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Old 30-10-2012, 05:09   #1
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Opinions on Setting up Efficient Refrigeration Pls

So I'm almost done rewiring, and my new headliner and the next on my list is refrigeration.
We're going to be liveaboard (family of 4).
Currently we have a eutectic system and old thin insulation on fridge and freezer that sit on either side of the stove. Both are about 4.5 cubic feet.
So far the plan is....
Put a heat shield between stove and refrigeration wall. Gut the old insulation and liner out and rebuild using 3" of aerogel.
I'm leaning towards using as large of "O" evaperator as I can fit. To use as the freezer. We will only convert one box for now and use the other for dry goods etc.
For the system. I have 2 main choices in Australia. Novakool and Isotherm.
Novakool is a little more but the BD 35 has a radiator style condenser with shroud/ Fan and the isotherm just as a very open larger convection type and a muffin fan near the compressor.
Having said that I'm wondering if the BD 50 would be more efficient?
Any opinions on the two makes?
What about size of compressor?
Any add on's or tips for maximizing efficiency?

Ps I have read as much info I can find but have not found the specific information I am after.

Thanks
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Old 31-10-2012, 19:56   #2
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Re: Opinions on setting up efficient refrigeration Pls

I debated if we needed to go with the BD50 and for us I'm glad that we didn't as it just isn't need for our box. It is about 4 cu. ft. total with an evaporator freezer section of about 1/2 cu. ft. which I think is what you are talking about.

We used a lot of insulation, but nothing exotic and the compressor hardly ever runs. I'm guessing about 15 amp-hrs/day after using it for about 3 months. We recently bought some hour meters and I'll put one on the fridge when we go back for accurate amp-hrs usage.

We went with a 35, but I found that there was two different models available with one being recommended for smaller boxes and one for larger boxes (the one we used).....

Coolmatic 84

The fan was shrouded, but the condenser was not shrouded....



...but I made a simple shroud for it...



...and it seems to work very well. I also supplied a number of inlet air passages to where the compressor/condenser sits.

The whole build with a lot of pictures and such can be found here....

Endeavour 37 Interion Mods Index

Best of luck,

Sum
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Old 31-10-2012, 20:03   #3
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Re: Opinions on setting up efficient refrigeration Pls

I'm impressed with Isotherm, but not familiar with Novokool. Good move to put the heat shield between the stove and fridge.

On my last boat, the best thing I ever did for the fridge was to put a muffin fan near the compressor. That makes a huge difference. I put mine on a toggle: on in the summer; off in the winter. (That's USA summer, of course.)

Sounds like you're doing everything right.
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Old 31-10-2012, 20:27   #4
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Quote:
Originally Posted by Bash
I'm impressed with Isotherm, but not familiar with Novokool. Good move to put the heat shield between the stove and fridge.

On my last boat, the best thing I ever did for the fridge was to put a muffin fan near the compressor. That makes a huge difference. I put mine on a toggle: on in the summer; off in the winter. (That's USA summer, of course.)

Sounds like you're doing everything right.
Bash, was your fridge air cooled? I am wondering because I just installed a keel cooled frigoboat, which I am very impressed with. That said, the compressor gets pretty hot, but I sort of figured that this wouldn't matter because the system is water cooled. Now i am thinking...
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Old 31-10-2012, 20:40   #5
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Re: Opinions on setting up efficient refrigeration Pls

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Originally Posted by malbert73 View Post
Bash, was your fridge air cooled? I am wondering because I just installed a keel cooled frigoboat, which I am very impressed with. That said, the compressor gets pretty hot, but I sort of figured that this wouldn't matter because the system is water cooled. Now i am thinking...
If you don't have a small fan inside the box, try hanging one in there temporarily.
Right after rebuilding our box, we left on vacation with limited tools aboard.
The fridge temp sensor didn't get the message that the top was warm and the bottom was freezing, but I managed to come up with an old 3" computer fan from my stash on the boat.
I hooked it up with scraps of wire and duct taped it into the top of the box.
It made a HUGE difference for us.
It only ram when the compressor is on.
It cut the compressor time WAAY down and as a result, the compressor never gets more than slightly warm.
I installed it permanently as soon as possible in the top of the fridge with about 1/4 inch of clearance blowing straight down.

MAJOR IMPROVEMENT.
BTW we have a Vitrifrigo with a BD35 and roughly 4 cu ft box with an inch or so of Aerogel.
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Old 31-10-2012, 20:57   #6
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Re: Opinions on setting up efficient refrigeration Pls

mischief, i think you're going in the right direction.

