Thetford 3 way fridge.

Trotter

Trotter

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Looking on the Self Build forum, at Wildebus's Autotrail tweaker. I was gob smacked at the amount of power he say's a Thetford 3 way uses on 240v.
Now I know where my battery power goes. 240w?
I would never doubt Dave for a minute. Someone tell me this isn't a typo?
 
The specs for Dometic 3 way show 2 to 2.2 Kwh per 24 hours, so that's getting towards a average of 100w
 
A more meaningful guide to the amount of electricity is kwh (or ah) per 24 hours.
Watts is just a way of saying how quickly power is consumed and thus what size fuse & wire are appropriate.

A typical 3 way absorbtion fridge will use 2 to 3 kwh per day on 230v (running on 12v is only applicable when engine running.
If the power is using an inverted then battery use is 2000 or 3000 / 12 ah = over 200 ah so that is a flat battery in no time.

Before fitting a fridge please research the difference between compression & absorption and define your proposed use.
 
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Why don't you post a link to the thread?
He's usually very good on these things, so is it peak power, or a big fridge, or just that Dometic are a little optimistic?
Either way, running a 3 way on 12v isn't very efficient.
 
colinm said:
The specs for Dometic 3 way show 2 to 2.2 Kwh per 24 hours, so that's getting towards a average of 100w
Click to expand...

That assumes a constant use, fridges turn on & off a lot. The wiring and fuses need to support the peak wattage. This will should also be in the specification.
 
colinm said:
Why don't you post a link to the thread?
He's usually very good on these things, so is it peak power, or a big fridge, or just that Dometic are a little optimistic?
Either way, running a 3 way on 12v isn't very efficient.
Click to expand...

Yes I totally agree, why would you run a 3 way absorption fridge offline using leccy.
They are designed for gas use when offline.
 
colinm said:
Why don't you post a link to the thread?
He's usually very good on these things, so is it peak power, or a big fridge, or just that Dometic are a little optimistic?
Either way, running a 3 way on 12v isn't very efficient.
Click to expand...
I've only just mastered posting a photo on here. Posting a link would be, One step beyond.
Now some clever sod is going to put a Madness video up.
 
r4dent said:
A more meaningful guide to the amount of electricity is kwh (or ah) per 24 hours.
Watts is just a way of saying how quickly power is consumed and thus what size fuse & wire are appropriate.

A typical 3 way absorbtion fridge will use 2 to 3 kwh per day on 230v (running on 12v is only applicable when engine running.
If the power is using an inverted then battery use is 2000 or 3000 / 12 ah = over 200 ah so that is a flat battery in no time.

Before fitting a fridge please research the difference between compression & absorption and define your proposed use.
Click to expand...
Thanks for the explanation.
My van is a tailor made and comes with the Thetford already fitted. I've increased the battery bank significantly, and have been exploring their boundaries. I do successfully run a 12v compressor freezer. Should the Thetford fail, I'd install a 12v compressor fridge as a matter of course.
 
Fisherman said:
Yes I totally agree, why would you run a 3 way absorption fridge offline using leccy.
They are designed for gas use when offline.
Click to expand...

I do.
When the sun shines why use gas? Yes our 3 way fridge uses a lot of power on 12V but LPG is getting more difficult to find, if the sun doesn't shine it runs on LPG.
 
Trotter said:
Thanks for the explanation.
My van is a tailor made and comes with the Thetford already fitted. I've increased the battery bank significantly, and have been exploring their boundaries. I do successfully run a 12v compressor freezer. Should the Thetford fail, I'd install a 12v compressor fridge as a matter of course.
Click to expand...

Our van is similar and I'd swap for a compressor fridge when the day comes. We have a single 95Ah AGM battery, the fridge runs through the inverter when its SoC above 80+ %. If it drops below that it reverts to LPG.
 
The numbers I would have quoted will have covered both power when running (the on time) and also the power (Wh) used over a certain time, which would have encompassed the full duty cycle - on and off - over that time.

I am guessing this is the graph mentioned? This shows the fridge running on 240V AC. The initial period was the cooldown and then we see the duty cycle coming in
1615063805499.png

Taking away the baseline power of around 50W when I was looking at this, you see when the fridge is on, it uses around 200W and is typically on around 65% of the time.

Compare that 200W 65% of the time with a 240V AC Compressor Fridge of a fairly comparable size in my Campervan ....

FridgeAC by David, on Flickr
Ignoring the peak power (which last around 2 seconds), this shows the compressor fridge draws 40W (a 5th of the power of the 3-way) and the duty cycle, instead of being around 65% on, is around 20%.

There really is no comparison between the two in terms of power.
(as an aside, both fridges were powered by the same Victron 2400W PSW Inverter - though not at the same time of course!)


