Main Breaker trips - HELP !!

17 years ago

Hi,

When my A/C unit runs, it trips my main circuit breaker. Not always. Its random. sometimes it trips 3 or 4 times a day. then runs fine for a day, then trips again. The breakers inside my house are not tripped. they look fine. I had to go outside my house and OFF the breaker and then turn it ON. I had called my utility company. They told me first to replace the main breaker and if it happens again then there is a problem inside the house.

Should I call a electrician first ? can I replace the main braker myself ?

Thanks.

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Comments (6)

bob_brown
17 years ago
I would probably inspect all electrical connections. Somewhere you either have an excessive load or a poor connection. A hot day will add to the resistence of the system. Resistence equals amps, which will cause the breaker to trip.

A compressor that is overcharged can cause the breaker to trip on a hot day. A fan motor that has a bad capacitor can cause the breaker to trip. A weak breaker can also trip. I have found poor connectors between the wire from the pole and the house feed wire to cause a voltage drop, which affects everything in the house.

Finally, if the wiring to the condenser is too small, it can cause the breaker to trip.
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hendricus
17 years ago
What else is running when the main breaker trips? Is this a new installation? How large is your electric service? Does it trip when the air is on, dryer is running, four burners and the wall oven and the vacuum and then you turn on the pinball machine?
There is either too large an electrical load or the breaker is bad.
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GFCI (ground fault circuit interrupters) work by sensing the difference between the outgoing current and return current. A typical fault limit is 5 miliamp difference. I am assuming that you have GFCI also known as GFI. Also, the return current should pass through the same hole in the breaker box as the outgoing current. Trouble may develop if the return path is somewhere else. In fact, anywhere one lead passes through a hole in metal, its partner lead should also pass through the same hole. My first suspicion is your dryer. If it is a gas dryer, then a likely source for a sneak ground path is the motor or one of the controls. Relay coils can leak. If the motor is a capacitor start type, the start winding and its capacitor is suspect. If the dryer is by electric heaters, there is ample opportunity for heating elements to leak to the frame of the machine. As a first check, measure the voltage between the appliance frame and a solid ground such as a metal water pipe. Clip on the meter and turn on the appliance while watching the meter. (An analog meter works better than a digital for this test since the voltage jolt may be too short for the digital to respond whereas the needle on an analog will jump or twitch enough for one to see it. However, if short is present and persists for more than a second, a digital meter will also have a response.) There should be no voltage. If you see a voltage, note its value. If it is line voltage, you have a very dangerous situation. Electrocution may result if a user touches a metal part of the machine and a ground such as a water faucet at the same time. If you are not comfortable with using a volt-ohm meter, then get an electrician or technican who can trouble shoot your setup. The GFI is telling you that something is wrong. Of course, a GFI contains electronics and could fail, but GFIs from major manufactures have a good reliability record. Most manufacturers recommend that a GFI or ordinary circuit breaker should be replaced if it has opened a short.
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mr_havac
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When was the last time you had the system serviced? Chances are its something like a plugged up condenser coil in a low end unit that doesn't have any hi or low pressure controls, or badly corroded or loose terminals. Many times the compressor terminals are overlooked when checking electrical connections and they do get loose.
If its been a while have your system serviced first before you go calling an electrician.
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maverick9001
Original Author
17 years ago
Thanks for your replies...
The HVAC unit is 9 yrs old.

when the breaker tripped the microwave was running once, other time the dryer was running.. all other times it was the A/C and probably TV was running.. no other appliances were running..

I changed the breaker for HVAC (its a 30 amp breaker) and it still trips..The main breaker outside is 100 Amp.

I'm calling a HVAC contractor tommorrow for servicing. what should I ask him to check for ? are checking AMPS or leaks part of the service ?

I finished my basement last fall and also ran a seperate line for microwave(both done by a contractor). but after this I have used my heating, washer, dryer, microwave etc. simultaneously. never tripped.

thanks for your input guys..
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maverick9001
Original Author
17 years ago
How much would it cost on an average to service a heating & cooling system ? I live in Central New Jersey.
Thanks..
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daddo
17 years ago
I agree- have the a/c checked out first.
The 100 amp breaker may be going bad and the stabs it connects to in the panel may be corroded some. If there is a loose connection or corroded stabs, this will overheat the breaker and sometimes slowly cook it to the point it needs replacing.
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Main Breaker trips - HELP !!

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