HELP! Compressor now trips breaker on start up??

here's some basic electric wiring/code specs for the u.s. - i don't know if these are the same in "canook" land.

house lights can be wired with "14-3" size wire but all outlets should use "12-3". 12-3 wire is a heavier wire and can be used for a 15 amp breaker or a 20 amp breaker. 10-3 size wire is used for up to 30 amp draw appliances. some wall outlets are 20 amp. you can tell these from standard 15 amp outlets as they have a little "cross" opening on one of the slits where the plug goes in. a 20 amp plug has a similar copper cross shaft. if you have a 20 amp wall outlet, that circuit has to have a 20 breaker. most houses use 15 and 20 amp breakers for most things. electric stoves, hot water heaters and dryers use 30 amp breakers. outside air conditioner pumps, electric furnaces and "hot tubs" generally use 60 amp breakers.

your 120volt air compressor should run on a standard 15 amp outlet. however, there are two measurements of electrical draw on electric motors - "startup" draw and "running" draw. your compressor probably draws 13-14 amps when it first starts up and then drops to 10-11 amps when it is running. the same thing happens with your refrigerator. this makes a difference if you have any other appliances hooked to that circuit. for example, if you have garage lights or any other outlet with something plugged into it wired to the same circuit where your compressor is, the other devices may be drawing 1,2,3, etc. amps and when you go to turn on your compressor, the "start-up" draw of 13-14 amps trips the breaker. try and find an outlet that you know has nothing else drawing from that circuit and plug your compressor into that. if it starts up without tripping the circuit, then the total amprege draw is probably the problem. i have a 120v compressor in my garage and it is plugged into a dedicated compressor only 15 amp outlet.

another possibility is that the breaker that is tripping could be weak. breakers do develop fatigue over time. you could also try replacing the subject breaker with a new one - but get someone to do that for you if you are not familiar with electrical work as you usually have to take the cover off of your electric box to change breakers. if you have a main shut-off breaker for the entire house, you could switch that to off and then all the electric to your box will be off and you could change the noted breaker.

one last thing to remember. there is more pressure - and more amprege required - when a compressor starts when there is high pressure air in the tank. so if you are turning on your compressor with 100 lbs. of air in the tank your motor is going to draw more amps than if the air tank is empty.

finally, you should also check for lose wires/bad connections on the motor. a loose connection will cause an arc or interfear with correct amp draw.


ps. i didn't see your comment about the 20 amp circuit ... my other comments might be helpful