power usage of Compressor vs Absortion fridge

redg

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Hi All,

Just taken out an absorption fridge from our van, as was very old and had no external air input/output or external exhaust for the burner, and combined with the expense of a new unit, fitting these would have been quite expensive. Plus they would have been behind the sliding door, which could have been a tricky fit, and greatly reduce their effectiveness whenever the door is open (as often as possible!).

So, have now stripped out the gas pipework and am planning buying a new DC/AC fridge to replace. I get the impression that a compressor will use less power than an absorption, but can't seem to find any categorical answer. Any info gratefully received.

Also, it seems 12v compressor fridges are more expensive, and a bit deep - most seem to be around 500mm and I really need about 400mm?
 

Nabsim

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It’s the opposite, a compressor fridge will use much more 12v than a 3 way. Mine averages 45 ish amps for day but I always have it turned on.
 

mistericeman

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Absorbtion fridges on 12v use a lot more power than compressor types (most absorbtion types don't operate a thermostat on 12v for a start.... So power is drawn continually)

My waeco 40l uses less than 3 amps AND only when running.

It's been running none stop 24/7/365 for the last 4 years on 3 x 100ah batteries and 2 x 100w solar and Durite vsr....

Never needed mains barring a couple of times in winter when we've not been away for a few weekends.

Best place for absorbtion fridges is in the skip ;-)
 

channa

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The other thing to consider, is especially if you foray to warmer climes absorption fridges tend to cool in direct correlation of ambient temperature conditions whereby a acompressor fridge aims for a given figure eg 5 degrees irrespective of what the ambient temperature is
 

Nabsim

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Absorbtion fridges on 12v use a lot more power than compressor types (most absorbtion types don't operate a thermostat on 12v for a start.... So power is drawn continually)

My waeco 40l uses less than 3 amps AND only when running.

It's been running none stop 24/7/365 for the last 4 years on 3 x 100ah batteries and 2 x 100w solar and Durite vsr....

Never needed mains barring a couple of times in winter when we've not been away for a few weekends.

Best place for absorbtion fridges is in the skip ;-)
My understanding is 3 way fridges do not operate properly on 12v and it’s only meant to try and keep cool while travelling and should run on gas to best effect. Is that wrong?
If right then you would rarely use hab battery for 3 way so less power in practice
 

mistericeman

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My understanding is 3 way fridges do not operate properly on 12v and it’s only meant to try and keep cool while travelling and should run on gas to best effect. Is that wrong?
If right then you would rarely use hab battery for 3 way so less power in practice
Absorbtion types are as you say designed to just maintain temp on 12v (hence fitting relays and auto changeover on more modern types)
However...
If you have solar and run a compressor type (with adequate batteries) either directly OR a 240 domestic type via a high efficency inverter.... The power is effectively free AND as Channa rightly says you can wave goodbye to absorbtion woes of poor cooling in high temps/needing vents/and to be level and wind being in the wrong direction etc.

Absorbtion types belong in the dark ages of caravanning and gas, mantles etc.
 

Fisherman

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My understanding is 3 way fridges do not operate properly on 12v and it’s only meant to try and keep cool while travelling and should run on gas to best effect. Is that wrong?
If right then you would rarely use hab battery for 3 way so less power in practice
I believe that’s correct.
The main point here is I doubt if 12v would sustain a compressor fridge either.
You would require mains to maintain temperature within a compressor fridge of reasonable size. When wild camping an absorption fridge run on gas would be much more effective and better on consumption than a compressor fridge working on 12v. Also some compressor fridges can be noisy.
A three way fridge I reckon offers the best option for varying types of use from campsites to wild camping. If compressor fridges were the better option I am sure that they would be fitted in most Motorhomes, but they’re not.
There are advantages and disadvantages to both, ultimately it’s up to each individual to do as they please, in line with their personal requirements.
 

wildebus

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My understanding is 3 way fridges do not operate properly on 12v and it’s only meant to try and keep cool while travelling and should run on gas to best effect. Is that wrong?
If right then you would rarely use hab battery for 3 way so less power in practice
You are right that a 3-way fridge will use typically less battery stored electricity than a Compressor Fridge over a typical day if you work on the basis that when parked up, you will either plug into Camphook or fire up the gas (and when driving, the power used is effectively from the alternator)

But ... the actual current draw of an 3-way (absorption) fridge when running on 12V is much more than a Compressor Fridge by a factor of around 3 times or more greater.


Hi All,

Just taken out an absorption fridge from our van, as was very old and had no external air input/output or external exhaust for the burner, and combined with the expense of a new unit, fitting these would have been quite expensive. Plus they would have been behind the sliding door, which could have been a tricky fit, and greatly reduce their effectiveness whenever the door is open (as often as possible!).

So, have now stripped out the gas pipework and am planning buying a new DC/AC fridge to replace. I get the impression that a compressor will use less power than an absorption, but can't seem to find any categorical answer. Any info gratefully received.

Also, it seems 12v compressor fridges are more expensive, and a bit deep - most seem to be around 500mm and I really need about 400mm?
If you want to switch to a Compressor Fridge, then you will need suitable battery power to run one. The basic motorhome is equipped with a fairly small battery on the basis that your Fridge will be running on Gas or mains mostly and on 12V only when travelling (and when travelling most of the time the engine would be running to provide power).
It is quite probable you would need a battery upgrade to support it.
You will also need to upgrade the current wiring going to the fridge. Whilst the absorption fridge draws more current than a Compressor Fridge, the way the Compressor works means you need a fairly substaintial cable (min 4mm, pref 6mm) for the power.

