[the_nite_owl]

Hi All,
I have a new air conditioner that is on it's own circuit.
The breaker is new and rated at 15 amps.
The air conditioner is supposed to use 15 amps at peak.
I believe the wire to the outlet is rated at 15 amp.

The air conditioner has it's own circuit breaker on the plug which has not tripped though it will if you use the test button.
The unit works fine, often for long periods, until it gets the room cool enough that it cycles to fan only and sometimes (not always) when it tries to kick the compressor back in it seems to pull so much current that it seems to suffer from a brown out for several seconds and if we do not kill the power on it the circuit breaker will trip downstairs.

I know these things can pull a much heavier load when starting up but thought that the peak draw of 15 amps meant it actually used less and only spiked to that amount on startup.

What is the best fix? Is there a slow trip circuit breaker that can handle a couple seconds of high draw when the compressor engages?
Do I need to replace the wiring and circuit breaker with 20 or 30 amp ratings and rely on the AC unit's own circuit breaker to handle problems?

Would you not set the dedicated breaker to the rating of the device using it?

Thanks.

[shunned]

Nowadays receptacles are on 20A circuits and lights on 15A circuits.
If this is a dedicated receptacle (orange) the wires should be 12G and the breaker 20A as long as this AC is 110V.
If it was mine I would pull new wire and replace the breaker.

[tkrussell]

The Locked rotor Amps, the load that is when a refrigeration motor starts, is very great when starting cold. It is even higher if the compressor has operated for a while. Has to do with the normal viscosity and the pressures of the refrigerant in the compressor that cause the rotor to get "locked".

You should find a warning in the instructions about not turning off and on quickly, to wait several minutes, before turning back on.

I realize this is happening by itself. The thermostat seems to be too sensitive or a too short a temp differential that is causing the compressor to start prematurely. You may have a new defective thermostat. You should make a claim under warranty now.

The nameplate should also state the maximum size circuit breaker. If for some reason this unit states running amps of no more than 12 (not a typo) amps, and a breaker larger than 15 amps, and your circuit is #14 wire, you may install that larger breaker on the #14, only if the outlet and circuit is only for the AC unit.

[the_nite_owl]

This AC unit was bought to replace another one exhibiting the same problem.
The old unit was about 10 years old and was 15000 BTU unit running off 120v.
I had thought the age of the unit and it's high output were factors in constant triggering of the circuit breaker so we bought a 12000 BTU to replace it and I put in a new circuit breaker and all new wire to give it a dedicated circuit with all new connections start to finish.

I am certain the manual said it required 15 amps but perhaps I misread it thinking 15amp was the peak.

If the running amps is 15 then I would need to replace the wire with #12 and put it on a 20 amp circuit? And if it is 12 amp I can leave the #14 wire and put in a 20 amp breaker as long as nothing else runs on the circuit?
And I am sure it is still advisable to have nothing else on the circuit even with #12 wire and 20 amp breaker.

The room this is in had at one time been the deck off the back of the house which had been fully enclosed to make into an extension of the house. The wiring is inadequate for it's use and outlets are needed in more locations so I have been planning an eventual rewire of the entire room onto several circuits anyway so when I begin finishing the basement I will probably run numerous new lines to the room so they are in place for an eventual rewire.
I am probably better off running new #12 wire for the AC outlet at the same time.

Thanks for the info. If you think a 20 amp breaker will be safe it would be a big help until new wire is run and connected.

[tkrussell]

#12 cable and 20 amp breaker is fine, and recommended, esp if you are not sure of the amp load of the unit. Find the nameplate on the unit and it will at least tell you the running load, it may tell you the locked rotor amps, (LRA), and it should tell you the minimum size wire and the maximum size breaker.

You will get a small clue from the plug. If the plug has two blades straight and parallel, it is a 15 amp plug, if one blade is horizontal and one vertical , it is a 20 amp plug. The amp rating of the plug should be stamped on it someplace.

Like I stated in my other post, circuits for air conditioning are done differently. The wire is sized according to the running amps, and the breaker is sized to the LRA. All, or most AC units usually state the max size breaker. If you see a rating for MCA, this is the Minimum Circuit Amps. Short explanation is for AC units, you may have small wire on a large breaker.

Find the nameplate on the unit, and get back with all the details. But the unit seems to be cycling too short, the compressor is coming back on too soon after is has reached temperature, and sounds like this is what is causing the CB to trip.