Domestic RM122 fridge help

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Domestic RM122 fridge help

Postby petethefeet » 24 Jun 2017, 17:28

Hi all,
I have a RM122 two way (12v and gas) fridge in a 1982 Devon, all working and no problems.
I know there was a 3 way (12 , 230 and gas) version, is it a simple to add the 230 volt option; new element and suitable wiring?
I run on the 907 gas bottles that run out at the wrong time and they are expensive. For the last 4 days I could have run it on 230 v if I could without using up my gas.

Any ideas?

Thanks :ok
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Re: Domestic RM122 fridge help

Postby richlaz » 24 Jun 2017, 17:44

You would need the cylinder which the heating element sits into. Would be a bit complicated...

Best solution would probably to use a 240v AC to 12v DC power supply / transformer...

Then you could use the existing 12v element when on hook-up :)
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Re: Domestic RM122 fridge help

Postby petethefeet » 24 Jun 2017, 17:49

Rich,
The transformer/power supply route was my second option as i can then charge the leisure battery from it as weĺl if needed.
Will keep looking at all the options

Thanks for the input
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Re: Domestic RM122 fridge help

Postby a1winchester » 26 Jun 2017, 19:47

12v refridgeration isn't great. It hardly holds its own on a warm day.
240v seems the best of the 3 (on mine anyway). So maybe look for a replacement 3 way fridge?
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Re: Domestic RM122 fridge help

Postby petethefeet » 27 Jun 2017, 11:45

I assumed the 12vdc and 230 vac heaters were the same wattage and hence the same cooling ability.
I don't really want to replace the fridge because it works well on 12 v and gas, it is good condition as well as the additional cost involved.
If I could buy the 230 heater element and sort all the wiring I would go that route but it appears I need more bits to get the conversion sorted.

Regards
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Re: Domestic RM122 fridge help

Postby bootie3367 » 27 Jun 2017, 16:03

a1winchester wrote:12v refridgeration isn't great. It hardly holds its own on a warm day.
240v seems the best of the 3 (on mine anyway). So maybe look for a replacement 3 way fridge?


I can second that.
I have a 3 way which I plugged in overnight on 240v and it was C H I L L Y in the morning. Unplugged and switched over to 12v........
unfortunately we decided to drive through Spain at the start of the heatwave last week, 42 plus in the cabin and the fridge temp kept climbing.
Parked up for the night and changed over to gas, yeah, that was OK started to bring the temp down but again it was battling the elements and even with the fan going full time it still struggled.
It wasn't until we got into North England and Scotland that the 12v came into it's own.
Not just holding a temp but actually dragging it down which was nice.

Sorry for hijack.
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Re: Domestic RM122 fridge help

Postby petethefeet » 31 May 2018, 20:14

Well, for a bit of an update.
I fitted a 230vac to 12vdc power supply that runs the 12v heater for the fridge, we ran it last weekend for the first time, it ran really well getting ice cubes for the G&T :ok .
It was almost running too cold with a build up of heat in the compartment the power supply is in so I was thinking of adding a thermostat to the trigger the power relay to the fridge to control the fridge temp and reduce the heat output of the power supply.
I think later dometic fridges had a thermostat as standard, where was the thermocouple sited to sense the compartment temp? Did it sense the fridge temp or the freezer element temp?

Thanks for your help
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Re: Domestic RM122 fridge help

Postby petethefeet » 17 Jun 2018, 21:01

Another update.
I fitted one of these from EBay item=223020482199 with the sensor cable tied to the plastic mouldings around the cooling element. I used it to trigger a high current relay that runs the fridge.
Appears to work well when left over night to pre cool the fridge prior to going on a trip
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Re: Domestic RM122 fridge help

Postby petethefeet » 08 Jul 2018, 15:21

Update to an update.
After 2 weeks in France, the power supply and fridge set up worked will. One issue was the ambient temp in the van on some days, this would be am issue with any fridge. The top of the fridge was almost too hot to touch a few times due to the heat running up the back and not being drawn away due to the Devon design, if a small fan was placed to blow in at the front low down the heat dropped considerably. I can see why some conversions have large plastic vents top and bottom.
So it probably saved me at least a £25 gas cylinder as it ran on mains or 12v all the holiday.
I will try to insulate the top of the fridge a bit more and possibly fit a small pc fan to give a bit of air movement round the back of the fridge.
The power supply was fitted in the cupboard next to the fridge, this got hot as well so we took the door off when we were parked up, nice and easy as it just slots onto two pins.
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Re: Domestic RM122 fridge help

Postby adie89 » 14 Jul 2018, 21:36

Fit one of these in your upper vent to draw the hot air out. It will help keep your van cool and the fridge run more efficiently, and so draw less power and create less heat.

If you don’t want to splash out, a coup,e of old computer fans, cable ties powered off the fridge supply will help, you can enhance the cheaper option with a thermostatic switch if you like to achieve the same as the linked Brunner fridge vent

https://www.amazon.co.uk/Brunner-Double-fridge-fan-Electr/dp/B001CUY03K/ref=pd_sbs_263_1?_encoding=UTF8&pd_rd_i=B001CUY03K&pd_rd_r=8311e567-87ad-11e8-b707-a7ec52204a2a&pd_rd_w=8wC0k&pd_rd_wg=drr1U&pf_rd_i=desktop-dp-sims&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_p=5179604776422437276&pf_rd_r=ZP2HBT7BJYSM1WEG9PAD&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=ZP2HBT7BJYSM1WEG9PAD
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Re: Domestic RM122 fridge help

Postby petethefeet » 18 Jul 2018, 20:04

Hi, thanks for the info on the fans, bit expensive but a good idea. We don't have a upper and lower vent on the side of the van just a Dometic vent for the fridge gas burner, this is an original Devon conversion so they were never fitted to our van.
Will look at a pc fan option, just enough to move the air slightly will probably do the job.
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