Marine Air Systems A/C

[Doorpro]

Hello all,

about 5 years ago I bought two Marine Air Systems VTD12KZ-410A units to replace two rusted out units and one of them has worked flawlessly since day one. The other has been working off and on for the past couple of years and I have checked almost everything that I know to check.
Firstly I have checked the water pump and it works fine and feeds the unit. It is a huge pump feeding five units through a manifold and when I turn one or all five A/C units on the pump starts and strong flow of water is evident and the other four units run flawlessly so I'm thinking that the pump and plumbing is fine. I have also had the diver check the through hull and I have checked the strainer and they are both clear and clean.
I should say that the unit that I am having trouble with will run for a couple of days with only one HPF fault early on when starting the unit and then will run great but then on most days like today I turned the unit on and it starts up for a second or two and then shuts down with the HPF fault showing and today the unit has not kicked back in after a minute or two like it will sometimes do. I have noticed that the moment the HPF fault is registered the water pump turns off however the fan will continue to blow.
I think that I have mentioned most things going on here and I hope that someone can give me some insight on where the look next. I have had the cover off of the controller to see if there was a loose wire to the pump but all seems fine in there although the control unit may be bad but I have no way to test it unless I remove the one that I know is working and try that on the malfunctioning unit.
I have read a few threads here and one mentioned running city water through the condenser and I was wondering if I should try that and if I should is it as easy as removing the hose from the pump and attaching a hose to run fresh water through the unit?
Any help will be gratefully appreciated and I thank everyone in advance for looking at this thread.

regards,
Doug.

[DeepFrz]

Check the cooling water flow to the unit that doesn't work. Try a dock hose to the input of that unit and see if it blows out a bunch of crap. Also look at current thread on this subject.
Need Advice: CruisAir Water Pump Troubleshooting - No Water Coming Out - Page 2 - Cruisers & Sailing Forums

[Doorpro]

Hi,

I will do that and I thank you for suggesting it however when this unit works it does have a strong flow of water from the pump and as stated in my thread this pump runs four other A/C units without issue.

regards,
Doug.

[DeepFrz]

Right, I wasn't thinking of the pump but you may have some restriction in the coolant passages. Could also be something else as well. I'm certainly no AC guru but it seems that many of the problems we see with AC are due to scale buildup, mud plugging the cooling system, wasps nest in the cooling system, etc.

[sailjumanji]

Ok, I had the same issue. Have a Dometic 8k btu unit and an oversized March pump. It is about five years old, but not many hours and was getting the hpf error and shutting down. I talked to a couple of techs and they said what is probably happening is that the cooling coils either have silt in them or a buildup in the coils. That would reduce the heat transfer and trigger the hpf. First recommendation was to remove the hoses in and out, hookup a garden hose to it, and see if any silt could be washed out with the hose. That didn't yield much, and still got the alarm. Next thing recommended and tried was Barnacle Buster solution circulated into the coils. I mixed some up in a bucket and used a plunger pump to pull it into the coil. Directions say let sit for 12 hrs, or either circulate. I did not have a pump, so let sit. After about three hours I pumped new solution thru which kicked out the old stuff. Dark black fluid came out with some solids. Let it sit the balance of the 12 hrs, then circulated new solution thru (I had extra in the bucket, and was just pulling that thru). What came out looked like clean solution, so most of the dissolve work was done in the first few hours. Hooked everything back up and ran it. Cooled much faster than before, plus did not hpf alarm. However I only ran it a couple of hours. But it seemed to be much more efficient so I think I have it fixed.

[Doorpro]

Sail,

a very promising prospect. I will look into a solution to clean out the coils and i'm thinking that it might be prudent to either rent or buy a pump and let it run as you suggest.
Will let you know.

regards,
Doug.

[DeepFrz]

A small bilge pump is all you need to circulate the Barnacle Buster or RydLyme. Follow cautions.

[Doorpro]

Also, when I plumbed the unit It wasn't clear If there was a way the water should flow through the unit. Is It possible that I have it plumbed in reverse and If so would that make a difference?

[transmitterdan]

Is this a self contained unit or are the condenser unit and evaporator in different locations?

HPF has 2 predominant causes. First is insufficient cooling and this is most common by far. Flushing the system with a mild acid (even white vinegar) can help. Direction of water flow isn't too important.

Second issue is the water temp itself. What is the water temperature in your location. I have had the experience of high water temp causing HPF. Had to remove some refrigerant to resolve. This requires a professional these days.

