What size Inverter for fridge

[Barneyp]

I'm currently fitting out my grp canal cruiser, my plan is to have a basic 12v electrical system for lighting, water pump, and phone charging. 

I would also like a fridge,  given the price of 12v fridges it seems a standard 240v fridge and an inverter may be cheaper. But what size inverter do I need? 

Will a 300w Victron be enough? It will cover the basic power consumption, but do fridge compressors need a surge to get started?

[Tracy D'arth]

Minimum 1000W or the fridge won't start.  Depends on the fridge obviously. Go for 1500W to be safe. Bear in mind you need more battery capacity to run the inverter as well.

And the inverter eats power even when the fridge is not running, so you need an inverter with a low quiescent current use.

Edited April 15, 2022 by Tracy D'arth

[Tony Brooks]

Also be aware that whatever you take out of the batteries will need putting back in plus another 1/3 to 1/2 as much again so make sure you can actually recharge the batteries. If you have an outboard it may have  a very low charging output so check.

[MtB]

7 minutes ago, Tracy D'arth said:

Minimum 1000W or the fridge won't start.  Depends on the fridge obviously. Go for 1500W to be safe. Bear in mind you need more battery capacity to run the inverter as well.

And the inverter eats power even when the fridge is not running, so you need an inverter with a low quiescent current use.

 

Work round this by choosing a fridge with n on/off thermostat not some fancy electronic logic control. 

 

Then disconnect the thermostat from the compressor and arrange it to turn the inverter on and off instead. And wire the inverter directly to the compressor obviously.  

[beerbeerbeerbeerbeer]

 I’m determined to keep to 12v for all me appliances. 
 

I think needing a good inverter and the extra battery capacity it might be more cost effective and less bothersome to keep with 12v. 
 

Good solar should keep things ticking over in the summer and a fridge can be forgotten about in the winter. 
 

Oh, and Victron ain’t cheap either. 
I’m sure someone could recommend something of equal quality for less money. 

Edited April 15, 2022 by Goliath

[PaulJ]

Have a look at Sunshine inverters-reasonable quality and prices. 

https://www.sunshinesolar.co.uk/Category/PureSineWave12V?gclid=Cj0KCQjwr-SSBhC9ARIsANhzu14jAqC-k0dTCoJdFQZXusLdqs_MJd1z34H5VFFQgNYLeUdjsyRfPb8aArxTEALw_wcB

The 1200 should do you (have fitted one thats still going strong) but the 1500 is only a tenner more at the mo so would go for that.

Edited April 15, 2022 by PaulJ
Add info

[Barneyp]

Thanks for all the responses 

It works out that an inverter (£200) plus 240v fridge (£100+) is cheaper than a 12v fridge ( £500+). So going to stay with this option, yes the inverter will use some power, but I am a leisure boater and will likely only be on the boat when the sun is shining to power the solar.

Thanks for the link PaulJ, will get one of those, and will try MtB's wiring work around.

[Alan de Enfield]

2 minutes ago, Barneyp said:

Thanks for all the responses 

It works out that an inverter (£200) plus 240v fridge (£100+) is cheaper than a 12v fridge ( £500+). So going to stay with this option, yes the inverter will use some power, but I am a leisure boater and will likely only be on the boat when the sun is shining to power the solar.

Thanks for the link PaulJ, will get one of those, and will try MtB's wiring work around.

 

Why pay £500+ for a 12v fridge ?

 

 

When for £379 you can get one delivered in a couple of days.

 

50 Litre 12v Compressor Fridge DC50 Like The DOMETIC WAECO CRX CRE Campervan VW | eBay

[Barneyp]

7 minutes ago, Alan de Enfield said:

 

Why pay £500+ for a 12v fridge ?

 

 

When for £379 you can get one delivered in a couple of days.

 

50 Litre 12v Compressor Fridge DC50 Like The DOMETIC WAECO CRX CRE Campervan VW | eBay

Still more than the combined cost of a 240v fridge and inverter.

