Why Doesn’t My Mini-split Heat Pump / Air Conditioner Work?

I recently had an interesting question – a reader asked what could cause a Fujitsu mini-split air conditioner to cause the air to become *more* humid. In fact, they noted that the air became highly moisture laden and the house was just yucky humid.

I really scratched my head on this one because, from a physics standpoint, under “normal” conditions, this is impossible with a mini-split. Why? Because a mini-split system has an air handler unit in the house with the only connection to the outside (and outdoor humidity) is through a small hole in the wall where the electrical and refrigerant lines run. And yet it happened.

The questioner noted that multiple units were involved and that various parts of the electronics had been changed, and yet the problem persisted. He noted that he’d heard of a number of other people with the same problem. I admit, I was baffled!

Then it came to me. In fact, I had worked with an associate, helping them to track down this exact problem. While I can’t state with 100% certainty that the problems were the same, the symptoms are the same. In addition, I realized that my own home’s systems exhibited the same issues, but I automatically made the adjustments to make the systems work properly!

Here’s what’s going on…

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The Energy Geek Video 3: Ultra Efficient Heat Pump Review

I bumped this back up to top of the list since it’s one of the most popular posts I’ve ever done. I also just had the misfortune of losing ALL THREE indoor units during a recent storm and power surge that killed appliances all around my development. Argh! However, they’re up and running again, good as new.

I love these heat pumps! There’s one in the bedroom, one in the basement “party room” and one in the large, living room that’s full of windows – a space that has been uncomfortable for years.

After installing these systems, I don’t know how we dealt without them before. The summer comfort is waaay better than ever. And in our basement room, I turned off the main heating system and used the Fujitsu exclusively all winter.

Keep in mind that this is one special little unit. There are many mini-split systems on the market that look like this, but most of them are barely half as efficient as this one. They’re just not in the same league.

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