Running a 3-way fridge

[Sooz52]

Hi, can I have basic run down of how to run a fridge for a full timer with good solar panels and propane please?
I was thinking 12v all the time, step to gas if I’m low on battery juice, and the odd 220v got rare plug ins. But I think the previous owner of my a Hymer said that 12v won’t run when driving. Is that right? Also someone mentioned that gas isn’t great at keeping low temps, instead the cooling relates to degrees below the surroundings, so in high summer my stuff wouldn’t be cold. Is that right?
Do I just leave it on auto and not worry?

 

[Lot lover]

Our old Electrolux fridge will only run on 12v when engine is running. For a while in Portugal recently we did not have 230v so had no choice but to run on gas. IMHO this was colder than electric and it was over 20 during the day.

 

[Carolyn and Kev]

You cannot run a fridge efficiently on 12 volts at all. 12 volts is ideal when running. Gas or 240 when on site. Gas tends to bring it down quickly to temperature then switch over to 240 volts when on EHU. Dont plan on using the solar to help top up the batteries when you are using 12 volts to power the fridge. It cannot keep up!

kev

 

[Jimbohorlicks]

When your previous owner advised the van won't run on 12v when driving, that correctexcept for the fridge. No internal lights or sockets will work whilst the engine is running. But the fridge will.
When you park up you need to switch the fridge to gas or ehu, 240v,.it will not run 9n 12 v. If your fridge is automatic it will select the optimum energy source and should switch to 12v when driving and gas when parked without ehu.

 

[peterc10]

When your previous owner advised the van won't run on 12v when driving, that correct

Not on a Hymer Jim. Only UK motorhomes switch off the 12v.

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[TinaLes]

I consider that when the engine is running, and the fridge is on 12 volt, that its acting more like a cool box, trying its best to store the cold that has been built up from being on Gas or Hookup, we dont open the doors unless we have to. We even place frozen water bottles in the fridge door when travelling to help keep the fridge contents cold.
We have 200 watts of solar and a good regulator, in the summer months with sun on the roof we manage to keep the Gel Batteries topped up each day, using everything we need in the day/evening.

In winter its a different story, no sun, just wet clouds, so a B2B charger needs to be considered as it will recharge the leisure batteries even on shortish runs, whereas without you would maybe have to drive half the day plus, to charge from engine alone.
Gas is always best for cooling the Fridge down quickly from room temp down, 240V is OK if you have enough time on Hook up, and it should maintain a cool temp.

We do struggle with our large Dometic Fridge/Freezer when away for long periods off hook up, when we go shopping & replenish the fridge with new stock at room temp,this in turn warms up the all of the fridge contents, it can take ages until all the contents new & existing are cooled down sufficiently.
So short life stock has to be quickly used or chucked out, nothing like the Fridge at home in terms of performance, "ts camping after all", or that's what they tell us.
Its common sense I guess not to add too much new room temp stock at the one time, stagger it, give the fridge a chance etc, etc, but when you need a beer or three, its sometimes very difficult
Even after 2 years, We are learning every time we take the van on a new adventure.
LES

 

[The Old Man]

I keep three large freezer packs in the ice box of the fridge.

Place them in just as leaving home.

With the 12v whilst driving they help keep the temperature down whilst slowly defrosting.

Once on 240v or gas they refreeze and act as back up cooling when required.

 

[Allanm]

I’m pretty impressed with our Dometic fridge, since I cleaned the burner jet a few months ago. I installed wireless temperature sensors ( ok, thermometers.....) in the fridge and freezer and a display on the wall. The fridge will go down to 4 degrees C whether on hook up, gas or 12v, with the fridge temp setting in the middle. Freezer goes down to about -10 or 12. Before I cleaned the burner jet, we were lucky if the fridge temp dropped below 12degrees on gas.
I always thought 12v was just to keep the fridge at an even temperature, ours seems to cool it down properly.

 

[peterc10]

Hi, can I have basic run down of how to run a fridge for a full timer with good solar panels and propane please?
I was thinking 12v all the time, step to gas if I’m low on battery juice, and the odd 220v got rare plug ins. But I think the previous owner of my a Hymer said that 12v won’t run when driving. Is that right? Also someone mentioned that gas isn’t great at keeping low temps, instead the cooling relates to degrees below the surroundings, so in high summer my stuff wouldn’t be cold. Is that right?
Do I just leave it on auto and not worry?

The Dometic fridge and freezer in our Hymer works better on gas than it does on 12v. Not a lot of difference in performance between gas and 220V. I would recommend that you use gas when you are parked up without EHU, 220v when you are parked up with EHU, and 12v only when you are on the move. And we have found that the easiest way of doing that is to just put the fridge onto Automatic, and leave it to its own devices.

 

[Sooz52]

Brilliant thanks everyone

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[autorouter]

Hi, can I have basic run down of how to run a fridge for a full timer with good solar panels and propane please?
I was thinking 12v all the time, step to gas if I’m low on battery juice, and the odd 220v got rare plug ins.

