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Old 08-06-2015, 09:20   #1
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Join Date: Sep 2012
Location: San Francisco
Boat: J/30
Posts: 23
Isotherm Retrofit into Icebox

Hello all!

Earlier this year I installed an Isotherm air-cooled holding plate system in my icebox. I plan on using the boat for weekend trips every now and then, and thought it would be nice to have some sort of built in refrigeration when doing it.

The compressor I mounted under the quarterberth just aft, in a large-ish space with admittedly poor ventilation. It worked okay for a while, though the box never really got as cold as I would have liked (the holding plate never really frosted over, even when I left the unit running on max for 24h+). It didn't seem to be a problem with ventilation, the compressor space never heated up very much. The box is ~4 cubic feet and the old system was sized for a bit larger, but that might have been generous given the 36 year old insulation behind my icebox.

Anyways, it quit working recently. I left it run all night recently and when I came back the next day the plate was still room temperature. The compressor didn't sound any different so I'm wondering if the system lost its coolant (r134a) somehow.

When I picked this system, I opted against water-cooling due to the increased complexity. I'm reconsidering that now, especially because I feel it would be much more efficient with the cold water here in San Francisco Bay. Here's the draft plan:

Intake: The compressor mounts near the thru-hull for the engine raw water intake. I'm thinking I can tee off of that. Actually, I'd tee after the engine strainer and include a check valve to prevent the engine pulling water through the compressor when it's on. I would have to make sure the fridge is not turned on without the thru-hull being open - which does worry me a little if I decide to leave it running when not aboard.

Output: Run a hose from the compressor aft to a small thru-hull high up in the transom, with another check valve to prevent backflow in a following sea.

Alternative: Another idea was to add plumbing to my freshwater tank and use that water for heat exchange instead of raw water. It'd be a lot of extra hoses and the freshwater isn't as cold as seawater, but it might work?

Think this is worth doing?

alx is offline   Reply With Quote
Old 09-06-2015, 13:07   #2
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Join Date: Aug 2004
Location: Ft. Lauderdale
Posts: 702
Re: Isotherm Retrofit into Icebox

Water cooling is not a solution to your problem
The first thing I would do is finf out if compressor is actually running.

Any time someone tampers with refrigerant and compressor will not run there is a possibility of too much refrigerant or it is contaminated. Low or no refrigerant or will not prevent a Danfoss BD compressor from running. These are the tests I advised you to do:
  • Confirm compressor was truly not running by letting it run at least 20 minutes to see if it gets slightly warm. If it does not get warm there is an electrical problem. If compressor gets warm and there is little or no cooling problem is with refrigerant volume or flow. If compressor is truely running add refrigerant and test and repair leaks, See REFRIGERANT CHARGE on my web site for servicing and testing refrigerant because you may need to advice a serviceman on the correct way to service this unit.
  • Compressor does not run Disconnect wires from module thermostat and place a jumper wire across module thermostat terminals. If compressor runs thermostat or its wiring is bad.
  • Compressor does not run Disconnect Black fan wire from module. Now see if compressor gets warm confirming it is running. If compressor now runs replace fan.
  • The most important test you must do correctly is to bypass all of the boats wiring, switches and circuit breakers by connecting module positive and negative power fused wiring direct to a fully charged battery. Forget the voltmeter unless you have Supermanís eyes, because a millisecond low voltage spike that will stop modules safety circuit from starting compressor can not be detected without an oscilloscope.
The one percent left after you completed the above tests, and no one has tampered with refrigerant and I tested your module problems in compressor or module connection at compressor are possible.

Richard Kollmann is offline   Reply With Quote
Old 09-06-2015, 18:24   #3
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Location: daytona beach florida
Boat: csy 37
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Re: Isotherm Retrofit into Icebox

Forget water cooling. It will only add "parts" to your system and contribute nothing to your cooling. Your problem lies elsewhere, as outlined by Mr. Kollman. You also need to get cool air blowing across your condensor. Mounting a secondary fan and ducts might help.
Take two at low eight
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Old 09-06-2015, 20:07   #4
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Join Date: Aug 2006
Location: Morro Bay, CA
Boat: 1978 Hudson Force 50 Ketch
Posts: 3,154
Re: Isotherm Retrofit into Icebox

From the description it sure sounds like you have a unit that lost some charge in shipping (which is why your plate never really frosted up all the way from the start) and then the leak continued to the point where it fell off the low refrigerant level cliff and now isn't cooling at all.

If you are correct that the compressor is indeed running, then this sure looks like a charge issue to me. Anytime a system leaks refrigerant, it brings with it tiny droplets of compressor oil. So run your fingers around the charge ports, refrigerant coupling connections, and any joints you can see. If you feel an oily, you found the leak.

These compressors are darn near silent and the electric circuitry in the black box controller for the compressor and 12v fan are different, so just because your condenser fan is running does not mean your compressor is. You need to put your hand on it to feel vibration and a unit with no refrigerant is doing no work, so it can fun for hours and not get that warm. If you have an Amp meter, that can also help you know if the compressor is running.

Forget about the water cooling issue...water cooling is a fiasco you don't want and it doesn't sound like an overheaded condensing unit is your real problem anyway....certainly not in San Fran Bay! Heck, I'm floating south of you on our mooring in Morro Bay running my diesel heater to say warm! are fortunate enough to have bought a unit from one of the few companies left out there that actually has someone there that KNOWS their product well and will pick up the phone to help! So give SeaFrost a call and Clive should be able to walk you through some easy routine trouble shooting tips to get you back up and running.

Good luck amigo...not having cold beer and ice cream aboard isn't civilized!
Rich Boren Living Aboard in Morro Bay, CA and the owner of:
Cruise RO Water High Output Water Makers
Technautics CoolBlue Refrigeration

SV THIRD DAY is offline   Reply With Quote

icebox, isotherm

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