Fridge modification.

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NeilandPat
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Fridge modification.

Postby NeilandPat » Sun Jun 11, 2017 1:02 pm

I have noticed what I think is a design flaw with the Waeco fridges.

The difference in temperature between the top and the bottom of the fridge is quite dramatic. As per the laws of physics all the cold goes to the bottom leaving warmer air in the top part, which is where the thermostat is.

This means that the fridge is working overboard to try and get the thermostat cool enough to turn itself off. This results is the bottom of the fridge nearly freezing and a thick coating of frost forms on the back. The frost acts as an insulator and compounds the issues.

I have today fitted a circulation fan within the fridge that sucks the warmer air from the top half and pumps it down to the bottom. My hope is that it will create a more even temperature within the fridge and hopefully make it more efficient.

The fan is connected to the compressor fan so it comes on and and off with the compressor.

I will let you know how it works .

Neil
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christyler
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Re: Fridge modification.

Postby christyler » Sun Jun 11, 2017 3:17 pm

Oh, now that's a cool idea, if you pardon the pun.

and very nicely executed if i might say, that should do the trick nicely.

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bromleyxphil
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Re: Fridge modification.

Postby bromleyxphil » Sun Jun 11, 2017 5:06 pm

NeilandPat wrote:I have noticed what I think is a design flaw with the Waeco fridges.

The difference in temperature between the top and the bottom of the fridge is quite dramatic. As per the laws of physics all the cold goes to the bottom leaving warmer air in the top part, which is where the thermostat is.

This means that the fridge is working overboard to try and get the thermostat cool enough to turn itself off. This results is the bottom of the fridge nearly freezing and a thick coating of frost forms on the back. The frost acts as an insulator and compounds the issues.

I have today fitted a circulation fan within the fridge that sucks the warmer air from the top half and pumps it down to the bottom. My hope is that it will create a more even temperature within the fridge and hopefully make it more efficient.

The fan is connected to the compressor fan so it comes on and and off with the compressor.

I will let you know how it works .

Neil

I hope you are going to start selling the kit at half price to forum members :D

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bromleyxphil
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Re: Fridge modification.

Postby bromleyxphil » Sun Jun 11, 2017 5:06 pm

Well done Neil......great idea.

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Brian-reynolds
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Re: Fridge modification.

Postby Brian-reynolds » Sun Jun 11, 2017 9:40 pm

Interesting idea Neil, cant wait to hear the results of that.

Also like to say it does look good, very professional.

B.

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Re: Fridge modification.

Postby Grommet1 » Mon Jun 12, 2017 6:32 am

I've noticed the same when I managed to burst some coke cans that iced up even though the constant temp monitor i had in the fridge was measuring a min temp of above 2 deg at the front of the fridge. By coincidence I was reading Steve's book yesterday and in one of the case studies of a Merc 1124AF owned by John Brooks he mentions fitting an internal fan to his Waeco.
I wonder if it might make it use more juice though from increased convection loss. Not easy to measure that.

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NeilandPat
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Re: Fridge modification.

Postby NeilandPat » Mon Jun 12, 2017 7:01 am

I met with John Brooks in Portugal a few months ago and we discussed this issue at length.

The idea really came from him.

I will let you know the results

Neil

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Re: Fridge modification.

Postby crinklystarfish » Mon Jun 12, 2017 7:11 am

Well executed Neil and I look forward to reading / hearing your impressions.

I agree that it'll make for a more even temperature but I'm sceptical of the logic that it'll improve efficiency (if by that you mean power consumption).

There are more physics at work than hot air rising. Warmer air will always relinquish its heat to cooler air. Granted the warmer air will rise but unless your goal is to have all shelves at a more even temperature that doesn't really matter in terms of power efficiency.

The mean internal temperature won't be affected and I have a hunch - and it is just a hunch - that it'll simply lead to more cycling: but that each cycle will last for a shorter period.

If this happens, given the power required at startup, it could even suck more power overall. I stress this is just intuition on my part and I hope it's wrong. I think upright CR-series Waecos are wretched things and I rue the day I bought mine.

I don't think it matters where the thermostat sensor actually sits, you can simply adjust it to reflect the temperature at that specific point in the cabinet.

As above, I stress I'm shooting from the hip with this and whichever way it goes it's great to see out-of-the-box thinking.

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Re: Fridge modification.

Postby crinklystarfish » Mon Jun 12, 2017 7:19 am

Should just add - the internal boxes I use in ours seem to do a good job of retaining some of the cooler 'fridge-bottom' air when the door is opened and providing they don't interfere with internal (passive) air circulation, cool-air-retaining boxes seem to be a good bet on the next-to-bottom shelves too.

The real answer is - of course - a chest design. I'm actually cooking up a plan to install a couple of small ones, one to be kept on, the other as insulated storage / stand by if the primary one fails. If (when) our CR110 fails again, that's where I'm going...

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NeilandPat
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Re: Fridge modification.

Postby NeilandPat » Mon Jun 12, 2017 8:10 am

You may be right Steve.

The power consumption is a secondary issue.

I had the situation where the bottom of the fridge was freezing food and the stuff in the top was going off as it was getting no cooling effect.
Hopefully it might resolve this issue

Neil


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