Thetford/Norcold fridge - run it on 12v permanently ?

[Deleted member 62288]

So, my installation only allows the fridge to run on 12v when the engine is running, a relay cuts out the 12v supply when the engine is off. This is normal and I understand that this is to prevent the fridge from draining the batteries, while stationary.

But I want to have this as an option, perhaps via a manual switch to switch on a 12v supply that enables the fridge to run on 12v rather than LPG while out "camping".

Now that I have got plenty of reserve with the new 460Ah victrons under the seat, I can possibly afford to use the fridge on 12v only.

Part of the reason for this is, the Hymer is badly designed regarding the fridge location, it is installed on the same side as the habitation door which means that it is risky when the safari room is deployed, the exhaust gases vent into the safari room, not good.
12v operation is a must, if it is feasible.

So my question for the good folks here (and the bad too, I'm not fussy), is have you tried this and what was the result, or if you have any views or opinions please share them.

I have a circuit diagram of the Elektroblock 100B but I can't fathom the logic/operation of the relays (It's in German which doesn't help). If I could track down the relay terminal that "outputs" the 12v directly to the fridge, I could "switch" it and provide direct 12v from the power reserve.

Access to the electrics at the back of the fridge is impossible without pulling the entire fridge out of it's housing so the modification needs to be done at the EBL end.

Is my logic correct here ?

TIA,

james

 

[Nesting Zombie]

Hi ya,
Yep it’s the same set up as I’ve got & I ONLY run it on 12v When The Engine is Running, Then it Automatically switched to 230v when a Power source is present, Never use it on Gas (Hardly Use Gas At all).
So yep you’re logic is sound if you have a vast amount of 12v available as you say, Then Why Not !.
You will have to try it & Test it Then iron out any Glitches but Yep Doable in my book.

 

[Deleted member 62288]

Hi ya,
Yep it’s the same set up as I’ve got & I ONLY run it on 12v When The Engine is Running, Then it Automatically switched to 230v when a Power source is present, Never use it on Gas (Hardly Use Gas At all).
So yep you’re logic is sound if you have a vast amount of 12v available as you say, Then Why Not !.
You will have to try it & Test it Then iron out any Glitches but Yep Doable in my book.

I've had a closer look at the circuit diagram and it seems that the EBL 100B provides the 12v switched to the fridge via EBL Block 1, Terminal 4 and the negative at terminal 3.

So If I had a double pole 25A changeover here I could switch the 12v from the leisure batteries into the factory wiring which seems simple enough, that looks like the next area of research.

james

 

[Deleted member 62288]

To be honest the amount of flue gasses being produced by a fridge are negligible, your burner is probably less than half a kw and the gas consumption will be around 30 gh .
There will be more than enough adventitious air for combustion in a safari room.
You may also find your fridge has a solar power input as the more modern ones are now being manufactured with this option available.

Thanks for that, problem with the wiring is no access to the back of the fridge to get at the wiring. It's 2004 vintage.

I think I've sussed the terminals at the EBL, now need to test and see if my understanding is correct and that I have identified the wires in the vehicle wiring loom that I need to switch.

james

 

[Full Member]

To be honest the amount of flue gasses being produced by a fridge are negligible, your burner is probably less than half a kw and the gas consumption will be around 30 gh .
There will be more than enough adventitious air for combustion in a safari room.
You may also find your fridge has a solar power input as the more modern ones are now being manufactured with this option available.

I'm with Charlie on this. Safari rooms are fairly drafty(!) places.
My Dometic fridge uses 0.25kg of gas per 24 hours so about 10g/hour.

Colin

 

[r4dent]

I don't know the spec of your fridge, but most 2/3 way fridges just keep things cool on 12v rather than cool things down.

A typical fridge uses 1.5 kwh per 24 hours (yours may be more because it is getting on a bit).

From 12v this is 1500 /12 amp hours per 24 hours = 120 amp hours a day. So to get you 400ah set up down to 50% will only take a couple of days !

