Adding a second evaporator plate?

[Sea Change]

We have a water cooled fridge, with two evaporator plates, each one cooling a separate compartment. Single thermostat so both compartments run at about the same temperature, which at maximum power will freeze things in contact with the plate but nowhere else.

I also happen to have an air filled compressor and matching evaporator plate, previously used in a freezer where it worked pretty well.

If I install this plate in alongside the existing setup, how are they likely to work together? I really, really want a freezer and the current system doesn't really give me that in any practical way. I'm hoping that adding the third plate would give me one fridge, one freezer, and the advantage of some backup in case either compressor fails. I've already had some problems with growth clogging the water cooled system so it would be good to know that all my eggs aren't in one basket.

I appreciate that it's a rather unorthodox way to go about the task. It would no doubt be better to arrange separate control of each compartment. But I don't want to disturb the existing system too much. The spare plate and compressor just use quick connects so I can install that myself, I just have to drill a hole for the pipes.

Any thoughts?

 

[lustyd]

The temperature is related to how the gas is filled in part, so to have one proper freezer and one proper fridge you'd need separate compressors too. The better way to do it would be to swap one compartment over to the new compressor rather than have two evaporators on different compressors in one compartment (which I think is what you're saying, perhaps I read wrong?)

 

[Sea Change]

The temperature is related to how the gas is filled in part, so to have one proper freezer and one proper fridge you'd need separate compressors too. The better way to do it would be to swap one compartment over to the new compressor rather than have two evaporators on different compressors in one compartment (which I think is what you're saying, perhaps I read wrong?)

Yes, one compartment would have a plate linked to the water cooled compressor.
The other compartment would also have that, but *also* a plate linked to a different compressor.

 

[vas]

if I got that right, too tired atm, it should work, only make sure that you have the thermostat for the water cooled compressor in the compartment that doesn't have the extra aircooled compressor plate, and obvs the aircooled compressor plate thermostat where the plate is

 

[lustyd]

Yes, one compartment would have a plate linked to the water cooled compressor.
The other compartment would also have that, but *also* a plate linked to a different compressor.

Yes personally I’d just keep the two plates you have but plumb one to the new compressor. You’ll need an FGas person anyway and the call-out is the expensive part there. Then they can gas one up for fridge temps and one at freezer for best efficiency and to make sure the freezer compartment doesn’t interfere with the gas in the fridge evaporator.

In theory your plan will work, but I don’t think it’s the best use of what you have.

 

[Sea Change]

Yes personally I’d just keep the two plates you have but plumb one to the new compressor. You’ll need an FGas person anyway and the call-out is the expensive part there. Then they can gas one up for fridge temps and one at freezer for best efficiency and to make sure the freezer compartment doesn’t interfere with the gas in the fridge evaporator.

In theory your plan will work, but I don’t think it’s the best use of what you have.

I'm sure you're right but I'm sitting on a pile of parts here, in the Caribbean where good fridge people are expensive if you can find them. And the plate/compressor I have are self sealing fittings so pretty idiot proof.

 

[Neeves]

We have a water cooled fridge, with two evaporator plates, each one cooling a separate compartment. Single thermostat so both compartments run at about the same temperature, which at maximum power will freeze things in contact with the plate but nowhere else.

I also happen to have an air filled compressor and matching evaporator plate, previously used in a freezer where it worked pretty well.

If I install this plate in alongside the existing setup, how are they likely to work together? I really, really want a freezer and the current system doesn't really give me that in any practical way. I'm hoping that adding the third plate would give me one fridge, one freezer, and the advantage of some backup in case either compressor fails. I've already had some problems with growth clogging the water cooled system so it would be good to know that all my eggs aren't in one basket.

I appreciate that it's a rather unorthodox way to go about the task. It would no doubt be better to arrange separate control of each compartment. But I don't want to disturb the existing system too much. The spare plate and compressor just use quick connects so I can install that myself, I just have to drill a hole for the pipes.

Any thoughts?

The insulation needed for a freezer is greater than that for a fridge using a 'standard' Danfos compressor. You are using water cooling but I don't think that will impact, or not, your insulation.

We had a conventional 'off the shelf' fridge with a Danfoss compressor and a custom built freezer with 15cm insulation all round located in the cabin sole (it was the only location with enough space for all the insulation) using an Engel compressor (which I think is similar to a Danfoss compressor). We ducted fresh air adding computer fans linked to the compressor, on when the compressor was on, from the bow locker to both compressors. Both our fridge and freezer worked well and we could quickly freeze down tuna fillets (once we had caught the tuna. ). But our fridge had about 4cm of insulation, standard yacht/caravan front opening fridge, and the freezer 4 times, or more, that amount of insulation, top opening freezer. We were strict with opening of the freezer, though being top opening the cool air stayed in the freezer box.

I'd move some of your focus to insulation - but suspect your intended freezer compartment might be lacking in insulation but it is what you have.

If the insulation is inadequate the freezer will need more amps to keep it cold and if linked to the fridge you may find the fridge compressor runs longer than will be needed - wasting all that solar power (but maybe that does not matter if you can reap excess solar etc etc.

Linking the 2 units together seems to introduce a weakness should one compressor go down.....????

I'd try to keep it simple - 2 independent units.

Running 2 independent 'fridges' means you can check amps consumed easily and independently.

 

[William_H]

My thought is that what OP needs is more air circulation around the existing evaporator plates. A small fan near the evaporator plate should aid this a lot.
Of course the existing system may have lost efficiency from loss of gas. The air cooled extra system will increase temps inside the boat and will not be as efficiant as water cooled one. ol'will

 

[Sea Change]

My thought is that what OP needs is more air circulation around the existing evaporator plates. A small fan near the evaporator plate should aid this a lot.
Of course the existing system may have lost efficiency from loss of gas. The air cooled extra system will increase temps inside the boat and will not be as efficiant as water cooled one. ol'will

I've never heard of putting a fan inside the fridge or freezer. Doesn't immediately strike me as a good idea.

There's absolutely nothing wrong with the current system, it is functioning exactly as designed. It just wasn't designed to be a freezer.

I could probably swap out the thermostat and I could create one large freezer, but I don't actually want to do that because there'd be nowhere to keep the tomatoes.

 

[Neeves]

And if it was not designed as a freezer, but designed to prolong the life of tomatoes - the insulation might be lacking. Freezing tuna, or water, needs colder temperatures than chilling tomatoes.

 

[lustyd]

Insulation is largely irrelevant here. The box is insulated so it can likely be used as a freezer. The trade off is how much power that takes to achieve, but it almost certainly can be achieved. Adding insulation reduces the time that the compressor must be on which is generally nicer but not required.

 

[Sea Change]

Insulation is largely irrelevant here. The box is insulated so it can likely be used as a freezer. The trade off is how much power that takes to achieve, but it almost certainly can be achieved. Adding insulation reduces the time that the compressor must be on which is generally nicer but not required.

I think you're right, it's a well constructed thing with good insulation. Probably better insulated than the freezer I built on a previous boat.
Power isn't a problem, we have 1350w of brand new bifacial panels which are working brilliantly.