Dave Plowman (News) <dave@davenoise.co.uk> wrote:
> In article <t3jstf$8k9$1@dont-email.me>,
> Fredxx <fredxx@spam.uk> wrote:
>> In terms of efficiency you have to take care comparing like with like.
>> Modern 230V fridge freezers take little power, and there is a thought it
>> is best to switch an decent inverter to provide the necessary power from
>> 12V to 230V.
>
> Think the problem in a caravan is often limited 12v storage. Gas is easier
> to store.
>
> My brother uses his caravan a lot. And seems to have endless problems with
> fridges. Usually the heating element - gas seems to be more reliable. Do
> they use the same heating element for 12v and 240v (via the caravan 12v
> PS)?
>

Not in the Thetfords, one of the common makes. There different elements for
12V and 240V, they fit into a cylinder like arrangement which is also like
a chimney for the gas burner, the whole assembly is wrapped in glass fibre
like insulation. A coolant pipe runs through it.

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
> In article <t3jstf$8k9$1@dont-email.me>,
> Fredxx <fredxx@spam.uk> wrote:
> > In terms of efficiency you have to take care comparing like with like.
> > Modern 230V fridge freezers take little power, and there is a thought it
> > is best to switch an decent inverter to provide the necessary power from
> > 12V to 230V.
>
> Think the problem in a caravan is often limited 12v storage. Gas is easier
> to store.
>
> My brother uses his caravan a lot. And seems to have endless problems with
> fridges. Usually the heating element - gas seems to be more reliable. Do
> they use the same heating element for 12v and 240v (via the caravan 12v
> PS)?

We have a boat, basically the same issues as a caravan. We've had a
few boats in different places over the years.

Once upon a time absorption fridges were the best solution because
they could run on gas and, though inefficient compared with compressor
fridges were OK because gas was cheap. Plus you can store a lot of
energy (and thus fridge running time) in a small space compared with
batteries.

However with increasing gas prices and more effecient (and cheaper)
inverters we now use a cheap standard domestic fridge running it on an
inverter when we are away from mains power.

It's a cheaper solution than a 12v compressor fridge because 12v
fridges are very expensive compared with a standard 240v fridge.

--
Chris Green
·

Brian wrote:

>Dave Plowman (News) <dave@davenoise.co.uk> wrote:
>> In article <t3jstf$8k9$1@dont-email.me>,
>> Fredxx <fredxx@spam.uk> wrote:
>>> In terms of efficiency you have to take care comparing like with like.
>>> Modern 230V fridge freezers take little power, and there is a thought it
>>> is best to switch an decent inverter to provide the necessary power from
>>> 12V to 230V.
>>
>> Think the problem in a caravan is often limited 12v storage. Gas is easier
>> to store.
>>
>> My brother uses his caravan a lot. And seems to have endless problems with
>> fridges. Usually the heating element - gas seems to be more reliable. Do
>> they use the same heating element for 12v and 240v (via the caravan 12v
>> PS)?
>>
>
>Not in the Thetfords, one of the common makes. There different elements for
>12V and 240V, they fit into a cylinder like arrangement which is also like
>a chimney for the gas burner, the whole assembly is wrapped in glass fibre
>like insulation. A coolant pipe runs through it.

My understanding is that the 12 V element is not fed via a
thermostat, because of the problem of switching dc cleanly
without introducing unacceptable hysteresis.

This is generally a workable compromise, on the basis that 12 V
is only used whilst on the move.

Chris
--
Chris J Dixon Nottingham UK
chris@cdixon.me.uk @ChrisJDixon1

Plant amazing Acers.

