[Glitch]

So decided to see if I could improve the hot air venting situation from behind the Waeco CR50 fridge we have fitted in our self build camper.

Its been on my list of "things to do" for the last few years, so eventually got around to doing it. It was supposed to only be a case of adding a vent to the blank furniture panel mounted above the fridge....however things soon developed into something else.I:

As you will see from the photos below, I had a friend of mine make me up a custom fridge vent (can put anybody in touch with him for any kind of grill required) for me out of 3mm pin seal ABS. Super glued some fine midge/mossy mesh from Ebay on the rear of it along with a couple of lengths of 5mm square steel bar, also from Ebay (more on that later). And finally added one of our Vans "FootPaw" logos to finish it off.

Took the fridge out so I could take the furniture board that was mounted above it out to cut the required sized hole with my trust jig saw. Painted the cut edge in some matt black paint I had lying around and mounted some small rare earth magnets (also from Ebay) to the edge of the hole in the furniture board which then gives me a "stealth" look no fixings i.e. screws method of holding the vent in place via the power of magnetism to the steel bars (which also add some rigidness to the vent).

But it was whilst I had the fridge out and looking at the fan that was already affixed to the rear of the fridge to draw air through the heat exchanger that I thought, emmmm I could assist the movement of hot air from the rear of the fridge out via my nice newly fitted vent via the addition of a extra fan or two.

So having a quick rummage through my various boxes of Computer bits and bobs I came across a brand new Dust proof 92mm AcoustiFan which is a very quiet PC fan (used in media centric PC's). I quickly realised that 92mm is also the same size fan as the one that was fitted to the rear of the Waeco CR50 as well.

A quick measurement of the available space in the void above where the fridge sits and I determined I could fit in a couple of 92mm fans to aid with air flow. I then decided to replace the fan already fitted to the CR50 with my original AcoustiFan and obtain a couple more form Ebay (£10 each).

At the same time as ordering the fans I also ordered a couple of 500mm lengths of aluminium angle so I could create a frame to mount the two extra fans into when the arrived.

Then knocked up my frame held together with rivets, painted it black (so it cant be seen through the vent), mounted the PC fans to it using some silicone anti-vibration mounts, the whole thing was mounted to a piece of MDF which was screwed to the furniture just above where the fridge sits.

Sorted he electrics out so the extra fans are stepped to down run at 5V DC for minimum speed but maximum silence, but still draw air though (the speed reducing cables/resistors come with the fans). They are connected in parallel with the fan fitted at the rear of the Fridge as they only draw an extra 350mA each when running.

 

[Rugosity]

Looks great. Has it had any effect on performance of the fridge?

 

[Glitch]

Looks great. Has it had any effect on performance of the fridge?

Not really had the opportunity yet to see, but going away in July so hopefully have some fine weather and be able to see how it performs.

Technically any improvement in the ability to remove warm air from around the rear of any fridge should give an improvement in its efficiency as long as the air being displaced is replaced with cooler air...well that's what a friend who is an Air-Conditioning plant engineer tells me.

 

[Vera]

Where does your fresh air come from Glitch?
I mean the air into the fridge space before we get any smart @sses on here....I:

 

[t18con]

I had issues at Easter with the good Irish weather and thought my fridge would struggle with our upcoming trip to Lake Como, so likewise I installed a 92mm 12v computer fan from Maplins in the end gable behind the drivers seat. on a good day the difference is day and night, rear of the fridge stays completely cool. it only really vents the warm air out, allowing fresher cooler air to rise up into the gap. i'd imagine a top vent would be even better.

 

[Glitch]

Where does your fresh air come from Glitch?
I mean the air into the fridge space before we get any smart @sses on here....I:

Its coming either from underneath the fridge or the sides of both the fridge an dthe two units either side of the firdge. The photos dont show it but there is a 1/4" gap between the units either side of the fridge and the side panels of the van, which allow cool air to enter.

I think I will see how it goes for another season to see if adding any extra cool air ducting will be of any benifit.

 

[Rod_vw]

I have a similar arrangement on a CR65 however with some extra control.

The circuit for the original Waeco fridge fan is monitored with a high impedance miniature relay. If you try to draw too much current on the original circuit the fridge control unit shows a warning that the fan is overloaded!

The contact of the relay supplies 12v to a pair of thermostats like this eBay item 171544735226. One is 45 degrees the other 60 degrees. These are fastened to the fridge heat exchanger away from the Waeco fan, the lower temperature one brings two 80mm 12v computer fans into operation at low speed whilst if the second one operates it brings the fans in at full speed.

