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kasper37 · Jul 24, 2008, 10:45 AM

I have a 100 amp service approximately 10 breakers 15 amp and 20amp with one of them being a 30amp that is hooked up to an ac unit. Well a few days ago I arrived home to realize that I had no power at home after checking the electrical panel I realized that my main 100amp breaker along with my a/c 30 breaker were trip I had to reset both of them well I did not check to see what was going on it was late so the next day I turned my a/c unit after 2 minutes the power goes out to my surprise I do not know what is going on given the fact that I have had the same systtem for over 7 years and I have not done any changes to the electrical panel I do not know if there is a short in the a/c circuit or if there is something wrong with the service entrance cables. Again I only have this probem when I turn the a/c unit on. What can possible be wrong?

tmentec15 · Jul 24, 2008, 10:52 AM

Was your A/C unit ever changed? Did you replace any major appliances? Usually if the main breaker trips it means that more than 1 item on 2 different breakers overloaded the circuits. If you have any other electrical appliances such as a heater, oven, or stove that was changed or added in chances are that your panel is too old. If you have more than one A/C unit such as a window A/C unit or second zone A/C chances are that the compressors will not turn on at the same time but if both units kicked in at the same time, this can trip a circuit breaker. An A/C unit takes the most power just when the unit first turns on.

Tev · Jul 24, 2008, 02:22 PM

My first thought here is that the compressor motor for your A/C unit is on it's last leg and is drawing more current as it starts up than it did when it was new. But really that's just a guess as A/C is not something I'm overly familiar with. I'd check all the connections to make sure they are good, then inspect the wiring looking for breaks in the insulation, then call a professional if you still don't see the problem.

Don Kelly · Jul 24, 2008, 02:46 PM

Both members who posted on the A/C question are on the right track. A/C (heat pump) for example need to be checked by a hvac tech every year. As the comptessor gets on it's last legs (so to speak) it takes more amps to start it turning. This overloads the drive motor which overloads the double pole 30 AMP breaker, which trips.

This explanation does not explain why the 100 AMP main breaker also trips. If in good condition it should not trip until briefly overloaded by variously 20%

The only thing more is you should have a shut off near the heat pump. It could be a pull out non fused switch or a lever shut off fused. The fused unit with time delay fuses I have found is best.

Don Kelly, retired Master Electrician

Missouri Bound · Jul 24, 2008, 06:29 PM

Well... you have already diagnosed the problem. Your main breaker is either overloaded or weakening from continued high amperage. You need to have someone check the draw of the compressor, and also the draw at the main breaker. (current draw) I'd suspect, just like the others that your compressor is probably going bad and drawing excessive amperage at start up. But have your whole electrical system checked out. Perhaps it's time to consider a 200 amp service.

Don Kelly · Jul 24, 2008, 08:34 PM

While touching on and diagnosing the reasons the double pole breaker keeps tripping, the owner of the problem touched upon the main 100 Amp breaker also tripping.

Missouri Bound it appears correctly suggested the installation of a 200 AMP service panel.

If one goes through the existing 100 AMP panel and adds up the breakers, several for 20 AMP circuits, some 15 AMP circuits for lights, 20 AMP water heater, 30 AMPs for the A/C unit, 40 AMPs for a dryer, 50 AMPs for a kitchen stove, one can see how the 100 AMP panel could be overwhelmed by demand.

If a 200 AMP upgrade is required, we can walk you through what all is needed, but that it appears is another thread. To be discussed upon request later.

Don Kelly

kasper37 · Jul 25, 2008, 11:30 AM

Originally Posted by tmentec15

Was your A/C unit ever changed? Did you replace any major appliances? Usually if the main breaker trips it means that more than 1 item on 2 different breakers overloaded the circuits. If you have any other electrical appliances such as a heater, oven, or stove that was changed or added in chances are that your panel is too old. If you have more than one A/C unit such as a window A/C unit or second zone A/C chances are that the compressors will not turn on at the same time but if both units kicked in at the same time, this can trip a circuit breaker. An A/C unit takes the most power just when the unit first turns on.

No I do not have any other units I only have 1 30 amp breaker the rest are all 20's and 15's

kasper37 · Jul 25, 2008, 11:31 AM

Originally Posted by Don Kelly

While touching on and diagnosing the reasons why the double pole breaker keeps tripping, the owner of the problem touched upon the main 100 Amp breaker also tripping.

Missouri Bound it appears correctly suggested the installation of a 200 AMP service panel.

If one goes through the existing 100 AMP panel and adds up the breakers, several for 20 AMP circuits, some 15 AMP circuits for lights, 20 AMP water heater, 30 AMPs for the A/C unit, 40 AMPs for a dryer, 50 AMPs for a kitchen stove, one can see how the 100 AMP panel could be overwhelmed by demand.

If a 200 AMP upgrade is required, we can walk you through what all is needed, but that it appears is another thread. To be discussed upon request later.

Don Kelly

Well, I am going to check my compressor motor I believe that may be the problem. Is that hard to change?

kasper37 · Jul 25, 2008, 11:35 AM

Originally Posted by Missouri Bound

Well....you have already diagnosed the problem. Your main breaker is either overloaded or weakening from continued high amperage. You need to have someone check the draw of the compressor, and also the draw at the main breaker. (current draw) I'd suspect, just like the others that your compressor is probably going bad and drawing excessive amperage at start up. But have your whole electrical system checked out. Perhaps it's time to consider a 200 amp service.

I really do not think that I need a 200amp service like I said before I have had the same systeem for the past 7 years or so and up to now I have never had any of those problems.

So you may be correct It is probably my compressor motor. Is that hard to change? And how much current should it be drawing I have an amp meter so I can definetely check that out. What is the normal current draw?

Missouri Bound · Jul 25, 2008, 02:14 PM

A compressor motor physically is not hard to change, it's a mechanical procedure. HOWEVER.. only technicians EPA certified can deal with refrigerants because of the link of said refrigerants to damaging the ozone layer. It's not a tedious job for someone mechanically inclined, but it is forbidden for those without qualification to do it. As far as the current draw, there should be a tag (metal plate) on the compressor somewhere which would indidate it's electrical specifics. Call a tech, get some quotes.

Good luck.