Fredxx <fredxx@spam.uk> wrote:
> On 18/04/2022 17:58, Rod Speed wrote:
>> On Tue, 19 Apr 2022 00:36:12 +1000, Fredxx <fredxx@spam.uk> wrote:
>>
>>> On 18/04/2022 15:34, Fredxx wrote:
>>>> On 18/04/2022 00:32, Brian wrote:
>>>>>
>>>>>
>>>>> I’ve just had an expensive few days - the ‘three way’ fridge in our
>>>>> motorhome died on our last trip. It was just out of warranty and, of
>>>>> course, it was the absorption (coolant) system which had failed, which
>>>>> isn’t repairable. To add to the joy, getting the old one out and the
>>>>> new
>>>>> one in wasn’t easy- the fridge is wider than the habitation door.
>>>>> They fit
>>>>> out the inside before putting on the roof when building these things.
>>>>> Fortunately, it did fit through the front  door ( passenger door)
>>>>> but this
>>>>> required it to be lifted over the front seats etc.
>>>>>
>>>>> Anyway, the new one is in- I replaced it with a compressor type,
>>>>> which are
>>>>> becoming more popular. They only run off 12v but seem remarkably
>>>>> efficient.
>>>>>
>>>>> But, back to absorption fridges.
>>>>>
>>>>> When ours first failed, I did some diagnostics - checking the gas or
>>>>> electric heaters were working etc, which they were. The fridge just
>>>>> wasn’t
>>>>> cooling. A call to a friendly engineer who services motorhomes etc
>>>>> confirmed my fears etc.
>>>>>
>>>>> On returning home, trying to find someone to replace it promptly
>>>>> turned out
>>>>> to be a problem.
>>>>>
>>>>> I also stumbled across mention of ‘burping’ absorption fridges.
>>>>> Basically,
>>>>> turning them upside down one or more times for varying times. How
>>>>> many and
>>>>> how long seems to be a black art.
>>>>>
>>>>> I opted for what seemed the most common mix, three or so inversions
>>>>> for an
>>>>> hour or so.
>>>>>
>>>>> After fitting back into place ( the inversions were done in the
>>>>> motorhome,
>>>>> the delights of getting it out the door were yet to come), I drove to a
>>>>> level spot (our drive slopes and absorption fridges need to be within 5
>>>>> degrees or so of level) and fired it up on gas. It worked. Within 2
>>>>> hrs the
>>>>> freezer section was down to -18 and the fridge at 4.5 degrees.
>>>>> Turned it
>>>>> off and headed home. I’d try again in the morning, if it worked I ‘d
>>>>> saved
>>>>> £1200 ( these fridges are grossly over priced).
>>>>>
>>>>> Let us just say, the next morning I was ordering a new fridge- which
>>>>> is now
>>>>> fitted.
>>>>>
>>>>> However, I’ve become intrigued by Absorption fridges. I understand
>>>>> they are
>>>>> still used domestically- some of the small fridges like those in hotel
>>>>> rooms are apparently absorption ones. I recall people have gas fridges.
>>>>> Three way fridges used in caravans etc are often absorption ones so
>>>>> they
>>>>> can use gas, 12 V when being towed, and 240v if available.
>>>>>
>>>>> They have no moving parts ( ignoring doors etc). Are all but silent
>>>>> - you
>>>>> can just hear the burner if on gas when it fires up.
>>>>>
>>>>> They can have a very long life.
>>>>>
>>>>> They can also die early, as ours did, I suspect due to being idle
>>>>> during
>>>>> lockdown etc.
>>>>>
>>>>> Does anyone have an absorption fridge in their house?
>>>>  Absorption fridges used to be popular on narrowboats too, but the
>>>> idea of venting burnt fumes into the cabin means you can no longer
>>>> buy one. I think new rules forbid new builds from having one fitted.
>>>>  In terms of efficiency you have to take care comparing like with
>>>> like. Modern 230V fridge freezers take little power, and there is a
>>>> thought it is best to switch an decent inverter to provide the
>>>> necessary power from 12V to 230V.
>>>
>>> I also question why you need a fridge-freezer. Fridges consume much
>>> less energy to keep cool. And still work at low temperatures.
>>
>> But frozen food lasts much longer, stupid.
>
> Perhaps I only go away for a few days at a time, and buy any food when I
> like, where I like.
>
> If you travel for months keeping the same food frozen in your freezer,
> then perhaps I can see your point.
>
>

The freezers aren’t huge - I forget the capacity but around size of a
single freezer drawer.

We tend to by most food as we need it but we like to have a some meals
we’ve made ahead and frozen, mainly for days we’ve been travelling etc. I
am also a fan of soup, make homemade soup in bulk. When I don’t fancy a big
meal, it is perfect.

