Thetford Fridge 3-Way on Gas

Markd said:
I got a discount down to £11.89 so not too bad 😀
The thermal inertia is quite high and when moving from freezer to fridge it took c30 minutes to come up - I should have left it outside in 25⁰ air for a few minutes if i was that bothered - another downside of being a cheap skate!

Anyway the bottom line is that my fridge-freezer is working fine with an initial cool rate to match the rejuvenated Thetford.
I got down to -18⁰ in freezer but this gave -3⁰ in fridge so my usual running position of about a third of the way round the dial is still a good setting.
It got me thinking as to where the thermostat is placed and I came to conclusion that it would probably be in the fridge any thoughts anyone?
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I guess the logical place would be by the fridges own thermostat so you can monitor the fridges behaviour?
If I could change one thing on the Govee units it would be to have the temp probe on a lead so you can position it just where you want (and maybe have the unit itself outside?)

Something which I have seen on a few youtube videos is a fridge fan to distribute and even out the air to eliminate cold/warmer zones - I am not referring to fans that you fit at the rear which is a common 'hack', but fans INSIDE the fridge itself.
This is a pretty fancy kit in this first video, but you can get little battery powered ones as well (like in the second video)

 
Not entirely sure what these would do - with evaporator at the top you get cold air falling naturally at the back and the less cold air rising.
I suppose if the fridge is packed a bit tight the full width kit might force some circulation through it?
 
Markd said:
Not entirely sure what these would do - with evaporator at the top you get cold air falling naturally at the back and the less cold air rising.
I suppose if the fridge is packed a bit tight the full width kit might force some circulation through it?
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you would think the natural action of cold air dropping would work, but it often doesn't, so a bit of a helping hand :) (I think the 3-fan panel does seem overkill though!)
 
Jenrai said:
Hello, thank you info. This is the same person that has come today to look at my faulty fridge. Everyone else was too busy. He is so helpful and once my new pcb arrives said he will swap it for me. Honestly I can't recommend this guy enough he is brilliant.
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Hiya - just booked Lee to come and do habitation check next week plus a list of other "niggles"!.
We are at the New Forest meeting later this week - hope to catch you there
 
ramblefrog said:
Hiya - just booked Lee to come and do habitation check next week plus a list of other "niggles"!.
We are at the New Forest meeting later this week - hope to catch you there
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Lee is awsome, he was so helpful. Come see me for a cold one 🍻
 
My fridge freezer has now settled down and using Wildebus' tip about rising humidity being and off cycle I can confirm that the duty cycle on mains is 40 minutes on and 20 mins off during which time the temperature rises about 1⁰ before the thermostat kicks in again.
 
Good stuff.

Getting my new fridge on Friday :p
Going to add a Vent Fan kit of some type with temp sensing control (y)
 
Did you find out where it dumps the heat from or is that going to be the first job?
It certainly makes sense to install ventilation assistance beforehand and maybe not use it that much rather than afterwards having to pull everything out again.
Fit and forget! It shouldn't need any attention for many years especially if you keep it ticking over at a maintenance temperature continuously.
Hope it goes in easily enough.
 
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With the top and bottom external vents will be able to do everything from the rear anyway :)
 
On my previous build, I used the typical Computer Fan on a bracket pointing at the compressor

Extra Fan on Fridge Rear by David, on Flickr
With a temp probe connected to a controller like this - https://amzn.to/3yd61OJ (the one in the link is an AC one - they are available as DC as well)
Worked very well and you could set the temperature to whatever you wanted for the connected device (the fan in this case) to come on or go off.

This time I have decided to go with a commercially produced fan set with variable fan speeds to see what that is like (product evaluation :) )
Thetford 3-Way has been sold and just waiting for it to be collected (y)
 
Markd said:
Did you find out where it dumps the heat from or is that going to be the first job?
It certainly makes sense to install ventilation assistance beforehand and maybe not use it that much rather than afterwards having to pull everything out again.
Fit and forget! It shouldn't need any attention for many years especially if you keep it ticking over at a maintenance temperature continuously.
Hope it goes in easily enough.
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I was playing a IR Thermometer around the back and sides of the current Inventor fridge today ....

Not quite what I expected (never done this before though). The sides had warm spots - some areas were around 20c, some went upto 27C or so. Same both sides. So not hot but it would suggestion some kind of piping on the sides?
Based on that and the fact that the new fridge wants side ventilation, I will loose the idea of adding insulation on the sides and just let it breath. Adding the fan kit (which arrived today) at the rear for some forced ventilation will be enough I think :)
 
It's what I expected so leaving the sides clear to allow a chimney is a good plan.
I expect you'll need space above it too so the heat from the sides can flow over the top and back to your high level vent.
 
well, got a big hole ready to fill now....
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Also got the fan kit just about installed. The fan position will depend a little on the layout at the back of the fridge but the rest can be done.
But where to put the controller? I am trying to avoid having components on show that don't go with the Interior style.
Got this cupboard where the table lives....
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Handy space?
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That'll do :D
 
Very early days (more like a couple of hours in fact) but the new fridge/freezer has looking very good :)
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Freezer down to operating temperature within an hour!

Freezer section always seems to take priority so Fridge is taking a bit longer but looking good as well
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And what is quite remarkable is the power consumption of the Fridge/Freezer when running. The Inventor Compressor used to draw around 36W or so when running. The new Fridge is a proper Fridge/Freezer with a 4* Freezer Compartment and is overall around 40% larger. It is also rated at A+ rather than A++ so I am expecting a significantly highly power consumption.

So seeing this performance is really good ... 49W!
1627676007435.png
When it first started and did the initial cooldown, it was pulling 60W (which was a lot lower than I was expecting anyway), but now down to temp, as well as having an on/off duty cycle, it seems to have a variable-power compressor? The test will be tomorrow to see the power pattern but right now looking excellent :D
 
Very impressive performance. definitely a good decision.
Traditionally compressors are either on or off but nowadays they are moving to variable speed so they match input energy to cooling demand.
Motors last longer and peak demand falls.
Sounds like your solar would cope with this very easily during the day.
 
Probably the last post really for me as have veered away from talking about the 3-way fridge, and that fridge is getting collected this weekend anyway so it won't be around to comment on anyway.

So just a note on how its replacement is looking after 12 hours of running, so will give us a reasonable idea of its power consumption


This is the last 6 hours, so the fridge is fully cooled down already so shows running use.
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Fridge kicks on again when the temperature has gone up 2C from the lowest (so at indicated 3C, up from 1C here).
When starting, it has the usual momentary compressor in-rush and once that is done, the compressor draws an average of around 52W, which for a Fridge/Freezer really is incredible. The Duty Cycle shown here is also very good in terms of energy use ... it is only on for 20% of the time, which means an average power use of 10.4Wh/Hour used by the fridge.
There is the Inverter overhead to consider of course. When the Inverter is feeding the Fridge, there is an increase of around 60W from the battery - so about 20% extra, so par for the course for an inverter (the multiplus is meant to be more efficient than that but the smaller the load the greater the overhead percentage as there is an amount of fixed losses regardless of load).
The inverter itself is in AES search mode, which means it only comes on when there is a load and is in standby the rest of the time. This AES search mode takes power, but on the 12/1600 model is estimated at just 2W.

Doing the maths for an hour period .... 60W for 20%, plus 2W for 80% adds up to 13.6Wh/Hr.
My Battery voltage during the period shown was between 13.2V and 13.1V, so the average Ah/Hr was 1.05Ah - that is WITH Inverter Overhead remember.
I'll be posting further updates on Motorhomebuilder.com :)
 
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