I have compressor fridge in the campervan. The cabinet it’s in has vents by the heat exchanger bit, but I’d like to get a bit more air moving past it to increase it’s efficiency so I thought I could wire in a small fan (something like a PC fan) that could blow the air past.

The 12V supply to the fridge is easily accessible in the place I’d need to put the fan. I obviously don’t want the fan running all the time, only when the fridge compressor is going, so is there some kind of switch/relay/doohickey I could wire in there that would sense when the fridge is running that I could use to power the fan?

Of course, there’s also the question of whether (well, actually, how much) the power needed to run the fan would offset any efficiency gains in running the fridge. Any idea?

If they’re both 12v, just splice the feeds Shirley?

IANAE

Raspberry Pi with a microphone, relay, and optionally a temperature sensor.

Send the audio from the microphone to Amazon’s Alexa service, having taught Alexa to recognize the compressor as your wake word. Then create an Alexa skill and hook that up to the Raspberry Pi which switches on the fan via a relay.

Easy.

Obviously only works if you’ve got an internet connection, but if that’s not working you’ve got much bigger problems than just an overheating fridge.

If they’re both 12v, just splice the feeds Shirley?

In which case the fan will run all the time, or only when I manually switch it on. I want it to come on automagically when the fridge is running.

IANAE

Clearly 🙂

Raspberry Pi with a microphone, relay, and optionally a temperature sensor.
Send the audio from the microphone to Amazon’s Alexa service, having taught Alexa to recognize the compressor as your wake word. Then create an Alexa skill and hook that up to the Raspberry Pi which switches on the fan via a relay.
Easy.
Obviously only works if you’ve got an internet connection, but if that’s not working you’ve got much bigger problems than just an overheating fridge.

Problem with this is that The Man will then know when I’m running the fridge. I prefer my beer cooling to be Off Grid.

In which case the fan will run all the time, or only when I manually switch it on

I presume he means splice it into the motor feed rather than the main fridge feed. A bit trickier to do but requires no additional sensing.

You could run the fan from a thermal switch. It’ll be a bit slow to react but it should come on when the cavity is warm.

I’d be tempted to just get a very low power fan and have it running all the time the fridge is on. The power use will be minuscule compared to a 12v fridge

Of course, there’s also the question of whether (well, actually, how much) the power needed to run the fan would offset any efficiency gains in running the fridge. Any idea?

No idea on the electrical side but I’d guess slim to negative on any actual gains from a heat transfer perspective. Making sure the condenser is kept clean of dust and fluff would likely give you better results.

My fridge compressor has a fan built into it – has yours not or is it deep in a plastic box so you can’t see….

This is mine – the fan is buried inside the heat exchange ‘grill’bit.

It’s not actually on that often – seems it has to get very hot before it bothers to turn the fan on. Nevertheless I could I guess split the cable to the fan and add another without much bother. Failing that I would play around with a multimeter and see which of the wires from the thermostat went positive when the compressor came on; split that and use it to trigger a second fan via a relay or mosfet.

I presume he means splice it into the motor feed rather than the main fridge feed. A bit trickier to do but requires no additional sensing.

Yeah, that was my first thought, but the main feed is the only one I have access to without a lot of furniture dismantling.

No idea on the electrical side but I’d guess slim to negative on any actual gains from a heat transfer perspective.

Really?

A small fan won’t actually move a significant amount of air and given that the temperature driving forces are fairly small I don’t think it will actually do a great deal but it’s just a guess. If it made a significant difference then we’d be using forced convection on all bits of heat transfer and we don’t. Like I said keeping the condenser clear of fouling will likely yield a better result.

You just need a thermostatic switch in the rear enclosure of the fridge cabinet, when it heats up the fan comes on, when it drops to preset temp fan goes off.
Simple.

RS components help line is a good start.

I have compressor fridge in the campervan. The cabinet it’s in has vents by the heat exchanger bit, but I’d like to get a bit more air moving past it to increase it’s efficiency so I thought I could wire in a small fan (something like a PC fan) that could blow the air past.

another one of those companies that thought it was a good idea to vent the fridge *exchanger* into the cabin.

boxed in exterior venting is the solution if efficiency is what you want. transferring some warm air into a warm living space will be minimal help.

Something like this just choose the temp at which you want the fan to cut in.
A small 12v fan should draw a lot less than one amp.

transferring some warm air into a warm living space will be minimal help.

Depends how much you want to heat the main living area…

You can buy dedicated caravan / motorhome fridge fans with a thermal switch. You install them someplace near the cooling fins to improve heat transfer, they switch on and off as required based on the heat coming off the fins.

