My Hitachi RAS09UH was protected by 15A circuit breaker since it was installed in March of 2006. Starting with March 19 2009, at totally random times the circuit breaker would pop, and the AC would become completely dead. Resetting the circuit breaker allows the AC to be restarted, but at totally random times it blows the breaker. Changed the 45MFD compressor run capacitor just today and the breaker popped after about 3 hours of operation. It is suspected to be a problem during the start-up of the compressor, but I had occasions where it popped the breaker after about 5 minutes of (what appeared to be) normal operation, and resumed uninterrupted operation for days thereafter. Suggestions?
Two things that you could check: 1) If you have access to an ampmeter, determine if the unit is drawing over over 14 or 15 amps, 2) replace the suspect circuit breaker in case it is beginning to go bad. Breakers only trip for overcurrent conditions or failure of the breaker itself. If it is pulling close to 15 amps, then it could heat up over time and trip.
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Many thanks for the recommendations.
Additional clarification:
This is a 9,000 BTU unit with a rated current of 8.5 A maximum.
According to the factory specs, the min. Ampacity [A] is 10A
Cooling Watts | Amps = 950 / 8
Heating Watts | Amps = 950 / 8
Max TD Fuse/Breaker [A] 20
Based on the above, I felt safe with a circuit breaker size of 15 A.
The choice of a 15A breaker was validated in my mind as correct by
the fact that the 15 A circuit breaker has not popped for the first
three years of the life of this product.
The power supply connection is 2x125VAC, fused by (2) 15 breakers,
one of which is an unused spare, held for future expansion.
Soon after the problem occurred a few times, I moved the AC supply
wire from the "popping" breaker to the heretofore unused (spare)
breaker.
The random popping still occurred.
Replaced the original (popping) 15A circuit breaker with a new 15A
circuit breaker and moved the A/C supply wire back to this (now brand
new) circuit breaker.
The random popping still occurred.
I realize that these units draw considerably more current during
start, so I will test with a clamp meter the actual current drawn
during start-up and during normal operation. This unit is running
at a 25-60% duty cycle to maintain the indoor temperature, meaning
that depending on the heat load, it runs a minimum of 3 to a maximum
of 8-10 minutes, then it rests as much as 20-30 minutes or as little
as 5 minutes before starting again.
As a last resort, I may even try a 20 A breaker, although as I said,
15A was perfectly fine for 3 years, and once the problem started,
two different (new) 15A breakers still tripped.
With many thanks,
Frank
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