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Hello,

I am looking for advice on what to do about a 10 year old Fujitsu Halcyon ASU24RL that apparently has a coolant leak.

First some background info. I use the unit to cool a 400 ft2 one-story home office located in San Diego. When I first installed the unit, I had multiple computer servers and equipment that generated a lot of thermal heat. Ignoring heat absorbed from the outside, my computer equipment and lights generated 10,300 thermal BTUs per hour 24x7. In the past 10 years I updated/consolidated my computers, switched to LED lighting and as a result I decreased this heat load by 79% to 2,200 thermal BTUs / hour. I mention this to explain the reason why I selected this unit and for sizing in case I need to replace it. FYI I live just a few miles from the coast, so summer days are usually low 80s but can get as high as 90 degrees.

Last summer the unit worked fairly well, although I seem to recall the air did not seem as cold as usual. I was not in my office as much as usual for personal reasons. When I tried to use the unit for the first time this year a month ago, it would not turn on. The indicator lights flashed in a sequence that said low coolant level. Last week I had an HVAC guy come out and inspect it. He confirmed there is a coolant leak, and tried to locate it using an electronic Freon detector. He spent 30 minutes scanning the outside and inside units, but could not locate an obvious leak. I have read that finding leaks can be tricky and that it could be a relatively quick process or all day event depending on luck. He suspects my leak is either in the outside unit or the wall unit and not somewhere in the lines inside my walls.

He gave me three options. The first was to drain the unit of all coolant, then fill it with a full charge and hope the leak is a small one and that the unit will work for the summer or multiple years. Cost is roughly $300. Option 2 is to do a thorough search for the leak which would start outside by fully disassembling the outside unit, using more involved detection methods (possibly dye or pressurized nitrogen) and if that fails, opening up the wall unit and repeating work inside. He estimated it will be $1,000 - $1,500 to find the leak, fix it and then refill the unit with coolant. The third option would be to replace the exterior and interior units. He said he would pressure test the inside lines, but is fairly confident we could use the same lines. The cost for this would be $3,000 or $3,500 for a 1.5 ton Greer 16 SEER or 2.0 ton Greer 16 SEER unit. I was a bit surprised at the cost as I can buy the smaller unit retail from Home Depot for $1,300. I imagine he gets a contractor discount and the installation should be relatively simple since he will not be doing any demolition.

Option 1 is very appealing due to its cost. I am leaning towards it but want to know if I should ask him to use a product like "Easy Seal" by Nu-Calgon to try and seal any minor leaks. Is it OK to use a leak sealant in a mini split? Are there any risks?

If after Option 1 the unit does not work through the summer, am I better off replacing the unit then spending perhaps $1,500 to repair a 10 year old unit? If I do replace it, what size unit should I get? With my reduced heat load, can I get by with a 1 ton unit? As an example, Home Depot is selling a Greer TERRA12HP230V1A - described as an Ultra Efficient 12,000 BTU 1 Ton unit for $1,500 out the door. This unit as a SEER of 25 vs. 18 for my Fujitsu. Would that be big enough for my needs? An online calculator said I would save 28% energy with the higher SEER which would be $200 a year at our high electric rates.

Greatly appreciate any insights. Thanks!

Chip
 

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First I am not an AC pro, have been researching mini's a bit. Mini's seem to be the unwanted step child of the AC industry.

From my reading the older Mitsubishi's have a life expectancy of 15 to 20 years.

My first thought is did the tech check the system pressure before looking for a leak? Looking for a leak in an empty or almost empty system might be a waste of time. If he did not check pressure I would get a second opinion, which would be a good idea anyway.

I am with you on having the system recharged and seeing what happens as the best option at this time. Mini's are sensitive to the amount of refrigerant in them, you will have to watch the tech and make sure the system is evacuated and the proper amount of refrigerant is put in, Don't let them just add refrigerant, very important.

I could not put $1500 of my dollars in a 10 year old system, not everyone is like

Only my opinion and worth what you are paying for it.
 
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