[mannix2]

Try replacing the HPF circuit breaker. I just went through the same issues and oddly enough that resolved the problem. The HPF breaker tripped randomly and repeatedly. One day I pushed the "Push to Reset" breaker and it did not spring back out. After replacing the breaker two months ago, absolutely no problems. Inexpensive solution if works for you. Circuit breaker cost about $10 from West Marine, or $6 from Amazon.

[Clamdigger62]

Doorpro, If I read your post correctly you are getting the HPF shortly after start up (couple of seconds). If this is the case it is not water flow causing the problem. The unit would run for a couple of minutes on start uo with no water before throwing a HPF code. I think your unit is equipped with a low and high pressure switch. At start up the low pressure side gets pulled way down and if the freon is low it will get pulled down low enough to trip the low pressure switch, throwing a HPF, The HPF means High Pressure Fault but is a misnomer, it covers many problems including low pressure.

As far as the pump running, it is programmed to only run when a compressor is running. You can get int the programming and change it to continually run.

When diagnosing AC problems being able to hook up a gauge manifold and see what the high and low pressures are doing takes 90% of the guess work out.

I beat with your problem you would see the low side pulling down into the negative side on start up. You are low on freon is my guess.

[gonesail]

the marine air system can be pretty nasty. i have found live shrimp and crabs in the strainer along with silt .. i'm sure things get past there and into the cooling coils. check the intake hose too. it's always a challenge maintaining these things

[ranger58sb]

Originally Posted by Doorpro

Sail,

a very promising prospect. I will look into a solution to clean out the coils and i'm thinking that it might be prudent to either rent or buy a pump and let it run as you suggest.
Will let you know.

regards,
Doug.

If you use the sit-and-soak method, you can also just use the normal water pump to feed to systems, and in fact you can clean all 5 at once, that way.
Helps to have at least one other person to help, 'cause you can't be in three places at once.

Open your sea strainer, be prepared to pour a boatload of solution into it, turn on one of the AC compressors, let the pump suck solution into all 5 systems and once.

Stop the compressor when your product starts coming out a thru hull. Let it do the work from there.

Probably with 5 systems to feed, you might actually want to rig up a supply bucket with a hose fitting and something you can clamp down (by hand) on top of your sea strainer, so you can have enough solution ready for the pump, and so you don't have to do any Keystone Komedy routine to feed it.

If that doesn't work...

Five ACs on one pump seems a bit adventurous.

Or... it might be the head (length and distance of upward lift required), if any, is maybe a bit much on this one unit.

-Chris

[DeepFrz]

ranger42c posted: If you use the sit-and-soak method, you can also just use the normal water pump to feed to systems, and in fact you can clean all 5 at once, that way.
Helps to have at least one other person to help, 'cause you can't be in three places at once.

By doing this how can you be sure each system gets cleaned? Your solution may be the reason he can't even blow air through the cooling coils of the problem unit.

clamdigger posted: Doorpro, If I read your post correctly you are getting the HPF shortly after start up (couple of seconds). If this is the case it is not water flow causing the problem. The unit would run for a couple of minutes on start uo with no water before throwing a HPF code.

So why does the manufacturer say that it can happen on startup?

[Doorpro]

Ok guys,

wouldn't you know it, I turned on the AC this morning when it was cool and the damned thing ran like a champ and is still running.
Anyway, I removed both hoses from the unit and ran city water through the coils and nothing but clear clean water so no blockage there. I even plumbed the water from the pump back onto the unit but kept the hose on the out feed just in case the flow through the hull was the problem and still get a strong flow of water.
I am now stumped unless the problem only appears when its hot out because yesterday I needed the air when it was super hot aboard but as soon as the pump came on the HPF lit up as usual and I couldn't get it to work all day even though the other four are great.
I should also say that this issue only started after changing to these new units and everything worked great until then, I even had a marine AC plumber check out the system when it started years ago and they agreed that it is a well built system and as long as there are no blockages will last for ever and just told me to watch the strainer and I do.
Clamdigger, I have read what you added and I'm now thinking that if this problem only rears its ugly head when trying to start a hot unit that perhaps it is a Freon issue, yes? no?
Anyway, I will try to start it again later when I really need it and see what happens and of course when I need it I will start wondering why I turned it off this morning however the one good thing that came out of the tests that most of you have suggested is that there are no blockages.

regards,
Doug.