Circuit trips in the evenings

[aftershock]

Nice trouble call I got going here.
Customer has a circuit which controls the upstairs receptacles.
MWBC
10 rec on this circuit (give or take 1)
Other circuit is for a heater/fan/light combo in bath.
2 TVs, 2 VCRs, 2 lamps, 2 printers, 1 computer, 2 or 3 table clocks.
3 UPS (Uninterrupted Power Supply)
1 is a apc Model BE500R. Namplate shows input: 115 volts 12 amps
2 are apc model BE350G input 115 volts 8 amps
I have already found and remade wire joints in the homerun box and we checked every receptical outlet. It has never tripped while I was there and the circuit was only drawing 5 amps at the most with everything running.

The 2 UPS listed I find hard to believe draw that much amperage and if the do then they are doing it at a time when I am not there. But this is the only thing I can think of that would be the problem. I figured I would run it by you fine folks on this forum.

 

[cowboyjwc]

Maybe and outside light controled by a photocell? I had the same problem with a sign they would call me every day and tell me the circuit tripped and every day I would go over and hang around for a half hour or so and nothing would happen. Got there just towards dusk one night and the sign was on and suddenly the parking lot lights started to come on and pop. Never realized the parking lot lights were on with the sign which had a time clock and the lights had a photo cell too.

I'm gonna edit this one too, you could have a load problem, if I read what your saying right. Everyone is home in the evening and everything starts to get powered up and someone goes into the bathroom....

 

[brian john]

Min max multi meter with amp clamp.

 

[aftershock]

Keep in mind that the bath fan/light/heater is on a separate circuit which shares the neutral with the circuit in question.
I have checked the outside lights and they are also on a different circuit.
The last time the circuit tripped , the HO's were out for dinner or visiting some friends and arrived back at home at about 6:30 pm (still daylight out) to find the circuit off. Seems only 2 people live at this house. The HO powered down the computer and for a 24 hr period the circuit did not trip, but since this is not an every night thing, we cant call dibbs on the computer yet.
I told the HO to take the UPS' out of the equation and see what happens.

I have asked pretty much all the normal questions:
Have you had any work done recently?
Added anything?
Replaced anything?
Drove a nail into a wire somewhere?


I just know it is going to end up being something simple.

 

[Split Bolt]

Aftershock, is their printer a Brother laserjet printer? I have a commercial client that has one of these and it would create problems on all 3 of the 3 phase MWBCs that shared the neutral. During my troubleshooting, I googled the model # and found A LOT of sites with people complaining about them. I will try to dig through my old notes and see if I can get you a cat. #. Try googling "brother printer problems" for a start.

 

[480sparky]

Min max multi meter with amp clamp.

Recording meter that will tell you what time it happened.

 

[aftershock]

Aftershock, is their printer a Brother laserjet printer? I have a commercial client that has one of these and it would create problems on all 3 of the 3 phase MWBCs that shared the neutral. During my troubleshooting, I googled the model # and found A LOT of sites with people complaining about them. I will try to dig through my old notes and see if I can get you a cat. #. Try googling "brother printer problems" for a start.

I will remember to check the printers next time. Remember it tripped while the HO's where out so no activity by any person in the house.

Im leaning towards those UPS' over amping the circuit but am skeptical. Maybe something the HO is not telling me.

 

[Split Bolt]

Right. But do they receive faxes? This unit was an all-in-one and I remember a lady on one of the Brother complaint blogs saying she loved it because no matter where she was in her house, she could tell she received a fax by the dimming lights! Also, add up the amperage of all devices plugged into the UPS boxes to make sure they are not overloaded. Maybe this is not what your client's problem is, but I remember some bizarre things happening on all 3 of the MWBCs that shared the neutral! It all went away when I ran a dedicated line with its own neutral to the machine. Good luck!

 

[Ken9876]

I'd check the printers, a Laser printer will draw a lot of power and will keep itself warmed up.

 

[Jim W in Tampa]

I rather dought the UPS's are at fault , i have the apc 1250 and 4 others. They do not draw any extra amps till the battery kicks in. There could be something disterbing the sine wave and kicking them in for a split second. Triping while not being used does sound crazy. Are the computers off ? Mine stays on 24 / 7 because it generates cash from my night club. Check the breaker as they can be weak. If its a 2 pole breaker are you sure its not the other circuit causing common trip. Office loads can add up fast but if nothing being used should not matter. Have them remove 1 load at a time till located. Buy 50 foot extinsion cord and see if locating some of the loads to another circuit helps.
Could something be almost touching and differance in temp making it short out.

 

[Ragin Cajun]

Even is the printer, or something else, is the offender, it sounds like a good time to add some circuits just for the computers.

I have a home office and I am very careful about the computers being on their OWN circuits. I don't need trips when I'm working!

RC

 

[Jim W in Tampa]

Even is the printer, or something else, is the offender, it sounds like a good time to add some circuits just for the computers.

I have a home office and I am very careful about the computers being on their OWN circuits. I don't need trips when I'm working!

RC

That is the reason behind buying a UPS. Even a small flicker could mess up or restart computer

While a new circuit might be nice it might not be needed and could be very costly.