Optimising fridge performance on 12V

[acropolis22]

I know there are various reasons why an absorption fridge in a motorhome doesn't perform optimally when on 12V. Cable thickness etc etc.

I'd love to hear from the experts their top three points to check and fix.

 

[acropolis22]

Bump?

 

[Two on Tour]

Fans to extract heat out of the top vent grille is the number 1 must.

Getting rid of the crap thermal paste on the back of the fins on the fridge and freezes compartments and applying a good quality thermal paste greatly improved our cooling.

Check with a sheet of paper that your fridge doors seal is sealing all round, and the usual, don't open the fridge door more than you have to, and don't stand there gazing into the fridge with the door opening wondering what to have.

 

[acropolis22]

Fans to extract heat out of the top vent grille is the number 1 must.

Getting rid of the crap thermal paste on the back of the fins on the fridge and freezes compartments and applying a good quality thermal paste greatly improved our cooling.

Check with a sheet of paper that your fridge doors seal is sealing all round, and the usual, don't open the fridge door more than you have to, and don't stand there gazing into the fridge with the door opening wondering what to have.

Your second point is a new one on me. Cheers. Presumably this is about removing the fins and reapplying them with good quality paste to whatever they are attached to? You can tell I've never seen the back of one of these fridges.

 

[bigtwin]

Your second point is a new one on me. Cheers. Presumably this is about removing the fins and reapplying them with good quality paste to whatever they are attached to? You can tell I've never seen the back of one of these fridges.

You evidently haven’t seen much of the inside of your fridge either as that’s where the fins are located!

Ian

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[Two on Tour]

A fresh coat of thermal paste behind the aluminium cooling fins on our fridge.

 

[acropolis22]

You evidently haven’t seen much of the inside of your fridge either as that’s where the fins are located!

Ian

Really confused now............ Give us a clue. The photo shown by Two on Tour seems to show a compartment accessed by removing something. The inside of the fridge is definitely the wife's domain. I've no idea what it looks like. Can't see the van till tomorrow.

 

[Two on Tour]

Really confused now............ Give us a clue. The photo shown by Two on Tour seems to show a compartment accessed by removing something. The inside of the fridge is definitely the wife's domain. I've no idea what it looks like. Can't see the van till tomorrow.

 

[Folkranger]

Fans to extract heat out of the top vent grille is the number 1 must.

Getting rid of the crap thermal paste on the back of the fins on the fridge and freezes compartments and applying a good quality thermal paste greatly improved our cooling.

Check with a sheet of paper that your fridge doors seal is sealing all round, and the usual, don't open the fridge door more than you have to, and don't stand there gazing into the fridge with the door opening wondering what to have.

But I always stare in the fridge. How else can I make my mind up?

 

[autorouter]

You need to work out if the poor performance of the fridge is just on the 12V, or the same on all the heat sources (gas, 240V, 12V). The fixes suggested, such as renewing the thermal paste, affect the whole cooling circuit, whatever the power source. If it's fine on 240V, but poor on 12V, then thermal paste is not going to help.

The cooling circuit works best if just the right amount of heat gets to the pipes - not too much and not too little. Check the power of the mains heater element - it's probably 150 to 200W. Ideally the 12V element will be the same power. However voltage drop/cable losses can have a significant effect. For example, a 10% loss of voltage causes a drop in amps, so the power loss is about 20%.

Measuring the voltage at the 12V heater element is usually quite easy, but measuring the amps is a bit tricky. The easiest way is to read the display panel, it's likely to be reasonably correct. Or use a DC clamp meter, which clips around one of the wires without needing any disconnection. If you know the volts and amps, the power (watts) is volts x amps. Does this compare with the power of the 240V heater? or even the rated power of the 12V heater in the fridge spec list?

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[cmcardle75]

I know there are various reasons why an absorption fridge in a motorhome doesn't perform optimally when on 12V. Cable thickness etc etc.

I'd love to hear from the experts their top three points to check and fix.

Before everything else is considered, note that 12V is only for when the engine is running. It is not used when stationary. Before anyone goes any further, can you confirm that the engine is running?

 

[Off da Grid]

If you’ve got a frozen freezer block or frozen food in the freezer the fridge part will work better as more of the cooling action works on the fridge side.
The 12v heating element is usually lower power in comparison to the 240v.
Get the fridge down to the right temperature to start with and it should stay cold.
After all it’s a large cool box.
When ours was playing up on gas and we were camping off grid on a site for 5 days we kept ours cold enough just using freezer blocks swapped in the morning and evening.

 

[Lenny HB]

The 12v heating element is usually lower power in comparison to the 240v.

Yep our 12v one is 190 watt the 240v one 250 watts, so you are never going to cure that problem.

 

[Lenny HB]

Before everything else is considered, note that 12V is only for when the engine is running. It is not used when stationary. Before anyone goes any further, can you confirm that the engine is running?

Every Motorhome we have had the fridge with run off the hab batteries when switched to 12v.

 

[acropolis22]

Before everything else is considered, note that 12V is only for when the engine is running. It is not used when stationary. Before anyone goes any further, can you confirm that the engine is running?

Yup.

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[acropolis22]

Every Motorhome we have had the fridge with run off the hab batteries when switched to 12v.

Ours doesn't seem to.

 

[acropolis22]

Yep our 12v one is 190 watt the 240v one 250 watts, so you are never going to cure that problem.

But are they always lower power?

 

[autorouter]

Every Motorhome we have had the fridge with run off the hab batteries when switched to 12v.

Inside a Schaudt Electroblock, as used on Hymer and many other European MHs, there are two entirely separate fridge relays. One is connected to the leisure battery via a fuse, the other isn't. The converter chooses which supply to implement. Many, like Hymer, choose the one with the leisure battery connection. I think most UK MHs don't have the option of running from the leisure battery.

 

[acropolis22]

Inside a Schaudt Electroblock, as used on Hymer and many other European MHs, there are two entirely separate fridge relays. One is connected to the leisure battery via a fuse, the other isn't. The converter chooses which supply to implement. Many, like Hymer, choose the one with the leisure battery connection. I think most UK MHs don't have the option of running from the leisure battery.

Interesting. We have a Pilote. It has the Elektroblok EBL271. I've not checked yet to see if there are 2 relays but the fridge just bleeps at me if I select 12V with the engine off.

 

[autorouter]

Interesting. We have a Pilote. It has the Elektroblok EBL271. I've not checked yet to see if there are 2 relays but the fridge just bleeps at me if I select 12V with the engine off.

Yup, wrong again... there's only one relay in the EBL271, and it isn't connected to the leisure battery.

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[steveh57]

My Toptron distribution box on a Knaus will supply the fridge with 12V via the Habitation battery when D+ is active. I wish it didn’t though. I guess there’s a way round this but that’s beyond my skills.

 

[Lenny HB]

My EBL30 has two fridge relays, when the engine is running fridge is connected to the starter battery & when stationary fridge is connected to the leisure battery. You can run the fridge off 12v by selecting 12v manually on the fridge.
I also make use of the AES output on my Votronic Solar Regulator so when there is plenty of sunshine & the batteries are charged the fridge switches to 12v.