On Tue, 19 Apr 2022 03:17:38 +1000, Fredxx <fredxx@spam.uk> wrote:

> On 18/04/2022 17:58, Rod Speed wrote:
>> On Tue, 19 Apr 2022 00:36:12 +1000, Fredxx <fredxx@spam.uk> wrote:
>>
>>> On 18/04/2022 15:34, Fredxx wrote:
>>>> On 18/04/2022 00:32, Brian wrote:
>>>>>
>>>>>
>>>>> I’ve just had an expensive few days - the ‘three way’ fridge in our
>>>>> motorhome died on our last trip. It was just out of warranty and, of
>>>>> course, it was the absorption (coolant) system which had failed,
>>>>> which
>>>>> isn’t repairable. To add to the joy, getting the old one out and the
>>>>> new
>>>>> one in wasn’t easy- the fridge is wider than the habitation door.
>>>>> They fit
>>>>> out the inside before putting on the roof when building these things.
>>>>> Fortunately, it did fit through the front door ( passenger door)
>>>>> but this
>>>>> required it to be lifted over the front seats etc.
>>>>>
>>>>> Anyway, the new one is in- I replaced it with a compressor type,
>>>>> which are
>>>>> becoming more popular. They only run off 12v but seem remarkably
>>>>> efficient.
>>>>>
>>>>> But, back to absorption fridges.
>>>>>
>>>>> When ours first failed, I did some diagnostics - checking the gas or
>>>>> electric heaters were working etc, which they were. The fridge just
>>>>> wasn’t
>>>>> cooling. A call to a friendly engineer who services motorhomes etc
>>>>> confirmed my fears etc.
>>>>>
>>>>> On returning home, trying to find someone to replace it promptly
>>>>> turned out
>>>>> to be a problem.
>>>>>
>>>>> I also stumbled across mention of ‘burping’ absorption fridges.
>>>>> Basically,
>>>>> turning them upside down one or more times for varying times. How
>>>>> many and
>>>>> how long seems to be a black art.
>>>>>
>>>>> I opted for what seemed the most common mix, three or so inversions
>>>>> for an
>>>>> hour or so.
>>>>>
>>>>> After fitting back into place ( the inversions were done in the
>>>>> motorhome,
>>>>> the delights of getting it out the door were yet to come), I drove
>>>>> to a
>>>>> level spot (our drive slopes and absorption fridges need to be
>>>>> within 5
>>>>> degrees or so of level) and fired it up on gas. It worked. Within 2
>>>>> hrs the
>>>>> freezer section was down to -18 and the fridge at 4.5 degrees.
>>>>> Turned it
>>>>> off and headed home. I’d try again in the morning, if it worked I ‘d
>>>>> saved
>>>>> £1200 ( these fridges are grossly over priced).
>>>>>
>>>>> Let us just say, the next morning I was ordering a new fridge- which
>>>>> is now
>>>>> fitted.
>>>>>
>>>>> However, I’ve become intrigued by Absorption fridges. I understand
>>>>> they are
>>>>> still used domestically- some of the small fridges like those in
>>>>> hotel
>>>>> rooms are apparently absorption ones. I recall people have gas
>>>>> fridges.
>>>>> Three way fridges used in caravans etc are often absorption ones so
>>>>> they
>>>>> can use gas, 12 V when being towed, and 240v if available.
>>>>>
>>>>> They have no moving parts ( ignoring doors etc). Are all but silent
>>>>> - you
>>>>> can just hear the burner if on gas when it fires up.
>>>>>
>>>>> They can have a very long life.
>>>>>
>>>>> They can also die early, as ours did, I suspect due to being idle
>>>>> during
>>>>> lockdown etc.
>>>>>
>>>>> Does anyone have an absorption fridge in their house?
>>>> Absorption fridges used to be popular on narrowboats too, but the
>>>> idea of venting burnt fumes into the cabin means you can no longer
>>>> buy one. I think new rules forbid new builds from having one fitted..
>>>> In terms of efficiency you have to take care comparing like with
>>>> like. Modern 230V fridge freezers take little power, and there is a
>>>> thought it is best to switch an decent inverter to provide the
>>>> necessary power from 12V to 230V.
>>>
>>> I also question why you need a fridge-freezer. Fridges consume much
>>> less energy to keep cool. And still work at low temperatures.

