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Old 08-07-2012, 01:04 PM   #1
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Cleaning AC Condenser Coils

Hello all, I am trying to get my front 16000 unit, self contained, to flow water overboard like the rear 16,000 btu split unit. This weekend the Admiral and I flushed every hose and fitting in both systems. This has the rear flowing better than ever, but the front was not really improved. I reverse flowed both systems using our "more than necessary" dock water pressure, and after reversing back I can get the front unit to shoot water out correctly. If I push the pump water back through it is not any better. I have one pump feeding both units, and even if I block the flow to the rear unit the flow does not improve. I'm convinced I have scale build up. A couple of weeks ago I ran a mild acid solution through both for about 30 minutes, using a 5 gallon bucket and a small sump pump I have. Is it possible I am flowing the solution too fast? Not long enough? Not strong enough? Thanks in advance.
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Old 08-07-2012, 06:50 PM   #2
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If the unit flows well with tap water you need to look at the line from the sea water pump to the unit to see if there is a blockage in it. that is if you used tap water at the unit and not at the pump. Have you checked the impeller?
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Old 08-07-2012, 08:14 PM   #3
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Is the front unit higher than the rear? The head affects the water flow.
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Old 08-07-2012, 09:59 PM   #4
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Is the front unit higher than the rear? The head affects the water flow.
Good question. Actually the rear exits about a foot higher than the front.
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Old 08-08-2012, 07:34 PM   #5
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Muratic acid concentration

Let me throw this out there. When cleaning the coils, what percentage is suggested, how long to run it and what style pump do you suggest?
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Old 08-09-2012, 07:34 AM   #6
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I too think you have a head (pressure that is !) problem. The exit point being higher doesn't matter. What counts is the length of piping from pump to unit and the height of the AC unit above the pump. Even small differences in these parameters between your two units can make a difference. I have a single pump providing raw water to 4 AC units: 2 are 16kBTU in the saloon; one 12kBTU serving mid- & v-berth cabins; and a 6kBTU serving the aft cabin. I installed shut-off valves in the lines to the two cabin units to direct the whole raw water flow to the saloon units and still found a big difference in the raw water flow to each....due to total head differences alone. The marine air pro's recommend using two water pumps instead of manifolding to 2+ units OR a much bigger raw water pump (the former approach can be plumbed to provide pump redundancy).


To answer your acid dilution question (finally): the correct de-scaling ratio is 1 part acid (assuming pool acid here) to 3 parts water. Rather than running this through your whole ac plumbing system, just disconnect the Inlet and Outlet spigots on the unit itself and fit them (use hose clamps and do it securely) with clear acid-resistant pvc tubing of roughly equal length and long enough that you can work comfortably a little away from the unit. Tie the tubing from the Out spigot to something so that it stays vertical. Use a funnel to pour the 1:3 diluted acid (you only need about 300ml....1/3 of a quart) into the tubing attached to the IN spigot. Pour slowly, watching for the acid mixture to appear in the tube from the OUT spigot that you tied up vertically: you now have the unit's coils filled with the diluted acid. Leave the acid in the unit for 20 minutes: you should see flecks of algae and scale appear in the clear tubing. You can un-tie the tubing attached to the OUT spigot and if you are lucky, you will be able to poke it well down the still-detached permanent plumbed discharge line...which will cause the acid mix to drain from the unit and flush out the discharge line on its way out of the boat. If you think you have a serious scale problem (you might if you haven't acid-rinsed annually and you are in salt water) then repeat this procedure but leave the acid in the unit for 4 hours. YOu will have a spic-&-span clean unit now and if you still have a raw water flow problem, a 2nd pump or a bigger pump is the only solution. Good luck...keep us posted on progress !
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Old 08-09-2012, 08:13 AM   #7
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I have seen muriatic (pool) acid used to clean heat exchangers, a/c units etc. This has always worried me because these things are often made of copper/brass with soldered joints and muriatic acid eats the zinc out of those materials. I use RydLyme which can be pumped/poured into an a/c system and left to do its work without causing damage. It is odorless, doesn't produce fumes, doesn't burn your skin or clothes and can be re-used. With a/c units costing in the $1,000's, RydLyme at around $20/gal seems like a fair investment.

