We installed a window air conditioner two days ago. Unit operated fine with no problems up until yesterday when it began tripping the circuit breaker. The unit is 120V and is the only thing plugged into the circuit (We have unplugged every other single item). The tripping of the circuit happens only during the hottest parts of the day. It is 115 in my area today. The unit works fine but it seems to be an issue on extremely hot days. Please advise.

I believe the un it is short cycling, causing the compressor to start too soon on the next cycle, after shutting down the previous time when the stat was satisfied.

Starting the compressor too soon after shutting down will usually cause the CB to trip. Can the stat be adjusted down a bit? Probably not much you can do to the stat. Be sure the unit has good airflow with no obstructions.

Have heard of several new units with stats too sensitive, not enough range, that causes this to happen.

Maybe this air conditioner is drawing too many amps? Is it an older model? How old is the breaker?

Tkrussel told you about a thing called short cycling, this can realybe a problem if your units amprege rating is very close to the 20 amps that you breaker is rated.
If this proves to be the problem you can have a service man install a time delay on your compressor that will stop the short cycling.

The house is 97 years old but all of the wiring was replaced in 1997 including a new fuse box and wiring to the box. The AC unit is brand new Samsung 14000 BTU purchased from Lowe's. It was suggested to run a heavy duty extension cord from the plug to the unit. We tried this today and all seems to be better... but this is just a temporary solution and one that I would not like to continue doing on a long term basis.

The last thing that should be done is to run an AC unit on an extension cord. Did they tell you how this would help? Read the instructions and I an sure they will tell you no extension cord. Many fires have started because of AC units on cords.

The other last thing that should be done is a clerk at Lowe's passing out any information of any trade, unless he has a license in his pocket.

The high amp draw heats up the added connections of the cord, and the cord adds voltage drop.

I am not entirely familiar with new AC units, my guess is that the thermostat is probably electronic and too sensitive. Not sure if you are given any means of adjusting.

A 14KBTU unit will draw about 12 amps at 120 volts. You state the circuit is now dedicated for the AC unit. The minimum size breaker you should have is 15, which may be too small to handle the short cycling.

Since the unit operates fine during the normal portion of the day, the breaker seems to be handling the load OK. What size breaker is on this circuit? And what size wire?

Is your unit #AW149CB? I found this unit at the Samsung website. This unit ,according to the manual, has a built in three minute delay to prevent short cycling, and to prevent the unit from starting prematurely, which would cause the CB to trip.


Have you reviewed the temp and humidity operating ranges of the unit, and does your situation fall with in those ranges?

The only other thing that can be done, if your circuit is a 15 amp CB with #14 wire, is either install a new 20 amp circuit with breaker and #12 wire, or change the 15 amp breaker with a 20 amp breaker, with restrictions.

You are allowed to run the unit on a 20 amp CB on the existing #14 wire, ONLY if the circuit is completely dedicated for the AC unit. Nothing else ,at all, can be on the circuit.

You may get advice from other electricians that this is wrong to do. Ask them to read and understand Article 440 of the National Electric Code, and he will discover that a larger breaker can protect a smaller wire for an AC unit.

Please take the unit off the extension cord. The instructions state that the unit should not be used with a cord, bring this to Lowe's attention, and ask them if they would cover the loss of your home in the event of a fire due to poor advice.

If there is something that needs more clarification, please get back with your questions.

Thanks for all of your help. According to the directions (which I guess I could have read before posting :-)), the unit is designed to operate in temperatures between 70-110 degrees. Anything higher and the unit will trigger an automatic protection feature which will cause it stop. I am not sure if this feature will trip the circuit breaker but we did not start having problems until the temperature reached its highest point. Unforturnately the unit is installed in a window which receives some direct sunlight in the later part of the day, which is probably causing it heat up even more. We used it all last night with out any problems but again the temperature had dropped significantly. Thank you for all of your recommendations... you were a great help.

Is it possible to install the unit in a north facing window? This will help with getting the unit out of direct sunlight.

Glad to be of help.