a/c efficiency?

[PascalG]

I noticed that when running, the a/c on my 53 MY seems to be loosing some efficiency... these days, instead of maintaining 75/76 deg in the salon (on the digital control) the system can't bring it down below78/79...

I'm guessing it has to do with the amount of heat building up in the engine room and while there is very little that can be done, it occured to me that insulating the a/c raw water lines coudl help.

there is about 6 feet of hose which gets hot after a while and I have a feeling this heat probably increase the temperature of the water by the time in gets to the units?

probably not a problem up north but down here where sea temps reach hot tub level in the summer.... could it make a difference?

[Top Shelf]

Pascal, how about this, I've got 3 A/C units on the Stb side of my engine room ('89 48 CNV). Just messin around with my infrared thermometer one night. I lit up the sides of each compressor. One was 99 deg F, next was 119, the last was 126...all compressors were "picked". They seem to be running fine. Any experience on the wide varience.

My Buddy told me to get the hell out of there, and leave well enough alone :}. Thx.

[67HAT34C]

I HAVE DISCUSSED AC IN DETAIL WITH SOME INSTALLERS AND MANUFACTURERS.

WE ARE IN FLORIDA AND ARE EXPERIENCING VERY WARM WATER THIS YEAR. THE AC PEOPLE TELL ME THAT IT IS HARDER FOR AC UNITS TO COOL WITH THE INCREASED WARM WATER. WE ARE IN STUART ON THE OKEECHOBEE WATERWAY, SHALLOW AND WARM. SOMETIMES BY INCREASING THE SIZE OF YOUR WATER PUMP CAN HELP. LET ME KNOW IF I CAN BE OF FURTER ASSISTANCE

STEVE HIERHOLZER
SHIERH@AOL.COM

[PascalG]

well I'm running a 1200 GPH pump which was the biggest I could get...

for a while, I tried 2 pumps on the same strainer with Y fitting as suggest by the pump manufacturer but one failed after a few months. they didn't suggest to use check valves but thinkin about it I wonder if that wouldn't have been necessary as if one starts/primes quicker it has to prevent the second one from getting enough flow...

When I don't run the boat, it cools fine... it's when the engines are running and for a few hours afterward that the 3 to 4 extra degrees make all the difference between nice and barely comfortable...

pascal
70 53MY

[Genesis]

... the H/Es in the AC units are clean.

A simple way to clean them is to take a bucket, and stick the output hoses (from the through hull to the outside) into it. Then stick the intake hose in there. Now pour in 5 gallons of white vinegar, and activate the PUMP (not the AC unit!) - this can usually be done by bridging one of the trigger inputs on the CruiseAir units.

Let it run for a few hours. You'll be surprised at what comes out of there.

If you want to get more aggressive, use Ph-ospho-ric (available at Home Depot), but don't let that run for more than a half-hour or so.

If your AC units have been running for more than a couple of years, they likely have salt and mineral deposits inside the tubes which severely impacts the cooling. This is the same issue you run into with your main heat exchangers.....

[PascalG]

thks Genesis... yeah that was the first thing I did a few days after I got the boat last sept. wasnt' pretty and indeed it helped.

it's jsut the difference between before and during/after running the boat that's telling me that insulating the hoses may help. they are a couple of feet from the engine (along the bulkhead, can't move them further) and we all know how much heat can soak out of those lumps!

pascal

[dshuman]

Didja' check the freon level? Maybe it's marginally OK enough to cool until the engine room gets hot. Maybe you just need a recharge.

[Genesis]

... low freon will cause all kinds of problems which you won't like, including freeze-ups of the evaporator coil (paradoxially - you'd think it would do the opposite!)

Marine AC systems, especially the "split systems" in these larger boats, are notorious for having small leaks.

Also, in convertables, the engine room being below the salon doesn't help - the heat comes up directly from the floor as well....

[PascalG]

I need to get an A/c guy to check one of the unit which pops its breaker whenever the compressor starts so I'll have them take a look at the freon pressure...

on the 53, with the split engine rooms, the heat soaks thru the guest sr, companionway and galley ...

pascal

[jim rosenthal]

is a good one. I would first clean the heat exchanger coils like Karl said, also you would probably get some advantage by ventilating the engine room and getting some of the waste heat out of there. Also, is your line voltage high enough? Everyone else on the dock is probably running their AC as well...if the voltage sags the units won't run efficiently and will overheat.

[jim rosenthal]

with cleaning the heat exchanger coils with vinegar (acetic acid): my AC seawater pump is not self-priming- it relies on a flooded inlet like most of these pumps which are centrifugal pumps. When I winterize the system, I have to use a gravity-feed setup to get the antifreeze to go through. I can't think of any way to set this up that would allow the system to recirculate the cleaning solution as you said.
Would it be just as effective to close off the coils, flood them with acetic acid, and go through five or six changes of it to clean it and then hook it back up to seawater? Otherwise, I am going to have to figure out a way to hook up a positive-displacement pump to push it through and circulate it...

[PascalG]

yes, voltage seems fine from what I've seen on the voltmeter althought it could be inacurate (i'll double check with a digital) , happens on the 18kw genset too.

when I had the coils cleaned, the guy used a bucket with a pump inside to circulate the mixture thru the coils and back into the bucket. I didnt' see what kind of pump it was but even a small bilge pump would work for that.

pascal

[rufuschamblee]

Jim,

I use the same method as Karl with this exception: I use a small 12V bilge pump in the 5 gallon bucket instead of the A/C cooling water pump, connect the hose to the input side of the heat exchangers. This bypass the A/C circuit all together.

Rufus

[Genesis]

It works - you have to get it primed originally, which I do by pouring the vinegar into the lines BACKWARDS from the exit towards the pump. Once the inlet is submerged the air will be expelled.

Just have the bucket above the seawater pump and once the loop is full it'll work fine.

[rich]

Would you know if on my 1972, 36C which has 2 AC units one in V berth and one in Salon, if in the "start" position I can clean with vinegar as described above? The pump is on. Raw water flows.
When you go to "run" the AC is on.
Thank you
Rich

[jim rosenthal]

OK, I have it now. I can use one of those methods and clean them out. It has probably never been done, it will be interesting to see what comes out of there.