Hitachi RAS09UH randomly pops 15A circuit breaker

Jul 09, 2009

- 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