Reverse air not heating well - SailNet Community
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post #1 of 13 Old 03-13-2010 Thread Starter
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Reverse air not heating well

What would cause my reverse air air conditioner to not heat very well this weekend. It has always heated and cooled very well before.
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post #2 of 13 Old 03-13-2010
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Is it low on refrigerant? When was the last time you used it? How is the water flow through the heat exchanger?

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post #3 of 13 Old 03-13-2010
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Where are you located and how cold is the water?

Reverse-cycle heating relies on pulling heat from the water, so it is less effective as water temps drop.


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post #4 of 13 Old 03-13-2010
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I think SecondWind is on the right track, depending on where you are. The most likely issue is that the water you are floating in is too cold - less than about 40F will result in no heat. The next most likely thing is growth in the heat exchanger and cooling water lines, requiring an acid wash. A refrigerant leak is possible but less likely than the others if the original installation was decent.

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post #5 of 13 Old 03-14-2010 Thread Starter
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I'm on lake texoma and the water temp is in the high 40s. I've had the boat for two winters and it's always heated extreamly well. The last time I used was for cooling though and if I remember it may have not cooled quite as well either. The water flow is good. Maybe it just needs refrigerant. How do I do an acid wash? Is that something I can do or does it need to be someone specialized? We don't use it that much for heat but do use it when docked during the summer. So I would rather fix it now before it gets hot.
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post #6 of 13 Old 03-14-2010
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Is growth an issue on your boat bottom? If it is, as I suspect, then growth in the heat exchanger is more likely than low refrigerant (which is also possible). Flow can look good even if the heat exchanger isn't capable of enough heat transfer.

Acid washing your A/C heat exchanger is a very reasonable DIY job if you are handy. It does require working with very hazardous chemicals and could result in serious personal injury if mishandled.

I'll tell you what I do and you can decide if it is appropriate for you.

I have a small (spare) submersible bilge pump with a long power cord ending in a cigarette lighter/power plug. Put the pump in the bottom of a large bucket, like a 5 gallon mud bucket. Disconnect the A/C cooling water outlet from the thru-hull, and the A/C cooling water inlet from output of the circulating pump. Using additional hose as needed connect the bilge pump up so that fluid flow will run in reverse. Put enough water in the bucket to dilute muriatic acid available at most hardware stores. I use "Acid Magic" which includes other ingredients that reduce the risk of damage to metal parts in the A/C. Remember: "do as you oughta, add acid to watah." Pouring water into the acid will result in spatter and out-gassing. Try not to breath the fumes - they are very bad for you. Run the acid through the A/C for about 15 or 20 minutes. I then use baking soda to neutralize the acid. If you don't neutralize the acid it qualifies as hazardous material and there are disposal issues. When you are done, run the A/C circulation pump manually for a couple of hours to ensure any residual acid is washed out.

Alternatives: remove the A/C (easy if it is a single-frame unit) and take it to someone who can acid wash it for you, or even better remove it and boil it (which will require recharging the refrigerant). You can also have someone come to the boat and do it all for you.

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post #7 of 13 Old 03-14-2010
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Quote:
Put the pump in the bottom of a large bucket, like a 5 gallon mud bucket. Disconnect the A/C cooling water outlet from the thru-hull, and the A/C cooling water inlet from output of the circulating pump. Using additional hose as needed connect the bilge pump up so that fluid flow will run in reverse.
Excellent suggestion.... Good thinking!

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post #8 of 13 Old 03-14-2010
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Thanks.

I meant to also point out that once you have the spare bilge pump on board with a long power cord your days of pumping out the dinghy by hand are over! *grin*

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post #9 of 13 Old 03-14-2010
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One more simple thing to check is the compressor's air filter. If it's dirty it can reduce air flow and the AC units performance.
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post #10 of 13 Old 03-14-2010
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+1 to MJBrown. Agreed.

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