No affiliation etc, just a satisfied user. BTW, RydLyme also cleans the inside of Perko strainer cylinders without turning them cloudy.
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Old 08-09-2012, 12:02 PM   #8
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Quote:
Originally Posted by Aquabelle View Post
I too think you have a head (pressure that is !) problem. The exit point being higher doesn't matter. What counts is the length of piping from pump to unit and the height of the AC unit above the pump. Even small differences in these parameters between your two units can make a difference. I have a single pump providing raw water to 4 AC units: 2 are 16kBTU in the saloon; one 12kBTU serving mid- & v-berth cabins; and a 6kBTU serving the aft cabin. I installed shut-off valves in the lines to the two cabin units to direct the whole raw water flow to the saloon units and still found a big difference in the raw water flow to each....due to total head differences alone. The marine air pro's recommend using two water pumps instead of manifolding to 2+ units OR a much bigger raw water pump (the former approach can be plumbed to provide pump redundancy).


To answer your acid dilution question (finally): the correct de-scaling ratio is 1 part acid (assuming pool acid here) to 3 parts water. Rather than running this through your whole ac plumbing system, just disconnect the Inlet and Outlet spigots on the unit itself and fit them (use hose clamps and do it securely) with clear acid-resistant pvc tubing of roughly equal length and long enough that you can work comfortably a little away from the unit. Tie the tubing from the Out spigot to something so that it stays vertical. Use a funnel to pour the 1:3 diluted acid (you only need about 300ml....1/3 of a quart) into the tubing attached to the IN spigot. Pour slowly, watching for the acid mixture to appear in the tube from the OUT spigot that you tied up vertically: you now have the unit's coils filled with the diluted acid. Leave the acid in the unit for 20 minutes: you should see flecks of algae and scale appear in the clear tubing. You can un-tie the tubing attached to the OUT spigot and if you are lucky, you will be able to poke it well down the still-detached permanent plumbed discharge line...which will cause the acid mix to drain from the unit and flush out the discharge line on its way out of the boat. If you think you have a serious scale problem (you might if you haven't acid-rinsed annually and you are in salt water) then repeat this procedure but leave the acid in the unit for 4 hours. YOu will have a spic-&-span clean unit now and if you still have a raw water flow problem, a 2nd pump or a bigger pump is the only solution. Good luck...keep us posted on progress !
Great info. Thanks!
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Old 08-09-2012, 12:48 PM   #9
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I'm no expert, but a couple of thoughts anyway.

1. The amount of water flow through the coil makes a really big difference in how well the unit cools. I have a pump for each of my units, it helps a lot. It is also nice to know that if a pump shuts down (loses it's prime etc) taht I am only risking damage to one unit, not both. I know today's A/C units have high pressure/high temp shut down switchs that SHOULD save the compressor if water flow stops but still....

2. Not the most enviromental thing to do, so take it FWIIW, but I know some people who drop 3 or 4 chlorine tabs into their stariners periodically to cut down growth. I have heard it works well in our high temp, high growth water here in N. Florida, so it will likely do the same in LA.

3. My A/C guy doesn't like to use acid, he says it scores the inside of the coils which creates a surface that is easier for marine growth to attach to.
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Old 08-09-2012, 02:06 PM   #10
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Hopefully it was obvious anyway, but just in case.....when you have finished with the diluted acid de-scale, you should immediately re-connect your raw water fittings and run the unit for a while to remove all acid: you are not winterizing here !

Rydlyme is a very good alternative to acid and for the reasons given poster #7, may be preferred. Use it in the same fashion I have described for the dilute acid solution.

But stay away from chlorine in the air-con system: it WILL eat at the solder joints inside ac condensor tubing and anyway, deals more with algae than mineral scale deposits.
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Old 08-09-2012, 04:03 PM   #11
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Rather than using an acid mix, we have had very good results with CLR found at any grocery. Place the intake and discharge in a bucket of the CLR. Let it circulate for about 20 minutes. Hook it all back up and you should be good to go. You may see a lot of debris turn up in the bucket. A piece of nylon over the intake hose will keep the debris from getting sucked back in. Be sure and only run the pump and not the AC unit. Chuck
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Old 08-09-2012, 05:15 PM   #12
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But stay away from chlorine in the air-con system: it WILL eat at the solder joints inside ac condensor tubing ...
Yeah, it might reduce the lifetime by as much as a week or two over thirty years.

Those condensers are not lead soldered and even if they were the corrosion of a few minutes in bleach 10 times stronger than you are able to buy would scarcely be measurable. The copper in your condenser sees more chlorides from seawater than chlorine bleach.
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Old 08-10-2012, 08:55 AM   #13
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The owners manual for our Marine Air AC recommends annual maintenance of coils with a 5% Muriac Acid solution for 15 or 20 minutes.
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Old 08-15-2012, 11:38 PM   #14
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I have had excellent results with this stuff in many different kinds of circulating water systems................Arctic Traveller

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Old 08-23-2012, 08:54 AM   #15
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I have had excellent results with this stuff in many different kinds of circulating water systems................Arctic Traveller

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I've heard good things about that product and that's what I will use when the time comes.
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