12v heater while travelling.

[Richard n Ann]

Been driving through France and Spain the last couple of days and now I've got the temperature logger in the fridge and another in the condenser fins I can see exactly what happens..

We set off at 12 noon today and the condenser drops to ambient virtually straight away, stopped at 9pm and switched to gas, the sensor is on the left but the wind blast must affect the heater too...
Condenser log:

The internal temperature suffers too:

The evap still frosts but it must just be at something like -2° instead of -8°
The 12v element is 120w
The 230v element is 125w

Wonder if it would perform better with the bottom cover on while driving
Or even both

 

[Spriddler]

Never worried me as I've no sensors or loggers.

Ignorance is bliss.

 

[Landy Andy]

Mmmm. Numbers, graphs.

Only one question.

Was your beer cold enough when you stopped?

That is the important bit.

 

[Badknee]

12 volt is the weakest of the three. Personally I think gas really does the job quickly followed by leccy then 12v.

 

[Richard n Ann]

Mmmm. Numbers, graphs.

Only one question.

Was your beer cold enough when you stopped?

That is the important bit.

Haven't got any the coke was just about cold enough though.
I'm always on the look out for efficiency improvements

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[Googlebot]

Please try with the covers on and report back.

I haven’t got a data logger and find when on 12v and not moving it’s ice cold, however when driving the fridge seems to warm up. I have long suspected it’s the air flow due to driving.

So thanks for the info.

 

[Richard n Ann]

Much better today on gas, you can see the fans cutting in and out holding the condenser temp down to 40 ish degrees..

 

[Richard n Ann]

Please try with the covers on and report back.

I haven’t got a data logger and find when on 12v and not moving it’s ice cold, however when driving the fridge seems to warm up. I have long suspected it’s the air flow due to driving.

So thanks for the info.

Yes will see if I can rig something up, the proper cover is at home but I suppose anything will do

 

[donkey]

Have you checked that you are getting a good feed and earth at the 12v fridge element. Some vans have very poor spec wiring. Your element is drawing about 10 amps, so a good supply is essential.

Geoff

 

[Richard n Ann]

Have you checked that you are getting a good feed and earth at the 12v fridge element. Some vans have very poor spec wiring. Your element is drawing about 10 amps, so a good supply is essential.

Geoff

Good point, that needs checking. I've got the clamp meter with me

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[Richard n Ann]

A blank has to be made in 'Apollo 13' fashion. Everything used must come from aboard the ship

(Except anticipating the problem I fetched a takeaway pizza last night maybe the original crew didn't have that option)

We'll be travelling about 3 hours today.

 

[Richard n Ann]

Well that made sod all difference, guess what time we set off

I only blocked of the lower vent though. I'll block ¾ of the top vent off for the next journey, I'll leave the fans on so it can't overheat. In Benidorm now so not moving anywhere for a few weeks.

Internal temp:

 

[Hoovie]

I see you have a reading for Humidity available as well as temp?

Something that I have found from the temp data loggers in my Freezer and Fridge is the humidity rises virtually instantly as soon as energy (be it 12V power, 240V power or Gas) is removed from the fridge - and then drops as soon as energy restored.
Have a look at the humidity info and that will give you much better info on how the power sources are working on the unit as it gives you real-time info compared to the temp which is slower reacting.

 

[Richard n Ann]

I see you have a reading for Humidity available as well as temp?

Something that I have found from the temp data loggers in my Freezer and Fridge is the humidity rises virtually instantly as soon as energy (be it 12V power, 240V power or Gas) is removed from the fridge - and then drops as soon as energy restored.
Have a look at the humidity info and that will give you much better info on how the power sources are working on the unit as it gives you real-time info compared to the temp which is slower reacting.

As suggested I'll have to check the current draw.

 

[Hoovie]

This is a screenshot to illustrate what I mean. In this case the fridge is on AC, but all three sources do the same thing when on ... chill the vanes which then cool the air and lower the humidity.

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[cmcardle75]

You could just get a compressor fridge that actually works and spend all the money on B2B/solar instead of data loggers!

 

[pyro]

You could just get a compressor fridge that actually works and spend all the money on B2B/solar instead of data loggers!

Agreed, assuming that the fridge is dead level in the first place, as absorption fridges are notoriously unstable on any incline (pooling).

