AC System Cleaning

[eze2bme]

I have just returned from the Hatteras Owner's School this week and one topic of discussion concerning the AC system pertained to cleaning the water circulation side of the system on a regular basis (every two years) to remove calcium and other deposits. I wanted to express their thoughts for all to consider and get any feedback.

I hope I got all this correct: Even though you may be getting what you perceive to be good water flow as evidenced by the water exiting the system overboard, there may be deposits inside the plumbing that can cause lower water flow than what is desirable which can lead to the pump overheating, higher electrical usage and possibly eventually causing the pump to fail. They recommended running a cleaning solution through the system in a closed loop for at least 30 minutes. This can be accomplished using a five gallon bucket with a suction hose hooked to the pump and a discharge hose hooked to the discharge side of your system. MAKE SURE TO CLOSE THE SEA COCK FIRST! Turn on the system to the pump or fan setting (not heating or cooling) and let it run for 30 minutes. Your cleaning water solution will get increasingly dirty. Afterwards the system needs to be flushed with vinegar water to neutralize it.

This is important in salt water and fresh water.

If I have any of this wrong please make corrections!!!

 

[MikeP]

Totally agree that it should be done occasionally. OTOH, I did mine last year and there was no difference in cooling that I could tell. Very little "stuff" came out of the pipes. As far as I know, it had not been done in at least 5-6 years and maybe much longer. So as far as doing it every 2 years, maybe it depends on the local water.

 

[Pascal]

"This can be accomplished using a five gallon bucket with a suction hose hooked to the pump and a discharge hose hooked to the discharge side of your system"

"Turn on the system to the pump or fan setting (not heating or cooling)"

well that's rarely going to work since it depends on where the pump is installed... remember that the AC pumps are NOT self priming and installed below the water line. in the typical install, it doens't leave you much room to put the bucket in a position where the pump will be able to prime.

also, in most systems (depending on the controls) turning it on to fan will not start the pump... it shoudl only come one when a compressor calls for flow

a much more practical solution is to get a small bilge pump and use that in the bucket as circulation pump.

what did they recommend as a cleaning solution? Ospho is pretty good, many folks use acid but that's a pain to dispose of and nasty to use.

Tehre is a FAQ written up by Genesis descripbing the procedure.

 

[ppat324]

"This can be accomplished using a five gallon bucket with a suction hose hooked to the pump and a discharge hose hooked to the discharge side of your system"

"Turn on the system to the pump or fan setting (not heating or cooling)"

well that's rarely going to work since it depends on where the pump is installed... remember that the AC pumps are NOT self priming and installed below the water line. in the typical install, it doens't leave you much room to put the bucket in a position where the pump will be able to prime.

also, in most systems (depending on the controls) turning it on to fan will not start the pump... it shoudl only come one when a compressor calls for flow

a much more practical solution is to get a small bilge pump and use that in the bucket as circulation pump.

what did they recommend as a cleaning solution? Ospho is pretty good, many folks use acid but that's a pain to dispose of and nasty to use.

Tehre is a FAQ written up by Genesis descripbing the procedure.

HUH????? ppat

 

[MikeP]

I did mine with a small bilge pump as Pascal describes and muriatic acid. If you do it with a bilge pump, be sure that the pump/bucket is above the compressors to ensure that the cleaner totally fills the tubing. I did each compressor separately with the bucket on the side deck and extension hoses running through the engine room air intake to the compressors.

 

[SKYCHENEY]

I am going to clean mine with the bilge pump method. You may not see any difference in flow or in the cooling but it was mentioned that you may see lower amp draw as the units will be more efficient after a good cleaning. I figure it can't hurt and I'll give it a try.

 

[Walter P]

I have had very good success using a closed loop setup and a material called TRAC Barnacle Buster. It is very effective and is absolutely safe to discharge overboard which is not recommended with any of the acids. The stuff gets really dirty after just a few minutes of circulation and I usually let it run for about an hour. After cleaning just reconnect the suction and return hoses and run your system. Depending on how dirty and whether it is run in salt water or fresh, you will note an improvement with lower power draw and better transfer of heat/cold which makes sense since any kind of crud build up in the system serves as an insulator and if it's constricted at all, the power draw is also higher before cleaning. Try it, you'll like it......

