What product do you recommend to flush the AC/Heating unit?

D

Dave S

Well-Known Member
TECHNICAL Contributor
Oct 3, 2006
6,014
Upstate South Carolina
Boat Info
Boatless
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Boatless
My AC/Heating unit is not performing up to par anymore and I think after nearly six years of almost constant use maybe it is time to flush the unit itself. My strainer is clean but I still suspect there is some build up and maybe some growth on the inside of the unit that is affecting how well it cools and heats. Also, how exactly do you go about flushing the unit?

Thanks.

Dave
 
Dave,

Home Depot sells a product in the paint department called Etch and Prep, by Clean-Strip......about $15/gal. It is phosphoric acid based solution ..........it takes me one gallon, reduced with another gallon of water, so one gallon will be adequate. Run the solution thru the system using the cooling pump then let it sit in the system about 5 minutes. Hook up a hose and flush it out then run for a couple of hours on regular lake/sea water.

DO not use muriatic acid because it can attack and weaken soldered joints in the a/c cooling coil.
 
Thanks for the information Frank.

Is flushing it with a hose necessary or will it get flushed out adequately just by running the pump after I get it hooked back up to the strainer and Sea Water pump? The only reason I ask Frank is because I will probably have to rig up something on the input line to attach a garden hose so it would simplify things if I didn't need to do that.

Dave
 
Dave,
I have a 340 DA and was experiencing what I considered to be less than par performance with my AC unit this past summer. I clean my strainer regularly each month and flush the lines with fresh water (from the dock) for about 10 to 15 minutes. I keep my unit on 24/7/365. I was experiencing what I considered to be an anemic water flow issue. Without good flow, doesn't have to be spraying feet away from boat, but needs to be a full flow out the exit port in order to have good heat exchange. Your unit should be working toward a 18-20 degree temperature air differential. You can measure it with an infrared heat sensor tool/device purchased from Sears or anywhere else.

To make a long story short what I found was the hoses from the seacock to the strainer and strainer bowl were clogged with barnacles and sea shells. Without good intake you won't have good exit flow. I removed the bowl and cleaned it (there is a drain plug on the lower section and flow should be good if plug is removed) and replaced all of the hoses to the strainer. I then filled the strainer bowl with MARIKATE SHIPSHAPE On & Off Hull/Bottom Cleaner ($12 from West Marine) and closed the cap. Make sure that you don't breathe the fumes or get this on your hands. I then turned on the AC unit until I just saw the first trace of water flow off the boat and immediately shut it off (takes an extra person to help with that part). Allow the cleaner and (now) seawater mixture to sit for about 10 minutes. Then turn on the AC unit and you should see any deposits exit with the flow. Hopefully this helps. It did for me.
 
Dave,

I like the hose hook up because the pressure is greater and it helps blow out anything the acid killed. The hook up is east......remove the ell at the sea strainer inlet side and replace it with a T, then hook the hose up to the extra opening. All the fittings are available at Lowes/HD.............
 
Bateau, just an FYI... ON/OFF's main ingredient is Hydrochloric Acid, A.K.A. Muriatic acid. It's great stuff, but Frank is right that it can dissolve solder so it would be best not to use it for this particular purpose.
 
If you want to be slightly friendly to the environment - try Triton Marine A/C flush. It is a synthetic version the acid and it works better (in my opinion) than most others I have tried. And it wont dissolve solder or gaskets etc.

Their hull cleaner works wonders as well and I got my 210 select back to "factory" new after having about 1 1/2 inch of growth with barnacles etc. all over my boat. First a waveblade to scrape of the worst - and then Triton Marine Hull cleaner to get all the barnacles bases off the hull.
 
Thanks everyone for your comments and recommendations. I guess the first thing I need to do is some plumbing work as Frank suggested. We don't have to deal with barnacles at our lake and the water flow out the Heat Pump looks as good today as when the boat was new. But I think (hoping) there must be some growth in the unit that is causing the cool down and heat up to be reduced. If that doesn't work then I will have to look elsewhere for the cause.

Am I correct in assuming that you hook up a piece of hose and a funnel to the T-Fitting then pour the solution into the funnel with the pump running?

Dave
 
Dave,

I put a bulkhead fitting in the bottom of a 5 gallon bucket and use a short length of garden hose with male and female ends on it to connect to the T I added. I set the bucket on the cockpit floor and let the acid feed directly from the bucket into the strainer. I don't like pouring acid into a funnel on a boat.
 
Thanks Frank. I have a winterizing kit that I used to use for my 240SD that is essentially what you described. I will use that for the acid.

Dave
 
I tried bleach one time in an attempt to clean ours. I poured it in straight and let it sit for an hour. I just reconnected the normal pump to rinse. When it came out the thru-hulls it was a nasty mix so it must have did something! I'm sure every water has its own scum which would require a certain chemical to clean. I'm sure Frank's idea would fit all!
 
I use barnacle buster. Pour it in strainer, let it sit overnight, and watch the stuff that spits out when you start the unit the next day. It's the best stud there it. If your units really bad do it a couple times or just add a bit more every 5 hours. I do gen and AC yearly now with it.
 
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