Converting 240 volt fridge to 12 volt

[Bob Boden]

We have a 240 volt fridge which consumes lots of power. We would like to convert to 12 volt. We cannot buy a 12 volt fridge that will fit into the space. We believe that it is possible to convert the existing fridge. Can anybody advise us how and who can do it, please. Boat in Banbury area

[OldGoat]

Converting a 240V fridge to 12V wont save much energy unless your inverter is very inefficient - so hange the inverter...

 

This chap will convert your fridge for you -

http://www.12v-fridges.com/

but he's not near Banbury - you could cruise to him.

He won't convert fridges that are taller to 1200mm

Cost around £400 just for the compressor and control box.

[Phil Ambrose]

Surprised you can't find a 12v fridge to the space of a 240v one, the cabinets are generally the same size. My 12v fridge is a Shoreline which is based on a LEC 240v fridge, its a larder fridge of 120ltr capacity.

Switching to 12v means changing the compressor for a Danfos 12v one. Who would do this for you, I've no idea.

Phil

[Paul C]

What is the fitment space?

[Tiggs]

Why would a 12V one use less power?

 

(other than the extra for the inverter - should be a few % on non-sine)

[Paul C]

Why would a 12V one use less power?

 

(other than the extra for the inverter - should be a few % on non-sine)

 

Its going to be much more than a few % - it will be whatever the conversion efficiency is, BUT then you need to also take into account the quiescent current 24/7 (unless you have some kind of custom switching arrangement where the thermostat of the fridge can turn the inverter off, not just put it into idle/standby).

[Tiggs]

 

Its going to be much more than a few % - it will be whatever the conversion efficiency is, BUT then you need to also take into account the quiescent current 24/7 (unless you have some kind of custom switching arrangement where the thermostat of the fridge can turn the inverter off, not just put it into idle/standby).

 

 

I looked up efficiency and even for sine wave its 95% ish which I thought it would be, and many have auto standby anyway (Victron for e.g.). Given a class A++ 240V fridge and an older model 12V of the same size there is not going to be much in it.

 

 

http://www.es-store.co.uk/documents/product/Datasheet_-_Phoenix_Inverter_1200VA_-_5000VA_-_rev_03_-_EN.pdf

Edited October 28, 2015 by Tiggs

[Tony Brooks]

 

 

I looked up efficiency and even for sine wave its 95% ish which I thought it would be, and many have auto standby anyway (Victron for e.g.). Given a class A++ 240V fridge and an older model 12V of the same size there is not going to be much in it.

 

 

http://www.es-store.co.uk/documents/product/Datasheet_-_Phoenix_Inverter_1200VA_-_5000VA_-_rev_03_-_EN.pdf

 

Is there a BS or DIN test for inverter efficiency? If not I would be highly sceptical of any quoted efficiency. You can bet your life it would have been done under conditions that returned the highest figure.

 

If an inverter used (say) 0.5 amp to run itself then when supply (say) 350 mA to charge a simple phone battery I make that less than 50% efficiency.

 

However I agree with your and Old Goat's view that changing it for a 12V one will only make a marginal difference. I am tempted to add why not put the cost of the conversion towards some solar.

[Paul C]

 

 

I looked up efficiency and even for sine wave its 95% ish which I thought it would be, and many have auto standby anyway (Victron for e.g.). Given a class A++ 240V fridge and an older ,model 12V of the same size there is not going to be much in it.

 

 

http://www.es-store.co.uk/documents/product/Datasheet_-_Phoenix_Inverter_1200VA_-_5000VA_-_rev_03_-_EN.pdf

 

This is when it gets complicated......when you consider the specification of the inverter which has auto standby, and its cost, it wipes out any cost saving of using a 240V fridge vs a 12V fridge. Even if you need an inverter for something else, a fair comparison must include an element of its cost. And its also not fair to compare an older model 12V fridge with a class A++ 240V fridge on that basis alone - by all means compare on equivalent size/age/performance/price though.