Best stick to gas (or the "G" word) when EHU is not an option.

 

[Byronic]

To be honest the amount of flue gasses being produced by a fridge are negligible, your burner is probably less than half a kw and the gas consumption will be around 30 gh .
There will be more than enough adventitious air for combustion in a safari room.
You may also find your fridge has a solar power input as the more modern ones are now being manufactured with this option available.

My mid size Thetford 3 way has a burner rated at 186W
high setting, 86W low. Uses c. 0.24kg gas over 24 hours
on mid setting. Would have to be a hermetically sealed
safari room to be a hazard I would have thought. After
all domestic gas fridges are only vented into a room,
often a titchy kitchen.

A few years old now, so latest models may well perform
more efficiently.

I carry an emergency camping gas 907 cylinder 2.7kg
reckon on getting c.10 days fridge running out of it.

 

[Deleted member 62288]

I don't know the spec of your fridge, but most 2/3 way fridges just keep things cool on 12v rather than cool things down.

A typical fridge uses 1.5 kwh per 24 hours (yours may be more because it is getting on a bit).

From 12v this is 1500 /12 amp hours per 24 hours = 120 amp hours a day. So to get you 400ah set up down to 50% will only take a couple of days !

Best stick to gas (or the "G" word) when EHU is not an option.

Are those figures a guesstimate or actual ?

I agree up to a point, that if the compressor was running 24x7 I might agree with those numbers, but the thermostat kicks in and out, mostly out so I would guess a fraction of that daily load is perhaps more reasonable.

But really I need to temp jerry-rig it and see what my installation uses in amps per day and make a judgment from there.

I'm hoping that other members may have tried this and might share their experiences.

james

 

[Byronic]

Gas so much energy in a small package. Not so heavy either,
13kg. bottle + 13kg of gas = 26kg. Compare that to battery
power, a couple of average batts will weigh more, and give
a lot less.

 

[maingate]

Keep a few hundred pounds in reserve for when your EBL charger burns itself out trying to recharge 460Ah of batteries.

 

[Deleted member 62288]

Keep a few hundred pounds in reserve for when your EBL charger burns itself out trying to recharge 460Ah of batteries.

I agree with you, but the EBL can mind it's own business as far as managing the 460Ah victrons, it only contributes when the engine is running or the shoreline is plugged in.

I have a current thread here where I have described my project to upgrade the van's electrics so that I could do this type of thing.
https://www.wildcamping.co.uk/forum...batteries-if-money-not-factor.html?highlight=


The specific reason that I have upgraded my installation is that the EBL is old technology and is inadequate for my needs.
I have purposely by-passed the EBL for my solar system

That is why I installed a Victron MPPT 40A controller for the 340 watts of panels.

 

[n brown]

whatever your power supply , the 12v fridge element is still a weedy heat source compared to gas. i doubt it would cope with cooling your fridge if the door is in use on anything more than a coolish day. i find the average fridge takes a couple of hours minimum on 12v before anything starts to happen , and sometimes double that before ice starts to form. any way , easy enough to experiment

 

[wildebus]

I understand (and this was also posted by someone else) that when running on 12V it is just maintaining a cooler temperature rather than being a true fridge.
So ...
option 1 - use an inverter and run the fridge at 230V for a period of time while you have the excess power
option 2 - bin the three-way fridge and get a compressor fridge and run it off the batteries all the time. This is what I do with my 440Ah of batteries running a 230V Domestic Fridge

 

[Deleted member 62288]

I understand (and this was also posted by someone else) that when running on 12V it is just maintaining a cooler temperature rather than being a true fridge.
So ...
option 1 - use an inverter and run the fridge at 230V for a period of time while you have the excess power
option 2 - bin the three-way fridge and get a compressor fridge and run it off the batteries all the time. This is what I do with my 440Ah of batteries running a 230V Domestic Fridge

Thanks, I've got an Avondale caravan which has had a domestic 220v fridge installed by the previous owner, great for static with ehu but useless on the road when being towed.
So I upgraded the batteries and installed an inverter, ran an alternative supply to the fridge and was planning on hauling this around europe. That never happened, so I've robbed the inverter for the Hymer, temporarily.

