New Fridge Freezer 12v vs 240v

[Blazeaway]

Just been looking at the pro's and con's of replacing our woefully inadequate and small fridge with something a bit more suited to our needs.

 

In an ideal world we'd like something a little closer to what we have at home, ie 200 litre freezer 300 litre fridge.

 

I know its a compromise, we are to become "liveaboards" and will be off-grid cruising during spring to autumn, and on mooring for winter with 240 hookup available.

So power consumption whilst cruising is a key factor in the decision making process on what to buy. The newer high efficiency 240v fridge freezers look interesting so I thought I'd compare one of these with a known good 12 volt unit.

 

So, with that in mind, I have found some interesting data on 12v vs 240v units.

 

12 Volt example

http://www.shoreline-marine.co.uk/fridge-freezers/fridge-freezers---medium/fridge-freezer-fd206

Shoreline FD206 Cost £615

Fridge/Freezer 12/24 volt DC

97 litre Fridge

33 litre Freezer

This is quoted as 2.1 AHr per hour average

So whilst off grid it would consume 24 x 2.1 = 50.4 Amp Hrs per day

 

240 Volt example

http://www.liebherr.co.uk/HG/en-GB/products_uk-hg.wfw/id-1555091-0_36075-1

Leibherr CP3813 Cost £599

Fridge/Freezer 240 volt AC

229 litre fridge

90 litre freezer

This is quoted at 153 kwHr/annum

So whilst off grid it would consume 38.8 Amp Hrs per day

 

Calculations used to arrive at 38.8

1.) 153000 W / 12 = 12750 amp hrs per annum

2.) 12750/365 = 34.9 amp hrs per day

3.) to allow for 90% inverter efficiency 34.9 / 0.90 = 38.8 amp hrs per day

 

So at first glance it looks like the 240 volt Leibherr is twice the size and will consume less power than the 12 volt Shoreline. Downside is the inverter will run when the engine is not running.

 

Also, fyi we do have the space available to take the 240v Leibherr and it will fit through our side hatch.

 

So my questions are

 

1. Are my calculations correct ?

2. Are there any flaws in my logic/reasoning ?

3. Are there any other less tangible issues to be aware off ?

[Robbo]

 

Calculations used to arrive at 38.8

1.) 153000 W / 12 = 12750 amp hrs per annum

2.) 12750/365 = 34.9 amp hrs per day

3.) to allow for 90% inverter efficiency 34.9 / 0.90 = 38.8 amp hrs per day

 

As well as inverter efficiency you also need to counter the fact it's switched on which is usually around 8-13watts for something like a Victron Multiplus.

 

Also you can't really compare 12v fridges as it's stats are against the manufactory conditions which can be different between each manufactory, where the 240v domestic ones are meant to be against a standard set of tests and conditions.

Edited December 10, 2014 by Robbo

[Blazeaway]

 

As well as inverter efficiency you also need to counter the fact it's switched on which is usually around 8-13watts for something like a Victron Multiplus.

 

Also you can't really compare 12v fridges as it's stats are against the manufactory conditions which can be different between each manufactory, where the 240v domestic ones are meant to be against a standard set of tests and conditions.

 

Thanks Robbo

 

Good point about the quoted performance figures and the power consumption of the inverter too.

 

Cheers

[cuthound]

I would use an inverter efficiency of 0.8, because you will only achieve the manufacturers claimed efficiency at a particular load (around 90% IIRC).

 

It still gives 34.9 x 0.8 = 43.625A.

[Blazeaway]

I would use an inverter efficiency of 0.8, because you will only achieve the manufacturers claimed efficiency at a particular load (around 90% IIRC).

It still gives 34.9 x 0.8 = 43.625A.

Thanks Cuthound

At 43 its still better than the smaller 12v unit.

 

These results seem to go against the percieved wisdom to use 12v to use less energy, maybe a change is coming.

[b0atman]

Insulation is the big factor .

Inlander or a good fridge guy could fit a 12v compressor to your 240v model.

[DaveP]

I replaced a Shoreline 12v fridge-freezer with a Currys Essentials one (about half the storage capacity of yours) last year.

 

It's quoted at 214kWh/yr and I found it was drawing about 1.5A (36Ah/d) on average (from an attached energy meter over several days) as opposed to the 2A (48Ah/d) one would get from the rated figure. I put this down to not opening doors and having the cabin at a lower temperature than the standard test setup.

