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  #1  
Old 08-13-2010
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Air conditioner questions

Hi,

I have an '83 hunter. The original owner (I'm #3) put in a reverse cycle ac/heat pump. My guess is that the unit is probably 15 years old but I don't know for sure. When I bought the boat (3 years ago) the AC worked fine dropping the temp inside within an hour or so (mid 90's to 75).

This year has been hot & I've been at dock a lot so I've tried running it this year. The unit will only drop the inside temp 5 - 10 degrees total. Also it takes a long time to cool off ~2 degrees per hour.

I've measured the output temp at the vent @ 58 degrees. Most sites say a 15-20 degree differential is nominal. I've got that, in fact a bit more, temp in the boat is in the mid 80's. I don't understand why the air temp isn't dropping down more & why it seems to be taking a long time.
I've checked the air filter (clean) and cooling water is running fine. Does anyone have any suggestions as to why/what is going on?
Thanks
Brian
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Old 08-13-2010
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The temp difference has to be measured AT the evaporator as CLOSE AS POSSIBLE (meaning a couple of inches) air in air out SHOULD BE 18-20 DIFFERENCE In heating mode 10-15.

The water in and out the condenser should be 10-15 degrees but closer to 10 In cooling mode it's warmer, in heating mode it's cooler.

Things you forgot to mention,
size of boat,
model or size of unit

Dropping at 2* and hour is not bad in the heat conditions we've been having. don't forget a boat is no where near as insulated as a house. the deck/cabin is like a big solar collector! Running cool water on deck would help in sweltering conditions (imho)

Hope this gives you some insight!

ps; ck or clean the tube in tube condenser, or pump for algae build up . vineger or acid pumped through it would clean it. Use acid as a last resort is my opinion.
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Old 08-13-2010
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A shade cover over large areas of your deck can make a huge difference. Also, a hose spray of water on the deck and the heat removed with evaporation will greatly increase your AC performance. I also use the soft rubber (latex?) teather of a surfboard leash to run through the raw water coils. This may remove a film of mud/slime coating that will reduce your rate of heat exchange.Take care and joy, Aythya crew
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Old 08-13-2010
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Quote:
Originally Posted by saillife View Post
Hi,

I've measured the output temp at the vent @ 58 degrees. Most sites say a 15-20 degree differential is nominal. I've got that, in fact a bit more, temp in the boat is in the mid 80's. I don't understand why the air temp isn't dropping down more & why it seems to be taking a long time.
I've checked the air filter (clean) and cooling water is running fine. Does anyone have any suggestions as to why/what is going on?
Thanks
Brian
Brian--

When you first get to the boat, before going aboard, give the boat's decks a good soaking with water (until the water in the hose runs cool). As the water evaporates, it will suck heat out of the decks and reduce the heat load on the boat. Then open everything up and let the hot air out and the wind blow through the accomodation for 10-15 minutes while your A/C unit is getting up to speed. When the air from the unit feels cold, close everything but your overhead hatches, leaving them cracked some so that hot air can continue to escape. It will also help to put a little portable fan on the floor deck somewhere to blow cool air upward.

Cold air is heavier than hot and it has to "fill up" the boat. If you keep the boat closed up tightly, the hotest air gets trapped between the overhead and about waist level and the boat continues to feel hot while cool air is recirculated from waist level down.

We use the foregoing on our boat here on the southwest coast of Florida and a little 16,000 BTU Unit keeps the boat "as cold as a meat locker" (per my wife).

It will also help if you have a cover that will shade the deck and topsides during the heat of the day. A good cover can reduce the temperature in a boat by as much as 15 degrees, especiall if the deck is misted from time to time.

FWIW...
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Old 08-13-2010
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Brian-
Technically, you need a wet/dry sling hydrometer to measure the relative humidity and temperature (both at the same time) to see how well an AC unit is working. But the air coming off an AC unit, right in the outlet duct, should typically be 45-50F if you stick a thermometer in it. The exact temperature will depend on relative humidity (there are published tables in AC repair guides) and how hot the outside air is, i.e. sometimes you can expect a 40F drop in air temperature, sometimes 30F, depending on the system and the environment.

The odds are that your system has gotten old and lost some of the gas ("Freon") charge due to slow leaks in old age. 15 years is a good long life for an air conditioner, especially in a marine environment.

I'd look for obvious physical problems, i.e. does anything need cleaning? Is the unit getting good power, no wiring problems? Filter really clogged? and if there are none--then it is time to find out what a service call will cost you, to see if it just needs gas, or needs a leak repair, or outright replacement.

Somewhere on the unit it will say what gas type it takes (R22, R12, R134a) and depending on that, it may or may not be feasible to repair.

While DIY repairs to AC are not impossible, doing it right takes a bit of equipment and study, so it can be faster-simpler-cheaper to call in a pro for a one-shot project.
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HyLyte, It's remarkable how similar our advice is, but then we are both keeping cool in Florida! Take care and joy, aythya crew
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Quote:
Originally Posted by CaptainForce View Post
HyLyte, It's remarkable how similar our advice is, but then we are both keeping cool in Florida! Take care and joy, aythya crew
Yes--I suspect we were penning our replys at the same time and their similarity does serve to illustrate that great minds do seem to think alike, eh?

A full shade cover does make quite a bit of difference, particularly this summer which seems to be unusually hot.

Cheers...
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