I'll temp rig it up direct to the batteries, but I haven't found the 2 wires in the vehicle wiring loom yet.

 

[Nabsim]

My 110ltr Waeco compressor fridge seems to use very little leccy power if that info is any use, downside is they look a tad expensive to buy. From posts I have seen the 3 way fridge doesn't function properly on 12v but thats just what I have seen in threads rather than know for a fact. Think you are best finding out if that is correct before going much further. You dont want salmonella running tests

Edit: My EBL 100-2 passes 12v to the fridge constantly, fridge, step door light are constantly live whether on starter or leisure battery if you use the fridge take off. Is yours designated a 100B, if you say exact model I may be able to get the english manual

 

[Deleted member 62288]

I'm in the process of exploring the capabilities of the upgraded system so that I know exactly what limitations I will have once on the road.

I know that running the fridge off the gas is the most efficient/cost effective option. But what do I do say, when I run out of gas atop a mountain in Spain ? Luckily I have a gaslow external connection so that I can use external bottles. But lpg refill stations are not that common when off the beaten track..

Bottom line is, if the batteries can take it and the fridge efficiently is not impacted, then it is worth the effort of having an additional option of running on 12v provide free from the solar panels.

I'm at the "proof of concert" stage at this point in time, I have the opportunity to explore the system limits before I get back on the road.

Anyway it's a fun way to spend time which provides me with more and better options down the line.

james

 

[Deleted member 62288]

My 110ltr Waeco compressor fridge seems to use very little leccy power if that info is any use, downside is they look a tad expensive to buy. From posts I have seen the 3 way fridge doesn't function properly on 12v but thats just what I have seen in threads rather than know for a fact. Think you are best finding out if that is correct before going much further. You dont want salmonella running tests

Edit: My EBL 100-2 passes 12v to the fridge constantly, fridge, step door light are constantly live whether on starter or leisure battery if you use the fridge take off. Is yours designated a 100B, if you say exact model I may be able to get the english manual

yes, it's an EBL 100B art-nr 911.502

I can't get it to run off 12v when engine is off even though the terminals are live at the ebl end. I'm assuming that the relay switching all happens at the ebl end of the wiring loom rather than inside or close to the fridge, unless there is a box somewhere in the vicinity of the shoreline connection that has another relay, I haven't found it yet.

many Thanks indeed, james

 

[n brown]

another option is to not have such a pressing need for a fridge. we never had one for years when full timing , and rarely turn on the one we have now. so if you do run out of gas up a mountain , either drive to get more [it's never far] or eat the food as necessary

 

[Byronic]

How long are you going to be on the top of this mountain in
Spain lol?

For me it's 2x13kg bottles of gas (Spanish). One bottle will last a month,
then it's time to start looking for an exchange, so say + 6 weeks static
is possible on average, much depends on season and whether space heating.
I carry a camping gas R907, belts and braces, never used it.
Relying on Gaslow may not be the best decision in isolated circumstances.

But... you can run out of sunshine for weeks up a Spanish mountain at times!

 

[wildebus]

Thanks, I've got an Avondale caravan which has had a domestic 220v fridge installed by the previous owner, great for static with ehu but useless on the road when being towed.
So I upgraded the batteries and installed an inverter, ran an alternative supply to the fridge and was planning on hauling this around europe. That never happened, so I've robbed the inverter for the Hymer, temporarily.

I'll temp rig it up direct to the batteries, but I haven't found the 2 wires in the vehicle wiring loom yet.

Not all domestic fridges are created equal.... My 230V Fridge has been on virtually continuously since last October. My batteries are back to 100% SOC well before noon