85 volts on a 120v lighting circuit

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etbrown4

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In a coastal location, my customer has 5 exterior lights on one circuit, previously controlled by a photocell. With photocell disconnected and lights straight wired I'm getting 85 volts at each fixture. At the initial junction box with all wires disconnected I have 120v.

I have checked the joints at each fixture and all appear to be clean.
 
If you want to be sure it's the neutral, check the hot and neutral to an extension cord to determine which conductor is dropping the voltage. I agree with nick that is sounds like a bad neutral connection.
 
Note that whichever side the voltage drop is on, the high resistance is dissipating a wattage of 35V times the load current at reduced voltage.
If it is at a single location rather than a long run of high resistance wire, there is a good potential for starting a fire.
 
etbrown4 said:
In a coastal location, my customer has 5 exterior lights on one circuit, previously controlled by a photocell. With photocell disconnected and lights straight wired I'm getting 85 volts at each fixture. At the initial junction box with all wires disconnected I have 120v.
Click to expand...
A suggestion is to wire a low wattage incandescent lamp as a load at the initial junction box, and then see if that causes any significant voltage drop below the 120V you now have without the load. If so then you need to focus on the wiring and connections upstream of that junction box to identify where the voltage drop is occurring.
 
etbrown4 said:
In a coastal location.
Click to expand...

Is that East Coast or West Coast ? The first thing to do when trouble-shooting is to try and isolate the problem.

Sorry about that, just making a little joke.

You didn't give much information about the wiring to these fixtures, are they on the side of a building or maybe a fence or light poles. Any underground wiring?
 
The voltage readings were with lamps installed, mostly leds.
Will try with no lamps.

Nothing underground, all on building exterior.

Here's something that probably supports the bad neutral theory. There are two romex circuits which supply 5 fixtures.

From the single hot wire, in free air, attached to nothing here's what it reads with a fluke digital meter:
To ground 120v
To one neutral 108v
To the other neutral 105v
 
etbrown4 said:
From the single hot wire, in free air, attached to nothing here's what it reads with a fluke digital meter:
To ground 120v
To one neutral 108v
To the other neutral 105v
Click to expand...

If I got those reading I would start by checking the connection at the neutral bar back at the panel.
I have found a lot of those that were either corroded or not very tight.
 
etbrown4 said:
The voltage readings were with lamps installed, mostly leds.
Will try with no lamps.

Nothing underground, all on building exterior.

Here's something that probably supports the bad neutral theory. There are two romex circuits which supply 5 fixtures.

From the single hot wire, in free air, attached to nothing here's what it reads with a fluke digital meter:
To ground 120v
To one neutral 108v
To the other neutral 105v
Click to expand...
So you think you have two bad neutrals then.

What are the voltages at the panel or service entrance?
 
Turns out, no bad neutrals.

Unbelievably it was a combination of a new led light fixture, with the led board built in. This fixture alone pulled the circuit voltage down to 85 volts.

Then problem 2. I had several Sylvania regular Led lamps in the circuit. Each would pull the circuit voltage down to around 90 volts.

All i had on hand were some Walmart brand Led lamps to try. With those in place the circuit is about 100v.

We've got some beach rental houses to relamp with several hundred regular base Leds. Clearly need to research this topic further.
 
etbrown4 said:
Turns out, no bad neutrals.

Unbelievably it was a combination of a new led light fixture, with the led board built in. This fixture alone pulled the circuit voltage down to 85 volts.

Then problem 2. I had several Sylvania regular Led lamps in the circuit. Each would pull the circuit voltage down to around 90 volts.

All i had on hand were some Walmart brand Led lamps to try. With those in place the circuit is about 100v.

We've got some beach rental houses to relamp with several hundred regular base Leds. Clearly need to research this topic further.
Click to expand...
You still have a problem, neutral or not. You have fixed nothing.
 
etbrown4 said:
In a coastal location, my customer has 5 exterior lights on one circuit, previously controlled by a photocell. With photocell disconnected and lights straight wired I'm getting 85 volts at each fixture. At the initial junction box with all wires disconnected I have 120v.

I have checked the joints at each fixture and all appear to be clean.
Click to expand...
For what it's worth, I just had a case almost identical except interior wall sconces, 85V at fixtures, 120V at junction, just like you checked wiring connections at fixtures all looked good, pulled switches a 4WAY circuit, 120V at 1st 3w. Found old 3w switch that cause high resistance in addition bad old cloth wrapped wire with fractured insulation to that switch, reducing to 85V, replaced switch, and bad wire, all better.
 
Added finding...
With all lamps removed, circuit reads a solid 120v. Photocell has been removed and there are no switches.

Will test the seemingly problematic Sylvania lamps, will read voltage in a troulble light with one led lamp installed.
 
etbrown4 said:
The voltage readings were with lamps installed, mostly leds.
Will try with no lamps.

Nothing underground, all on building exterior.

Here's something that probably supports the bad neutral theory. There are two romex circuits which supply 5 fixtures.

From the single hot wire, in free air, attached to nothing here's what it reads with a fluke digital meter:
To ground 120v
To one neutral 108v
To the other neutral 105v
Click to expand...
1. Two romex circuits each? supplying 5 fixtures? If so, are both circuits problematic?
2. If you are testing mid way in lighting circuit (assumption from 2 neutrals) and all wire in air nothing connecting (are grounds still twisted?) except your meter, you shouldn't be getting any return on one of the neutral unless you have a neutral-ground high resistance short (assuming grounds twisted ... open grounds and retest). Also is this a metal building? I've seen that act as a high resistance ground return path when a wire got pinched when hanging fixture.
Hopefully not the LED lighting (as you suggest in later post) that would cause me to ?? any usefulness of LED technology if it causes that significant of a voltage drop.
 
More readings taken today on the 2 lighting circuits.

With lamps installed, but not on, One branch circuit neutral to the hot feed reads 108v.
The other branch circuit from feed to neutral reads 112v.

Supply from the panel, in open air, the hot to neutral reads 121v.

I then isolated the Romex run to the first lighting fixture. No other wiring connected. Total Resistance out and back from the first fixture, with no lamps was about 1 ohm
At the one first fixture isolated from other fixtures, with the lamp not installed. after connected to the supply, Hot to neutral reads 121v.
With an LED lamp installed, hot to neutral reads 106v. Amprobe shows .1 amp load.
With a 60 watt incandescent lamp installed, hot to neutral reads 111v

Today with LED lamps in all 5 fixtures, hot to neutral reads 105v.

Sure looks like these LED lamps are creating unusual voltages.
 
I suggest measuring between neutral and equipment ground at the first fixture, both with and without loads. You should see very little voltage with the low currents you are running.
 
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