Running 240V fridge via inverter

[Metabarca]

With my boat's fridge kaput, for this year I am thinking of making do with a small camping fridge I have at hand. But my query is: can I run a 240V fridge (same sort of size as a boat's fridge) via an inverter plugged into a cigarette-lighter type outlet? Unfortunately, I cannot find any information online as to the fridge's consumption. Its label reads VOE, OF789, R134a, 220-240V-50Hz. The inverter can handle (if I remember correctly) 150W. So three bus: can the inverter handle it? Can the cigarette-lighter outlet handle it? Should I put in a fuse between the outlet and battery? Naturally, the fridge would only be operated with the engine running (or via shore power, in which case there's no issue).
Thanks!

 

[pmagowan]

My understanding is that you should always have a fuse (or alternative) anywhere where wire needs protected. your inverter is small but I also have no idea about your fridge. I suspect it won't work but that is only a guess. Some people that are more knowledgable about magic battery pixies will be along soon to tell you more!

 

[RichardS]

Cigarette outlets will usually handle around 10A so the issue will be whether the 150W inverter will run the fridge. It will probably be fine even if it complains at bit on inital start-up. Why don't you give it a go as the worst that can happen is that you blow a fuse and I've done that so many times in my cigarette lighter circuit in both the car and the boat that I've lost count.

Richard

 

[DannyB]

Is the fridge a compressor type ? If it is I doubt if the inverter will start it. On the plus side the inverter is probably protected against overload, so trying it might not do any harm.

 

[jac]

and just to point out that many small fridges with cigarette lighter plugs are by nature designed to run from the cigarette lighter / accessory power socket in a car which ( as mentioned earlier) tend to be 10 amp @ 12v nominal so it shouldn't take out the power on the boat. I would try it.

 

[duncan99210]

Putting OF789 into goggle produces a string of Chinese sites, all marketing a small fridge/freezer compressor. Most seem to refer to 115 watts cooling capacity, so presumably this will roughly equate power required to make the thing work. So, your inverter will power the fridge provided the start up current doesn't exceed the inverters capacity. However, if you take the 115 watts and convert that into amps at 12v, it comes out at somewhere about 9.6 amps, which is a fair whack to be taking out of your battery bank and may be on the edge of what your cigar lighter socket can sustain. You might do better having a slightly larger inverter (say 300 watts) and hard wiring it to the battery via a switch and fuse ( in the +ve lead).
The RF134a is the refrigerant used in the beast.

 

[bedouin]

I think you need a lot of spare capacity in the invertor to start the fridge compressor. I don't fancy your chances of it working on a cheap 300W invertor.

 

[Zen Zero]

Yes I think it will be alright.

Camping fridges these days are very frugal and an inverter adds very little to the overall power consumption. My Waeco Tropicool camping fridge's label claims 64w with its 230vac power supply (curiously only 46w with 12v). But 64w down an inverter will probably draw between 6 and 7 amps. So assuming your fridge is similar to mine you'll probably be ok. You should always have a fuse or a circuit breaker between the consumer and the battery.

I've just read Duncan's post 115w plus inverter loss will equate to about 12A. Doable but with care and thick wires.

It'd be interesting to know what your broken 12v fridge drew.

I've stopped using my boat fridge, except as a cool box powered by frozen 1.5l bottles of water from the grocer's shop on the shore; and am waiting for her ladyship's approval to buy a new modern low power replacement.

 

[owen-cox]

I would be extremely surprised if even a 300W inverter will start a compressor. The recommendation usually is you need one 5 times Power of the compressor. If its a 115 W compressor you would need 575W at least. I have done it in the past and used a 1kW inverter which was fine. Ive triedon a 300W andit wouldnt work and suspectif it did it would not work for long as itwould be putting it under a very high load for start up. Once running they dont nees mych to keep going but start of reciprocationg compressors is always tough. Large powerboats have problems abroad with shore power not being enough for multiple conpressors on air conditioning systems. Ive had to fit VSD systems to allow a slow ramp up and that way you can reduce start up current to no more than full load current but its not worth it on a small fridge.

 

[William_H]

I understand that domestic 240v AC fridges will need a pure sine wave inverter as they run an induction type motor.
OP has not mentioned if inverter is cheap "modified sine wave" or pure sine wave type which are more expensive.
he modified sine wave which is really modified square wave contain a lot of power in high frequencies which cause heating in the 50 hertz coils of the motor. So overheating and inefficiencies. About 100w when running seems right. Certainly inverter should be hard wired with heavy wiring and large fuse to the battery. good luck olewill

 

[Metabarca]

Hm, lots of (sometimes conflicting) food for thought here. Frankly I can't remember much about the inverter; I'll check when I'm next down at the boat.
I'll perhaps try it like this: hefty wire from battery to a 240V plug in which to plug the inverter, and with 10A fuse on it. Then power up the engine and press 'on'. Test inverter for overheating and fridge for smooth running. Sound right?
But it sounds as though I may have to run the fridge only on shore power. Which means packing it with blue freezer bricks and cranking the fridge to max. Then upon slipping my mooring, upend the fridge on its back so the cold doesn't pour out on opening the door. Other qu: or could I operate it like this? Presumably not...
Sorry for the ignorance and thanks for all past and future comments!

 

[pmagowan]

Fridges like to be kept upright

 

[Kelpie]

Fridges like to be kept upright

When running, yes. But he was talking about doing this with it switched off. I think if he sits it upright and gives it a few minutes for the refrigerant to settle before switching on, it should be fine.

 

[syneraida]

I would suggest that the important point regarding power is the starting current, for all intents and purposes you are just starting a motor.

The problem here is that the motor starting current can be between 3-7 times normal current, you need to provide enough power to magnetise the winding's in the motor as well as start moving the mass of the rotor inside the motor. If the fridge is 115w then starting current will probably be between 400-700 watts, that said most inverters can cope with double their rated capacity for short (surge) periods, so you will likely get away with a 300-400watt inverter.

The other issue to consider is that you are running a motor which is an inductive load load and will likely have a power factor of around 0.7-0.8. I wont go into the detail, but the result is that you need to pay attention to the kva and not the kw you are using. All of that said if you get a 300-400 watt inverter for a 115watt compressor and you can get the thing to start it should run fine.

I'd give it a go and see what happens worst case the inverter will alarm and trip.

 

[pmagowan]

When running, yes. But he was talking about doing this with it switched off. I think if he sits it upright and gives it a few minutes for the refrigerant to settle before switching on, it should be fine.

Most of them have relatively strict instructions about keeping upright prior to use for quite considerable times!

 

[Metabarca]

"I'd give it a go and see what happens. worst case the inverter will alarm and trip."

That's what I like to hear. I don't want anything going 'bang'!

 

[Giblets]

Most of them have relatively strict instructions about keeping upright prior to use for quite considerable times!

Agreed. It's not to do with the refrigerant settling but the oil in the compressor returning to the correct level. Get that wrong and a new compressor will be required.