Voltage dropping on branch? Why?

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cwsolo

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Went to a mobile home, customer wanted to ad 3 dedicated receps in a room being used as an office. Room had 3 cpu's and one larger copy machine, one laser printer, one fax machine, and a ups for the cpu's. I was told that the lights keep dimming periodically, and sometimes the power in the room flickers. No breakers tripping, I checked voltage on a recep in the room and sure enough the voltage held at 120v then when the lights dimmed about every minute or so the voltage would drop to 111v.
L-N voltage 120
L-G voltage 120
N-G voltage 2.4volts
I'm thinking possible loose connection or nicked wire leaking voltage under load. No load seemed to be kicking on and off, just the lights would flicker every min or so. I checked for the voltage drop at the service and there was no drop at all.
What have you found to be the cause of a problem like this?... could it just be all the cpu equipment and maybe the circuits should have a super neutral?
 
Re: Voltage dropping on branch? Why?

I would check to make sure there was no voltage drop at the service panel first. If everything there is fine, since it's a mobile home I would suspect a loose connection in a j-box under the home. This is common on the double and triple wides, they make connections underneath, sometimes poor ones and moisture also gets in these. I have personally seen Voltage Drop like this a number of times on mobile homes, everything tests fine at the panel, and it turns out the problem is in a J-box underneath. I would also recommend placing some anti-oxidant compound on your new connections if the problem is underneath the house.
 
Re: Voltage dropping on branch? Why?

Sounds like the laser printer or copy machine is cycling every minute or so. I'm pretty sure that they use some sort of heater to quickly dry the ink which would cycle on and off while the unit was standing by. This may be the cause of the problem. I'd try disconnecting and reconnecting each of the loads one at a time to see if the problem goes away.

Seems rather odd that a loose connection would drop the voltage at fairly regular intervals with a constant voltage drop.
 
Re: Voltage dropping on branch? Why?

You have a receptacle or switch burning out. I suspect you have those modular switches and receptacles and they crimp on. Sometimes under heavy load they burn out their contacts and need to be replaced. I go around and use my receptacle tester and wiggle each receptacle and see what happens to the voltage. If it manifests itself, replace the device with a cut in box(shallow). They only have 4 inch tails on the wire so be judicious when replacing them.
 
Re: Voltage dropping on branch? Why?

I checked the service no drop there.
Sounds right that the laser printer could be causing it, but I have a laser printer that does not cause this problem which also leads me to believe it may be a combination of the equipment and possibly a loose or bad connection.
The lady said the trailer is a 2005 and is under warranty but if the manufacturer or set-up people do not fix it aside from adding the receps, I'll be fixing it at T&M.
 
Re: Voltage dropping on branch? Why?

The reason I said a loose connection underneath is because this has been the most common problem I have run into a number of times on mobile homes, even newer ones.

The second cause I forgot to mention has been back-stabbed receptacles and switches, poor connection there sometimes.

In regards to the laser printer, some of them pull quite a bit of current. As the current draw increases and decreases with the printer cycling, so will the VD, which is why it probably varies when you measured it. However, to go from 120 to 111 volts (about 8%) is a good indication that something is wrong somewhere.
 
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