I installed one in ours, it makes a difference, actually, I just leave it running all the time as its pretty quiet. I also used wood to block the air channel so that the air pulled by the fan must go through the fins, that also helped.

another one of those companies that thought it was a good idea to vent the fridge *exchanger* into the cabin.

… transferring some warm air into a warm living space will be minimal help.

TBF, it has two vents, one into the boot and one into the underseat space. The latter especially is usually pretty cool. I’d probably get the fan(s) to suck this cooler air through to the heat exchanger.

Something like this would work, wouldn’t it?

https://www.amazon.co.uk/KKmoon-Current-Detection-Sensing-Detecting/dp/B01N4DEHG0

and

https://uk.rs-online.com/web/p/axial-fans/7897867/

Depends how much you want to heat the main living area…

It tends to be in the summer when you really really want the fridge to be efficient the interior of the van is solar gain heated to hotter than haides

Seriously though venting the fridge properly to the exterior made a huge difference to efficiency and speed of cooling of my fridge over the manufacturers stock piss poor excuse for an install vented to the interior.

Seriously though venting the fridge properly to the exterior made a huge difference to efficiency and speed of cooling of my fridge

I don’t doubt it, but it’s not an option in this case. As above though, I am looking to vent it to/from the underseat area, which always stays cool, and/or the boot space, which is always at least left on latch, so effectively venting outside.

@IHN that sounds like an Amdro with Waeco top loader? I think the controller has a fan output on it. It’s on my list of job that I might get around to eventually, although it’s never been an issue, even in 25*C plus heat. I did manage to plug the main power feed back on to the Spade terminals without taking the furniture apart so you might be able to reach to push a couple of connectors on.

Don’t know what conditions the fan runs in, e.g. if it’s on with the motor or temperature controlled?

Seriously though venting the fridge properly to the exterior made a huge difference to efficiency and speed of cooling of my fridge over the manufacturers stock piss poor excuse for an install vented to the interior.

Are you talking compressor or absorption fridge?

@IHN that sounds like an Amdro with Waeco top loader? I think the controller has a fan output on it….I did manage to plug the main power feed back on to the Spade terminals without taking the furniture apart so you might be able to reach to push a couple of connectors on.

Indeed it is, I can’t get to the controller though (or am looking in the wrong place). What I can get to is the connection to the ‘main’ van electrics (two spade connectors) which is just through the square hole at the back of the unit.

I’d 2nd/3rd venting to the outside – our motorhome fridge can pump some significant heat out of the top vent when it’s running in summer and the air in the van is a lot warmer than ambient outside.

There’s probably switched supply soemwhere in the fridge and it’s worth finding it so you get the benefit of any fan assistance when you’re not around.

Are you talking compressor or absorption fridge?

it makes no odds . both need a temperature difference across the condenser. the bigger the difference the less mechanical input required.

it makes no odds . both need a temperature difference across the condenser. the bigger the difference the less mechanical input required.

I find that our compressor fridge is fine, previous Vans with absorption fridges have needed vents to the outside world or at least some fans to draw heat away.

@IHN if you look through the right hand section of the cupboard under the sink you can see the side of the compressor/heat sink. I can reach in and feel the connections on the side of the controller so you should be able to connect up a couple of Spade connectors & then take a photo to check you’ve connected up to the right terminals.

Here’s a couple of photos I’ve just taken by reaching in.

He’s asking about efficiency.

Proper venting will improve effiency of both types of fridge.

I’m not disagreeing, it would definitely help, but knowing the layout of his van it’s not practical. I’m just pointing out that compressor fridges aren’t as bad compared to absorption fridges.

As an aside an old van I had with internal vents top and bottom of an absorption fridge unit didn’t even start to get cold in summer temperatures until I added fans, with a couple of computer fans it was more than acceptable and would make ice cube in the middle of the summer in Southern France & Italy.

Phil, that’s wicked, thanks.

As an aside an old van I had with internal vents top and bottom of an absorption fridge unit didn’t even start to get cold in summer temperatures until I added fans, with a couple of computer fans it was more than acceptable and would make ice cube in the middle of the summer in Southern France & Italy.

I moved mine to gas and abandoned the 12v side of the fridge as It uses next to no gas and on full will freeze the milk in the main compartment on even the hottest day on anything but the lowest setting.

And best of all complete silence.

Phil, that’s wicked, thanks.

No worries, let me know how you get on. I might do it too one day.