>> But frozen food lasts much longer, stupid.

> Perhaps I only go away for a few days at a time, and buy any food when I
> like, where I like.

And don't eat icecream when away in the van.

> If you travel for months keeping the same food frozen in your freezer,
> then perhaps I can see your point.

I have icecream or a icecream drumstick after most evening meals.
https://www.google.com/shopping/product/9161158743711447663

I realise that you poms are mostly too poor for that and that in
that frigid little soggy island they are still frozen when you leave
them outside the van even in your pathetic excuse for a summer.

Chris J Dixon <chris@cdixon.me.uk> wrote:
> Brian wrote:
>
>> Dave Plowman (News) <dave@davenoise.co.uk> wrote:
>>> In article <t3jstf$8k9$1@dont-email.me>,
>>> Fredxx <fredxx@spam.uk> wrote:
>>>> In terms of efficiency you have to take care comparing like with like.
>>>> Modern 230V fridge freezers take little power, and there is a thought it
>>>> is best to switch an decent inverter to provide the necessary power from
>>>> 12V to 230V.
>>>
>>> Think the problem in a caravan is often limited 12v storage. Gas is easier
>>> to store.
>>>
>>> My brother uses his caravan a lot. And seems to have endless problems with
>>> fridges. Usually the heating element - gas seems to be more reliable. Do
>>> they use the same heating element for 12v and 240v (via the caravan 12v
>>> PS)?
>>>
>>
>> Not in the Thetfords, one of the common makes. There different elements for
>> 12V and 240V, they fit into a cylinder like arrangement which is also like
>> a chimney for the gas burner, the whole assembly is wrapped in glass fibre
>> like insulation. A coolant pipe runs through it.
>
> My understanding is that the 12 V element is not fed via a
> thermostat, because of the problem of switching dc cleanly
> without introducing unacceptable hysteresis.
>

I’m not sure about that.

Some claim on 12 V 3 way fridges / freezes don’t get cooler, they just stay
cool on 12v. That isn’t out experience. We were total beginners in 2011
and, on our first trip, ( only to a site 90 mins or so away) I popped some
water in the ice cube tray. It certainly froze during the trip. That fridge
was a more basic one. Maybe the older ones. The newer ones are more
sophisticated.