If you need a slimmer Fridge, Dometic/Waeco make a model with a compressor that can be repositioned to allow the main unit to fit in a shallower cabinet. The last time I looked at this option a few years ago, I think the model was something like an 40RF (or maybe RF40?).
Whichever it maybe, yes, it will be expensive - 12V Compressor Fridges for 'Motor Caravans' are way overpriced.


Having said all that, it may sound I am saying it is a bad idea, but nope, a Compressor Fridge is the way to go for sure :)
 

trevskoda

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I and others < wildbus>have done the test work,my comp 230v with a smart inverter will run happy 24/7 on two 200w solar and two 90ah batteries,its now going to be fitted to my van,cost of fridge 50 bucks and about the same for a smart soft start 500w inverter which does not run until a signal is sent for start up.
 
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mistericeman

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I believe that’s correct.
The main point here is I doubt if 12v would sustain a compressor fridge either.
You would require mains to maintain temperature within a compressor fridge of reasonable size. When wild camping an absorption fridge run on gas would be much more effective and better on consumption than a compressor fridge working on 12v. Also some compressor fridges can be noisy.
A three way fridge I reckon offers the best option for varying types of use from campsites to wild camping. If compressor fridges were the better option I am sure that they would be fitted in most Motorhomes, but they’re not.
There are advantages and disadvantages to both, ultimately it’s up to each individual to do as they please, in line with their personal requirements.

Plenty of folks running 12v compressor/240 domestic/inverter set ups without needing hook up...

I could have managed easily with less solar/ batteries in the transit compressor fridge wise BUT went for more as, all our cooking was electric (microwave /slow cooker /toaster/kettle etc)

Never even wired the 240 hook up socket in as we didn't need it.

Manufacturers are slow to change (most are still gluing caravans on the back of a chassis cab) and don't like to be early adopters (though some ARE now fitting compressor types)
I truly wouldn't be without a compressor unit now when camping as, it's just so much less pfaff.
 

Fisherman

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I and others have done the test work,my comp 230v with a smart inverter will run happy 24/7 on two 100w solar and two 90ah batteries,its now going to be fitted to my van,cost of fridge 50 bucks and about the same for a smart soft start 500w inverter which does not run until a signal is sent for start up.
Trev what about winter when there is very little solar.
 

Fisherman

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Plenty of folks running 12v compressor/240 domestic/inverter set ups without needing hook up...

I could have managed easily with less solar/ batteries in the transit compressor fridge wise BUT went for more as, all our cooking was electric (microwave /slow cooker /toaster/kettle etc)

Never even wired the 240 hook up socket in as we didn't need it.

Manufacturers are slow to change (most are still gluing caravans on the back of a chassis cab) and don't like to be early adopters (though some ARE now fitting compressor types)
I truly wouldn't be without a compressor unit now when camping as, it's just so much less pfaff.
We use our van in winter and there is very little solar particularly from December to February. I have added a second 120w panel and a second 95ah battery.
Do you reckon that a compressor fridge would be an option then, this is my main concern. Cheers.
 

Fisherman

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The fridge will run 24hrs on the batts,so over night using lights and loo flush will be no prob,move next day and batts will be charges again.
So you would have to move Trev, and possibly a fair distance.
We normally spend two nights out in winter in one location.
I bow to your vastly superior knowledge Trev.
I take it you use an inverter also Trev.
 

mistericeman

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We use our van in winter and there is very little solar particularly from December to February. I have added a second 120w panel and a second 95ah battery.
Do you reckon that a compressor fridge would be an option then, this is my main concern. Cheers.
We tend to move around a fair bit so even when the panels weren't doing much (cheap ones) the Durite VSR shouldered the heavy work....

I've gone for 400w bifacial panel on the Moho AND a ring rscdc30 to make the most of the harvesting... Being MPPT rather than PWM should hopefully maximise things.
 

2cv

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As Fisherman says, it’s up to personal preference with neither being better for everyone. I have no room for more batteries or solar so really would struggle with a compressor fridge, particularly in Winter. Having had a compressor fridge on a boat (lots of batteries) I also prefer a 3 way in my van because of the noise issue. I look for quiet spots and they would be ruined by the noise of a compressor running.
 

mistericeman

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As Fisherman says, it’s up to personal preference with neither being better for everyone. I have no room for more batteries or solar so really would struggle with a compressor fridge, particularly in Winter. Having had a compressor fridge on a boat (lots of batteries) I also prefer a 3 way in my van because of the noise issue. I look for quiet spots and they would be ruined by the noise of a compressor running.
You must have very sensitive hearing... We slept on top of the compressor fridge in the transit and couldn't hear a thing.
 

mistericeman

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I do, but as I said it’s horses for courses. It drove me nuts on the boat.
It was the auto bilge pump that used to drive me mad when I lived on the narrow boat...

Always seemed to kick in just when I was in deepest sleep.
 

channa

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Absorption fridges invariably use ammonia as the refrigerant which is vey old hat, compressor fridges use more modern refrigerant gasses which give better performance which when coupled with a compressor allow target temps to be achieved

Power supply is as explained as previous

The only disadvantage that I can see is that in the middle of the night there is a possibility you can hear the compressor...but the advantages outweigh any disadvantages
 

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