An absorption fridge (also called a 3-way or AES) has a cooling circuit that contains a mixture of liquids and gases. When heat is applied at the bottom of the circuit, there's a complex process that forces the coolant round the circuit and the result is cooling. A 3-way fridge has a choice of three heat sources: gas, 12V element and 220V element. The idea is that all the heat sources are about the same power, so will all cool the fridge in the same way, as Allanm has said.

If the 12V wiring is a bit thin, there will be voltage drop that results in power loss. If the gas burner is not set up correctly or needs maintenance, then it will also lose power, hence all the other stories about one heat source being better than the other.

Your Hymer will have an Electroblock (EBL) which has 12V fuses and several inbuilt relays to control the switching of the 12V circuits. Probably there will be a fuse (possibly not fitted) that will enable you to run the fridge from the leisure battery when the engine has stopped. Depends on exactly which model of EBL you have.

However that is not really a good idea, because it takes too much 12V power to run 24/7. It will run a 100 amp-hour leisure battery flat in a few hours. It's better to run on gas when mains hookup is not available.

Even using solar, you'd need 400 to 500 watts of panel even in summer to keep an absorption fridge cool, which is more than most MHs have.

But I think the previous owner of my a Hymer said that 12v won’t run when driving. Is that right?

If the 12V power to the fridge doesn't work when driving, that is a definite fault. It can be one of several things, like a blown fuse, bad connection or failed 12V heating element - usually fixable without much fuss and expense.

 

[Sooz52]

Wow thank you, extremely informative. I’ll check today. I’ll put the fridge on as I start my full time adventure on Friday, so need to cool it. I’ll switch the fridge on, so then it should light up with gas automatically - then when I start the motor it should switch across to 12v, and motor off back to gas.

 

[peterc10]

Wow thank you, extremely informative. I’ll check today. I’ll put the fridge on as I start my full time adventure on Friday, so need to cool it. I’ll switch the fridge on, so then it should light up with gas automatically - then when I start the motor it should switch across to 12v, and motor off back to gas.

Just be aware that when you switch off the engine the gas will not light immediately. It will wait for 15 minutes or so. That is to ensure that it does not try sparking up on the garage forecourt when you have just stopped to fill up with fuel.

 

[Reallyretired]

They can be very variable, possibly depending on location and wiring thickness etc. Ours will freeze on 12v when running though is most efficient on gas next most effective ehu and 12v the least.

 

[Sooz52]

I’ve just found I don’t have an auto switch. So that means I need to remember to switch to 12v when driving, then back to gas when stopped? It seems easier just to leave it on gas permanently- I suppose except when filling up fuel - does that sound about right?

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[peterc10]

I’ve just found I don’t have an auto switch. So that means I need to remember to switch to 12v when driving, then back to gas when stopped? It seems easier just to leave it on gas permanently- I suppose except when filling up fuel - does that sound about right?

How old is your Hymer and what model is your Fridge? Is there a button with "A" on it on the fridge, that should be the button for automatic mode.

In order to keep the gas running while you drive you should have a securemotion gas regulator which is supposed to automatically switch off in a crash and also anti-rupture valves on the bottle end of your pigtails which will shut off the gas flow if the pigtail is ruptured.

And it will only take one forgetful moment before you pull onto the garage forecourt to cause a disaster.

 

[tonyidle]

They can be very variable, possibly depending on location and wiring thickness etc. Ours will freeze on 12v when running though is most efficient on gas next most effective ehu and 12v the least.

You're correct. The 12v element is as effective as the mains element. The ONLY reason for poor performance on 12v is incorrect wire size (or a poor connection fault of course).

 

[Sooz52]

How old is your Hymer and what model is your Fridge? Is there a button with "A" on it on the fridge, that should be the button for automatic mode.

It’s 2004, fridge is a dometic, not sure of the model but there doesn’t seem to be an A anywhere

 

[jezport]

You cannot run a fridge efficiently on 12 volts at all. 12 volts is ideal when running. Gas or 240 when on site. Gas tends to bring it down quickly to temperature then switch over to 240 volts when on EHU. Dont plan on using the solar to help top up the batteries when you are using 12 volts to power the fridge. It cannot keep up!

kev

It depends on the fridge, most modern ones now work well on 12v and use the thermostat. Some older models run the 12v element constantly and can over cool.
Modern AES fridges have an S+ connection to connect to solar regulators that have an S+ output. Older AES fridges can use the D+ as long as you know what you are doing and diode protect it. Connected eithe of these ways the fridge will run on 12v when the solar regulator detects the batteries are in an appropriate state.
None of this is worth doing unless you have a good battery bank and sufficient solar panels. Many fridges take 170A to run the 12v element.

 

[Wagoneer]

I’ve just found I don’t have an auto switch. So that means I need to remember to switch to 12v when driving, then back to gas when stopped? It seems easier just to leave it on gas permanently- I suppose except when filling up fuel - does that sound about right?

