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Voltage drop on newly installed 120 receptacle

Francis Davis

Jun 8, 2018
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I added a outside ground fault receptical to a shed that already had an older panel with 2 60 amp barrel fuse circuits. Below them were 4 30 amp fuses with 2 circuits in operation for lights.
Long before I added the new receptical, I was able to run a planer, chop saw, sawsall and other power tools without any problems off the existing circuits. The new receptical is 2 feet from the panel
First I installed the added receptical using vacant screws in the panel. Voltage drop ensued.
Next I disconnected old circuitry and connected new circuit nstill boltage drop.
Finally I changed groubd fault receptical to a common duplex outlet. Still voltage drop and unable to get proper power to run a 7 1/4” skill saw, or chop box
I’m at a loss. Could the ground at the meter have gone bad?
 

Tha fios agaibh

Aug 11, 2014
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I'm not sure what you mean by voltage drop ensued. What was existing before your added outlet should remain the same.

Its possible that when you tightened the wires to your circuit breaker you broke a bus connection under the breakers leaving a weak point in the circuit. This can show you have full 120v available, but voltage will collapse once a heavy load is applied.
 

davenn

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Sep 5, 2009
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Finally I changed groubd fault receptical to a common duplex outlet. Still voltage drop and unable to get proper power to run a 7 1/4” skill saw, or chop box
I’m at a loss. Could the ground at the meter have gone bad?


some clear/well lit photos of what you are talking about would help lots
 

kellys_eye

Jun 25, 2010
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What do you mean by 'a voltage drop'??? 1V, 10V? mV?

Is the volt drop at the same at the main distribution point?

What size cable did you run to the new outlet?

Are all connections 'clean'? Screws tight? etc
 

shrtrnd

Jan 15, 2010
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Not sure, like others here, what the issue might be.
My first thought however, is what is the current rating of the GFI you installed?
I believe the normal rating for common GFI's used in the house is 15A.
I would suspect if you've got a GFI rated for 15A, with fuses rated at 30A.
There might be a problem with the electronics inside that GFI when power demands exceed it's specs?
Don't know, but that's what comes to mind.
 

kellys_eye

Jun 25, 2010
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There might be a problem with the electronics inside that GFI when power demands exceed it's specs?
Don't know, but that's what comes to mind.
GFI devices measure current going 'in' and current flowing 'out' - under ideal conditions these will match and no fault condition exists. If the measurement of the in/out differ then the GFI assumes some of the current is flowing to earth and trips the breaker.

It has nothing to do with volt drop unless the wiring at the screw terminals is loose.

A common problem is pushing a wire into the 'wrong side' of the cable screw-down connector - you 'think' you've fastened the screw down tight but in actuality the wire is just 'jammed' in the hole and the poor connection results in a volt drop.

But volt drop is EXPECTED in all installations - the level of which varies but (here in the UK) should not exceed 5% for outlets and 10% on lighting circuits (IIRC).
 

Tha fios agaibh

Aug 11, 2014
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Volt drop is EXPECTED in all installations - the level of which varies but (here in the UK) should not exceed 5% for outlets and 10% on lighting circuits (IIRC).
I would expect the op to say "my newly installed GFI outlet keeps tripping", if that's what's happening.

Here State side, acceptable voltage drop is 3% for branch circuits, and 5% total including feeder.
 
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