down to 122, then it goes back up to 123 during normal operation.

Receptacle on circuit 2 is about 90 feet (90 feet of conductors) from the panel. With the same load, the initial voltage drop on start-up is about 16 volts, from 123 down to 107, then it goes up to 116 volts during normal operation.

The shop vac's initial startup draw is 22 amps. Running is 11 amps (normal as spec'd on the label). Measured with an analog amp clamp.

Are my voltage drops normal?

The reason I’m even measuring is because when there is a heavy load (power tool or vacuum, etc), the lights on that circuit dim greatly during the tool start-up. The circuit with the large voltage drop. The light basically shuts off for a split second.

The electric company already put 3 new connectors outside of the house. They said they will replace the transformer sometime soon because my house is the last house on the street.

We’ve already checked all connections at the panel and at the receptacles. No fix. So we tried an all new circuit. Still dims. I'm wondering if the long run is what is causing the dimming. The receptacle at 5ft doesnt dim. The receptacle at 90 ft dims.

Thank you.

 

[frankush]

Electronic driver in an LED fixture or electronic ballast in a florescent fixture doesn't like that low voltage and that's why they go out. As soon as the voltage recovers, light comes back on. Easiest fix is to put the the lighting on a separate circuit or at the least move it to a different circuit. You generally don't have these issues in anything other than a residential setting because power and lighting are kept on separate circuits. I doubt you have a utility issue.

Was the new circuit you tried it on, on the same phase as the lighting? If the lighting is on A phase, try the vac on a B phase circuit and see if you still have the issue.

 

[wyliesdiesels]

2 different circuits. All new wiring, new 15 amp circuit breakers. Both 14 gauge. Resting voltage is 123 volts measured with digital multimeter.

Receptacle on circuit 1 is 5 feet (5 ft of conductors) from the panel. With a heavy load (shop vac) running, the initial voltage drop on start-up is about 1 volt, from 123 volts down to 122, then it goes back up to 123 during normal operation.

Receptacle on circuit 2 is about 90 feet (90 feet of conductors) from the panel. With the same load, the initial voltage drop on start-up is about 16 volts, from 123 down to 107, then it goes up to 116 volts during normal operation.

The shop vac's initial startup draw is 22 amps. Running is 11 amps (normal as spec'd on the label). Measured with an analog amp clamp.

Are my voltage drops normal?

The reason I’m even measuring is because when there is a heavy load (power tool or vacuum, etc), the lights on that circuit dim greatly during the tool start-up. The circuit with the large voltage drop. The light basically shuts off for a split second.

The electric company already put 3 new connectors outside of the house. They said they will replace the transformer sometime soon because my house is the last house on the street.

We’ve already checked all connections at the panel and at the receptacles. No fix. So we tried an all new circuit. Still dims. I'm wondering if the long run is what is causing the dimming. The receptacle at 5ft doesnt dim. The receptacle at 90 ft dims.

Thank you.

90’ is a bit too long for 14 gauge wire. Shouldve used #12. Thats your first issue.

If you want to know what the calculated voltage drop is, reference the formulas i put on the electrical FAQ sticky.

In regards to your clamp meter measurements, an analog clamp meter will not give you accurate in-rush current measurements. You need a digital meter that has the circuitry that can measure in-rush current. Meters like The fluke 374 does this. In-rush current is 4x-8x FLA.

 

[dragonballz]

90’ is a bit too long for 14 gauge wire. Shouldve used #12. Thats your first issue.

If you want to know what the calculated voltage drop is, reference the formulas i put on the electrical FAQ sticky.

In regards to your clamp meter measurements, an analog clamp meter will not give you accurate in-rush current measurements. You need a digital meter that has the circuitry that can measure in-rush current. Meters like The fluke 374 does this. In-rush current is 4x-8x FLA.

Is the 90’ 14ga okay for strictly a lighting circuit? Under 2 amps if all lights are on.

 

[dragonballz]

90’ is a bit too long for 14 gauge wire. Shouldve used #12. Thats your first issue.

If you want to know what the calculated voltage drop is, reference the formulas i put on the electrical FAQ sticky.

In regards to your clamp meter measurements, an analog clamp meter will not give you accurate in-rush current measurements. You need a digital meter that has the circuitry that can measure in-rush current. Meters like The fluke 374 does this. In-rush current is 4x-8x FLA.

