3 way fridge on boat

[Tony Brooks]

3 minutes ago, Alan de Enfield said:

 

I'm guessing that "his" 2-way is 12vdc & 230vac, rather than Gas and 12vdc, or gas and 230vac.

 

It seems it is the use of gas that is concerning him.

 

Just buy either a 12v OR a 230v fridge and be done with it.

 

If that is what he means I fear he may be going down the Peltier route and if so he will be back to high electricity demand. Especially of the 240V is via a wall wart. As you say, just get a 12V or 240V COMPRESSOR fridge and be done with it.

[MtB]

31 minutes ago, Tony Brooks said:

 

If that is what he means I fear he may be going down the Peltier route and if so he will be back to high electricity demand. Especially of the 240V is via a wall wart. As you say, just get a 12V or 240V COMPRESSOR fridge and be done with it.

 

 

I think you're right. I've never seen a 12Vdc/240Vac compressor fridge. They might well exist but if they do, they are rare. I'm also not sure the OP understands the different refrigeration technologies and how much they differ in power consumption.

 

Careering off at a tangent, I'm vaguely surprised there are not 12Vdc fridges on the market from third-party companies who professionally integrate an inverter into the fridge rather than the swapping the compressor to a generic 12Vdc/24Vdc unit. Fitting an inverter must be a cheaper way to create a standalone 12Vdc compressor fridge out of a cheap 240Vac fridge than changing the compressor.

[Alan de Enfield]

1 hour ago, MtB said:

Careering off at a tangent, I'm vaguely surprised there are not 12Vdc fridges on the market from third-party companies who professionally integrate an inverter into the fridge rather than the swapping the compressor to a generic 12Vdc/24Vdc unit. Fitting an inverter must be a cheaper way to create a standalone 12Vdc compressor fridge out of a cheap 240Vac fridge than changing the compressor.

 

That is how 12v Microwaves are (normally) converted.

[MtB]

16 minutes ago, Alan de Enfield said:

 

That is how 12v Microwaves are (normally) converted.

 

So I wonder why fridges are not done the same way.

 

My guess is finding an inverter to deliver a high enough transient start-up current but cheap enough and reliable enough. 

[BEngo]

11 minutes ago, MtB said:

My guess is finding an inverter to deliver a high enough transient start-up current but cheap enough and reliable enough. 

Probably.  If such an inverter existed it would be so handy for DIY installations  of 240 V fridges so there would not be much call for a professional integration.    Plus  finding space, and ventilation for an integral  inverter unit.   The 'hole behind the veg drawer' is a crap place to put an inverter because it is already pretty  full of compressor, which also warms the space up when running and makes the inverter's life harder.  A BD35 and purpose designed electronic unit  just replaces the similar sized 240v compressor.  A bit of pipe work, do up a few nuts, add gas and the jobsaguddun.

 

From a technical point of view, adding an inverter also introduces another point of failure and so reduces overall reliability.

 

N

[Alan de Enfield]

30 minutes ago, BEngo said:

Plus  finding space, and ventilation for an integral  inverter unit. 

 

And, running 12v cables from the batteries to the fridge ( 50 foot each way of volt drop ?) capable of carrying the current / volt drop would not be a simple DIY task for many who are just wanting a plug & play device.

 

May as well just use a mains fridge plugged into a mains socket and use the already suitably installed inverter.

Are there many boats these days that do not have an inverter ?

 

Edit to add :

My Waeco fridge manual suggests that for a 12Vdc fridge at 20 metres from the batteries it would require ~25mm2 cable.

Edited August 1, 2022 by Alan de Enfield

[cuthound]

2 hours ago, MtB said:

 

So I wonder why fridges are not done the same way.

 

My guess is finding an inverter to deliver a high enough transient start-up current but cheap enough and reliable enough. 

 

Yes, typical inrush of a compressor is 8 times running current.

 

Good inverters can support a short overload of twice the badge rating, therefore an inverter at least four times the running current would be needed. Probably cheaper just to install a 12 volt compressor.

[Tracy D'arth]

18 minutes ago, cuthound said:

 

Yes, typical inrush of a compressor is 8 times running current.

 

Good inverters can support a short overload of twice the badge rating, therefore an inverter at least four times the running current would be needed. Probably cheaper just to install a 12 volt compressor.

They are not simply 12v DC compressors but have windings sequentially powered by the electronic module that does the clever switching. At least that is how the popular Danfoss ones work. Explains the cost to some extent.

[Tony Brooks]

Just now, Tracy D'arth said:

They are not simply 12v DC compressors but have windings sequentially powered by the electronic module that does the clever switching. At least that is how the popular Danfoss ones work. Explains the cost to some extent.

 

And as far as I can tell expensive powerful permanent magnet rotors that allow them to get the same power from less electricity.

[OldGoat]

I borrowed a lower cost 1200W inverter from Bimble a couple of years ago and it ran not only a very efficient 3/4 height FF but (separately) an ancient full sized FF with two compressors without any trouble.

However it would not start either when on the reduced standby setting.

IMO the 'challenge' with running 240v compressor fridges is the standby power requirement of the inverter.

It's less of  a problem IF folks had a more than basic battery capacity - which looking at threads on this forum is as reare as hens' teeth.....

[Tracy D'arth]

22 minutes ago, OldGoat said:

I borrowed a lower cost 1200W inverter from Bimble a couple of years ago and it ran not only a very efficient 3/4 height FF but (separately) an ancient full sized FF with two compressors without any trouble.

However it would not start either when on the reduced standby setting.