Just like xslivergs, I have setup the motorhome so I can provide inverter power to the fridge when the SOC is above 80% and when the battery drops below that, the power is cut and the Fridge AES makes it switch to Gas.
And similar to him and Trotter, if the fridge breaks I would swap it out for a Compressor model if it was more than a nominal cost to fix. I am actually in two minds to just swap it out anyway and sell it as it is in perfect working condition and could suit someone who just needs a good 3-way swapout.
 
The freezer I bought is one of the Chinese small chest fridge/freezers. From memory about 18 ltr. Big enough as a freezer, probably a bit small as a fridge, especially as a milk bottle wouldn't stand upright. If replacing the Thetford, I'd get a 30 - 40 ltr chest fridge, put on draw runners using the recess the fridge site and the "air space" behind the fridge would/should be long enough to pull the fridge or freezer into the aisle.
That's the theory anyway.
 
Trotter said:
The freezer I bought is one of the Chinese small chest fridge/freezers. From memory about 18 ltr. Big enough as a freezer, probably a bit small as a fridge, especially as a milk bottle wouldn't stand upright. If replacing the Thetford, I'd get a 30 - 40 ltr chest fridge, put on draw runners using the recess the fridge site and the "air space" behind the fridge would/should be long enough to pull the fridge or freezer into the aisle.
That's the theory anyway.
Click to expand...
A top-opening chest fridge or freezer is the most efficient design as much less cold air is lost when opening it up. I think this is why the Waeco CoolFreeze compressor coolboxes are more efficient than their conventional 12V compressor fridges despite having the same compressor.
You can also get full extension draw runners so wouldn't need to have any space behind if you didn't want to :)
This is the little kitchen pod I made for my T4 from an IKEA kitchen unit...
image.jpg15 by David, on Flickr image.jpg14 by David, on Flickr
 
wildebus said:
A top-opening chest fridge or freezer is the most efficient design as much less cold air is lost when opening it up. I think this is why the Waeco CoolFreeze compressor coolboxes are more efficient than their conventional 12V compressor fridges despite having the same compressor.
Click to expand...
(y) Cold air sinks
 
This looks like a good option to replace a 3-way fridge - https://www.jacksonsleisure.com/caravan-motorhome/inlander-rir99dw4-12v-24v-fridge-freezer/ and is fitted with the Danfoss compressor. But you would need to add a door catch if fitted in a Motorhome.


Inlander RIR99DW4 12v 24v Fridge freezer For Narrowboats
The Low Power No Gas Alternative
The Inlander RIR99DW4 is a compressor fridge freezer, with very similar dimensions to the larger 3 way Narrow boat fridge freezers by Dometic and Thetford, but with a very low power consumption figure of just around an average of 2.1AH (amps per hour) (Over 24 hrs)
Ideal Narrow boat Fridge Freezer
With it's Dimensions of 1225H x 500W x 540D (mm) the RIR99DW4 replaces the older types of 3 way fridge freezers from Thetford and Dometic, being 25mm less wide overall, and spot on height, without the need for external venting, or complicated re-wiring (Please check depth carefully)
Shore Power Option
Also available with Shore Power (Mains) option, which will prioritise mains (Shore Power) when available automatically, and return to the low voltage supply when no longer available.
This makes this low voltage Fridge Freezer perfect for your Narrow boat, whether you are on a mooring with Shore Power, or are relying on your 12v 24v Narrow boat battery bank.
Choice Of Colours
The RIR99DW4 12v 24v Fridge Freezer is available in a choice of Black, White or Silver to suit the interior of your Narrow boat, shepherds hut or static, or wherever a low voltage fridge freezer is required *
Specifications
  • Dimensions 1225H x 500W x 540D (mm)
  • Power Consumption 2.1AH (amps per hour) (AVG. Over 24 hrs)
  • Capacity Fridge 93 Litres
  • Capacity Freezer 46 Litres
  • Capacity overall 139 Litres
  • Compressor type Danfoss BD35
 
wildebus said:
A top-opening chest fridge or freezer is the most efficient design as much less cold air is lost when opening it up. I think this is why the Waeco CoolFreeze compressor coolboxes are more efficient than their conventional 12V compressor fridges despite having the same compressor.
You can also get full extension draw runners so wouldn't need to have any space behind if you didn't want to :)
This is the little kitchen pod I made for my T4 from an IKEA kitchen unit...
image.jpg15 by David, on Flickr image.jpg14 by David, on Flickr
Click to expand...
Didn’t see this last night, possibly an edit by Dave after I’d shut down.
This is the idea I had. Fridge piggybacking on top of the freezer. Each with their own drawer sliders.
Difference between the above and my idea is the price of white goods. Bob Wells (CheapRVliving) has recently put up a YouTube video explaining why he has gone from an expensive fridge to a Chinese one. In short, the one he’s replacing cost him $700, 3 years ago. The Chinese one was $200 and if it only lasts 2 years, he’d be in pocket buying another.

I know I haven’t explained that very well, watch the video and you’ll understand what I mean.

edit. A picture, or in this case, a video, speaks a thousand words. See over page. Thanks Chris 👍
 
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