Getting Desperate- Modify the Shape of Store Bought Refrigerator?

[rslifkin]

If 6 cu ft is enough, Nova Kool makes a 5.8 cu ft marine fridge. They also sell the same unit as a freezer, so you could put a pair side by side, although they're a little too deep for the space you're wanting (so they might have to go against the aft bulkhead).



Otherwise, building a custom box is probably the best bet. Building a fridge shouldn't be too hard. Basic structure is just a frame, make a fiberglass liner for the inside, a bunch of foam for insulation, then add the refrigeration system of your choice. I seriously considered a custom build for my boat before I bought my current fridge.

[Chotu]

Originally Posted by rslifkin

If 6 cu ft is enough, Nova Kool makes a 5.8 cu ft marine fridge. They also sell the same unit as a freezer, so you could put a pair side by side, although they're a little too deep for the space you're wanting (so they might have to go against the aft bulkhead).



Otherwise, building a custom box is probably the best bet. Building a fridge shouldn't be too hard. Basic structure is just a frame, make a fiberglass liner for the inside, a bunch of foam for insulation, then add the refrigeration system of your choice. I seriously considered a custom build for my boat before I bought my current fridge.

I’m going to have to get down there in a couple weeks to see. I think the daggerboard trunk is in the way for a side by side.

I’m trying to avoid building because I have an entire boat to build. So the less projects the better. Although it would be the best fit. Definitely.

Between a rock and a hard place with the refrigeration.

[rslifkin]

Using 2 separate units rather than a real side by side might help with the daggerboard issue, as you could leave room in the middle for the trunk if needed.

[Chotu]

Originally Posted by rslifkin

Using 2 separate units rather than a real side by side might help with the daggerboard issue, as you could leave room in the middle for the trunk if needed.

True. A pair would work. Although it basically doubles the energy requirement compared to a larger combination unit that has both refrigerator and freezer in one.

By the same token, a single one of those (ideally 8cuft refrigerator only) and a chest freezer elsewhere works. But again, doubles the energy requirement.

The best of all is a combination unit because they all use about 70AH per day. Of course that’s the one I can’t fit anywhere except the bridge deck and the aft bulkhead since they are wide, square and tall.

Just going around in circles with this design.

[rslifkin]

If the systems are well designed and well insulated, having 2 smaller units should only use slightly more power, far from double. Power requirement should be more related to volume being cooled and target temperature (bigger space or colder temperature with the same insulation will need more power). I'd expect the boat will stay a bit cooler down in the hulls, so a unit down there will use a little less power than one up on the bridge deck would.

[Tupaia]

Yes this is possible. The units do not last long but are exceptionally cheap $100 or less. They have a useful life of 5-6 years mostly it is the door that corrodes and we have even bought a new unit changed the door put the old door on the new unit and resold it. Remove the compressor and braze on some quick fit fittings to match your 12 v compressor we have a Frigoboat keel cooled unit much more than $100. Cut away the metal case to fit hull shape paint raw edges with anti-rust paint and tape for safety. Add some external fridge foam 6in either side and varying amounts top and bottom. You need to vacuum down for 24 hours and re-gas to the right pressure.

[Chotu]

Originally Posted by rslifkin

If the systems are well designed and well insulated, having 2 smaller units should only use slightly more power, far from double. Power requirement should be more related to volume being cooled and target temperature (bigger space or colder temperature with the same insulation will need more power). I'd expect the boat will stay a bit cooler down in the hulls, so a unit down there will use a little less power than one up on the bridge deck would.

You know, that’s what I thought too.

But when I actually did the math, an energy star 12 cu ft, 24” wide refrigerator takes 70 A*H a day.

A 5cuft chest freezer is 44AH a day.

A 5cuft or 6cuft refrigerator only is 66 AH a day.

It’s significantly higher to split them up. Double was an exaggeration, but not much of one.

70AH a day for 12cuft of refrigerator/freezer in one.

110AH for 10 or 11 cuft of divided up units.

[Chotu]

Originally Posted by Tupaia

Yes this is possible. The units do not last long but are exceptionally cheap $100 or less. They have a useful life of 5-6 years mostly it is the door that corrodes and we have even bought a new unit changed the door put the old door on the new unit and resold it. Remove the compressor and braze on some quick fit fittings to match your 12 v compressor we have a Frigoboat keel cooled unit much more than $100. Cut away the metal case to fit hull shape paint raw edges with anti-rust paint and tape for safety. Add some external fridge foam 6in either side and varying amounts top and bottom. You need to vacuum down for 24 hours and re-gas to the right pressure.

Whoa!!!! This EXACTLY what I’m looking to do. Just with a larger unit that continues up above counter height.

I do have a spare Isotherm air cooled 12v compressor hanging around as well.

Does this one have a freezer and refrigerator?

I do have the vacuum pump and gages to top off R-134a

[rslifkin]

The off the shelf 120v home fridges aren't necessarily all that well optimized (especially in smaller sizes, as seen by them using more power than the colder chest freezer), so with different component choices, you could do better.

FWIW, my 9.1 cubic foot (2.5 freezer, 6.6 fridge) single BD35 compressor NovaKool marine fridge comes in around 60 - 80 ah per day typically with just a little bit of added insulation. Better insulation and some other improvements would be able to reduce that more.

