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Old 23-10-2012, 08:21   #1
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Excessive Moisture on Evaporator?

Built a new fridge over the winter and have been very pleased with its performance running 24/7 since july as we live aboard. It is a frigoboat unit with a flate plate evaporator. I keep the the fridge set at 38*F. We get quite a bit of moisture on the evaporator that eventually drips off and periodically needs to be sponged out of the bottom of the box. Im wondering if there is anything to be done about it? Box stays easily at temp and system uses very little power. Evaporator gets plenty cold and ices up some but we dont get a big layer of frost like the old system. This I think is a good thing meaning we dont have air leaks in the box. The moisture is not the end of the world Im just wondering if there is anything to do about it? Heading for the tropics once the weather systems cooperate so I suspect humidity will be much higher than Annapolis.
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Old 23-10-2012, 10:08   #2
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Re: Excessive Moisture on Evaporator?

Moisture condensing on the evaporator coil comes from one of four sources: the food in the fridge (not very likely), the drain hole (put a cork in it, but not very likely), opening the fridge a lot, and seal leaks.

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Old 23-10-2012, 10:15   #3
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Re: Excessive Moisture on Evaporator?

When you take something out then put back wipe off the condensation the forms on it. Its kind of a pain but better than having to defrost. Also second the reply on seals we put a rubber backed mat on top to help.
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Old 23-10-2012, 17:07   #4
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We have an airtight box with a double sealed lid assembly from R parts. I'm pretty sure were not getting air leaks. Also there's nothing to defrost because even after running 24-7 since July there is no frost build up on the evap. Just a light coating of ice.

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Old 23-10-2012, 17:22   #5
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Re: Excessive Moisture on Evaporator?

Nice looking fridge. Just wondering about this comment....

Quote:
Originally Posted by SV Demeter View Post
.. July there is no frost build up on the evap. Just a light coating of ice.
What is the difference between 'frost' and 'ice'?

I still need to seal the top of ours better and we have ice/frost buildup on ....



...the one end of the evaporator, arrow. That is about 2 months worth in our case. We don't have any dripping but I would think that if the frost was at a place were it was getting warmer air, in your case 38 deg., that it could then start melting at that point on the evaporator and drip,

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Old 23-10-2012, 17:40   #6
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Re: Excessive Moisture on Evaporator?

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Originally Posted by SV Demeter View Post
We get quite a bit of moisture on the evaporator that eventually drips off and periodically needs to be sponged out of the bottom of the box. Im wondering if there is anything to be done about it? Box stays easily at temp and system uses very little power. .
Thats sounds actually not bad - since you say you have no airlock you mostly get moisture from the food and when opening the fridge. Thats to a certain extend normal and will increase in the tropics. That frost/ice melts during the "compressor off" phase - which saves you defrosting for some time. Sounds perfect to me.

One of my fridge has a vented radiator style evaporator - ice buildup is a problem in the tropics, particular with this kind. So I programmed the digital thermostat to keep the compressor off for 30 - 40 mins between cycles. Since then the ice has time to melt and I just de froste once every month. But yes I have sometimes some water in the fridge - but on purpose
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Old 23-10-2012, 19:01   #7
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Re: Excessive Moisture on Evaporator?

Yeah I think that what is actually happening is frost (white flakey stuff) is not forming on the evaporator because I use a flat plate evaporator and only set the fridge to run as a fridge, not a freezer. So the evaporator is getting cold enough during cycles to keep the box temp between 38-39 degrees. Moisture forms on the evaporator as its condenses from the air in the box. When the unit cycles this moisture freezes into ice (clear not white flakey). Between cycles the evaporator's temp rises to that of the box or close say 35-36 degrees maybe. At this temp the ice melts back to condensation and sometimes drips off. Every other week I need to sponge it out of the bottom of the box. So all in all this is probably not a problem its just the result of setting my box to run as a fridge and not a freezer. Im using a Dometic CF-40 standalone unit as a freezer, set to 0*F it pulls about 2.5amps when running and runs about 10hrs per 24.
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Old 23-10-2012, 20:21   #8
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Re: Excessive Moisture on Evaporator?

Ah the joys of refrigeration. Any cracks in the lid or box will allow moisture to be drawn into the box. The evaporator act's like a sponge and any little crack will allow moisture (in the air) to be drawn into the "lower dew point chamber", AKA the Ice Box. Plus every time you open the box the air inside gets saturated again and is wrung out on the plate all over again.. Its a feature, not a problem...

I know so not helpful.. Sealing the box up tight will help a little...
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Old 26-10-2012, 17:47   #9
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Quote:
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I programmed the digital thermostat to keep the compressor off for 30 - 40 mins between cycles.
Are you using an after market thermostat? If so, can you share where you got it?

I'd love to replace my analog thermostat!
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Old 26-10-2012, 18:36   #10
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Re: Excessive Moisture on Evaporator?

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Are you using an after market thermostat? If so, can you share where you got it?

I'd love to replace my analog thermostat!
Hi, off course, I used the following ordered from Frigoboat US: Coastal MK II Digital Thermostat/Thermometer was 125 USD or so - you can see a pic of both thermostats on my blog under projects. Tip I saved money and did just ordered thermostat with sensor but not prewired

This is some kind of industrie part - the delivered manual just provides basic information but there is the full manual online from the same guys: http://www.veco-na.com/images/Coasta...ion_Manual.pdf

Good Luck.
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Old 26-10-2012, 19:08   #11
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Thanks!
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