 

There's pros and cons to using 12V vs 240V fridge but to do a thorough comparison is not easy - partly because the real world running figures simply aren't available (for 12V fridges) so you must make some kind of assumptions; and real world inverter efficiency must also be considered, not necessarily the one in the specification. Also relying on an inverter introduces another mode of failure - the inverter going wonky. Inverters can and have caught fire, which could be an issue if the boat is left unattended with the fridge on.

[Graham.m]

Possible idea, why not give the fridge its own 300/350 watt inverter. The inverter would run at near full load, thus max efficiency, its standby usage would be low. Cost about £120, plus fusing and cable

 

Just a though.

[Guest]

Possible idea, why not give the fridge its own 300/350 watt inverter. The inverter would run at near full load, thus max efficiency, its standby usage would be low. Cost about £120, plus fusing and cable

 

Just a though.

start loads can be a problem with inverter powered fridges. I once considered this idea myself but it would have needed a fairly large inverter to start the compressor.

[Neil Smith]

I had mine converted by buying a 12v compressor and controller for £160 and £60 to have it fitted.

 

Neil

[OldGoat]

Possible idea, why not give the fridge its own 300/350 watt inverter. The inverter would run at near full load, thus max efficiency, its standby usage would be low. Cost about £120, plus fusing and cable

 

Just a though.

The flaw in that idea is that the starting current for a 240V fridge is around 6-9 times the run current. Even though it's only needed for a fraction of a second it WILL trip the inverter if undersized.

 

Whereas as a MSW inverter may well run the fridge (it may well inhibit the starting of the induction motor) its standby power may be quite high and its peak handling capacity much less that the

equivalent good quality pure sine unit - have a look at other threads on the topic here.

[Graham.m]

start loads can be a problem with inverter powered fridges. I once considered this idea myself but it would have needed a fairly large inverter to start the compressor.

 

That is why I went for a 300/350 watt pure sine wave it has a peak load of 700 watt which should be enough to start a compressor of that size. http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-180VA-1200VA-EN.pdfand with a zero load consumption of 3.1 watts is probably the a good compromise.

[Guest]

 

That is why I went for a 300/350 watt pure sine wave it has a peak load of 700 watt which should be enough to start a compressor of that size. http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-180VA-1200VA-EN.pdfand with a zero load consumption of 3.1 watts is probably the a good compromise.

Interesting.

I think I am right in saying that pure sine wave copes better with the start load.

[Graham.m]

The flaw in that idea is that the starting current for a 240V fridge is around 6-9 times the run current. Even though it's only needed for a fraction of a second it WILL trip the inverter if undersized.

 

Whereas as a MSW inverter may well run the fridge (it may well inhibit the starting of the induction motor) its standby power may be quite high and its peak handling capacity much less that the

equivalent good quality pure sine unit - have a look at other threads on the topic here.

 

Personally I would never use a MSW inverter, too many problems, equipment that will not run on on MSW . They maybe cheaper but in the long run pure sine wave will give a better overall result and service.

[Top cat]

Having just replaced my MSW inverter ( it blew up - literally) with a pure sine wave unit I notice the following changes.

 

No longer get buzzing from the stereo speakers even when the stereo is off

The TV no longer buzzes when on

The breadmaker sounds less stressed when kneading

The standby current is much the same

The inverter fan comes on at a lower power and is slightly noisier ( not a big issue as its in a cupboard at the back)

No longer paranoid about ensuring the washing machine breaker is off before turning on inverter.

Phone and tablet chargers dont buzz and run cooler.

 

Top Cat

[OldGoat]

 

That is why I went for a 300/350 watt pure sine wave it has a peak load of 700 watt which should be enough to start a compressor of that size. http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-180VA-1200VA-EN.pdfand with a zero load consumption of 3.1 watts is probably the a good compromise.

 

OK - I'll bite on that - So you're running a fridge with a 350W Victron unit? What sort of fridge is it - make / size / model is it - pretty please?

There's so much confusion around as to what does / doesn't work. It's even difficult to find out what size (power) compressor is fitted to mainstream units.

 

So I'd be most grateful for any information that you have!!

[ditchcrawler]

A few years back Midland Chandlers sold a fridge/inverter package to run a mains fridge on a boat. I have a feeling that was only about 350W. Maybe someone with an old magazine could find an advert for it