Tripping main

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Old 06-29-16, 09:34 PM
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Tripping main

Time to use my air conditioner, I have a 120 V floor standing unit and a 120 V window unit, I had both of them running last year no problems, this year the floor unit has tripped the main breaker multiple times while plugged into the same outlet, so I tried the window unit and it was fine until my wife turned on the microwave and it tripped the main again. The only other stuff being powered are a tv computer router ect. What bothers me most is why tha main is tripping and not the individual circuit breaker, my service is maxed. What to do? I would post a pic if I can figure out how, my main is only 50 amp, house built in 73
 
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Old 06-29-16, 09:41 PM
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Welcome to the forums.

You only have a 50A service..... it at least a 120/240v service ?
You may have a weak main breaker.
 
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Old 06-29-16, 10:12 PM
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Yes 120/240 service but none of the 220 stuff is on. Still can't figure out how to post a pic from my phone
 
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Old 06-29-16, 10:16 PM
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My dryer works fine and no tripping, my220 compressor is hard wired but switch is off, my 220 welder is plugged in but turned off as well, stove was not on when the main tripped ether.
 
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Old 06-29-16, 10:19 PM
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Are both air conditioners on the same leg of the panel? How old are the A/C?
 
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Old 06-29-16, 10:23 PM
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I believe seperet circuits, the floor unit is fairly new within 5-10 yrs, the window unit is all steel, older but not sure how old
 
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Old 06-29-16, 10:23 PM
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This is a link for picture posting but not for phones. Many phone pictures are too large for the board to host directly. http://www.doityourself.com/forum/el...-pictures.html
 
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Old 06-29-16, 10:30 PM
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The A/Cs really need to be on dedicated circuits. At the very least they should be on seperate circuits and those circuits should have no heavy loads like a microwave.

To diagnose what is happening with the main breaker you need a clamp on amp meter. You can get a cheap one from Harbor Freight if you don't have one. You need to put it on one of the hots to the panel and watch the amperage on the main breaker as things are turned on.
 
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Old 06-29-16, 10:40 PM
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Thanks for the replys! Will my Multimeter be enough to measure amp draw? I'll have to come back to this in a while, at work and got to get busy..
 
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Old 06-29-16, 10:44 PM
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Will my Multimeter be enough to measure amp draw?
No. You need a clamp-on amp meter. You need to measure a hindered times more amps then most multimeters are capable of and there would be no safe way to connect it. Example: http://www.harborfreight.com/digital...ter-95652.html
 
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Old 06-30-16, 03:42 AM
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Here's a pic of my maxed service, The 2 incoming cables appear to be aluminum strand and not copper, the outer sheath measures approximately 3/4" so looking at the picture i would guesstimate 1/2 to 9/16 diameter on the wire strands, but i cannot determine if its 3/0 or 4/0.

I'm sure the 2 air conditioner units are plugged into separate circuits, the floor unit it in the dining room, the window unit is in the back bedroom. The microwave is suppose to be a dedicated circuit.

The main breaker is an original unit, never been replaced since i have been in the house, 1989 to present.

If i buy that amp gauge i would need better instructions on where to attach, i'm assuming on the 4 awg cable coming off the main breaker but does it matter which?

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Old 06-30-16, 03:42 AM
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Carefully reading the original post leads me to believe that Mike has a "split-bus" panel. ALL the 120 volt circuits are coming off the 50 ampere sub-main for the lower section of the panel. The individual circuit breakers are not tripping because the loads on the individual circuits are not exceeding the rating of the individual CB but the total of all the 120 volt circuits IS greater than the 50 ampere sub-main circuit breaker.

That stated, I don't recall ever seeing a split-bus panel that had anything less than a 60 ampere sub-main breaker. It may have a 50 ampere because of the total 240 volt load. I think I would go to a 60 ampere sub-main as long as the wiring from the sub-main to the lower bus bars is sufficient to handle the increased amperage. In the long run, replacement of this panel with a more modern single main breaker model should be seriously considered.

Added: Picture confirms it is a split-bus panel. If the conductors from the 50 ampere sub-main are indeed #4 then going to a 60 ampere sub-main is acceptable.
 

Last edited by Furd; 06-30-16 at 03:46 AM. Reason: Saw picture after posting.
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Old 06-30-16, 10:56 AM
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Heres a close up picture of the wire leading from the 50 amp breaker to the bottom of the bus bar.

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This is a cuttler Hammer box. I know there are 2 parallel bus bars but is it a split buss? not sure..

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Question:
I was wondering of this box has a limit for the main size as well, if i could go up even if it meant using a larger wire in place of the 4 AWG??

Moving this question back to the top:
If i buy that amp gauge i would need better instructions on where to attach, i'm assuming on the 4 awg cable coming off the main breaker but does it matter which?
 
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Old 06-30-16, 11:13 AM
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The amp meter would clamp around one of the large wires to the 120 breaker section of your panel.