On 18/04/2022 19:28, Brian wrote:
> Fredxx <fredxx@spam.uk> wrote:
>> On 18/04/2022 17:58, Rod Speed wrote:
>>> On Tue, 19 Apr 2022 00:36:12 +1000, Fredxx <fredxx@spam.uk> wrote:
>>>
>>>> On 18/04/2022 15:34, Fredxx wrote:
>>>>> On 18/04/2022 00:32, Brian wrote:
>>>>>>
>>>>>>
>>>>>> I’ve just had an expensive few days - the ‘three way’ fridge in our
>>>>>> motorhome died on our last trip. It was just out of warranty and, of
>>>>>> course, it was the absorption (coolant) system which had failed, which
>>>>>> isn’t repairable. To add to the joy, getting the old one out and the
>>>>>> new
>>>>>> one in wasn’t easy- the fridge is wider than the habitation door.
>>>>>> They fit
>>>>>> out the inside before putting on the roof when building these things.
>>>>>> Fortunately, it did fit through the front  door ( passenger door)
>>>>>> but this
>>>>>> required it to be lifted over the front seats etc.
>>>>>>
>>>>>> Anyway, the new one is in- I replaced it with a compressor type,
>>>>>> which are
>>>>>> becoming more popular. They only run off 12v but seem remarkably
>>>>>> efficient.
>>>>>>
>>>>>> But, back to absorption fridges.
>>>>>>
>>>>>> When ours first failed, I did some diagnostics - checking the gas or
>>>>>> electric heaters were working etc, which they were. The fridge just
>>>>>> wasn’t
>>>>>> cooling. A call to a friendly engineer who services motorhomes etc
>>>>>> confirmed my fears etc.
>>>>>>
>>>>>> On returning home, trying to find someone to replace it promptly
>>>>>> turned out
>>>>>> to be a problem.
>>>>>>
>>>>>> I also stumbled across mention of ‘burping’ absorption fridges.
>>>>>> Basically,
>>>>>> turning them upside down one or more times for varying times. How
>>>>>> many and
>>>>>> how long seems to be a black art.
>>>>>>
>>>>>> I opted for what seemed the most common mix, three or so inversions
>>>>>> for an
>>>>>> hour or so.
>>>>>>
>>>>>> After fitting back into place ( the inversions were done in the
>>>>>> motorhome,
>>>>>> the delights of getting it out the door were yet to come), I drove to a
>>>>>> level spot (our drive slopes and absorption fridges need to be within 5
>>>>>> degrees or so of level) and fired it up on gas. It worked. Within 2
>>>>>> hrs the
>>>>>> freezer section was down to -18 and the fridge at 4.5 degrees.
>>>>>> Turned it
>>>>>> off and headed home. I’d try again in the morning, if it worked I ‘d
>>>>>> saved
>>>>>> £1200 ( these fridges are grossly over priced).
>>>>>>
>>>>>> Let us just say, the next morning I was ordering a new fridge- which
>>>>>> is now
>>>>>> fitted.
>>>>>>
>>>>>> However, I’ve become intrigued by Absorption fridges. I understand
>>>>>> they are
>>>>>> still used domestically- some of the small fridges like those in hotel
>>>>>> rooms are apparently absorption ones. I recall people have gas fridges.
>>>>>> Three way fridges used in caravans etc are often absorption ones so
>>>>>> they
>>>>>> can use gas, 12 V when being towed, and 240v if available.
>>>>>>
>>>>>> They have no moving parts ( ignoring doors etc). Are all but silent
>>>>>> - you
>>>>>> can just hear the burner if on gas when it fires up.
>>>>>>
>>>>>> They can have a very long life.
>>>>>>
>>>>>> They can also die early, as ours did, I suspect due to being idle
>>>>>> during
>>>>>> lockdown etc.
>>>>>>
>>>>>> Does anyone have an absorption fridge in their house?
>>>>>  Absorption fridges used to be popular on narrowboats too, but the
>>>>> idea of venting burnt fumes into the cabin means you can no longer
>>>>> buy one. I think new rules forbid new builds from having one fitted.
>>>>>  In terms of efficiency you have to take care comparing like with
>>>>> like. Modern 230V fridge freezers take little power, and there is a
>>>>> thought it is best to switch an decent inverter to provide the
>>>>> necessary power from 12V to 230V.
>>>>
>>>> I also question why you need a fridge-freezer. Fridges consume much
>>>> less energy to keep cool. And still work at low temperatures.
>>>
>>> But frozen food lasts much longer, stupid.
>>
>> Perhaps I only go away for a few days at a time, and buy any food when I
>> like, where I like.
>>
>> If you travel for months keeping the same food frozen in your freezer,
>> then perhaps I can see your point.
>>
>>
>
> The freezers aren’t huge - I forget the capacity but around size of a
> single freezer drawer.
>
> We tend to by most food as we need it but we like to have a some meals
> we’ve made ahead and frozen, mainly for days we’ve been travelling etc. I
> am also a fan of soup, make homemade soup in bulk. When I don’t fancy a big
> meal, it is perfect.

A fridge freezer with a small freezer box will consume 50% more energy
than a standard fridge.

By way of example:
https://www.argos.co.uk/product/7957709
https://www.argos.co.uk/product/7957761

If you're travelling every day such such your leisure batteries are kept
charged then it shouldn't be such an issue.

I suppose I'm more familiar with live-aboard boats where solar isn't as
effective as one might hope!

Brian wrote:

>Chris J Dixon <chris@cdixon.me.uk> wrote:
>> My understanding is that the 12 V element is not fed via a
>> thermostat, because of the problem of switching dc cleanly
>> without introducing unacceptable hysteresis.
>
>I’m not sure about that.

In what way?

>Some claim on 12 V 3 way fridges / freezes don’t get cooler, they just stay
>cool on 12v. That isn’t out experience. We were total beginners in 2011
>and, on our first trip, ( only to a site 90 mins or so away) I popped some
>water in the ice cube tray. It certainly froze during the trip. That fridge
>was a more basic one. Maybe the older ones. The newer ones are more
>sophisticated.

