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Old 06-12-2014, 00:05   #1
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Help with new Novakool return line icing up!

Hopefully Richard or other knowledgable ones will be able to help.
I have a relatively small ice box. About 450mmX 450mm x 500 less the curve on the hull side.
I purchased a Novakool conversion kit with the small O evaporator. The evaporator takes up about 30% of the box.
The box has 2" of old expanding foam insulation but appears dry.
Being pressed for time and now living aboard we wanted refrigeration sooner than later and I opted to not rebuild the box at this time. I figured the bigger O would compensate somewhat and was worried it would actually cause the whole box to be a freezer.
So to make a bit of a spillover system I added a single wrap of 10mm thermobreak closed cell foil faced insulation and sealed the edge. Installed the unit with the following things that I think maybe a problem. The copper line goes from the evaporator up along the top of the inside wall which was covered and insulated (so about 300mm of the line is free in the box the next 450mm is insulated where t travels along the top wall and exits) the next 400mm has the factory closed cell foam wrap. After that almost all the line is in a coil on the wall of the cabinet where the compressor is.
This ices bad although box temp is not quite cold enough.

So far this is what's happened and what I've done.
After running a bit the evaporator frosted to 100% on inside and the return line iced. I used zip ties on the ends of the closed cell tube wrap to stop the condensation freezing on the line there but the rest of the coil ices with about 1" of ice. The fridge portion of the box pulled to 8 degrees. The compressor ran full time.
I then tried using the medium resistor to see if the compressor pulled down and chocked perhaps the ice would disk late on the return line.
No joy on setting 3 the box pulled to 6 degreed c would not cycle off and iced return line with 3" of ice!

So I thought it must be the insulation keeping the evaporator too cold. I removed in sections and it has improved. But with the compressor running at medium speed and the insulation pulled off 3 of the four sides the box temp in the fridge side pulled to 4.5 degrees C but the ice stayed unchanged on the return line.
I then went back to the compressor running at low speed after defrosting the ice off the return lines and now the compressor still runs constantly and it's re-icing up. Maybe an 1" of ice so far the fridge temp is now 5.5 degrees and the freezer section just delivered cheese came that was only semi frozen :-(
All items in the fridge come completely down to temp and the freezer box is 80% full with the fridge being about 70%
All changes made over days to make sure it has settled before making another change.
The temp in the boat has been comfortable and only around 23degrees.

My next plan is to pull the evaporator forward enough to strip the rest of the insulation off.
Is the insulated run of the return line causing issues?
Is there too much gas in the system and I'm flogging a dead horse looking for other causes?

Certainly I should be able to run the system in open air and not have the return lines freeze?

Once I work this issue out I plan to insulate the outside of the box further with slow rise 2 part foam. Knowing I will rebuild the box in a couple years and will gut the whole thing out.
Arrrggggggg!Click image for larger version

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Icing up on return line starting to form
Again.
Click image for larger version

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Bit of food removed to see the setup.

:-(


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Old 17-12-2014, 23:00   #2
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Re: Help with new Novakool return line icing up!

Well surprised nobody could offer any help on this.
Turns out my suspicion of too much gas was correct.
Pulled some gas out now seems to be working great


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