# Dometic Fridge freezer performance.



## Paddy7 (Aug 22, 2012)

I am carrying out some tests on the Dometic unit installed in our Bailey Approach 745se, mainly to confirm that the unit is working correctly and to understand which power source gives the best performance. 

To this end i have purchased a data logger and measured the internal temp of the freezer over two days last weekend, the attached graph shows the activity.

All appeared to work well in real life, but the graph shows some erratic activity, which i will investigate further in case the fluctuations are due to the logger itself. 

But assuming the logger is good any techies got any ideas why the unit temp changes like this?
I am fairly certain the door was securely closed.

Paddy.


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## peribro (Sep 6, 2009)

A guess but possibly the spikes are the auto defrost function. It looks as if the freezer was cooling down after being switched on for the first day or so.


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## aldra (Jul 2, 2009)

Having accidentally failed to close our fridge door properly one night

Found everything in the freezer well and truly frozen

Even the fridge was still cold

Prob a bit expensive on gas though

Aldra


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## Rapide561 (Oct 1, 2005)

*Dometic*

Can't comment on your figures but we think the Dometic freezer is far colder than any Thetford we have used - and we have used four!

Proper ice cream - not sloppy stuff!

Russell


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## pete4x4 (Dec 20, 2006)

I don't think the coin cell is rated for -20 so you might be experiencing a voltage drop on the logger rather than a drop in temperature.
Why not try a new cell and place in the fridge once it is already cold and see if it does the same.


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## pete4x4 (Dec 20, 2006)

Just notice that they are no longer coin cells so if yours is a new one battery may not be the issue


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## Paddy7 (Aug 22, 2012)

I have just checked the spec of the logger and there is no mention of the battery being affected by temperature, the unit is fitted with a long life lithium battery. The temperature range is from -35 to +80 deg C.

Paddy.


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## cabby (May 14, 2005)

Surely a domestic fridge/freezer thermometer would be sufficient to check if the appliance is working as it should.
As to which is more efficient, well if no hook up then I would plump for gas.
What more could one want.

cabby

Ps. take note that when set on auto, changing from 12v to gas there is a delay of around 30 mins.


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## Spacerunner (Mar 18, 2006)

cabby said:


> Ps. take note that when set on auto, changing from 12v to gas there is a delay of around 30 mins.


15 mins according to my handbook. 8)


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## pete4x4 (Dec 20, 2006)

Paddy7 said:


> I have just checked the spec of the logger and there is no mention of the battery being affected by temperature, the unit is fitted with a long life lithium battery. The temperature range is from -35 to +80 deg C.
> 
> Paddy.


Mine is an USB-Lite version which takes a coin cell and only works to -10so sorry for the confusion.

Check your logger in your fridge/freezer at home to eliminate the logger.

To be honest it has to be a good lithium battery to work at -35.Most don't go below -20 but do recover.


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## spykal (May 9, 2005)

Hi Paddy

Sorry for the late reply, only just had this thread pointed out to me while talking about fridge problems with Gaspode (ken)

We have a Thetford fridge in our Autocruise which behaves in exactly the same way as your Dometic fridge. The freezer compartment temperature varies between -9c and -20c over a period of a couple of hours or so. It seems that the thermostat differential must be a little too large ... IMHO part of the problem, is that the single thermocouple that controls the fridge and freezer temperature is located on one of the vanes in the chiller part of the fridge and in normal use, in the UK, temperatures in the chiller are easily kept to 4-5C so the cooling is "off" for quite long periods. Your data logger info confirms that. During the "off" cycle the temperature in the freezer rises above the recommended -18C

The previous fridges we have had in caravans and motorhomes were not AES and had a cooling unit which ran continuously. By that I mean that when on gas the gas flame burned continuously and the fridge temperature was controlled by the flame height which was set by the knob on the control panel.... simple but it worked. 

Our new fridge is obviously technically superior to those old types in that it automatically chooses the energy source but the variation in temperature inside the freezer box is a worry since -18c is usually regarded as the "safe" frozen food temperature. 

When taking fridge temperatures the best practice is to insert the temperature probe into the food that is stored or into a container with water as you should test the stored food not the temp of the air inside the fridge or freezer ... my temperature probe is small and just sits inside the freezer compartment, so I do realise that any of large frozen products stored inside the freezer will most likely still be colder than minus 9c even when my thermometer is showing -9c but smaller items are affected and do deteriorate ....which is annoying because I like Magnums and often they get a bit soft inside  


Mike


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## Paddy7 (Aug 22, 2012)

Hi Mike, thanks for the information.

My logger unit has actually failed during a test on my home freezer, therefore i am returning it and having a replacement delivered. I will then start again with a test at home first then another trip in the van to test the freezer, as good a reason as any  

Watch this space for updates.

Paddy.


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## aldra (Jul 2, 2009)

I'm confused

My freezer keeps everything rock hard solid

It is seperate from the fridge tho

We dont carry ice cream though

But need to remember to get things out for a long defrost

Aldra


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