1. between novakool and isotherm i think isotherm has a better reputation.

2. we used to have 6 cf, but found it was too much. reduced it to 3.5cf and that seems just fine, particularly if you cruise in areas where shopping is handy.

3. i bought the smaller 'O' evaporator and wish i had bought the larger one. just keep in mind that you will have to defrost regularly; so provide a drain at the bottom of the box (mine drains into the bilge).

4. we have a bd50. i thought i would need it for the original 6cf box; could probably have gone with the bd35. but if the bd50 is not much more expensive i think you should get it because it might not have to work as hard.

5. like bash said, add a muffin fan over the condensor. it will also blow over the computer control module. according to fridge genius richard kollman, overheating the control module is the principal cause of failure.

6. as long as you're rebuilding the whole box, add a small fan in the bottom of the box to circulate the cold air at the bottom back up to the top. makes a world of difference in keeping temperatures even throughout the box.

7. i built mine seven years ago and it's worked flawlessly ever since. it's an adler barbour brand, don't know if you have it in oz. nice to know that they run so well for so long. friend of mine had an adler barbour that ran fifteen years, almost continuosly...
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Old 01-11-2012, 02:57   #7
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Re: Opinions on setting up efficient refrigeration Pls

Thanks everyone so far for your insight.
Couple things.
1 definetly I will include a circulation fan I plan to have it pick up air from the bottom and deliver over top the o evaperator and under the top of box so it is as high as possible.
2 I think I will likely go with the BD 35. But the isotherm 35 only had the very open convection style condensor.
Novakool is more expensive but has the radiator style condenser and I'm thinking might be better as long as I keep the fins clean, thoughts?

I think I read somewhere that Kollman recommends a Thermal control valve instead of the capillary tube. Thoughts here? Is it worth the effort?
Finally are there any electronic controllers that improve on eficientcy? Wondering if something sort of like a ASU that could beinifit thin evaperator plates?

With an O evaperator is it worth putting a slight amount of insulation underneath so that it takes a little longer for the cold to escape the evaperator plate? That way the compressor run time may be slightly extended but the freezer section would semi act like a cold storage plate? I'm only talking about it working as a fraction of a eutectic plate. Would there be any bennifit?

Finally do I need 3" we'll actually thinking slightly less 70 mm of aerogel?
That would be just under R 30 is this overkill?

Cheers
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Old 01-11-2012, 10:03   #8
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Re: Opinions on Setting up Efficient Refrigeration Pls

We used 10mm Aerogel.
Four layers over the freezer area and three around fridge walls, top and bottom.
Two layers in the door (that's all that would fit).
BD35 in a Vitrifrigo keel cooled unit.
I don't feel any need for more than that.
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Old 01-11-2012, 10:21   #9
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Re: Opinions on setting up efficient refrigeration Pls

Quote:
Originally Posted by mischief View Post
....With an O evaperator is it worth putting a slight amount of insulation underneath so that it takes a little longer for the cold to escape the evaperator plate? That way the compressor run time may be slightly extended but the freezer section would semi act like a cold storage plate? I'm only talking about it working as a fraction of a eutectic plate. Would there be any bennifit?..


Our evaporator sits on/in the aluminum tray above and that blocks off the bottom and also provides a way to drain it if we defrost it slowly and let it drip. We did defrost twice in 3 months, but there wasn't much ice build up and we really didn't use the drain.

If you have the box well insulated like what it sounds you are doing one problem you might have is that it is hard to get the freezer section real cold. In our case with the thermostat set so the main box is around 35 the freezer section is in the low 20's and won't keep ice cream hard. If we set the thermostat lower then things in the main box are going to start freezing that are near the evaporator.

This is not a problem for us as we want the freezer section for meat not ice cream and it will keep it frozen well enough that if we use it within 2-3 weeks it will be fine. We don't need to keep things frozen for months like we do at home so no need for the freezer to be below zero.

If you want a freezer to be really cold I think you need to go to a separate freezer or a spill-over type box. We considered the later, but didn't go that way since it takes more space to pull it off and we didn't have it.

Quote:
Originally Posted by mischief View Post
......Finally do I need 3" we'll actually thinking slightly less 70 mm of aerogel?
That would be just under R 30 is this overkill? Cheers
We are using cheaper extruded polystyrene insulation with an R-5 value per inch. Our top/lids are R-15, sides R-20 and the two bottom sections are R-35 and R-45. In a house insulation in the attic is going to pay off more than the wall as that is where there is the biggest thermal difference between the inside and out side of the house. With a fridge I believe that it is just the opposite since the cold air drops in the box and you have warm air under it. If this is the case then more insulation on the bottom is going to pay off. So I wouldn't necessarily try to have the same R-value on all surfaces of the box.