Walt

P.S. I used a clean 30 gallon trash can between the engines to do mine. I also do the engines every few years...no more overheating issues.

 

[REBrueckner]

"You may not see any difference in flow or in the cooling but it was mentioned that you may see lower amp draw as the units will be more efficient after a good cleaning. I figure it can't hurt and I'll give it a try."

That's a great solution for the guy doing the cleaning work for pay; much less so for the guy paying the bill.

It's also just about impossible...the unit will perhaps run longer if the heat transfer is impeded, but the compressor just keeps running and if the refrigerant is a tad warmer I don't think the compressor runs any 'harder'...just longer. So it's a lot more likely you'll save some POWER because the unit may run for less time.

Likely it won't hurt anything, but cleaning with harsh acids every two years without any cooling issues is unwise and unnecessary:

I'd be a LOT more inclined to use an infrared temperature sensor and monitor the water temperature in and out. Record your results after some fixed operating time, say 15 minutes, and ambient air temperature at start. That way you can compare year over year, perhaps best to do the same month each year, and if the circulating water temperature difference remains the same, why subject the copper cooling system to harsh cleaners and waste your time.

Don't fix it if it ain't broke.

 

[MikeP]

"I'd be a LOT more inclined to use an infrared temperature sensor and monitor the water temperature in and out."

That's WAY too scientific. We don't do "scientific" here, we do "I heard somewhere that some guy said..."

 

[krush]

It's also just about impossible...the unit will perhaps run longer if the heat transfer is impeded, but the compressor just keeps running and if the refrigerant is a tad warmer I don't think the compressor runs any 'harder'...just longer. So it's a lot more likely you'll save some POWER because the unit may run for less time.

Lowering head (high side) pressure results in lower amps from the compressor. This pressure is lowered by better cooling on the heat exchanger--meaning if you reducing the fouling on the condenser and allow better heat transfer, the compressor will "work less" and draw less amps, which reduces energy consumption.

Here's some technical talk about it, but it's beyond most here: http://www.hvacfun.com/a-understanding-fund-of-head-press-control.htm

 

[REBrueckner]

Good to know.....AND makes sense....


"...we do "I heard somewhere that some guy said.."

Love it!!!!!!!!!!!!!!

But that can be good as well!!!!

 

[spcoolin]

"You may not see any difference in flow or in the cooling but it was mentioned that you may see lower amp draw as the units will be more efficient after a good cleaning. I figure it can't hurt and I'll give it a try."

That's a great solution for the guy doing the cleaning work for pay; much less so for the guy paying the bill.

It's also just about impossible...the unit will perhaps run longer if the heat transfer is impeded, but the compressor just keeps running and if the refrigerant is a tad warmer I don't think the compressor runs any 'harder'...just longer. So it's a lot more likely you'll save some POWER because the unit may run for less time.

Likely it won't hurt anything, but cleaning with harsh acids every two years without any cooling issues is unwise and unnecessary:

I'd be a LOT more inclined to use an infrared temperature sensor and monitor the water temperature in and out. Record your results after some fixed operating time, say 15 minutes, and ambient air temperature at start. That way you can compare year over year, perhaps best to do the same month each year, and if the circulating water temperature difference remains the same, why subject the copper cooling system to harsh cleaners and waste your time.

Don't fix it if it ain't broke.

Sorry REBueckner...Yes I am a service guy & have been for well over 20 years...You are about as far off base on this one as anyone can be...

Heat transfer IS what it is all about...Scale build up is a fact, and does act like an insulating blanket preventing efficient transfer (like a dirty radiator in your car)

Poor heat transfer causes high operating temp & thus pressures...The compressor has to pump against that higher than nominal pressure and thus works harder & draws more amperage doing so...

It can mean the difference of two systems operating on one 30 amp shore line as installed...Or Not...
Many Hatteras models were built with two systems on one 30 amp 115 volt shore line...Brand new that configuration was within an amp or two of the 30 amp limit...Dirty it up the least bit and you are over that limit.