As a thought, separate compressors for fridge and freezer might actually do better than expected, at least with 12v Danfoss compressors. Provided the fridge evaporator is big enough and maybe has a fan on it, the fridge evaporator can be run at much higher temp than a freezer or combo unit evap. And with the Danfoss compressors, higher evap temp increases both cooling capacity and efficiency, all other things kept the same. Because of this, I figure the dual compressor version of my fridge that they now sell probably uses very little extra power if a few modifications are made (evap fan in fridge and appropriate thermostat setting). Making that same modification to the dual compressor version is a no-go, as the freezer stops being a freezer when you do that (I tried).

[Tupaia]

Originally Posted by Chotu

Whoa!!!! This EXACTLY what I’m looking to do. Just with a larger unit that continues up above counter height.

Easily achieved, we decided against this as it is next the dinette and we valued the worktop space.

Originally Posted by Chotu

I do have a spare Isotherm air cooled 12v compressor hanging around as well.

The air cooled units do not perform well in the tropics, also they circulate the hot air from the matrix inside the boat. Keel cooled are very efficient and no heat gain within the boat. Much more expensive though.

Originally Posted by Chotu

Does this one have a freezer and refrigerator?

You can get them with "ice boxes" inside but ours is just a fridge we have a separate freezer.

Originally Posted by Chotu

I do have the vacuum pump and gages to top off R-134a

Make sure you get the pressure right too high is just as bad as too low.

[Chotu]

Originally Posted by Tupaia

Easily achieved, we decided against this as it is next the dinette and we valued the worktop space.



The air cooled units do not perform well in the tropics, also they circulate the hot air from the matrix inside the boat. Keel cooled are very efficient and no heat gain within the boat. Much more expensive though.


You can get them with "ice boxes" inside but ours is just a fridge we have a separate freezer.

Make sure you get the pressure right too high is just as bad as too low.

I remember that from building an r-134a refrigerator before.

I had to add and add the refrigerant until the evaporator nozzle was spraying correctly but not too much.

I’m ok with inefficiency in the tropics. As long as the ice cream stays frozen.

[Chotu]

Originally Posted by rslifkin

The off the shelf 120v home fridges aren't necessarily all that well optimized (especially in smaller sizes, as seen by them using more power than the colder chest freezer), so with different component choices, you could do better.

FWIW, my 9.1 cubic foot (2.5 freezer, 6.6 fridge) single BD35 compressor NovaKool marine fridge comes in around 60 - 80 ah per day typically with just a little bit of added insulation. Better insulation and some other improvements would be able to reduce that more.

As a thought, separate compressors for fridge and freezer might actually do better than expected, at least with 12v Danfoss compressors. Provided the fridge evaporator is big enough and maybe has a fan on it, the fridge evaporator can be run at much higher temp than a freezer or combo unit evap. And with the Danfoss compressors, higher evap temp increases both cooling capacity and efficiency, all other things kept the same. Because of this, I figure the dual compressor version of my fridge that they now sell probably uses very little extra power if a few modifications are made (evap fan in fridge and appropriate thermostat setting). Making that same modification to the dual compressor version is a no-go, as the freezer stops being a freezer when you do that (I tried).

I’ll take a look. To do this type of split up I’ll have to measure out a couple things in terms of width. That’s something that wasn’t a concern with my other plans.

Did you happen to notice your 9.1 cuft unit modified and with extra insulation uses the same power per day that the 12cuft off the shelf Home Depot refrigerator does?

[rslifkin]

Originally Posted by Chotu

Did you happen to notice your 9.1 cuft unit uses the same power per day that the 12cuft off the shelf Home Depot refrigerator does?

I did. My unit isn't the most efficient you could put together, as the insulation is a little thinner than ideal in search of maximum capacity. And there are a few other design factors that limit efficiency. My numbers are also based on me keeping it set pretty cold, about 34 - 35* in the fridge (which keeps the coldest part of the freezer around 8 - 9*). Turning it up a few degrees would likely save some power.

[Chotu]

Originally Posted by rslifkin

I did. My unit isn't the most efficient you could put together, as the insulation is a little thinner than ideal in search of maximum capacity. And there are a few other design factors that limit efficiency. My numbers are also based on me keeping it set pretty cold, about 34 - 35* in the fridge (which keeps the coldest part of the freezer around 8 - 9*). Turning it up a few degrees would likely save some power.

Yeah. They undoubtedly use a 70 degree room and 40 degree box temperature when rating the refrigerators. Ha ha.

This is one of those really taxing decisions. I had it all sorted out until we decided to move the galley. My smaller, darker, less airy galley (half built, but working), has the refrigerator against the aft bulkhead. It’s an 8cuft refrigerator/freezer primarily run from propane.

Now nothing works. Fighting an uphill battle to move the galley , but it’s also best for the boat once I can get these details worked out.

Better weight distribution and better cooking conditions.

[rslifkin]

I'd say figure out each possible spot where the fridge / freezer can go, and then measure those spots. Then it should be easy enough to determine if there's an off the shelf solution that fits the available space and you'll be happy with, or if you're better off building something.