Domestic a/c runs fine for hours then trips circuit breaker
I have changed out the circuit breaker, but it continues to trip. What is weird is that it does this when it is cooler outside, around 70 degrees. In the hot part of the day, around 80-90 degrees it runs fine. It usually starts around 7pm and trips all night until it warms up the next day. This a/c is in a motorhome.
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Re: Domestic a/c runs fine for hours then trips circuit...
Check the difference between your incoming voltages at these times, it may be, if your plugged in to park power, the voltage getting to you may be less due to neighbors using more. If you have a genny, try using it when this happens and see if it trips. More lights, TV's etc are probably being used at night by others.
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The magnetron probably has a partial short pulling more current than normal as it runs, the other two items that give trouble is the high voltage diode, "sometimes cracks" to the high voltage capacitor, "usually shorts"
A tripping circuit breaker is an indication of an overload. You say there is no load on the breaker - how are you making this determination? Are you using an amprobe or some other meter?
A circuit breaker with NO load shouldn't ever trip. Likewise a circuit breaker carrying up to 80% of of the current it is rated for shouldn't trip either. Circuit breakers that carry more than 80% of their load will trip - if the load remains connected long enough. This is called "duty factor" or "service factor" The greater the load is in excess of 80%, the less time that the breaker will carry it before tripping.
An example of a 100 amp breaker with different loads on it (this 100 amp value was chosen for ease of doing the math):
80 amps - never trips 85 amps - trips after 48 hours 90 amps - trips after 16 hours 95 amps - trips after 8 hours 100 amps - trips after 4 hours 105 amps - trips after a few minutes 120 amps - trips after a few seconds 150 amps - trips instantly
This is only an example to show how a certain circuit breaker might trip under a load less than the rating stamped on the body or handle.
A circuit breaker that trips with no load or a load equal to or less than 80% of its rating is most likely defective. You need an amprobe or ammeter for amp readings. If the load is found to be 80% or less, there may be an issue of harmonics that is causing the tripping. You'll need to have special equipment and qualified persons to check harmonic problems. Most harmonic problems occur when the loads are not linear device (transformers). Examples of non-linear devices are "switching" (or solid state) power supplies like those in computers.
I hope this helps and good luck. Please rate my reply. Thank you.
Are there any heaters anywhere in the circuit for this breaker? (ie: bathroom fan w/light and heater) If yes, I would suspect and inspect them first. Also,any type breaker will trip more easily if the electrical connection screws on the breaker are not tight enough...check to make sure that's not the case.
it is normal for a breaker that is run right on the edge (50 amp and your furnance to use 45) to get weak after a while . the first thing you should do is change the breaker with the same type and amp rateing . it should take care if it