A lot depends upon ambient temperature. Without a thermostat, in
cool weather conditions over-cooling the fridge is a distinct
possibility.

I gather a potential problem with the latest designs is that even
when being operated on gas, the battery supply is still required
for the controls.

Chris
--
Chris J Dixon Nottingham UK
chris@cdixon.me.uk @ChrisJDixon1

Plant amazing Acers.

Fredxx <fredxx@spam.uk> wrote:
>
> If you're travelling every day such such your leisure batteries are kept
> charged then it shouldn't be such an issue.
>
> I suppose I'm more familiar with live-aboard boats where solar isn't as
> effective as one might hope!
>
We have a boat in Northern France, it has three full size (about 280
watt nominal) solar panels. In the summer months we can run our
standard under counter domestic fridge (with a small freezer
compartment) via an inverter. In the winter there's not enough sun.

I'd guess with more modern panels (now around 400 watt each I believe)
and a more efficient fridge we might get away with all the year round.

--
Chris Green
·

Chris Green <cl@isbd.net> wrote:
> Fredxx <fredxx@spam.uk> wrote:
>>
>> If you're travelling every day such such your leisure batteries are kept
>> charged then it shouldn't be such an issue.
>>
>> I suppose I'm more familiar with live-aboard boats where solar isn't as
>> effective as one might hope!
>>
> We have a boat in Northern France, it has three full size (about 280
> watt nominal) solar panels. In the summer months we can run our
> standard under counter domestic fridge (with a small freezer
> compartment) via an inverter. In the winter there's not enough sun.
>
> I'd guess with more modern panels (now around 400 watt each I believe)
> and a more efficient fridge we might get away with all the year round.
>

Interesting.

While I’ve bought and installed a 12v compressor fridge / freezer - which
cost a fortune- I have since looked in more detail at the inverter /
domestic approach.

A comparable domestic fridge freezer - a bit smaller but the nearest I
could find quickly- claims to consume roughly the same kWhr per year (no
running power given).

My 12v one takes about 3A at 13.8v. The makers claim you can run it for
about 3 days off 2x 95Ahr batteries to 50% so consuming 95Ahr in 3 days @
25 degrees C. To maintain the batteries you’d need about 30 Ahr / day.
Assuming 5 hours sun, that is only 5 A. Allow a bit for losses etc, say 7A.

That should be well within the capability of 280W of solar panels.

As a cross check. A 250W panel should produce 30kwhr / month ( online
number). About 1kwh / day.

The quoted consumption for my fridge is under 0.5kwhr/day, annual about the
same as a similar (slightly smaller) domestic one ( around 160kWhr).

It doesn’t seem to be your fridge that is the problem, even allowing for
inverter losses.

On 19/04/2022 10:17, Brian wrote:
> Chris Green <cl@isbd.net> wrote:
>> Fredxx <fredxx@spam.uk> wrote:
>>>
>>> If you're travelling every day such such your leisure batteries are kept
>>> charged then it shouldn't be such an issue.
>>>
>>> I suppose I'm more familiar with live-aboard boats where solar isn't as
>>> effective as one might hope!
>>>
>> We have a boat in Northern France, it has three full size (about 280
>> watt nominal) solar panels. In the summer months we can run our
>> standard under counter domestic fridge (with a small freezer
>> compartment) via an inverter. In the winter there's not enough sun.
>>
>> I'd guess with more modern panels (now around 400 watt each I believe)
>> and a more efficient fridge we might get away with all the year round.
>>
>
> Interesting.
>
> While I’ve bought and installed a 12v compressor fridge / freezer - which
> cost a fortune- I have since looked in more detail at the inverter /
> domestic approach.
>
> A comparable domestic fridge freezer - a bit smaller but the nearest I
> could find quickly- claims to consume roughly the same kWhr per year (no
> running power given).
>
> My 12v one takes about 3A at 13.8v. The makers claim you can run it for
> about 3 days off 2x 95Ahr batteries to 50% so consuming 95Ahr in 3 days @
> 25 degrees C. To maintain the batteries you’d need about 30 Ahr / day.
> Assuming 5 hours sun, that is only 5 A. Allow a bit for losses etc, say 7A.
>
> That should be well within the capability of 280W of solar panels.
>
> As a cross check. A 250W panel should produce 30kwhr / month ( online
> number). About 1kwh / day.
>
> The quoted consumption for my fridge is under 0.5kwhr/day, annual about the
> same as a similar (slightly smaller) domestic one ( around 160kWhr).
>
> It doesn’t seem to be your fridge that is the problem, even allowing for
> inverter losses.