The fans are mounted in the furniture to extract air from above the fridge.

The above arrangement seems to be working well in elevated ambient temperature conditions but I intend to change the thermostats to 35 degrees and 50 degrees respectively as I think the system will be better.

I am away in France at present, the thermostats will be changed when I get home (just ordered from eBay) and tried out on another European trip later this Summer.

Rod

 

[Glitch]

Rod, that's very interesting, may have to have a play myself at doing something similar, shouldn't be too hard to retro fit as all of my fans have inline plugs and sockets. And I have some spare plugs & sockets left over from the PC fans I used that were supplied with them.

 

[larny]

My Waeco CR50 worked brilliantly last year in France , 30 degrees plus, on electric hook up with only the minimum ventilation at the rear. On the other hand when i had a caravan with 3 way absorbtion fridge in the south of france it really struggled when the temperature rose to 30. I rigged up a fan on the outside vents to try and improve the ventilation.

 

[t18con]

My Waeco CR50 worked brilliantly last year in France , 30 degrees plus, on electric hook up with only the minimum ventilation at the rear. On the other hand when i had a caravan with 3 way absorbtion fridge in the south of france it really struggled when the temperature rose to 30. I rigged up a fan on the outside vents to try and improve the ventilation.

yeah but on 240v, electric your fridge could have been sucking serious amounts of power, while if you're running it off the 12v supply, every wee bit of assistance helps save the leisure batteries. (although in truth the longest mine went without either driving or 240v supply was 16.5 hours on the boat to france.

 

[riley]

I have an Indel Webasto Isotherm DR49 pull out fridge. It has the same Danfoss BD35F compressor as the Waeco CR50

I too though ventilation was not the best in my van as it came from the converters, the standard fan was butting up to the furniture board behind the drivers seat so I cut a hole and fitted an aluminium louvred vent there so cool air is drawn in through that vent and dissipates vertically behind the fridge.

I also made a speed controller mod for the fridge. It was irking me somewhat that the fridge compressor run time was quite short and I think power is wasted starting up the compressor every few minutes. by introducing resistors in the thermostat circuit you can control the rpm of the compressor. I got a 4 position 2 way switch with 3 resistors (the fastest speed has no resistor) on the 2nd set or poles on the switch I connected the fan supply such that it does not run on the slowest speed. I set it to the slowest speed at night when ambient temperatures are low this makes the fridge very quiet. The resistor values to use for this are listed on the Danfoss BD35F data sheet, My fridge already had a resistor that meant it did not run at quite full speed so that has to be taken into consideration when choosing the resistor values.

Of course the main issue with the compressor run time is the thermostat arrangement with it being attached to the cooling plate, its not really measuring the internal temperature of the fridge, rather that of the cooling plate. Thats why when you load up your fridge and turn it on the compressor runs for a few minutes and then turns off for a while, even though the fridge is nowhere near the temperature it should be.
What I plan to do is replace the thermostat with a digital one installed lower down in the fridge. These have an adjustable hysteresis so you can easily control the compressor run time. Once that is in I plan to make it integrate with my solar controller so that when the solar panels are producing more power than needed the fridge runs cooler, this can be achieved by using the switched 12v output on the solar controller to close a timer relay for 10 minutes or so at a time to alter the resistance of the temperature probe so the thermostat thinks the fridge is warmer than it is by a few degrees. That way you are storing excess power generated by the solar panels as extra coolness in the fridge which should mean it doesn't need to come on much in the night.

Isotherm actually sell a kit to do pretty much all of the above, only problem is that it costs £164, I reckon I could achieve much the same thing for £20

 

[wiltshirewombat]

im quite content with my wiring abilities for putting in a leisure battery, connecting some LED lights, sink pump via rocker switches etc, but if I want to install a thermostat to my fridges heat exchanger, can you confirm that I just need to connect the positive that would be going to the positive of the PC fan that I have installed in my end cupboard to one of the legs of the thermostat and then connect the other leg to the positive wire going to the positive of the fan?

in my minds eye, the thermostat would be normally open, except when the temperature rises above 60 degrees, the thermostat then closes, completes the circuit and the fan fires up.

hope someone can help.

 

[Rod_vw]

Your 'mind eye' sees things about right.

Just consider the normally open thermostat as being a normal switch as you say it closes at the required temperature. Most of these thermo switches have quite a large tolerance range probably about +or- 5 degrees.