IMO the 'challenge' with running 240v compressor fridges is the standby power requirement of the inverter.

It's less of  a problem IF folks had a more than basic battery capacity - which looking at threads on this forum is as reare as hens' teeth.....

I have been arguing this problem for years. To avoid the standing power, quiescent,  the inverter could be switched on by the fridge stat so that it is only on when required.

[David Mack]

2 hours ago, Alan de Enfield said:

My Waeco fridge manual suggests that for a 12Vdc fridge at 20 metres from the batteries it would require ~25mm2 cable.

But there can't be many narrowboats where the fridge and batteries are 20 metres apart!

[Alan de Enfield]

8 minutes ago, David Mack said:

But there can't be many narrowboats where the fridge and batteries are 20 metres apart!

 

Batteries in the stern, kitchen in the centre 33 foot apart  60+ feet boat (20 metre return trip for the electical fairies)

[Tony Brooks]

1 minute ago, Alan de Enfield said:

 

Batteries in the stern, kitchen in the centre 33 foot apart  60+ feet boat (20 metre return trip for the electical fairies)

 

But the Danfoss & Shoreline instructions are written in a way that only requires one leg of the supply to be measured. In other words they specify a cable of twice the size but for effectively half the total run length, so it works out correctly.

[Tracy D'arth]

2 minutes ago, Alan de Enfield said:

 

Batteries in the stern, kitchen in the centre 33 foot apart  60+ feet boat (20 metre return trip for the electical fairies)

Factor of 2 error.  Normally I allow 1sq M for every metre distance between battery and fridge not cable run length.

[Alan de Enfield]

Just now, Tracy D'arth said:

Factor of 2 error.  Normally I allow 1sq M for every metre distance between battery and fridge not cable run length.

 

I know that is the oft quoted figure but my waeco fridge manual is a bit more conservative.

[Richard10002]

6 minutes ago, Alan de Enfield said:

 

Batteries in the stern, kitchen in the centre 33 foot apart  60+ feet boat (20 metre return trip for the electical fairies)

That's not quite what you said, is it!?

 

"20 metres apart", is somewhat different from "20 metre return trip".

[David Mack]

1 hour ago, Richard10002 said:

That's not quite what you said, is it!?

 

"20 metres apart", is somewhat different from "20 metre return trip".

Exactly my point. For my 71ft 6in ex working boat I would have to have the batteries under the counter and the fridge in the bow locker to get them 20 metres apart!

[PaulJ]

6 hours ago, MtB said:

 

 

I think you're right. I've never seen a 12Vdc/240Vac compressor fridge. They might well exist but if they do, they are rare. I'm also not sure the OP understands the different refrigeration technologies and how much they differ in power consumption.

 

Careering off at a tangent, I'm vaguely surprised there are not 12Vdc fridges on the market from third-party companies who professionally integrate an inverter into the fridge rather than the swapping the compressor to a generic 12Vdc/24Vdc unit. Fitting an inverter must be a cheaper way to create a standalone 12Vdc compressor fridge out of a cheap 240Vac fridge than changing the compressor.

Waeco would also supply a mains /12 or 24v unit that ran the fridge off the mains when present and would automatically switch to 12v when disconnected from shore power.

They may not do them anymore ,dont know as I havent needed to look recently but I always thought it a good idea as did the folk I fitted them for.

 

[MtB]

5 minutes ago, PaulJ said:

Waeco would also supply a mains /12 or 24v unit that ran the fridge off the mains when present and would automatically switch to 12v when disconnected from shore power.

They may not do them anymore ,dont know as I havent needed to look recently but I always thought it a good idea as did the folk I fitted them for.

 

 

 

Interesting, thanks. But was it a compressor fridge?!

 

 

[Alan de Enfield]

There are 12/24v Dc and 230v Ac fridges but they are not what I would call a convetional fridge - they are more of a cool-box design that can either freeze, or refrigerate.

They are compressor 'fridges' and are available up to 60 litre

 

 

Dellonda 36L Portable Car Fridge/Freezer, 12/24/230V Dual Zone Compressor - DL13 : Amazon.co.uk: Automotive

 

60L Portable Car Fridge, Freezer, 12/24/230V Dual Zone Compressor - DL - Dellonda

 

 

[ditchcrawler]

4 hours ago, Alan de Enfield said:

Edit to add :

My Waeco fridge manual suggests that for a 12Vdc fridge at 20 metres from the batteries it would require ~25mm2 cable.

Most do , 1mm2 per meter run

[PaulJ]

27 minutes ago, MtB said:

 

 

Interesting, thanks. But was it a compressor fridge?!

 

 

Yep.Still do them though output is limited to 4A @24V 

https://www.piratescave.co.uk/waeco-coolpower-eps100-mains-adaptor-230v-12-24v.html?id=153580265&gclid=Cj0KCQjw852XBhC6ARIsAJsFPN3KTuZb6hCOyaqw6figwNNmuLEmcPeqEiLTcxnyxIDAVI4t3D7fbOsaAktgEALw_wcB

[Tony Brooks]

1 hour ago, ditchcrawler said:

Most do , 1mm2 per meter run

 

But only on one leg, not both. In reality 0.5 sq mm per meter of total wiring run length.

Edited August 1, 2022 by Tony Brooks

[David Mack]

50 minutes ago, Tony Brooks said:

 

But only on one leg, not both. In reality 0.5 sq mm per meter of total wiring run length.10 minutes with the specialist and a quick second visit and a condition she had suffered with for many years was considerably improved.

Your wife has wiring to her legs? And that improved her condition?

😁