I'm struggling to believe those numbers. My understanding of your 3A is
that's the average current taken, or if the motor is variable speed that
may be the continuous running current under normal conditions.

Can you provide the model details?

On 18/04/2022 11:37, Brian wrote:

> One major advantage for us is we can now pre cool the fridge and freezer
> before trips. The three way was an issue as our drive slopes and it is
> difficult to get the MH within 5 degrees.

Some compressor fridges have a block of some substance that is cooled
when power is available and keeps the fridge cold when it isn't. Also I
keep one of those freezer packs in the freezer compartment and put it in
the fridge part when off grid. When off grid I cut the power to the
fridge for the first 24 hours. It stays cold.

My 24V fridge draws 1.5A but it is only running for about a third of the
time in normal weather.

It's better to use fridges designed for marine use than for caravan use.

Bill

Fredxx <fredxx@spam.uk> wrote:
> On 19/04/2022 10:17, Brian wrote:
>> Chris Green <cl@isbd.net> wrote:
>>> Fredxx <fredxx@spam.uk> wrote:
>>>>
>>>> If you're travelling every day such such your leisure batteries are kept
>>>> charged then it shouldn't be such an issue.
>>>>
>>>> I suppose I'm more familiar with live-aboard boats where solar isn't as
>>>> effective as one might hope!
>>>>
>>> We have a boat in Northern France, it has three full size (about 280
>>> watt nominal) solar panels. In the summer months we can run our
>>> standard under counter domestic fridge (with a small freezer
>>> compartment) via an inverter. In the winter there's not enough sun.
>>>
>>> I'd guess with more modern panels (now around 400 watt each I believe)
>>> and a more efficient fridge we might get away with all the year round.
>>>
>>
>> Interesting.
>>
>> While I’ve bought and installed a 12v compressor fridge / freezer - which
>> cost a fortune- I have since looked in more detail at the inverter /
>> domestic approach.
>>
>> A comparable domestic fridge freezer - a bit smaller but the nearest I
>> could find quickly- claims to consume roughly the same kWhr per year (no
>> running power given).
>>
>> My 12v one takes about 3A at 13.8v. The makers claim you can run it for
>> about 3 days off 2x 95Ahr batteries to 50% so consuming 95Ahr in 3 days @
>> 25 degrees C. To maintain the batteries you’d need about 30 Ahr / day.
>> Assuming 5 hours sun, that is only 5 A. Allow a bit for losses etc, say 7A.
>>
>> That should be well within the capability of 280W of solar panels.
>>
>> As a cross check. A 250W panel should produce 30kwhr / month ( online
>> number). About 1kwh / day.
>>
>> The quoted consumption for my fridge is under 0.5kwhr/day, annual about the
>> same as a similar (slightly smaller) domestic one ( around 160kWhr).
>>
>> It doesn’t seem to be your fridge that is the problem, even allowing for
>> inverter losses.
>
> I'm struggling to believe those numbers. My understanding of your 3A is
> that's the average current taken, or if the motor is variable speed that
> may be the continuous running current under normal conditions.
>
> Can you provide the model details?
>

Thetford T2160

https://www.thetford-europe.com/gb/products/refrigerators/12v-refrigerators/t2160

I note the quoted daily consumption is just over 0.5kwhr / day - not just
under. A simple memory error.

The domestic one was some cheapie from Curry’s, about £180, and roughly
the same size - made in China.

I measured the current of the 12v one while running off a 13.8 v supply. It
is the current while the compressor is running, I measured it while in my
garage testing before fitting. Once the fridge was down to temp, the
current was naff all. I didn’t run it long enough ( or full of food) to get
a duty cycle but others say they run about 30% of the time. That is
consistent with my measurements and the claimed consumption.

Limited testing I agree but certainly looking good.

