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Refrigerator: Best Power Source (if there is a single one......)


Greg K

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As I have done at home if you only want a larder fridge with no icebox then convert a small freezer to be a fridge by using an external thermostat.

It will be smaller inside than an equivalent under counter fridge but will use way less electric than a normal fridge.

When the boat fridge dies it's what I will be doing hence the test at home.

 

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My opinion - the best option is the most readily available - anything for "Marine" usually involves a premium. So, 240V compressor is the cheapest, easily available, most efficient. Do your work on the other things needed to power it - Solar, batteries, inverter. The price difference in the fridge and the consumption costs make the economics more favourable down the years.

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18 minutes ago, alistair1537 said:

My opinion - the best option is the most readily available - anything for "Marine" usually involves a premium. So, 240V compressor is the cheapest, easily available, most efficient. Do your work on the other things needed to power it - Solar, batteries, inverter. The price difference in the fridge and the consumption costs make the economics more favourable down the years.

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If I had the space for the smallest 240V fridge, I would have bought one last year when my Waeco failed after only a few years.... particularly as I was on the verge of replacing my inefficient Sterling inverter with a Smart Victron.

 

Short of rebuilding my kitchen, I, (and probably many other narrowboaters), have no alternative to buying the compact 12V or 3 way fridges available for boats and caravan/motorhomes.

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1 hour ago, Tracy D'arth said:

Dedicate an inverter to the fridge, it will need to be close to 1000w to ensure proper starting of the compressor. Wire the fridge thermostat to the inverter on/off switch so that the inverter is only on when the fridge needs it.  Works for me.

As I mentioned, an 800w PSW Sterling inverter works reliably and has done so for me for the last 4 years.

 

I converted a highly insulated LEC tabletop freezer which fits with room to spare into the hole once occupied by a 3 way fridge and it's enhanced insulation makes it incredibly efficient.

 

I just used a cheap eBay 12v thermostat via a relay to turn on the freezer's dedicated inverter at 6 degrees and off again at 3 degrees. Obviously you can set the temperature and hysteresis to whatever you want.

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2 hours ago, Tony1 said:

 

Thanks Dave, the thing about poor insulation on some of the 12v models was something I saw reported elsewhere, I've not seen it myself.  Someone reported that they'd watched a 12v fridge get cut into, and the insulation was very little. 

I managed to find a cheap inverter that was 2kw but still only uses 0.5 amps when under no load, so I leave it on 24/7 for the sake of the fridge.

But if I abandon the fridge this winter, I'll start switching off the inverter at say 10pm, and save myself 10 hours at 0.5 amps... so maybe 5Ah saved.

 

https://www.amazon.co.uk/gp/product/B07DHKDTKB/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

 

I'm still pondering the idea of bodging together a heath-robinson setup, whereby I put a tube through the hull side with a very small fan on a timer, to suck in cold external air directly into the fridge for say 15 mins every hour.

From Oct to end of March, the external temp is generally cold enough to keep food decently well, and I could maybe turn off the fridge power supply for long periods- certainly overnight. 

The problem is there is a major risk that it just wont work very well, or will use almost as much power for the inlet fan as it would use for the compressor....  

 

 

Rather than draw cooling  air from outside  many of us draw it up from the bilge.  OK, it might not be as cold as the outside air but it is pretty cold in winter and it helps in summer too.

There are plenty of 12V fans on the web, and they draw tiny amounts of power.  I use a couple of 3 inch printer fans in  parallel.   Something like 3 W each. There is a dedicated fan control terminal on the BD 35 electronic unit, so the fan only runs once the fridge motor is going. There is even a short time delay to allow the condenser to warm up before the fan starts!

 The effect of the fan is noticeable.

A bilge fan helps keep the bilge dry too.

N

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36 minutes ago, BEngo said:

Rather than draw cooling  air from outside  many of us draw it up from the bilge.  OK, it might not be as cold as the outside air but it is pretty cold in winter and it helps in summer too.

There are plenty of 12V fans on the web, and they draw tiny amounts of power.  I use a couple of 3 inch printer fans in  parallel.   Something like 3 W each. There is a dedicated fan control terminal on the BD 35 electronic unit, so the fan only runs once the fridge motor is going. There is even a short time delay to allow the condenser to warm up before the fan starts!

 The effect of the fan is noticeable.

A bilge fan helps keep the bilge dry too.

N

 

That's a cracking idea, thanks.  very much

I didnt really want to put a hole in the side of the hull just for the sake of testing a rather flaky idea out, so the bilge sounds much better.

I can cut out a 15mm or 22m hole (big enough to put a standard sort of pipe down into the bilge) and site the hole behind the fridge itself so its well hidden. 

I was thinking I might have to put an exhaust valve at the top of the fridge if I keep pumping in air every hour or so, or I might (to paraphrase our dear Michael Caine) 'blow the bloody doors open'. 

I've no idea how cool it is in the bilge when I've got the stove going, but as you say it will certainly make a difference. 

I dont know if its full of space, or bricks, or some other kind of ballast under there- I guess I'll have to try a small test hole and see- ideally I can get close to the bottom plate, which will be pretty damn cold.  

In principle I like the idea of injecting cold air into the fridge, because (at an admittedly wild guess) it could save save 20Ah of power per day.

It also means I dont have to consider using the cratch for food storage, because- at the risk of turning this into a Carry On script- I must confess that my cratch is disgraceful).

 

I do also have a locker on the stern that I think I could fit a biggish bag of food into (alongside the spare gas bottle), so that's another option; although I dont fancy messing about with the heavy steel lid on a pitch dark and freezing January evening, just to grab a beer.

Still, anything that keeps my paws out of the larder cant be all bad, and the spiders will have all buggered off out of there by November. 

I'm not majorly worried about food theft from a stern locker tbh- if they need to pinch a few sausages that badly, let them have it I say. 

Beer theft is of course entirely another matter....

 

Edited by Tony1
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For those of you advocating a dedicated inverter for the fridge, please consider its location relative to anything supplied from another inverter. Ideally they should be at least 2 metres apart.

 

This is because the outputs of the two inverters will not be in phase and voltages of around 400 volts can appear if you get across the outputs of the two.

 

 

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10 hours ago, cuthound said:

For those of you advocating a dedicated inverter for the fridge, please consider its location relative to anything supplied from another inverter. Ideally they should be at least 2 metres apart.

 

This is because the outputs of the two inverters will not be in phase and voltages of around 400 volts can appear if you get across the outputs of the two.

 

 

Why two metres?

 

 

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3 minutes ago, StephenA said:

Why two metres?

 

 

 

It's to do with a human touching two different AC lines. I seem to recall it's the distance required between non-protected lights and the floor/bottom of a bath in a house bathroom, so probably derived from domestic electricity regulations.

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6 minutes ago, StephenA said:

Why two metres?

 

 

industry standards AND perhaps you'd be pushed to spread yourself that much to touch both wires at once.

 

IMO - anoway I can't see a reason to have two inverters because even the less powerful one will consume as much in standby as will the larger one.

(I tested several inverters from a 350w tiddler to a Sterling girt big hernia inducing one and the all consumer around one amp in stabdby,

 

beaten to it...

 

Edited by OldGoat
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