Mitsubishi Mini Split Hyper Heat Pump Loud Flushing Noise
I’m experiencing this problem that seems to be similar to an older post but the symptom is a little difference.
I’ve 3 outdoor units each served 2 to 3 indoor units. Whenever the temperature dropped to 37, the loud toilet flushing sound came out from the outdoor units. Before the flushing noise, some of the indoor units would also sound like they were sucking in a lot of air and 30 seconds later, a flushing noise also came out from the indoor units like they were releasing the air. About a minute later, the flap would come down and blow hot air like normal.
My installer came a few times, performed the pressure test, increased the length of some coils, add refrigerant, etc. But still couldn’t fix the problem. They just said everything was fine, it was just in defrost mode. When I said defrost wouldn’t occur every time the unit kicked in for a heating cycle (especially the outdoor temperature was just ~37), he started to use the term “preheat” instead of “defrost”.
I’m very disappointed with that because I spent a lot of money to get rid of my old and noisy steam boiler in Spring 2023 hoping to have a quiet and nice winter this year. But now figured out this monster even made more noise! I just can’t believe it’s normal as this heat pump should be capable to handle really low temperature! 37F is no way to be low temperature.
The installer said they talked to Mitsubishi tech support directly and they replied the noise was normal for each heating cycle. I’m curious to know the entire discussion between the two parties. Unfortunately I couldn’t reach the tech support directly.
Appreciate if anyone can advise on this 🙏
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