Dometic or Thetford fridge

[telsdog]

I’ve had enough of the piece of shite Dometic RMDT8505 that has always been a problem when temperature goes much above 20deg. I am thinking of replacing it with either a Dometic RMD10.5T or a Thetford N4145. Has anyone got one of either and can confirm they actually work in warm weather.

 

[Richard n Ann]

They are both absorption fridges so they work in a fashion, but compressor fridges sre great in high ambient temperatures

 

[TCG]

Yes we have the Dometic 10.5 compressor we had it fitted in February been to France for 2 sessions of 3 weeks.. and have to say it’s excellent… direct feed from the lithium…. Really quite does not make any noise at all, and I’m a light sleeper.. much bigger internally than our old 8555… Not cheap £ 2,300 but that was fitted. Had it done by the Dometic workshop in Tewkesbury

 

[Lenny HB]

We have the smaller 130Lt Dometic Series 10 had the cooling is much better that the 8000 series.

Previous two vans had 8505's never had any problems with them over 10 years but did need fans to cope with hot weather.

 

[M-J]

I’ve just switched from a 7655 to an 8505, hope I don’t get similar issues, I have fans installed which should help

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[telsdog]

We have the smaller 130Lt Dometic Series 10 had the cooling is much better that the 8000 series.

Previous two vans had 8505's never had any problems with them over 10 years but did need fans to cope with hot weather.

I have 3x 140mm fans in the top vent, 2x 50mm fans inside the fridge, replaced the paste and here are the temps. Outside temp is 22deg. Yesterday was 28deg and the fridge warmed up to 18deg and hasn’t recovered. Been on gas all day.

 

[Lenny HB]

I have 3x 140mm fans in the top vent, 2x 50mm fans inside the fridge, replaced the paste and here are the temps. Outside temp is 22deg. Yesterday was 28deg and the fridge warmed up to 18deg and hasn’t recovered. Been on gas all day. View attachment 946326

But the freezer is at -13 so the cooling is working. There is only one cooling circuit, you said you replaced the paste so that would suggest you have put the paste on too thick. Providing there is good heat transfer between the cooling pipe and the heat sink there is no way the freezer can work without the fridge working.

 

[telsdog]

I’ve had this van for 5 years and it’s always been the same. I complained to dealer after first trip and although they couldn’t find anything wrong they replaced the cooler unit. Next trip away it was the same, dealer insisted there was nothing wrong and it was the way we packed it. Below 20deg it works perfectly and whenever dealer checked it was always below 20deg. If you look at fridge temp you can see in small letters the min temp was 3.05 on September 5th, the day we left.

 

[DC4JC]

We've got the Thetford N4145 on our latest van and I have to say really pleased with it. Having had the 8 series Dometic previously, which I wrote to them and said wasn't fit for purpose after testing carried out by workshop.
No fans fitted or required, worked very well with temps in the mid to late 30s in France.

 

[telsdog]

We've got the Thetford N4145 on our latest van and I have to say really pleased with it. Having had the 8 series Dometic previously, which I wrote to them and said wasn't fit for purpose after testing carried out by workshop.
No fans fitted or required, worked very well with temps in the mid to late 30s in France.

Many thanks for your reply. That’s encouraging as the Thetford is £1000 cheaper than the Dometic.

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[Richard n Ann]

I’ve had this van for 5 years and it’s always been the same. I complained to dealer after first trip and although they couldn’t find anything wrong they replaced the cooler unit. Next trip away it was the same, dealer insisted there was nothing wrong and it was the way we packed it. Below 20deg it works perfectly and whenever dealer checked it was always below 20deg. If you look at fridge temp you can see in small letters the min temp was 3.05 on September 5th, the day we left.

It will do this if there hasn't been enough refrigerant put in it in the factory. By the time the refrigerant leaves the feezer it has all evaporated off to a vapour, and vapour won't cool the fridge very well at all.

Check the pipe exiting the condenser fins outside, if it's still hot you haven't got enough air flow, if it's cool the system is short of refrigerant. It should be just warm

PS on a cool day the freezer will have less heat to extract so there is liquid refrigerant to spare which cools the fridge

 

[telsdog]

Thanks. If it stops raining I’ll have a look. But why does the freezer still work in warm weather and not the fridge? As Lenny says, it’s the same cooler.

 

[Richard n Ann]

Thanks. If it stops raining I’ll have a look. But why does the freezer still work in warm weather and not the fridge? As Lenny says, it’s the same cooler.

Because it flows into the freezer first in it's liquid state, it boils away merrily at about minus 20c (refrigerant temp) cooling the freezer fins. There is no liquid left by the time it gets to the fridge evaporator, just refrigerant vapour which is much warmer

 

[telsdog]

Thanks for the information. So it’s buggered then, and has been since new. I’ve lost all confidence in it so won’t be spending anymore time a money on it. Just need to know which one to replace with.

 

[telsdog]

What did you use when you converted your fridge to compressor? Can you buy a kit?

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[Richard n Ann]

Thanks for the information. So it’s buggered then, and has been since new. I’ve lost all confidence in it so won’t be spending anymore time a money on it. Just need to know which one to replace with.

Just check that condenser pipe outside to confirm, if it's still hot the refrigerant may still be half in it's vapour state. The purpose of the condenser is to fully turn it back to a liquid.
If the freezer evaporator is receiving only half liquid half vapour that's another fault that may give the same problem

 

[Richard n Ann]

What did you use when you converted your fridge to compressor? Can you buy a kit?

Yes it was 300 odd quid, easy to do, the pipes connect with 2 nuts that automatically release the refrigerant when you tighten them up

 

[SVMC15]

I had an annoying issue with my unit for about six months. It would cool really well, be happy for about 24 to 36 hours and then start heating up, properly heating up to the point where the freezer would defrost. I turned the fridge off and let it settle overnight and turn it on the following morning, all fine for another day and a half!!

I tried all sorts of things, even had a motorhome dealer look at it. Eventually when I came to change the thermistor (even though measuring the resistance showed it was fine!) I noticed that it was not sat in its clip! Once I put it in place it has been fine for over four years. I have been waiting for it to pack up ever since though as the mixture has been boiled to death.

 

[Richard n Ann]

Yes it was 300 odd quid, easy to do, the pipes connect with 2 nuts that automatically release the refrigerant when you tighten them up

This is the kit, gone up of course, might be less expensive elsewhere..

Isotherm GE-80 Air Cooling Unit Fridge kit

Cool up to 80l of space in one go with the Isotherm GE80 Cooling Unit Fridge Kit, designed for motorhomes and boats. Shop All Isotherm Products

www.youboatmarine.com

 

[telsdog]

Thanks for the advice everyone. Has anyone else got one of the potential replacements and could comment on there suitability?