Converting 240v fridge & freezers to 12v (Searched forums)

[spaceyaface]

Good Morning All.

 

Have I imagined that this has been discussed at length and is relatively easy to undertake?

Can anyone help me locating kit to do this?

 

Forgive me if I've missed a thread somewhere.

 

Many thanks.

[Nickhlx]

Possibly - depending on level of skill you have...

 

"All" you need to do is to swap the compressor / motor with a 12 Volt one of appropriate size, cut out old mains one, solder in new 12V one and re-gas the system.

 

Nick

[Chalky]

It's a specialist job, not a DIY one. Extracting the gas from the fridge and re-gassing requires specialist equipment.

[Alan de Enfield]

I have tried (and lost it) 4 times to reply to this post so I am going to do it in stages :

 

I recently spent some time pondering this subject when replacing both our Fridge and Freezer. I came to the conclusion :

 

Buying a 240v fridge and 'removing the major component' replacing it with another similar part was an expensive exercise.

Buy a new compressor, de-gas fridge,pay someone to remove old compressor, &, install new one, re-gas fridge and void any warranty you may have had.

 

Running costs (power used) will not be hugely different between a 12v fridge and a 240v fridge - in fact the 240 V may actually be lower due to better efficiencies.

 

Take a 125 watt fridge as an example :

 

125 watt, 12 v fridge running 33% of the time = approximately 80Ah per day

125 watt 240 v fridge running 33% of the time (via an inverter) will take approximately 90Ah per day out of the batteries.

 

If you already have an inverter on board (or maybe even if you need to buy one) then the 240v option may be the most cost effective.

12v fridge £500+

240v fridge £110 +

 

I actually ended up with a 12v fridge and a 240v freezer as I like to have multiple systems

Edited September 28, 2015 by Alan de Enfield

[spaceyaface]

That's that sorted, then...many thanks.

[MtB]

 

If you already have an inverter on board (or maybe even if you need to buy one) then the 240v option may be the most cost effective.

12v fridge £500+

240v fridge £110 +

 

I actually ended up with a 12v fridge and a 240v freezer as I like to have multiple systems

 

 

What size inverter are you using? The motor on a compressor usually has a very high transient starting current so a 125W fridge probably needs an inverter with a continuous rating of as much as perhaps 1kW.

 

Do any inverter makers actually specify their transient, motor-starting rating as opposed to their (much higher) steady state rating?

[spaceyaface]

I've got a Sterling 600w and an unbranded type of 3k from China....so really one too many inverters and a thousand watts behind!

[peterboat]

ooohhhh richard thats serious stuff if you do your sums it will work, plus a lot of the triple aaa rated fridge freezers are bigger than the 12v ones so it gives you a bigger chouce, plus i am sure between us we have contacts in the fridge business rsy or something like that to get the compressor at the right money. it could even be a new business venture the problem for me is when my inverter failed last year if i had a 240v fridge/freezer the lot would have been defrosted its your choice

[Alan de Enfield]

 

 

What size inverter are you using? The motor on a compressor usually has a very high transient starting current so a 125W fridge probably needs an inverter with a continuous rating of as much as perhaps 1kW.

 

Do any inverter makers actually specify their transient, motor-starting rating as opposed to their (much higher) steady state rating?

 

1000w on the previous boat and 1800w on this one

 

(1kw immersion heater, 900w kettle, 900 watt toaster all need feeding via the 2 x 100amp alternators and 4 x 230 amp batteries)

 

The 240v freezer's actual usage is about 400 wh per day ( or about 40 ah per day from the batteries)

[Phil Ambrose]

I have tried (and lost it) 4 times to reply to this post so I am going to do it in stages :

 

I recently spent some time pondering this subject when replacing both our Fridge and Freezer. I came to the conclusion :

 

Buying a 240v fridge and 'removing the major component' replacing it with another similar part was an expensive exercise.

Buy a new compressor, de-gas fridge,pay someone to remove old compressor, &, install new one, re-gas fridge and void any warranty you may have had.

 

Running costs (power used) will not be hugely different between a 12v fridge and a 240v fridge - in fact the 240 V may actually be lower due to better efficiencies.

 

Take a 125 watt fridge as an example :

 

125 watt, 12 v fridge running 33% of the time = approximately 80Ah per day

125 watt 240 v fridge running 33% of the time (via an inverter) will take approximately 90Ah per day out of the batteries.

 

If you already have an inverter on board (or maybe even if you need to buy one) then the 240v option may be the most cost effective.