Thanks I will look at the formulas later today.

 

[pattenp]

Is the 90’ 14ga okay for strictly a lighting circuit? Under 2 amps if all lights are on.

Yes, at 120V #14 should handle a continuous load of around 10A at 90' with less than 5% VD.

 

[Showkey]

Simple solution........run tools like shop vac, saws etc on 20 amp 12g circuit.

 

[Zeke]

Simple solution........run tools like shop vac, saws etc on 20 amp 12g circuit.

Always. I never use 14 ga except for light circuits and I'm talking home, not shop where you may need more than a couple depending on many factors.

 

[nadogail]

FWIW, I no longer buy 14AWG wire and cable.

Keep in mind I squared R voltage drops. Heavy Current and Long runs of skinny wire add up to trouble.

 

[sberry]

The concern is wayyyyyy over rated. Most of them do not have "heavy current" There is a lot of assumption and speculation about this, outright panic and fear. The size of the breaker on it isn't the applied load,,, that seems to get lost.

Is the 90’ 14ga okay for strictly a lighting circuit? Under 2 amps if all lights are on.

Yes it is, anywhere under 10 is dandy. There is always some drop. Increases with load and losses add up over time. If we were adding a known load of 13 over 8 hrs a day,,, 24 hrs a day then someone could calculate the loss but 2 on common lighting ,,, if that all the time is irrelevant.
Some cases the smaller wire and breaker may be preferred, connections to fixture wires may be better, easier to train wires in to boxes and lowers the short circuit threshold to fixtures with small wires.

 

[sberry]

Other than a little 120V welding I cant even remember using anything larger than a 16 cord for a decade, maybe more. Cant recall ever burning something up low voltage. I have seen a couple others do it,,, got a gob of stuff along with the comp plugged in to a trouble light, wonder why it doesn't work. Was at a body shop where the dipsticks had a 140 on the trouble light, on with a 100 watt lamp in it and on 75 ft of 14 circuit with other building lights on, wonder why it trips and keep setting the breaker. Got them 50 ft of 12 to run back to an outlet with 12 local to the panel and it worked,,, along with changing the polarity of the machine they been using for 3 years.

 

[dragonballz]

Thanks everybody. I am currently renovating kitchen and baths. The house originally had all circuits on 15 amp breakers (except kitchen). In the rest of the house, the Lights and outlets on same circuits. I was getting dimming under heavy load on some circuits. After doing much diagnosing and not finding anything wrong, I’ve realized the ones furthest away from the panel had the worst voltage drop. There is no voltage drop when measured on the breakers at the panel.

I am doing a complete rewire to seperate the lighting and receptacles. All receptacles will now be 12ga 20 amp.

 

[Zeke]

Other than a little 120V welding I cant even remember using anything larger than a 16 cord for a decade, maybe more. Cant recall ever burning something up low voltage. I have seen a couple others do it,,, got a gob of stuff along with the comp plugged in to a trouble light, wonder why it doesn't work. Was at a body shop where the dipsticks had a 140 on the trouble light, on with a 100 watt lamp in it and on 75 ft of 14 circuit with other building lights on, wonder why it trips and keep setting the breaker. Got them 50 ft of 12 to run back to an outlet with 12 local to the panel and it worked,,, along with changing the polarity of the machine they been using for 3 years.

Many years ago I rented one of the first Ryobi tools and I can't even remember what it was because I have most everything. Could have been an SDS hammer drill. Anyway, I ran that turd on a 16 ga 100' cord and it lasted 10 minutes. The rental people were pissed but hey, I doan know nutin.

Then I see the locals doing all the work now with a Skillsaw on a 100' cord only 25 feet from the plug-in. I don't even think 2wice about it anymore.

I have nothing but 12 ga cords on the truck.

 

[TheEquineFencer]

Thanks everybody. I am currently renovating kitchen and baths. The house originally had all circuits on 15 amp breakers (except kitchen). In the rest of the house, the Lights and outlets on same circuits. I was getting dimming under heavy load on some circuits. After doing much diagnosing and not finding anything wrong, I’ve realized the ones furthest away from the panel had the worst voltage drop. There is no voltage drop when measured on the breakers at the panel.

I am doing a complete rewire to seperate the lighting and receptacles. All receptacles will now be 12ga 20 amp.

Great choice!