DIY Fridge

[vyv_cox]

Air cooled condensers can be adequate but at high external temperatures they are not as energy efficient as water cooled. On a hot Med day where the air temperature could be 35 degC and the sea temperature say 25degC you would have a 10degc advantage by using sea water to cool the refrigerant. This lower condensing temperature translate to less power used for the same amount of cooling. I am not suggesting you need to go water cooled for this project. I would use a small waeco air cooled unit. This will be ample for this application and not too pricey.

The post that you replied to by Charles Reed highlights the difference between installations and boats. His custom design fridge has massive insulation thickness and he is able to draw cool(ish) air from the bilge and route it outside once through the heat exchanger. On my Sadler the bilge is not cool because of the hull insulation and the route for air past the heat exchanger is tortuous and inadequate. It also vents into the saloon, making it even hotter in the Greek summer. Fitting a water cooled Danfoss unit to a standard Waeco fridge transformed its performance, the pump draws less then 1/2 amp when the fridge is running, which is somewhere between 1/4 and 1/3 of the time, 24 hours per day.

 

[geem]

The post that you replied to by Charles Reed highlights the difference between installations and boats. His custom design fridge has massive insulation thickness and he is able to draw cool(ish) air from the bilge and route it outside once through the heat exchanger. On my Sadler the bilge is not cool because of the hull insulation and the route for air past the heat exchanger is tortuous and inadequate. It also vents into the saloon, making it even hotter in the Greek summer. Fitting a water cooled Danfoss unit to a standard Waeco fridge transformed its performance, the pump draws less then 1/2 amp when the fridge is running, which is somewhere between 1/4 and 1/3 of the time, 24 hours per day.

Vyv, I agree. My water cooled Danfoss compressor I installed on my last boat used to average about 1 amp for 100 litres fridge/freezer in the Caribbean with sea temperatures up to 28 DegC. A great solution with the refrigerant going straight into the keel cooler. Air cooled wasn't a good solution for that boat as it effectively had no bilge local to the fridge compressor.
The current boat uses an air cooled condenser, drawing air from the bilges. It does exhaust air to the aft cabin but this will be modified to discharge outside via a dorade. This fridge has a minimum of 100mm of kingspan insulation all around and is only 85 litres so not heavy on the amps.

 

[jakeroyd]

Another vote for the Waeco CF18
mine fits in a treat where the navigators legs go on my tiny boat.
Only navigators with no legs can now sit at the nav table

 

[xeitosaphil]

Hello again
Thank you for the helpful advice from all when I was planning this project (see previous post 6-9-13). I am in the final stages of acquiring the materials having purchased a Waeco compressor and plate, Reticel 50mm insulation and construction materials. What still troubles me is the design of the lid and seal for the top loading storage cavity which I am converting. It is currently a large cavity housed within the internal BRP moulding and is accessed from the top by a simple small opening without a lid. I had complicated design worked out involving a SS liner with an in-channel fridge seal fitted around the lip but I note from looking at various boats at Excel that new manufacturers use little more than the weight of the lid and a "rubber band" seal. A worldly associate suggests that cold air is heavier than warm/ambient air and therefor a seal may not be needed at all!! The only reference I can find in other threads that specifically mentions lid design opted for a bevel edge but I am sceptical about getting it to fit flush to the existing worktop level and it being easily dislodged in heavy weather. I have no doubt I could eventually find a solution through trial and error but for the risk of cannibalizing the GRP mouldings that form the roof of the soon to be fridge and my wish to spend some of my advancing years sailing rather than correcting mistakes. It seems that I am a perfectionist so I do that too much already!

I did exactly what you are trying to do l now, last year, converted a cool box to a fridge and also incorporated a freezer as well, total volume about 40 litres using a Danfos BD35, I managed to buy at a local boat jumble.
Your suggestion for the lid with insulation on the underside and seals around the edges is what I have, and it is sufficient to keep the freezer @ -9 degree C and the fridge @ +5degree C (top opening)
But I do have to juggle the contents around at times and tweek the thermostat, to maintain the temps.

I have loads of photos of installation if you are interested, and if local, (as I see your in Devon ) could arrange a visit if helpful.

Philip

 

[david100952]

Sound advice from William but we have done the box routine for a couple of years now and last season 2 week cruise didn't quite manage us being in harbour when the shop with the ice was open - twice. Results are inevitable: feed fish and visit Tesco. Now that the grey cells are vibrating I'm thinking that given said large capacity refrigerated cavity one could still put in a lump of ice and lessen the cycling of the compressor thereby prolonging the battery life on longer passages under sail!