I tend to cruise May-Oct and have a mooring with shoreline for Nov-Apr. I have 500w of solar panels with 440Ah battery bank. I've found no problems running the unit whilst out cruising (including this year 10 days at Cropredy without moving). I did have an invertor failure meaning that the unit was without power for 2 days. The freezer contents were still frozen at the end of this time, although the fridge wasn't cold.

 

At the difference in cost (£190 vs £500 for a replacement Shoreline) I'm more than happy to keep my inverter running 24/7.

[Phil Ambrose]

Also remember if your inverter goes down so does your fridge freezer, my own take on this is we use a Shoreline larder fridge @ 110 ltr capacity and a Shoreline freezer @ 80 ltr capacity, thses are both under counter models, we only shop once a week and they hold all we need plus a bit of spare.
I have never seen the point of taking perfectly good 12v leccy and turning it into 240v leccy. Have never regretted our decision, over 14 years live aboard. 300 watts PV array does the job for 8 months of the year and helps the rest of the time.
Others will be along shortly to help, some will agree while others will not.
Phil

Edited December 10, 2014 by Phil Ambrose

[Loafer]

I'm for 12V and solar. I'd be hugging my batteries if I had to leave the inverter on for 24h.

[by'eck]

Sadly the two followings, mains or battery power for fridge/freezer seem to be as well defined and stubbornly followed as pumpout v cassette loo's. Its unlikely therefore anyone would perform an unbiased like for like power consumption test. Even if the mains powered version came out on top it would have to be by a fair margin before I considered having an inverter on 24/7.

[Loafer]

Sadly the two followings, mains or battery power for fridge/freezer seem to be as well defined and stubbornly followed as pumpout v cassette loo's. Its unlikely therefore anyone would perform an unbiased like for like power consumption test. Even if the mains powered version came out on top it would have to be by a fair margin before I considered having an inverter on 24/7.

 

Plus there's the additional failure risk (in the inverter). Even if your batts run down a bit too much watching telly, most inverters' cut-off voltage is too low IMHO, so you get your batteries caned more often, probably.

 

I've used the relay in my battery manager (Victron B600 or similar) to stop the fridge at 11.8V, not to come back on again until volts are back up to 12.5V, which means you are receiving some sort of charging.

 

Sorry. Just blah-ing now.

[OldGoat]

In this case the killer is - for the OP - that the largest Shoreline fridge freezer is miniscule when compared with his requirements - even if he had two units.

 

Game over.

 

 

[Blazeaway]

Main reason for the size of freezer we need is we have 2 dogs with allergies to proprietory dog foods so we cook them food from frozen fish and vegetables. If any dog owneŕs on the cut are interested we have totally eradicated the allergy problem and they are healthier now than ever, lovely thick coats and silky feeling.

Insulation is the big factor .Inlander or a good fridge guy could fit a 12v compressor to your 240v model.

Nice idea......I'll follow that up.

[ditchcrawler]

OK I have a240 volt LEC fridge with frozen food compartment its now 12 years old and getting do for replacement as the door seal has seen better days.

I have added 1" if Celatex to each side and the top. I also put a sheet of silver foil that they sell to go behind radiators between the condenser, motor/compressor and the cabinet. I also have two computer fans over holes in the floor at the back of the fridge.

 

The fridge plus inverter on 24 hrs a day now uses 3.5 amps at 24 volts and runs for between 5.7 and 6 hrs per day. This was not under test conditions but in normal use.

I suspect a 24 volt fridge would be better but it would have cost more and still need replacing. I am hoping that a new fridge will be more efficient.

[Phil Ambrose]

OK I have a240 volt LEC fridge with frozen food compartment its now 12 years old and getting do for replacement as the door seal has seen better days.

I have added 1" if Celatex to each side and the top. I also put a sheet of silver foil that they sell to go behind radiators between the condenser, motor/compressor and the cabinet. I also have two computer fans over holes in the floor at the back of the fridge.

 

The fridge plus inverter on 24 hrs a day now uses 3.5 amps at 24 volts and runs for between 5.7 and 6 hrs per day. This was not under test conditions but in normal use.

I suspect a 24 volt fridge would be better but it would have cost more and still need replacing. I am hoping that a new fridge will be more efficient.

