Heatsinks Question

Burt65 · Veteran Member

Heatsinks Question

Whenarewethere · Guru

It was one of those projects that got out of hand. The air output at the compressor is extremely hot after a few minutes. So I was just trying to cool the air as efficiently as possible, also in a tight space which doesn't help cooling.

The red heat sinks (red were the cheapest) were for RC (radio controlled) scale car motors. 2 heatsinks cut precisely to size & forced in the pipe with a bench vice. In 3 rows. It was a lot of work. It was not the ideal way to have the heatsink, but I looked endlessly for any heatsink that I could modify & that was the best I could come up with.

The external heatsinks were from LED light fittings, again modified. Also thermal paste under those. I also added a high volume 120mm fan.

I also have a moisture trap. It's also handy as it shows PSI & you can set it to the PSI you want. The system turns off at 135 PSI. I could go up to 150 PSI.

Later because I was "bored" I made an after cooler. The after cooler I can also drop in the fridge to help condense any moisture further. So I have refrigerated condensed air.

I have looked at a desiccant drier, but it's probably going a touch overboard. Also finding a space is another issue as they have to be a decent size.

When you pump up tyres any moisture in the air is multiplied by how much you compress the air. Unless the moisture is condensed in the system, it goes into the tyres.

With 3 compressors the system can supply 4.5 CFM at 90 PSI. Also have a 4 litre air tank. I have a second air tank but just couldn't find a space for it.

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Moisture trap 145psi_121306.jpg

IMG_9157 Moisture trapwater condensation freelander air compressor_073541.jpg

2 small oil coolers used for the after cooler.

The fans now have fan guards.

I have also mounted the compressors on quick release fittings so if they need to come out for one reason or another it is very easy. The airlines all have quick release connections everywhere.

I can also use the compressed air with a water venturi gun to clean the car in the outback at 0.5 litres per minute. The water used this way is slightly abrasive & cleans off dirt really well.

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It was a fun project to see how far I could push things. It Is a pleasure to use because it is so fast.

Burt65 · Veteran Member

Thank you Whenarewethere for the detailed reply...

Now that you mentioned the origin of the heatsink, I can actually see it. You would surprised by how many places in an RV there often needs of a better cooling solution.. That's why I was really interested to find out about the origin of those heatsink.. It is a great modification..

I completely understand where you are coming from.. I had a similar experience with the Dometic fridge RPD 218, advertised as a class T, where the website of the Chinese company that makes the compressor, clearly state that's only a class ST under the climate classification.. The truth was that while the freezer did perform well and within the T rating, the fridge part failed miserably, with an average temperature and fluctuation between 6-12° (this in my books is not safe for foods)

To cut the story short, after several modifications, I was able to get the fridge to perform a bit better when the outside temperature went above the 40°.. Still the other huge problem with the Dometic fridge is that in 2025 they still required to be defrosted manually.. To me, it didn't make any sense for a fridge so expensive to have still a 1970 design.. Eventually it was replaced with a new Samsung 320 litre frost free at a third of the cost of the latest Dometic RUC 6408 (still not frost free) and life got easy again..

Here some of the modifications:

The extra Maglev fan pointing directly at the compressor

The compressor completely covered in heatsink to further improve the overheating issues

I managed to get the fridge to work at the correct temperatures, but eventually the defrosting issue and the very small freezer, got the best out of us. This fridge had to go!

For the record, most of the heatsink are from Jaycar Electronics.. Another great source of heatsink is from old CPU fan and heatsink...

Brianvicki · Veteran Member

Just checking, was your dometic a 3 way fridge, and was the Samsung just 240v?

-- Edited by Brianvicki on Friday 18th of July 2025 10:48:38 AM

Whenarewethere · Guru

This thread explains extra insulation & other modifications to improve fridge efficiency.

https://thegreynomads.activeboard.com/t65059593/extra-fridge-insulation-wattage-test/

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Burt65 · Veteran Member

Brianvicki wrote:
Just checking, was your dometic a 3 way fridge, and was the Samsung just 240v?

-- Edited by Brianvicki on Friday 18th of July 2025 10:48:38 AM

As mentioned, it was the RPD 218 (2 way) 12/24 or 240. I believe the RMD model, was the 3 way one.. It has been a while now, so I can't really remember, but I think it is/was basically a 240V fridge with a voltage regulator built in. You can clearly see it, in the second picture, next to the compressor on the left. That also used to get really hot, (mainly I was using the fridge on 24 Volts)..

The Samsung it is a standard domestic fridge, so it is only 240V and it uses much less power, as there is no voltage regulator, (the inverter is already on all the times), and it doesn't stay on 14 hours per day like the Dometic used to. The Samsung does proper cycling and therefore cools more efficiently.. I don't think Dometic's fridges are the best option for people like us on the road 24/7/365, for several reasons..

Whenarewethere · Guru

Quite a few have changed to household fridges in caravans. They are a fraction of the price. More efficient. Cool better from comments I have read.

If it does break after X years you are nevertheless so way in front, what's not to like! Remove the dead end toolbox on the A frame & replace it with the a system compressor (35kg better than on the roof) & compact quiet evaporator inside.

Some of these manufacturers have to pull the finger out!

It's the same with 2.5kW split system air conditioning (I have 2 of them in properties, last one installed December 2024). They so efficient you can run it off batteries. Even a modest size AH capacity with careful running (& reasonable solar input)...

...cheaper, more efficient, cools better, if it dies you are ahead.

People have to think outside the box!

I did use a typical 4wd outback fridge/freezer/esky unit in my car, but I have a car only. I didn't care what brand, it had to fit in a space (it also required modifications).

I even considered buying a fridge/freezer kit they use in yachts, & totally build my own ice box insulation design (I may still do it for a "fun" project).

But at the very minimum, look at air flow/ventilation, dust/dirt (thermal blanket), additional insulation (if seperate condenser). Not difficult stuff for vastly improved system.

I even designed a fridge mount to 6mm thickness. The manufacturer's design was too high for the space I had.

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Not difficult stuff, & it is a PHD equivalent for us oldies!