You have a real mess there. You have a 30a and 40 amp 240 volt breaker in the 120 volt section of your panel plus all the spaces in the 240 volt section are filled. That tells me the panel needs to be replaced. It is overloaded. Since there is no main breaker I'd be a bit worried about a fire from overload. Unlikely but something to consider because the whole panel is not protected by a breaker but heavily loaded.
 
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Old 06-30-16, 12:55 PM
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This still brings me back to my original problem of why last summer i had no problem running both air conditioners with this setup but now a year later i'm popping the main.

I had the 40 and 30 amp breakers added for my welder and compressor, nether of them are used constantly, thankfully!

Not 100% sure if the air units are on the same side of the bus bar.

I do know its maxed and not ideal, and yes i have been a bit concerned about it so the reason i have been careful about using ether the welder, or compressor with no other major appliances being on.

Last time i tried to hire an electrician everyone i called didn't want to mess with a home job so i'm not sure who to call at this point..
 
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Old 06-30-16, 06:49 PM
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I had enough time today before work to try a test, i shut off the breakers for the welder and compressor, then i started turning on the AC units, then the microwave, Toaster oven, ceiling fan, more lights, TV, ect. Absolutely no problem at all.

Being as i didn't have an issue at all last year I'm let to believe that there could be something wrong with one of the two circuits for the welder or compressor, does this sound reasonable?

The old air conditioner is Holmes Accutemp, Model APE08AKM1, rated at 11 Amps
The new floor air conditioner is Lasko, model AGV05LBg1, rated at 5 Amps

I do understand the best solution is a box replacement, i am not taking that suggestion lightly. I have talked to an electrician today about it and if an inside or outside service box would be best, the inspection, ect. My garage is packed and doing an inside box would mean taking down my paint booth, my work bench and clearing out a lot of stuff in the general vicinity.
 
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Old 06-30-16, 07:17 PM
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That is definitely a split-bus panel. Split -bus means that essentially you have two panels in one, an "upper" section that holds a maximum of six, double pole (240 volt) circuit breakers and a "lower" section containing the rest of the circuit breakers. The lower section is powered through one of the upper section two pole circuit breakers, in this case the 50 ampere "sub-main" breaker.

Split bus panels were popular in the 1960s and into the early 1970s. They came about from a provision in the National Electrical Code (NEC) that allows up to six double pole circuit breakers in lieu of a single main circuit breaker. This was a cost-savings measure on the part of Cutler-Hammer (and many other manufacturers) because of the high cost of high-amperage circuit breakers at that time.

The downside of a split-bus panel is that since there is no single main CB the possibility of overloading the "service", the incoming wiring from the meter, is considerably higher. Also, at the time these were installed a 60 ampere service was considered adequate for the lighting and convenience receptacles in a typical residence. The new (at the time) convenience of circuit breakers over "one-shot" fuses was coupled with a surge of new 240 volt appliances such as central air conditioning and electric clothes dryers necessitating larger capacity electrical services.

As I stated in my original post, every split-bus panel I have ever seen used a 60 ampere sub-main CB for the lower section. The existing #4 conductors from your lower section to the 50 ampere CB are sufficient for a 60 ampere CB. It IS a "stop-gap" measure but replacing the 50 ampere CB with a 60 ampere model IS acceptable. This can be a DIY job IF YOU ARE CAREFUL! You will be working in an energized panel so if you have the slightest qualms about that you would be better off getting either a licensed electrician to do the change or at the least, a competent friend to help.
 

Last edited by Furd; 06-30-16 at 07:55 PM. Reason: Correct misspelled word.
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Old 06-30-16, 07:42 PM
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Yea its a hot one Is the best way to disconnect the main breaker from the buss then transfer one wire at a time to the new breaker? I have a friend that's an electrician and electronics guy, i'm going to see about if he can help me out too.
 
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Old 06-30-16, 07:50 PM
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Your panel doesn't have a main breaker. It has a breaker for the 120 volt section.
I have a friend that's an electrician and electronics guy, i'm going to see about if he can help me out too.
That might be best since you have no main breaker and will have to work on the panel hot unless you have the PoCo pull the meter.
 
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Old 06-30-16, 08:13 PM
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My garage is packed and doing an inside box would mean taking down my paint booth, my work bench and clearing out a lot of stuff in the general vicinity
This bothers me. WISHA (Washington State's version of OSHA) as well as the state electrical code requires a clear space of a minimum of 30 inches wide at an electrical panel (panel does not need to be centered) as well as 36 inches (might actually be 48 inches, I know it is in industrial applications) in front of the panel. This space must be clear of all non-electrical items from floor to ceiling. Please post a picture of the electrical panel showing the surrounding area.
 
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Old 06-30-16, 08:43 PM
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Yep, he's going to stop by next week and replace that main breaker and run some tests while he's there, he has seen the pictures, he has the proper insulated gloves, ammeter ect. And he agrees i need an upgrade, said he could do it for me too if i need.

The work bench was there when i moved in, I'm sure my paint booth is 36" away from the panel but its in the way of bench removal and moving enough stuff around.

Thank you everyone for the help and advice, I know right now i'm looking for a temporary solution, but then i can plan long term for the replacement service.
 
 

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