Hey Brian that is a brilliant result, might give it a go myself provided I can make room for the extra insulation. (on my 12v set up of course)

 

Phil

[peterboat]

I had a 240 fridge freezer but suffered 2 inverter failures lost the contents both times. The vetus inverters have gone back now have a MR controls one cheaper and more reliable plus a 12/24 shoreline fridge freezer would i go back no as my setup works for me. I can leave my boat for a week no inverter on and no problems. Both of the vetus inverters went faulty and produced large amounts of acrid smoke before I isolated them

 

Peter

[DandV]

Where we spend the bulk of the six months off our canal boat here in NZ we are off grid on solar and consume all our power through the inverter which is on 24/7. The DC is 24v. The vast bulk of the load is the fridge. The next biggest consumer is the inverter itself followed by lighting and then the electronics. Heating and water heating is by fire and cooking by LPG.

On the canalboat everything is 12v except the washing machine, power tools

and charging some electronics. Again the fridge is the biggest consumer. Generally therefore we only run the inverter when we are using the washing machine and time recharging electronics to coincide. This means the batteries are saved from the 24/7 inverter standby load and hopefully and I believe we should vastly extend its life.

In short I would recommend the 12v fridge and use the inverter only when 12v is not an option. As an aside our 12v Shoreline is vastly quieter then the Samsung.

Don

[Jambo]

I can heartily recommend Liebherr products. We have their most efficient fridge (no freezer compartment or ice box) and it nominally uses 14Ah per day (before inverter losses). Our boat is set up for 230V though with only the lights and pump running off 12V so the inverter is on 24/7 regardless of what kind of fridge we have. This means that the inverter losses are also attributable to our telly, wifi routers, laptops etc rather than just the fridge.

 

Given that you're getting more than 2 times the fridge freezer for about the same power consumption it's not really a valid comparison though. If you feel you need that much capacity then go for it. If it's just going to sit there half empty most of the time then it's probably worth sticking with 12V.

[Blazeaway]

I can heartily recommend Liebherr products. We have their most efficient fridge (no freezer compartment or ice box) and it nominally uses 14Ah per day (before inverter losses). Our boat is set up for 230V though with only the lights and pump running off 12V so the inverter is on 24/7 regardless of what kind of fridge we have. This means that the inverter losses are also attributable to our telly, wifi routers, laptops etc rather than just the fridge.

 

Given that you're getting more than 2 times the fridge freezer for about the same power consumption it's not really a valid comparison though. If you feel you need that much capacity then go for it. If it's just going to sit there half empty most of the time then it's probably worth sticking with 12V.

 

Appreciate your comments, and others too, thanks everyone.

We have been practicing fridge/freezer contents management at home as preps for future living aboard. We think we will need about the capacity in Original Post 200 fridge 90 freezer. Boat is well setup for 12v on almost everything else so may well go with either 240 volt unit or 240v converted to 12v compressor.

[Phil Ambrose]

Glad we were able to help with the decision making process, but have to say 200ltr fridge is mahoosive.

 

Phil

[Blazeaway]

Glad we were able to help with the decision making process, but have to say 200ltr fridge is mahoosive.

 

Phil

all the replies have been really helpful, 200 litres fridge is small in comparison to current home setup, We are a bit spoilt with a large american style fridge freezer and a standard builtin fridge freezer.

got a lot of downsizing still to do.

[Phil Ambrose]

Downsizing I suspect will be the hardest thing for you, I can well remember when we moved aboard, endless garage sales and ending up camping in the house prior to move day. Still we did manage to have a good few laughs.

Good Luck

 

Phil

[Blazeaway]

We will get there I'm sure.

I see you are on river lark. Its on our list of places to cruise to, to visit our daughter who lives near by.

[Phil Ambrose]

Temporary moorings available if ever you need one.

Phil

[George94]

The arguments in favour of 12/24V are simplicity and reliabilty. The arguments in favour of 230V are much greater choice and much lower cost (assuming you already have a suitable inverter).

 

So it really boils down to risk. I have only experienced one 230V fridge failure in my life, and no inverter failures over a much shorter period. The cost if one or t'other fails is the cost of what was in the freezer and gets spoiled. Unless it's all smoked salmon and foie gras I expect you could have several failures and still be quids in.

 

So, as my Shoreline is getting tired, it's replacement will be 230V.