12v fridge £500+

240v fridge £110 +

 

I actually ended up with a 12v fridge and a 240v freezer as I like to have multiple systems

Alan are sure about the power usage for your 12v fridge? you state 80a/hr, mine is in the region of 40a/hr

Phil

Edited September 28, 2015 by Phil Ambrose

[Alan de Enfield]

Alan are sure about the power usage for your 12v fridge? you state 80a/hr, mine is in the region of 40a/hr

Phil

 

It was solely an example using 120 watts (because its an easy divider by 240 and 12)

The actual wattage of my 12v Waeco fridge is 45 watts ( so 4 amps, 33% running time = 32Ah per day)

[Sea Dog]

My 12v fridge draws about 35 watts when it's running which is, of course, not continuous. Unless someone can better inform me, I can't really see a 240v fridge with a similar duty cycle plus the inverter, with its own current draw running continously to be on hand to power it, would beat that.

[MtB]

Alan are sure about the power usage for your 12v fridge? you state 80a/hr, mine is in the region of 40a/hr

Phil

 

What' does "40a/hr" mean? Is it "40 Amps per hour"?

 

If so, how many Amps will it draw in a minute?

[Alan de Enfield]

My 12v fridge draws about 35 watts when it's running which is, of course, not continuous. Unless someone can better inform me, I can't really see a 240v fridge with a similar duty cycle plus the inverter, with its own current draw running continously to be on hand to power it, would beat that.

 

http://ao.com/product/r50052w-lec-fridge-white-25045-30.aspx

 

This one is 106Kw per year which equates to about 290 wh per day ( or roughly 24 Ah per day + Inverter losses)

 

Your 35 watts is roughly 3 amps x 24 hours x 33% run-time = 24 Ah per day

[Bobbybass]

Didn't I see on here long ago..(maybe I didn't see on here long ago..?)..that it is better to get a 240v upright FREEZER..and change the thermostat..to a fridge 'stat'.....?

 

Reason was...that a freezer has better insulation...and thus the motor doesn't run so long....

[Sea Dog]

So it doesn't beat it then Alan, it matches it (reasonably enough given similar efficiency and insulation values) but the inverter being on 24/7 tilts the balance back to 12v. Now you have extra capital cost of 12v units V extra running costs of 240v plus inverter. No wonder this question seems perennial.

[Cas446]

Just been through the old 240v vs 12v fridge and choose to spent £60 on a 240v fridge instead of £550 on a 12v one. This made sense for me as a holiday boat with 200w solar so no extended off-grid time without running the engine.

 

Decided to take some actual load measurements using clip over CT and fluke. The fridge is a Currys Logic 68s12 although the online price seems to have gone up to £80 now. Good quality, much better than I would have expected at that price.

 

@240v standing load when compressor running is 150mA. It cycles for ~20mins in an hour.

@240v starting current with cold compressor 'out the box' was 5.4A, dropping to 4.5A when warm, so that's 1.3kVA dropping to 1kVA.

 

Converting that to 12v means, ~3A when compressor running and average of 1Ah per hour. My inverter (old Sterling badged blue box 1.5kW) is fine with the fridge. Compressor starts with same characteristics as when on mains, inverter does not make a sound when the compresssor starts and does not register the load. Inverter has 0.7A standby load so total load average is <2Ah per hour. This replaced a 3-1 gas fridge which consumed 6.8A continuously @12v and produced lots heat at the back for very little chill inside.

 

Hope figures are useful and make sense.

[Phil Ambrose]

 

What' does "40a/hr" mean? Is it "40 Amps per hour"?

 

If so, how many Amps will it draw in a minute?

Oops Mike has gone into pedant mode again, never mind, Alan didn't have a problem, why should it bother you so much. Don't bother going into it again ot I shall just have to start using "buckets" again. ?

Phil

[MtB]

Oops Mike has gone into pedant mode again, never mind, Alan didn't have a problem, why should it bother you so much. Don't bother going into it again ot I shall just have to start using "buckets" again.

Phil

 

 

So you acknowledge its a meaningless term then?

 

So why use it? Again? Even when you know it confused the hell out of newbies to the subject?

[George94]

Let he who is without sin cast the first stone.

[Phil Ambrose]

Let he who is without sin cast the first stone.

Thank you George, hope you are keeping well.

Phil

[Neil Smith]

I bought a 12v compressor and control for £160 from Poland and had it fitted in a 240v fridge freezer for £60, well happy.

 

Neil

[by'eck]

Had occasion to leave my boat unattended for 48 hours during this summer with no charge source and Shoreline RR5010 12 volt 100 litre fridge running exclusively. Battery monitor recorded just 40 Ah total usage. Wouldn't imagine much more with opening/closing of door.