Lower voltage on receps than at panel
#1
09-15-08, 11:44 AM
Lower voltage on receps than at panel
My office receptacles are showing 116 volts on a DMM and that voltage drops as low as 103 volts when my copier starts or when the laser printer fuser kicks in. At the load center about 50 feet away, the voltage is 121 on a separate branch circuit.
The problem I noticed was fluctuating fluorescent lighting to the point of being hard on the eyes. I ended up turning off the printer for now but there are enough other fluctuations that I wonder what else is going on.
The office was partially rewired last winter and I just moved back in here last week. I told the contractor it was poorly wired and I know they re-did most of the lighting wiring but I suspect backstabbed connections in the wall receps, which they probably did not re-do, and maybe one of those is bad.
I can't open anything up to look at it until after business hours but I am wondering if there's anything besides backstabs that I should be looking at. Thanks.
Just for the record I am not an electrician, and I won't be doing any work myself, but the contractor will need to be pointed in the right direction or nothing will happen.
The problem I noticed was fluctuating fluorescent lighting to the point of being hard on the eyes. I ended up turning off the printer for now but there are enough other fluctuations that I wonder what else is going on.
The office was partially rewired last winter and I just moved back in here last week. I told the contractor it was poorly wired and I know they re-did most of the lighting wiring but I suspect backstabbed connections in the wall receps, which they probably did not re-do, and maybe one of those is bad.
I can't open anything up to look at it until after business hours but I am wondering if there's anything besides backstabs that I should be looking at. Thanks.
Just for the record I am not an electrician, and I won't be doing any work myself, but the contractor will need to be pointed in the right direction or nothing will happen.
Last edited by ArgMeMatey; 09-15-08 at 02:27 PM.
#2
09-15-08, 01:13 PM
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Voltage drops are a normal occurance on wiring circuits and are the result of several factors - the length of the circuit from the power source (your panel), the load on the circuit (copiers and laser printers draw quite a bit of current), the size of the wire feeding the circuit (larger wire, smaller voltage drop), and even the method of running the circuit.
But a voltage drop of 13 volts (116v - 103v) from just a copier is pretty large. It is possible that the lighting was run on #14 wire and the receps tied into that also. What size is the breaker that feeds the recep? When you turn it off, do the lights go out also? How many lights, how many receps?
Your circuit is definitely undersized for the equipment you have on it. This doesn't mean that it is unsafe or wrong, but that you need to make some changes to correct this. It seems as though your lighting and recep are on the same circuit.
Your best bet is to address the load and/or the wire size portion of your circuit. Your copier and laser printer would be best served on a dedicated circuit. You probably also have a fax plugged in nearby as well.
Since you show about 121vac at the panel and 116 volts at your receptacle with the copier and printer not running, that tells me that your receptacle is on a circuit with something else that is using power - maybe other receptacles or lights. When your copier or the laser printer fires up, they add to the load on that circuit and cause the voltage to drop.
But a voltage drop of 13 volts (116v - 103v) from just a copier is pretty large. It is possible that the lighting was run on #14 wire and the receps tied into that also. What size is the breaker that feeds the recep? When you turn it off, do the lights go out also? How many lights, how many receps?
Your circuit is definitely undersized for the equipment you have on it. This doesn't mean that it is unsafe or wrong, but that you need to make some changes to correct this. It seems as though your lighting and recep are on the same circuit.
Your best bet is to address the load and/or the wire size portion of your circuit. Your copier and laser printer would be best served on a dedicated circuit. You probably also have a fax plugged in nearby as well.
Since you show about 121vac at the panel and 116 volts at your receptacle with the copier and printer not running, that tells me that your receptacle is on a circuit with something else that is using power - maybe other receptacles or lights. When your copier or the laser printer fires up, they add to the load on that circuit and cause the voltage to drop.
#3
09-15-08, 01:21 PM
While I hate back stabs, I doubt that they are causing your immediate problem. If they were, you would smell something burning. Even a few volts drop across a bad connection when higher currents are being drawn would create quite a bit of heat.
You said you measured 121 on a separate circuit. I am not sure what that means. You should measure on the effected circuit at the panel with it heavily loaded. Measuring another circuit would be meaningless, it could be on the other pole. What you want to determine is if the loss is in the circuit wiring or more than that is involved. My guess would be that the incoming voltage on that pole is actually going down also. While there would be additional loss in the circuit, it would not seem right for it to be that much (15+ volts) if the outlets are relatively near the panel and using #12 wire.
Do some more checking.
You said you measured 121 on a separate circuit. I am not sure what that means. You should measure on the effected circuit at the panel with it heavily loaded. Measuring another circuit would be meaningless, it could be on the other pole. What you want to determine is if the loss is in the circuit wiring or more than that is involved. My guess would be that the incoming voltage on that pole is actually going down also. While there would be additional loss in the circuit, it would not seem right for it to be that much (15+ volts) if the outlets are relatively near the panel and using #12 wire.
Do some more checking.
#4
09-15-08, 02:30 PM
i would have your electrican ck your service equipment for a loose connection on the netural wire. might be at the circuit breaker panel or in the meter socket. if your netural wire is loose i will really show up in your lighting. also would account for the voltage drop at the receptacles.
#5
09-16-08, 12:30 AM
I did a cursory check of the neutrals and there was nothing obviously loose.
I noticed the 600 Amp distribution panel is a Zinsco, however. Are those as bad as their lousy load centers? I've got a bunch of small Zinsco panels too, for the emergency circuits of all things ...
I am going to have to have somebody track down all these circuits before anybody can do any serious troubleshooting. It's a 4-story building and I am not up for all that running around. Plus the ceiling tiles are really tight and I'd rather someone else broke them.
I also have to bring in my analog meter because I found one circuit that was supposed to have been disconnected but it is showing 30V on my DMM. At any rate, the problems seem to be limited to this one circuit in the office.
I noticed the 600 Amp distribution panel is a Zinsco, however. Are those as bad as their lousy load centers? I've got a bunch of small Zinsco panels too, for the emergency circuits of all things ...
I am going to have to have somebody track down all these circuits before anybody can do any serious troubleshooting. It's a 4-story building and I am not up for all that running around. Plus the ceiling tiles are really tight and I'd rather someone else broke them.
I also have to bring in my analog meter because I found one circuit that was supposed to have been disconnected but it is showing 30V on my DMM. At any rate, the problems seem to be limited to this one circuit in the office.
