Boat fridge replacement of air cooled by hull cooled

[ashtead]

Our 4 year old isotherm fridge seems to be on a go slow in that its cooling but not as much as before. Could replace thermostat ? But have read regassing but surely not for a four year old unit .
Assuming repair isn't an option how easy is it to replace isotherm unit with a hull cooled version?
Any recommendations for fridge experts on south coast who might be able to diagnose current unit but am reluctant to pay out for a new unit if they only last 4 years. We don't livabord or occupy long term so maybe something else has caused the poor cooling ?

 

[john_morris_uk]

That’s lots of different questions?

I replaced our fridge with a water cooled version and we’re extremely happy. The biggest difference was increased insulation though. If it’s any encouragement to you, I have to be careful not to knock the thermostat or the whole fridge turns into a freezer.

Refrigerator units usually last for many many years so perhaps just fix yours?

 

[temptress]

Should last much longer. Double the insulation and checknfir a gas leak....

We replaced our 20 year old fridge 2 years ago. The new unit is.more efficient and uses much less power.

When we sailed off to the tropics the nest thing fpenthebfridfe was lots more insulation. This was a actually more work than replacing the compressor but made eh most difference.

 

[ashtead]

Thanks John . Yes first option would be to fix fridge . The thermostat is located at back of icebox which has always seemed a strange location but currently ice is not a possibility . It's just that if replacing unit is required getting a hull cooled unit might be a better investment than shelling out for another box with a four year shelf life.
I would like to fix mine if I knew how to or there was someone who might diagnose its ailments so right solution could apply. At the moment it's working but poorly though so reluctant to replace really though.

 

[sailaboutvic]

You can over ride the thermostat, just to see if that's the problem .
Re gas on it own don't always work , you may need it vacuum too .
I become a bit of a expert on fridge (not really just joking) after two years fighting with mine after having three engineers on board diagnose the problem and doing a repair , just got the same problem to return .
In the end I repleace with a new isotherm keep cooler .
Very happy and uses very little power in the med .

 

[superheat6k]

Here is what I would be checking. You will need an infrared thermometer. Set the thermostat in the mid position.

1 Does this make the compressor run ?

If not does increasing the number eventually make the compressor run.

2 Is the condenser (the grid on the back) well ventilated ?

Can you measure the temperature around the condenser with the fridge in its normal position ?

Is this excessive i.e. >30oC ?

Is is the condenser grid warmer at the top than the bottom ? What temperatures ?

3 What temperature is the ice box getting down to ?

4 Is the compressor running continuously ?

5 Is the ice box surface sweating or forming an ice layer - right across or just in places ?

6 Pull the fridge out of its location so you can access the rear and turn on, allow it say 30 minutes to settle. Can you measure the temperatures of the discharge pipe from the compressor (hottest pipe going to top of the condenser). Then suction pipe (cold pipe entering the compressor from the back of the fridge).

Does the operation improve with the fridge pulled out of its normal place ?

6 If you follow the pipes can you see any oily patches ?

Is there a charging point - a nipple similar to a car tyre valve normally with a cap on it. If so is this clean and dry.

Any oiliness would indicate if there is a leak.

Has an access fitting been applied - a clamp on device with a charging connection ?

If you PM me I am happy to talk you through this. Where is your boat ?

 

[sailaboutvic]

I found superheat very helpful in the pass , as he offered to talk you through it I would take him up on his offer .

 

[fisherman]

My fish fridge under performed, supplier's engineer came, "nearly half of these are under gassed when sold".
......"Then why don't you check them before charging £1300 to people like me?"

 

[wiggy]

Sound obvious, but is the fan on the condenser running, mine died and I replaced it with an identical fan designed for a PC , only a few ponds from eBay.

 

[TopBanana]

If you do end up replacing, I'll cast another vote for water cooled fridges. Mine is incredibly efficient now. £600 for the kit from Marinestore.

 

[Tim Good]

Broad question but some feedback from Frigoboat system.

1. Install an air cooled compressor first and then added the keel / hull cooler after. That was possible with my system so might be with yours. Benefit is you can use it out of the water too.

2. Set it to turn off at night for a couple of hours so the evaporator plate defrosts and remains clear.

3. Set a fan to circulate air at night.

4. Allow water to drain out of the bottom but remainder to put a drain pipe that loops upwards at the bottom so it catches a small bit of water and cold air doesn't just drain out.

 

[Daverw]

Water cooled will always be more efficient as cabin temp will always be higher, however always useful to get cooler air over air cooled condenser and stop the warm air building. Refrigeration efficacy is all about temp differential, if I had a choice would put compressor and condenser in the aft locker

 

[Tim Good]

Water cooled will always be more efficient as cabin temp will always be higher, however always useful to get cooler air over air cooled condenser and stop the warm air building. Refrigeration efficacy is all about temp differential, if I had a choice would put compressor and condenser in the aft locker

Mines in a locker with a computer fan which pulls air from the bilge. Then another on the locker door which pushes the warm air out into the cabin.

 

[SeaAndSea]

Is water cooled and hull cooled the same thing, and does it simply pull water to cool the condenser?

Is air cooled the same type that a domestic fridge at home uses?

Colin

 

[TopBanana]

Water cooled will always be more efficient as cabin temp will always be higher

It's a factor but more significant is the higher thermal conductivity of water

 

[TopBanana]

Is water cooled and hull cooled the same thing, and does it simply pull water to cool the condenser?

My water cooled setup looks like this. There's a coil just inside the hull, and water comes through the skin fitting to cool the refrigerant. It's designed to go under the sink, so you can replace your current sink waste skin fitting.


There are two things I've seen described as a keel cooler. One is a metal plate attached to your keel, turning it into a big radiator, and the other is a water / water radiator that is mounted outside the hull.

Is air cooled the same type that a domestic fridge at home uses?

Yep

 

[SeaAndSea]

Thanks TopBanana

 

[Daverw]

It's a factor but more significant is the higher thermal conductivity of water

That only means you need to pump less water than air or need less surface area for water cooled

 

[TopBanana]

That only means you need to pump less water than air or need less surface area for water cooled

Yes, making it much more efficient

 

[Hot Property]

I found superheat very helpful in the pass , as he offered to talk you through it I would take him up on his offer .

He should be, he runs his own refrigeration company!!!!