[Richard10002]

6 minutes ago, Barneyp said:

Still more than the combined cost of a 240v fridge and inverter.

And the seller seems keen to keep the make a secret, whilst trying to convince you that it's "just like a Waeco" etc..

[beerbeerbeerbeerbeer]

I’ll pay the few extra £100 for the 12v. 
 

but each to their own

 

and I’m probably on me own. 

[Tracy D'arth]

4 hours ago, MtB said:

 

Work round this by choosing a fridge with n on/off thermostat not some fancy electronic logic control. 

 

Then disconnect the thermostat from the compressor and arrange it to turn the inverter on and off instead. And wire the inverter directly to the compressor obviously.  

I seem to remember posting the same advice years ago........................................

[MtB]

1 minute ago, Tracy D'arth said:

I seem to remember posting the same advice years ago........................................

 

Yes I get that too. Come up with a Good Idea and it propagates across the forum. I certainly read it here but didn't remember it was you. You get the credit for the idea! 

[Tracy D'arth]

1 minute ago, MtB said:

 

Yes I get that too. Come up with a Good Idea and it propagates across the forum. I certainly read it here but didn't remember it was you. You get the credit for the idea! 

Thank you Mike, there are gents,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,then there are others!

[Richard10002]

12 minutes ago, Goliath said:

I’ll pay the few extra £100 for the 12v. 
 

but each to their own

 

and I’m probably on me own. 

No.. I'm with you on this  😀 

[MtB]

4 minutes ago, Richard10002 said:

No.. I'm with you on this  😀 

 

 

Me too. I much prefer the simplicity of a 12V fridge. No cheap inverter to spontaneously catch fire either.

 

 

[Tracy D'arth]

With a 240v fridge and an inverter you have 2 failure possibilities. Only one with a 12v fridge.

[Tony Brooks]

GRP canal cruisers are not known for having masses of roof space   what with skylights, hand rails and escape hatch so I am far from sure that the OP has given charging by solar for a fridge and inverters much investigation as he ought to.

[Barneyp]

Thanks for the concern Tony.

I can comfortably fit 340w of solar on the roof, which according to the solar calculator on bimble will give me enough power to run an efficient fridge and inverter. 

This assumes 4-5 hours of sun a day, and doesn't take account of the (limited) charging capacity of the outboard.

Also I'm not living aboard and will have plenty of opportunities to mains charge the batteries.

[MtB]

49 minutes ago, Barneyp said:

Thanks for the concern Tony.

I can comfortably fit 340w of solar on the roof, which according to the solar calculator on bimble will give me enough power to run an efficient fridge and inverter. 

This assumes 4-5 hours of sun a day, and doesn't take account of the (limited) charging capacity of the outboard.

Also I'm not living aboard and will have plenty of opportunities to mains charge the batteries.

 

When I had 300W of solar it used to run the fridge for about 7 months of the year. Adding a further 300W extended this to about nine months.

[Tracy D'arth]

Solar gives close to nothing for 4 months of the year no matter how big the panels.

[GUMPY]

26 minutes ago, Tracy D'arth said:

Solar gives close to nothing for 4 months of the year no matter how big the panels.

I got 156kWh out of mine in February

 

[MtB]

32 minutes ago, Tracy D'arth said:

Solar gives close to nothing for 4 months of the year no matter how big the panels.

 

It gives close to nothing at night too, although some swear blind theirs delivers some power from moonlight. I simply don't believe them!

 

 

[Tony Brooks]

27 minutes ago, MtB said:

 

It gives close to nothing at night too, although some swear blind theirs delivers some power from moonlight. I simply don't believe them!

 

 

 

More like the batteries recovering their voltage a bit as the plates even out the discharge and possibly shed bubbles.

[cuthound]

23 hours ago, MtB said:

 

It gives close to nothing at night too, although some swear blind theirs delivers some power from moonlight. I simply don't believe them!

 

 

 

I agree, if you want power at night you need lunar panels, but no boat that I know of has enough roof space for them.