Rod

 

[wiltshirewombat]

Thanks for the quick reply, much appreciated.

 

[Ollymuk]

I have an Indel Webasto Isotherm DR49 pull out fridge. It has the same Danfoss BD35F compressor as the Waeco CR50

I too though ventilation was not the best in my van as it came from the converters, the standard fan was butting up to the furniture board behind the drivers seat so I cut a hole and fitted an aluminium louvred vent there so cool air is drawn in through that vent and dissipates vertically behind the fridge.

I also made a speed controller mod for the fridge. It was irking me somewhat that the fridge compressor run time was quite short and I think power is wasted starting up the compressor every few minutes. by introducing resistors in the thermostat circuit you can control the rpm of the compressor. I got a 4 position 2 way switch with 3 resistors (the fastest speed has no resistor) on the 2nd set or poles on the switch I connected the fan supply such that it does not run on the slowest speed. I set it to the slowest speed at night when ambient temperatures are low this makes the fridge very quiet. The resistor values to use for this are listed on the Danfoss BD35F data sheet, My fridge already had a resistor that meant it did not run at quite full speed so that has to be taken into consideration when choosing the resistor values.

Of course the main issue with the compressor run time is the thermostat arrangement with it being attached to the cooling plate, its not really measuring the internal temperature of the fridge, rather that of the cooling plate. Thats why when you load up your fridge and turn it on the compressor runs for a few minutes and then turns off for a while, even though the fridge is nowhere near the temperature it should be.
What I plan to do is replace the thermostat with a digital one installed lower down in the fridge. These have an adjustable hysteresis so you can easily control the compressor run time. Once that is in I plan to make it integrate with my solar controller so that when the solar panels are producing more power than needed the fridge runs cooler, this can be achieved by using the switched 12v output on the solar controller to close a timer relay for 10 minutes or so at a time to alter the resistance of the temperature probe so the thermostat thinks the fridge is warmer than it is by a few degrees. That way you are storing excess power generated by the solar panels as extra coolness in the fridge which should mean it doesn't need to come on much in the night.

Isotherm actually sell a kit to do pretty much all of the above, only problem is that it costs £164, I reckon I could achieve much the same thing for £20

I know this is old now but have loved to see a write up with photos as a blog or video for this.

Having just spent a night sleeping in a van with a very noisy dometic CRX50, I'd love to have a better way if controller the * compressor and fan combo at 3am.

 

[Rod_vw]

In my latest camper (it's now six years old) I have a STC1000 temperature controller with a higher fixed thermal switch to provide fast speed of the fans in very hot situations. That has worked well with a Waeco CRX65 in Europe this summer.

Our fridge isn't at all noisy when sleeping in the rear of our LWB high roof T6 but I'm sure the actual installation of the fridge and insulation of the bodywork behind it makes a great difference to the noise.

I'm guessing that I will install something similar in the TGE when that is built and the fridge will be closer to the bed in that so it will be more critical.

 

[Ollymuk]

Interesting. I have an St 1000 managing my home brew ferment temperature so could repurpose that.

Have you then fed a temperature prob from the St 1000 in to the fridge by some means? Using a small drill hole or similar? And are you using the standard fan or did you use a different one? (I tried to shoe horn my favourite super quiet pc fan but it didn't fit in the space allocated in the compressor grill).

Any photos would be really welcome.

Olly

 

[Rod_vw]

Interesting. I have an St 1000 managing my home brew ferment temperature so could repurpose that.

Have you then fed a temperature prob from the St 1000 in to the fridge by some means? Using a small drill hole or similar? And are you using the standard fan or did you use a different one? (I tried to shoe horn my favourite super quiet pc fan but it didn't fit in the space allocated in the compressor grill).

Any photos would be really welcome.

Olly

No the temperature probe is on the hot side of the evaporator assembly on the back so switches on the additional fan when this reaches the set temperature (40 degrees C at present) this starts the additional fan but via a resistor to run it at a reduced speed. There is a fixed thermo switch (higher temp) across the resistor to short that out to bring the fan up to full speed. The additional fan is fitted in the top of the fridge enclosure to help the circulation of air across the fridge radiator. As my fridge is adjacent to the SMEV 555 grill there is an opening that allows the air from the fridge enclosure to exit to the rear of the grill and then out into the van via the vent at the top of the 555.

Yes I know I have probably got more space than you as this is a LWB High roof van (Reimo roof).

Three of my creations, newest at the rear...