We always have the gas turned off when traveling. It's not too difficult to remember to switch the fridge to 12v as part of your pre-drive checks......is it ?

PS. The fridge in your pic is manual. Same as in our 2002 Hymer. Looks like a bit of the door latch is missing.

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[jezport]

It’s 2004, fridge is a dometic, not sure of the model but there doesn’t seem to be an A anywhere

So it's a manual fridge, not worth the hassle rewiring to run on solar in my opinion. Plus this model uses 170w on 12v.
We had the AES version of your fridge and could run on our 240w of panels into 240AH battery using a MPPT regulator only during bright sun in the middle of the day. So not really worth the hassle to wire up to do it unless you live in a sunny area have lots of solar and lots of battery storage.

 

[autorouter]

Looks like a bit of the door latch is missing.

When I got our latest (used) MH, it had plastic sliders for the latches of the fridge and freezer - both broken. I bought two replacements, and they lasted about a week. So I removed them and now just use my finger to operate the metal latches when about to drive off. It's easier if I press the freezer door while latching.

I presume the metal latch was bent a bit by trying to close the door with the latch already closed. Never got round to fixing it, I think it just needs a bit of judicious bending.

 

[The Old Man]

An absorption fridge (also called a 3-way or AES) has a cooling circuit that contains a mixture of liquids and gases. When heat is applied at the bottom of the circuit, there's a complex process that forces the coolant round the circuit and the result is cooling. A 3-way fridge has a choice of three heat sources: gas, 12V element and 220V element. The idea is that all the heat sources are about the same power, so will all cool the fridge in the same way, as Allanm has said.

If the 12V wiring is a bit thin, there will be voltage drop that results in power loss. If the gas burner is not set up correctly or needs maintenance, then it will also lose power, hence all the other stories about one heat source being better than the other.

Your Hymer will have an Electroblock (EBL) which has 12V fuses and several inbuilt relays to control the switching of the 12V circuits. Probably there will be a fuse (possibly not fitted) that will enable you to run the fridge from the leisure battery when the engine has stopped. Depends on exactly which model of EBL you have.

However that is not really a good idea, because it takes too much 12V power to run 24/7. It will run a 100 amp-hour leisure battery flat in a few hours. It's better to run on gas when mains hookup is not available.

Even using solar, you'd need 400 to 500 watts of panel even in summer to keep an absorption fridge cool, which is more than most MHs have.

If the 12V power to the fridge doesn't work when driving, that is a definite fault. It can be one of several things, like a blown fuse, bad connection or failed 12V heating element - usually fixable without much fuss and expense.

I had that.

It was the big electronic control box.

There were two faults, from the box to the fridge and from the engine too the box that told it that the engine was running.

 

[SwissBob]

While free camping we use gas - it's an Eletrolux and appears to use very little gas but it freezes ice cubes in 30 mins even on minimum. 12v only when driving. EHU when on campsites as why wouldn't you?

 

[Deep Owl]

Wire a couple of 14cm quiet computer fans on a bracket inside the top fridge vent, on a switch, which will carry away excess heat in hot weather to make your fridge work better. Our AES fridge (2013) only maintains the temperature it was before driving off. As someone said, EHU on site (you’ve paid for it) or gas on an aire/ supermarket; then remember to check for “battery” as you drive off.

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[Sooz52]

I now feel the need to have a clipboard with a pre and post flight check list. Damn, in which box did I pack the clipboard?!

 

[Carolyn and Kev]

It depends on the fridge, most modern ones now work well on 12v and use the thermostat. Some older models run the 12v element constantly and can over cool.
Modern AES fridges have an S+ connection to connect to solar regulators that have an S+ output. Older AES fridges can use the D+ as long as you know what you are doing and diode protect it. Connected eithe of these ways the fridge will run on 12v when the solar regulator detects the batteries are in an appropriate state.
None of this is worth doing unless you have a good battery bank and sufficient solar panels. Many fridges take 170A to run the 12v element.

Think we will have to agree to disagree on that one sorry. The 12 v system would need to be relatively large in capacity to power it on a daily basis. Too much current drawer and the battery would be flat at no time.
That is why most fridges are gas 12v and 240v . Any that are purely 12 volts will not function as you and I would want it to.

Kev

 

[Deep Owl]

Think we will have to agree to disagree on that one sorry. The 12 v system would need to be relatively large in capacity to power it on a daily basis. Too much current drawer and the battery would be flat at no time.
That is why most fridges are gas 12v and 240v . Any that are purely 12 volts will not function as you and I would want it to.

Kev

I agree. Andy Harris, after discussion with Dometic, said you would need to tow a battery truck the size of your van to use 12v when pitched up. Things may have progressed since 2013?

 

[peterc10]

It’s 2004, fridge is a dometic, not sure of the model but there doesn’t seem to be an A anywhere

Aaaaah, long before AES fridges were used. I am afraid you will have to change things by hand

 

[Scattycat]

I might be teaching grandma to suck eggs, but to make the fridge run efficiently, don't forget, vent covers on below +6°c and off when temps are higher