On 19/04/2022 21:38, Brian wrote:
> Fredxx <fredxx@spam.uk> wrote:
>> On 19/04/2022 10:17, Brian wrote:
>>> Chris Green <cl@isbd.net> wrote:
>>>> Fredxx <fredxx@spam.uk> wrote:
>>>>>
>>>>> If you're travelling every day such such your leisure batteries are kept
>>>>> charged then it shouldn't be such an issue.
>>>>>
>>>>> I suppose I'm more familiar with live-aboard boats where solar isn't as
>>>>> effective as one might hope!
>>>>>
>>>> We have a boat in Northern France, it has three full size (about 280
>>>> watt nominal) solar panels. In the summer months we can run our
>>>> standard under counter domestic fridge (with a small freezer
>>>> compartment) via an inverter. In the winter there's not enough sun.
>>>>
>>>> I'd guess with more modern panels (now around 400 watt each I believe)
>>>> and a more efficient fridge we might get away with all the year round.
>>>>
>>>
>>> Interesting.
>>>
>>> While I’ve bought and installed a 12v compressor fridge / freezer - which
>>> cost a fortune- I have since looked in more detail at the inverter /
>>> domestic approach.
>>>
>>> A comparable domestic fridge freezer - a bit smaller but the nearest I
>>> could find quickly- claims to consume roughly the same kWhr per year (no
>>> running power given).
>>>
>>> My 12v one takes about 3A at 13.8v. The makers claim you can run it for
>>> about 3 days off 2x 95Ahr batteries to 50% so consuming 95Ahr in 3 days @
>>> 25 degrees C. To maintain the batteries you’d need about 30 Ahr / day.
>>> Assuming 5 hours sun, that is only 5 A. Allow a bit for losses etc, say 7A.
>>>
>>> That should be well within the capability of 280W of solar panels.
>>>
>>> As a cross check. A 250W panel should produce 30kwhr / month ( online
>>> number). About 1kwh / day.
>>>
>>> The quoted consumption for my fridge is under 0.5kwhr/day, annual about the
>>> same as a similar (slightly smaller) domestic one ( around 160kWhr).
>>>
>>> It doesn’t seem to be your fridge that is the problem, even allowing for
>>> inverter losses.
>>
>> I'm struggling to believe those numbers. My understanding of your 3A is
>> that's the average current taken, or if the motor is variable speed that
>> may be the continuous running current under normal conditions.
>>
>> Can you provide the model details?
>>
>
> Thetford T2160
>
> https://www.thetford-europe.com/gb/products/refrigerators/12v-refrigerators/t2160
>
> I note the quoted daily consumption is just over 0.5kwhr / day - not just
> under. A simple memory error.
>
> The domestic one was some cheapie from Curry’s, about £180, and roughly
> the same size - made in China.
>
> I measured the current of the 12v one while running off a 13.8 v supply. It
> is the current while the compressor is running, I measured it while in my
> garage testing before fitting. Once the fridge was down to temp, the
> current was naff all. I didn’t run it long enough ( or full of food) to get
> a duty cycle but others say they run about 30% of the time. That is
> consistent with my measurements and the claimed consumption.
>
> Limited testing I agree but certainly looking good.

0.55kWh => an average of 1.9A at 12V over 24hours. If you say it is on
for 30% of the time then the running current is 1.9 x 1/.3 = 6.3A

0.55kWh sounds about right for a modern fridge freezer ~ 200kWh per year.

So no more efficient than a current 230V fridge freezer.

On 19/04/2022 13:29, Fredxx wrote:
> I'm struggling to believe those numbers. My understanding of your 3A is
> that's the average current taken, or if the motor is variable speed that
> may be the continuous running current under normal conditions.

Mine uses 1.5A at 24V when it's running.

Bill

On 18/04/2022 09:10, Brian wrote:
> The 12v - at least the high current 12v - is normally only used when the
> engine is running. It powers a 12V heater and draws a lot of current.

17A

Bill

On Monday, 18 April 2022 at 00:32:07 UTC+1, Brian wrote:

> But, back to absorption fridges.

Mine used 1.2kg of ammonia as the working fluid. They seldom leak, but if they do one can kill a large number of people. I vaguely remember a report done on them concluding that the small number of them in houses constituted a serious danger to life. I got rid of mine.