In this case...If it ain't broke...It will if you don't maintain it.

Steve~

 

[GJH]

The beauty of Roger's system used at Jarrett Bay is that runs through the whole system from thru hull to thru hull. I got a ton of crud out after 2 1/2 years. It is not THAT aggressive though; it gets barnacles and such out, but my strainer glass still needs cleaning to get the Neuse River scum off it. I think the concern of it somehow, in a way undefined, attacks the system components, is a non-issue. The water flow and efficiency is noticeably better; water flow, not water temperature differential (which is a by-product as Steve says above), is the measurable here.

 

[Paul45c]

Fwiw, I flush mine about every 7 or 8 mos. Down here in sunny so. Florida, and I go mostly by the sound of it...the coolant pump and compressors literally sound different bore and after flushing.

I use Karl's phosphoric acid mix slightly more diluted and let it run for an hour or so. Works great and it's pretty mild.

 

[MicroKap]

I just want to make sure I'm correct. If you start at the thru hull and recapture at the discharge you would do all systems at once if all systems are turned on. I have 5 systems. Or, do you only turn on one system at a time without disconnecting any of the plumbing from the manifold. The picture of my systems is below. My water pump resides on the left side, with water coming through a strainer.

 

[REBrueckner]

"Poor heat transfer causes high operating temp & thus pressures..."

Agreed, I already acknowledged that. Do not want to accidentally mislead anyone....always something more to learn....


When I bought my YF, I flushed the a/c raw water lines...and got almost nothing...barely discolored water for a moment....that's in salt water in the LI sound area and I am POSTIVE the prior owner did nothing for the prior ten years...so I guess crud accumulation varies widely by local water conditions.

After my main engines were overhauled and cleaned at my purchase. I flushed the raw water cooling using the approach favored here...it was after about 7 or 8 years after overhaul, maybe 1,000 operating hours....it was hardly worth it.....saw very little discoloration and operating temps did not change....

So wasting time and effort with alternate year a/c cleaning in my area would be a waste of time...time far better spent with wine,women,and song....


In contrast, however, I had to clean barnacles off intakes and especially toilet discharges annually in those same waters.....they really grow FAST in LI waters....So getting your marina/yard to paint intake hull strainers and up inside discharge thru hulls is a must in our area. For the last several hauls and bottom painting of my Hatt I slept aboard the last day before launch...and inspected every discharge before launch .....and had to repeatedly nag the yard boss to paint up inside....

 

[REBrueckner]

"If you start at the thru hull and recapture at the discharge you would do all systems at once if all systems are turned on. .."


You need to flush all your heat exchangers.....normally one in each compressor unit .....from your photo it looks like you have one (painted gray) water circulating pump(??)...so that runs with any one system turned on (??)...then that's all you need to circulate cleaner through all 5 of your a/c compressor units.

You do not want to run in heat or cool mode since that will heat the flush liquid and probably strain your compressors as explained in earlier posts above....

 

[Pascal]

I just want to make sure I'm correct. If you start at the thru hull and recapture at the discharge you would do all systems at once if all systems are turned on. I have 5 systems. Or, do you only turn on one system at a time without disconnecting any of the plumbing from the manifold. The picture of my systems is below. My water pump resides on the left side, with water coming through a strainer.

you dont want / need to turn the systems on, you just want to run the pump. if you were to run the system the cleaning solution would quickly get very hot since it's close circuit.

you would need to disconnect the pump and power it manually, bypassing the relays.

i still don't see how you get the AC pump to prime out of a bucket, unless you have a valve at the bottom of the bucket to gravity feed the pump...

 

[MicroKap]

That's exactly what I have, a bucket with a faucet near the bottom. I also use it in the winterizing process. I just need to figure out how to turn on the saltwater pump to flush the entire system and then have the last discharge hose go back into the bucket.

 

[krush]

i still don't see how you get the AC pump to prime out of a bucket, unless you have a valve at the bottom of the bucket to gravity feed the pump...

Thru simple physics. Just get the air out of the suction line. Surely you've siphoned gas from peugeot scooter before