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Old 02-02-2007, 08:22   #1
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Flushing AC coils

I would like to hear from those that like me live in warm water areas where water conditions lend to fouling in the exchange coils of their marine AC systems. I know of people in my area that 2-3 times a summer run freshwater thru the system to flush sedement and "crud" from the system. I found some information on the web that suggests a 5% muratic acid flush to and clean the coils. What type of fittings or adapter is suggested? Should this be treated in the same manner that winterizing is done? I hope this post is some help to all.

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Old 02-02-2007, 13:39   #2

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I'd check with the makers to find out what your coils are made from, and what's compatible with it, so you clean the coils without eating away metal.

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Old 02-02-2007, 13:55   #3
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I'm certainly no expert, but...

I use a vinegar.

Whenever the a/c performance starts to suffer...

Turn off the a/c unit at the breaker, disconnect inlet & discharge hoses, place a spare a/c circulation pump in a bucket, run a hose from the pump to the inlet and another hose from the outlet and back into the bucket. Secure the loose end of the return hose!

Pour a gallon of vinegar into the bucket, add enough hot water to submerge pump, turn pump on and circulate vinegar for 15 ~ 30 minutes.

Reverse order upon completion.

OR - pay the a/c guys $150 to come and do the same procedure.

For some reason - the fridge condenser rarely needs cleaning.

Stay cool,

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Old 02-02-2007, 18:29   #4
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I use a vinegar.
Sounds like a better route. This year we had jelly fish so thick you could walk across the water. Did a lot of back flushing in both directions with a hose and city water connection. My problem was at the through hull not the coils. You really don't need to be using anything stronger than vinegar.

Muratic acid might be better for engine heat exchangers but not for light weight A/C coils. You need to be gentle on the chemicals.
Paul Blais
s/v Bright Eyes Gozzard 36
37 15.7 N 76 28.9 W
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Old 03-02-2007, 02:48   #5
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Kirk (Gallivanters) describes the generally accepted method of cleaning Condensers & Heat Exchangers.
I might add that a “spare AC pump” isn’t necessary. Since most Air-Conditioners need on the order of 200GPM of cooling water per Ton (12,000BTUH) of capacity, a cheap bilge pump (500GPH) could do the job.

Marine air conditioner raw water systems are typically manufactured from copper alloys, and lead/tin or silver solder. These materials are not generally harmed by proper cleaning with appropriate strength acid/water solutions, for limited amounts of time. Many Marine Air-Condittioner manufacturers sell cleaning solutions which are appropriate for their particular systems, and provide recommendations for using their cleaning agents, which are often acid/water solutions. If you have concerns about proceeding on your own, I suggest contacting the system manufacturer for guidance regarding your particular model air-conditioner.

* I believe that Cruise-Air (Dometic) recommends a 5% Muriatic or Hydrochloric acid/water cleaning solution, followed by a freshwater flush.

If the Heat Exchanger contains Aluminum, it would likely be severely damaged by using ANY kind of acid-based cleaning solution.
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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