I will say that I believe that the insulation is going to pay bigger dividends vs. the different compressor/condenser types and control circuits. We are extremely happy with what we now have and it uses much less power than any of the portables that I've seen or a lot of the fridges that people post about in their boats. The portables and a lot of the boat fridges are using basically the same compressor type. The difference is the insulation. If you have room for the R-30 in the wall and can afford that type insulation I'd go for it. I'd really look at the bottom more so though.

The other thing that I feel pays off is putting the insulation in the box in such a way that ...



...it overlaps and seals from one layer to the next like above. This will help control any air leakage and so forth since there are not seams between the inside and outside of the box.

The complete build is here...

http://purplesagetradingpost.com/sum...ide-index.html

Sum
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Old 02-11-2012, 16:13   #10
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Re: Opinions on Setting up Efficient Refrigeration Pls

Okay I'm pretty sure of the direction I'm heading with this.
Since my O evaperator will sit horizontal in the top of the box off to one side I think I will add a little insulation around it to allow for it to get colder before the thermostat reaches temp in the rest of the box. Ill experiment with it anyway.
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Old 02-11-2012, 17:15   #11
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Re: Opinions on Setting up Efficient Refrigeration Pls

Quote:
Originally Posted by mischief View Post
Okay I'm pretty sure of the direction I'm heading with this.
Since my O evaperator will sit horizontal in the top of the box off to one side I think I will add a little insulation around it to allow for it to get colder before the thermostat reaches temp in the rest of the box. Ill experiment with it anyway.
I looked at horizontal, but couldn't figure out how to avoid wasted space in front of it so that there was room to put items in and out of it.

One thing that we lucked out on was at the 'Dollar Store' they have....



...the plastic containers like above and we have found that...



... they just fit the box next to the evaporator. We can fill and stack them and they are easy to remove so that we can take items from the bottom ones. Much easier than just stacking food in there. Something like that might work well in front of the horizontal evaporator. They also allow us to run the evaporator a little colder.

Hope you take pictures and such and post them ,

Sum
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Old 02-11-2012, 18:11   #12
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We installed an engel ice box conversion kit, works great! Does not have a "freezer" section but is extremely efficient . Using about .7ah when not using heater, 1ah with heater on inside cabin.And our insulations sucks! very easy to install and quite cheap. Small and quite all in one unit. Automatically switches from 110 to 12 volt when 110 drops, then back to 110 when available. So far it has made life great, working everyday for the last 6 months! Ps we keep the refrigerator around 34- 36 degrees, that is a setting of 2 out of five on the dial
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Old 02-11-2012, 19:22   #13
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Re: Opinions on Setting up Efficient Refrigeration Pls

Quote:
Originally Posted by mischief View Post
Okay I'm pretty sure of the direction I'm heading with this.
Since my O evaperator will sit horizontal in the top of the box off to one side I think I will add a little insulation around it to allow for it to get colder before the thermostat reaches temp in the rest of the box. Ill experiment with it anyway.
So you don't have to reinvent the wheel, I did just that.
I loosely vacuum bagged 10 mm of Aerogel with our home's seal a meal unit.
I made up pieces for the back, both sides and bottom.
After several weeks of messing around to find the optimum (at least for our unit) I ended up with a piece on the back, and another on the bottom.
The top, door and sides are open.
We now keep ice cream hard in our boat's freezer in the middle of the summer (air temp in the '80's f).
The fridge usually runs on the lowest setting of the six speed electronic thermostat, set at 43 degrees.
The box has a fan as I already stated, and stays within a degree or two of that from top to bottom.
I vote for lower temp for the fridge, but the Admiral wants this setting.
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Old 04-11-2012, 01:50   #14
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Re: Opinions on Setting up Efficient Refrigeration Pls

Excellent that's the sort of thing I was thinking.
I have also thought about the plausibility of building a double walled box out of stainless with 20mm aerogel and applying a vacuum. Include a guage to minitor and top up occasionally if ever needed.
Realistically I think I will just use as much insulation as I can fit and build out of GRP and epoxy paint and possibly laminate a foil sheet sheet around all the aerogel.

I'll keep ya all posted
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