At 0.5A (6w) for the compressor compared to around 8+A (100w+) for the 3 way, the comparison is quite extreme. The 3 way or absorption fridges are indeed quieter, although optimised for static operation using gas, and are fitted to motor homes and caravans because they're £500 cheaper'. https://penguinfrigo.co.uk/2012/02/...v-compressor-fridges-over-traditional-3-ways/

I suspect that numerous highly knowledgeable people spent a great deal of time, money and effort designing and then making that absorption fridge, little knowing that someone armed with just an iPhone app and a DHT11 type of sensor would then come along and question their collective expertise.

 

[Hoovie]

You could just get a compressor fridge that actually works and spend all the money on B2B/solar instead of data loggers!

Good point.
PS. can you tell me where I can get a B2B & Solar for the £10 cost of the fridge data logger?

PPS. I run a compressor fridge in my Motorhome. Swapped out the 3-Way, but it is still useful to be able to check the performance

 

[pyro]

I rather think that response was targeted at the original poster, as indeed mine was, don't you?

As for the cost of substituting the £10 cost of a temperature probe with B2B & solar, taking into account the reduced current consumption, the reduced dependency on costly leisure batteries, the slight increase in mpg resulting from the need to constantly recharge them, the reduction in food spoilage, the increased autonomy and the considerable reduction in stress, I'd say it makes sound economic sense over the lifetime of the motorhome to consider replacing the fridge.

Otherwise you could always use it as intended, on level ground and on 12 volt only, when EHU and more efficient gas are not otherwise available. Works ok for most people, but whatever makes you happier....

 

[busby]

Never worried me as I've no sensors or loggers.

Ignorance is bliss.

Same here so long as my beer and the better half's wine is cold we are happy. BUSBY.

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[Richard n Ann]

I rather think that response was targeted at the original poster, as indeed mine was, don't you?

The original poster isn't biting
It's just a bit of fun to keep me occupied while we're away. I'm happy with our 3 way fridge, I think it's one of the good ones judging by how they get slated sometimes

 

[pyro]

The person responding wasn't offering to feed anyone, but trying to educate them.

As Dometic themselves say;-

"To prevent the refrigerator from draining the battery, make sure that the current supplied to the caravan is cut off when the vehicle engine is not running, for example by fitting an ignition control relay"

As for blocking any ventilation, I again refer you to the manual, they're there to facilitate combustion of gas, stabilise temperature in all modes of operation, provide ventilation, etc. Again, it's all in the book

Up to you how you waste your time on something that you say you're happy with.

 

[Hoovie]

The original poster isn't biting
It's just a bit of fun to keep me occupied while we're away. I'm happy with our 3 way fridge, I think it's one of the good ones judging by how they get slated sometimes

We all like to know what our naughty fridges are doing when we are not there to keep an eye on them

Here is an lovely graph of my Fridge temperature over the last 6 months....

(the little break end of July is when it changed from being a 3-Way to a Compressor) and I can also (if I can't contain myself) drill down at any time in those 6 months to see the temperature for any given minute

The excitement is unlimited

 

[Spriddler]

The excitement is unlimited

Is that why you haven't posted a graph for it?

 

[Hoovie]

Is that why you haven't posted a graph for it?

"it" being?

If you want a specific time and date and join in the unbridled fun, just shout!

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[gus-lopez]

I found it was far better to travel leaving it running on gas in the old van. The 12 v temeprature always rose , as has been noted.

 

[pyro]

I seem to remember at one time being told not to use gas whilst travelling, as the slipstream often blew out the light. I agree, gas is much more efficient, but I'm unsure of the safety issues, so I reluctantly use 12v

 

[cmcardle75]

The main reason not to use gas when travelling is that it is illegal, unless you have a crash cutoff device.

 

[robnchris]

We always use the gas when travelling and yes we have a cutoff device, never had it blow out.

 

[tonyidle]

I seem to remember at one time being told not to use gas whilst travelling, as the slipstream often blew out the light. I agree, gas is much more efficient, but I'm unsure of the safety issues, so I reluctantly use 12v

12v Watts are the same as 230v Watts. The elements are approximately the same output so the performance is the same whichever power source is in use. Problem is that fridges rarely see 12v because most van builders economise on wire size. A quick check on the supply at the fridge with the engine running usually sees 11v at best.

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