I have an 18,000 BTU A/C unit that blew a compressor last year. Perfect for a small project. I however could not find a professional to help me out, so maybe it's DIYable. I know just about enough about this to know I'm no match for a professional.

I thought it would be awesome to heat the pool and cool the house at the same time. The pool's a 24 foot above ground pool and has no heating right now, it averages about 70 degrees. Bonus is that it could act almost like a split system - the water could be piped right up to the unit rather than having the fan hanging off the back.


Condenser: I've sourced two American-made water heat exchange manufacturers and spoken to one of them. I really like the Aqua Systems model, but the smallest is rated at 2 tons - that's apparently 24,000 BTU. A very friendly guy there referred me to Edward's Coils - but they don't seem to have much data online. If I can't use the Aqua Systems model for technical reasons, I'll get in touch with Edward's coils and see what they have to offer. My question here is will the 2 ton unit overload the rest of the compressor, and why?

Compressor: The compressor is dead in the unit. It seems to be a sealed unit, I'm not sure about repairing it. If I was to replace it, is there any reason I should replace it with the exact same part? Is there a different compressor type that would better serve this purpose?


I'm going to have to find somewhere to evacuate the refrigerant in here. Any suggestions?

I'm good at soldering, however I've never soldered on an A/C unit before. Is there anything chemically different? I know coolant in automotive systems tends to seep into the metal and requires extra cleaning, I'm not sure if there's anything of that nature here.

If the condenser I remove has different size tubing than the new water cooled compressor, would an adapter suffice?

Any suggestions on where I can get it charged up after it's assembled? How would one calculate the refrigerant requirements?

  • So kinda like a geo-thermal system but using water from the pool instead of water passing through pipes in the ground?
    – lsiunsuex
    Commented May 23, 2013 at 16:21
  • That's pretty much the idea! Toronto does it large-scale with Lake Ontario - that's where the idea came from.
    – kavisiegel
    Commented May 23, 2013 at 16:29
  • 1
    You won't be able to replace the compressor. It takes tools and skills that are not available to amateurs. For example, you will need a specialized vacuum pump and a tank of refrigerant. This will not be easy or cheap. And if you do get them, the cost of a minor screw-up is a blown compressor and possibly contaminated coils and lines.
    – longneck
    Commented May 23, 2013 at 17:22
  • Fair enough, I'll have to find a professional to take care of that part. So far nobody wants to touch a window unit. I still need to figure out what parts to order though.
    – kavisiegel
    Commented May 24, 2013 at 12:08
  • 1
    Doing all this work with a window unit is crazy. At least upgrade to a mini-split and then you have an external condenser to work with. Plus a quieter interior. Commented May 24, 2013 at 13:03

2 Answers 2


There is no Yes or No to this question.

Chlorine & Copper

You will have to keep your chlorine and acidity levels in constant harmony, otherwise the acidity will corrode and pit your copper tubing. Using aluminum would be exponentially worse. It the cooler your pool water gets, the worse effects it would also have on the copper. You can find good information from the EPA.


A BTU is a British Thermal Unit. It takes one BTU to increase the temperature of one pound of water by one degree Farenheit. The average swimming pool is 20' x 30' x 5'. That would mean that the average swimming pool is about 22,500 gallons of water. Since one gallon of water weighs 8.34 lbs., the water in an average sized pool would weigh 187,650.

That means it would take 187,650 BTU's to increase that pool temperature by one degree. Since you would only have about 10% of that amount of BTU's required - it is very likely that the pool would simply absorb and disperse the heat transferred from your residence and never actually raise the temperature of the pool. Gullberg & Jansson has some great information on their website about heating pools.

Refrigerant and Line Set

In general it would take about 0.6 oz of refrigerant for each foot of copper tubing above 15'. Different manufacturers have different specifications of course. Considering it is a window unit, it would already have less refrigerant than say, a mini split unit.

The average 1.5 ton, or 18,000 BTU, mini split unit take about 3-4 lbs. of refrigerant and usually have about 15' of line set available 'in the box.' Depending on how long your copper tubing would be, you could be seeing so much heat loss just within the copper tubing itself, it would never "make it" to the pool. Plus, all of the possible extra refrigerant would be so hard on a compressor that small, compressor failure would always be right around the corner. Some good information can be found at ACHR News.

Legal Activity

In order to 'work' with Refrigerant, in fact, even buy (most) of it, you have to be EPA Section 608 Certified. There are 4 types of certification. There is Type I, Type II, Type III, and Universal. There is also EPA Section 609, but that is for motor vehicles. Without certification, you run the risk of EPA prosecution. And before you think that you will never get caught, there is a reward for turning people in. Information can be found at the EPA website.

Tools You Need

  • Recovery Machine
  • Recovery Tank
  • Vacuum Pump
  • Manifold Gauges
  • Low-Loss Fittings
  • MAPP or Oxy/Acetylene Torch Kit
  • Pipe Cutter
  • Pipe Reamer
  • Sand Paper/Emery Cloth
  • Silver or Silver Phosphate Brazing Rods
  • General Mechanics Tools
  • Possible a Bucket of Ice and/or Bucket of Warm Water
  • Various Other Tools Depending on the Task at Hand

As you can see, there is a lot of specific tools and machines that you need to perform the job, not only legally, but safely. They are also very expensive to the average person. It is not uncommon for a vacuum pump to cost between $150 - $500. You can double and triple that cost for a Recovery Machine. There is a reason that most technicians work for a company that provides all of the tools required. It is hard to start off in the industry self-employed when you require certifications and tools that all cost money.


I would find a local HVAC/R Technician and run the idea across him. Ask him to come out and see what the job would entail. Ask him for advice. Ask him for a material cost and/or a list of what it would take to get the job done. Remember, this is only estimate stuff - because he may just tell you it isn't worth it, isn't possible with the equipment provided, or would be much more hassle than the intended benefit.

You could hire me to do it! But that would cost you a plane ticket, a case of beer, and a good home cooked meal before I even consider it.

About Myself

I am a...

  • Section 608 Universal HVAC Technician
  • Section 609 MVAC Technician
  • Certified Commercial Mold Inspector
  • Certified Indoor Air Quality Technician
  • Certified Green HVAC/R Technician
  • CO2 Refrigerant Safe Handling Certified
  • R-410A Refrigerant Safe Handling Certified
  • Certified Home Inspector
  • Member of American Society of Heating, Refrigeration and Air Conditioning Engineers
  • Associate of Institute of Refrigeration
  • Member of International Association of Certified Home Inspectors
  • Member of International Association of Certified Indoor Air Consultants

I'll ask my dad about this for the proper professional opinion, but after working with him for a few years or so, I can already tell you that you don't have the required tools or EPA license to work with refrigerant.

Also the window unit isn't designed to handle a line-set even 1/4 that long. In general a window unit is much too small to handle such a job, and as such there are systems designed to heat pools. As far as no-one touching the unit, it's because they really aren't designed to be fixable. The ones I've seen have no service taps or any way really to replace parts.

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