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With a new HVAC unit installed the main breaker flips when another 220 appliance is running ( water heater mainly.) My A/C guy looked and said I had a weak breaker and to replace it. Now, to me that would make sense if the A/C breaker was flipping, but the panel cuts out. He checked and the unit is running at 42amps and I'm not sure what the water heater runs at but, with nothing else running that sounds like not much load for a 100 amp service. I want to do what I can to save money so I need help if it's a problem I can fix on my own. If not, I'll pay someone to fix it. It's a "SQUARE D" 100 amp service with apparently an older type breaker ( according to A/C guy,) that has to be at least 30 or 40 years old.
Thanks
Dustin
 

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Check the amps going to tthe main breaker to see if they pass the 100 amps.if yes...
disconnect the a/c and check the amps at the main breaker again if every thing is normal the problem is the A/C that in some times goes over the 42 amps to start the motor.
Usually a good solution is to change the breaker for a 200 amps and I believe you need to change the Circuit board for a New Version 200 amps.
 
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Joe - "usable" amperage of any breaker is approximately 80% of nameplate - so your 100 amp panel is good for 80 amps only so with the 42 amps of the airconditioner and about 24 amps for the water heater add a few lights and -pop- yep your main breaker will trip, sorry you are going to need to upgrade your panel box - also the feeder wire coming in to it, and possible meter base and riser or underground service. Talk to an electrician in your area, most are decent guys and won't charge much if anything to give you a quote. - Brennan
 

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OK, first off, you dont change a "change" a main breaker. You replace the whole service to go from 100 amps to 200. There is no such thing as a "circuit board". :rolleyes: It's called the main panel or breaker panel.

Second, the usable amps from a 100 amp srevice is 100 amps! The continuous (3 hrs. or more) load should be 80% or less.

A typical water heater is 4500 watts. At 240 volts this is 19 amps. plus your 42 is 61. It is unlikely that the rest of the house is pulling 40 amps @240v. There has to more on than you know about. If you are tripping a 100 amp main there has to be a reason. An amp meter on the mains is the only way to tell.
The main could be weak but IMO a service of that age is due to be replaced anyway. What condition is the service cable? Is it frayed? Is water leaking in anywhere? Is the panel or meter pan rusting?

42 amps is quite alot for an a/c in a house with only a 100 amp service.
I think it's time for a new 200 amp service.
 

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speedy - stress kills man. Air conditioners run for more than 3 hours. "quotes" are to simplify statements and surge loading of a starting a/c especially for non-bleed off types are quite large 75+ amps. and yes he probably needs a new service.
 
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well here goes my 2 cents worth. First off the only time a new a/c should draw more than 40 amps is on start up. The unit should drop back to around 10-20 amps depending on what size unit it is. Now that is for the condensor. The air handler should only pull 2.5 amps at the most when running in the cooling mode. As far as your a/c guy I thinks he need some more schooling or either to get out of the business. For god's sake next he will be burning your house down and telling you that the thermostat wire wich is low voltage is supposed to pull 50 amps also. sounds to me like you need to find a new a/c guy that knows his a$$ from a hole in the ground and see what the problem is,and if this this is a new unit i would recomend this ,for you are about to loose a compressor at this rate. And the unit should be under warranty. THAT IS IF IT WAS INSTALLED BY LICENSED CONTRACTOR. good luck.
 
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By the way if you think that i'm joking with you just walk outside and look at the nameplate data sticker on the condensor. It will give you the R.L.A. (run load amps) that is the amount of current the unit should be drawing at normal operating conditions. 42 amps just aint right!!!!!!!!!!!! hope you got enough $$$$$$ to buy a new condensor. This is coming from an experienced h.v.a.c. technician.
 
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