Chest Freezer problem

[Rapserv]

hello all,
I am having a problem with my 110Litre car chest freezer that uses a Dunfoss compressor.
Recently I had an issue with the freezer struggling to maintain it's set temperature (-15-to -18 C) and upon inspection found that the cap tube from the thermostat had failed due to metal fatigue near where it enters the chest freezer wall. I obtained an exact replacement and installed without any issues. The week prior to the thermostat replacement saw the freezer running non-stop ... no doubt as a consequence of the thermostat failure.
I thought that by installing a new part the problem would be sorted, however, this was not to be.
In fact now the freezer is struggling to maintain -12 to -13C.
After going over the issue many times in my mind it occurred to me that my current problem may be due to my own doing.
I have, several times in the past, cleaned out and defrosted the freezer by gently hosing out (with cold water) while standing the freezer on an angle (probably about 45 degrees) to allow the water to drain away through a drain plug on the opposite lower end of the freezer with regards to the compressor location without it even occurring to me that this may be upsetting the refrigerant level in the compressor. I was aware of this problem with a fridge but did'nt even think of it with the freezer
I think that if this is the case, I should be switching off the freezer and letting it sit for at least 24 hours to let the gas settle again.
Unfortunately, The freezer is currently full of frozen food and we are currently travelling around outback Australlia.
My question is, although it would be best to be able to switch off the freezer for a couple of days, if I just leave it running, will it eventually return to normal??

Thanks in advance .. Dave

[install monkey]

if its got food in it - keep it running- if it can only reach -12 then if you defrost it then it wont reach -12 again, i know a fridgie in nth qld, but he's probably on the capt morgans!

[Blueboy]

Hi Dave

I don't think cleaning the freezer out has caused the problem. In fact the refrigerant is a liquid and a gas at different times during the cycle and cannot Not be affected by tilting the freezer or fridge. The compressor oil can be effected if you left it on when you cleaned it out that could have damaged the compressor but I am presuming you unplugged it before introducing water to the excitement .

My guess is you have either a worn compressor which is no longer pumping efficiently and needs replaced or the heat is not getting away from the condenser very well.

There is nothing you can do about the compressor unless you are a fridge mechanic. But you can check the condenser is clean and if it has a fan motor that this is running . The condenser will be underneath or in the back wall. If it is in the wall it maybe the conditions in your vehicle are to warm .


Hope this helps

[xxargs]

I think your cleaning method is not a problem if you lets freeezer chest rest some minutes after cleaning before power on - Danfoss-compressor build for mobil and sea using is very robust and need handle all shaking and big angle on running same time your drive your car around...

check if compressor running non-stop - if not, and temperature are -12 - -14 degree C and want -18 degree C, you have still issue with thermostat.

if compressor running non stop - control if condenser fan running properly - if condenser is not cooled properly - freezing capacity remain low.

[mikeref]

Temperatures during the day are quite hot (being Summer) and portable freezers are struggling to maintain -16 degrees C depending on your freezer brand. 12/24 volt freezers are going to put a strain on your battery and if the voltage should drop to 10.5 ish at any time while running off a 12 volt battery, the compressor will cycle off. If your freezer has a "boost" switch, turn it off.
Captain Morgan :-)

[mikeref]

I have checked comments on R.E many times today,and OP has not bothered to log in...or is beyond mobile phone range. The latter is likely as Australian internet and phone services are practically non-existent in the vast expanse of nothingness.
Nope, I have a desire to stay this side of the Desert thanks.

[Rapserv]

hello all .... back in range again!! (internet that is)

Many thanks to all who replied to my problem and all posts much appreciated.
I should have mentioned also that this is a 12/24V system that I have currently running off a 240V power pack. (so power is not currently a problem)
Outside air temp is hovering around the 40C mark (in the shade) on most days so this does not help, although I have had these temps and higher in the past and still had the freezer working well (-18C) without too much of an issue. (EvaKool 110L Fibreglass chest & 95% full)
I have cleaned the entire compressor area fairly regularly however I will have another look over to make sure all is well.
Many thanks again for all your replies and I will post if I find a solution to the problem.
Cheers all !!

PS.. I have attached a photo of a mod I made to the fridge/freezer removable divider wall some time back... it's a bit rough, as this was done whilst on the road. Bottom fan near socket draws air from the freezer section and pushes this cold air to the other side of the wall where it is subsequently drawn towards and pushed through the upper fan back towards the freezer element where it continues the cycle. Made a huge difference to the ability of the far end of the freezer to freeze properly.

[xxargs]

Come your 'temperature issue' before or after this fan-mounted divider, if after, i think bigger 'active' volume with low temperature inside chest depend of fans give more load on compressor than manufacture of the chest calculate (ie they calculate more than few degree temperature in difference in the chest volume and now with fan, now is almost same and lower temperature and more heat leaking in...)

40 degree C is... quite high and if remember right, many of this boxes with 12/24 Volt compressor not gurantee -18 degree C if environmental temperature is above ~35 degree C or similar.

[joe-ice]

Is the freezer freezing evenly , the fact you have to defrost it regularly coupled with the constant running and high air temp points to been low in gas or very bad air infiltration

[mikeref]

Evaporator plate only services 1/2 the box suggesting this is a 2 temperature cabinet. 40% or so fridge space.

[Rapserv]

Come your 'temperature issue' before or after this fan-mounted divider, if after, i think bigger 'active' volume with low temperature inside chest depend of fans give more load on compressor than manufacture of the chest calculate (ie they calculate more than few degree temperature in difference in the chest volume and now with fan, now is almost same and lower temperature and more heat leaking in...)

40 degree C is... quite high and if remember right, many of this boxes with 12/24 Volt compressor not gurantee -18 degree C if environmental temperature is above ~35 degree C or similar.

hi xxargs, and thanks for your reply.
I originally used the chest as a fridge/freezer (50/50) and in this configuration it worked well with the freezer side around -18C and the fridge side somewhat cooler and not freezing.
I later decided to use the entire chest as a freezer by removing the 'removeable' centre divider.
I found that as the evaporater element was only on one end and a part of each side that items were frozen on that end and progressively became 'less' frozen towards to opposite end, and indeed, struggling to freeze anything near the top at the far end.
By modding the divider with a couple of fans this immediately fixed that issue and all items froze quickly throughout the chest ... better result than I expected.
The addition of the fans also worked better in that after initial freezing of the goods the compressor was cycling far less often ... so the extra power needed for the 2 fans (using around 100mA each) I believe was more than offset by the lower cycling time.
It has only been in the last couple of weeks that the freezer has been struggling, and since then I have tried 3 different new thermostats identical to the original.
I have now removed the end cover (over the compressor) to allow heat buildup to escape and have placed a high volume air fan in front of the heat exchanger to substantially increase air flow to assist cooling and this has had very little effect.
I checked the compressor temp with a laser thermometer and it read 73C, going into heat exchanger was 70C and coming out it is 50C I would have thought that these temps are far too high but not being a regrig mechanic I don't know.
Hope this helps

[Rapserv]

Is the freezer freezing evenly , the fact you have to defrost it regularly coupled with the constant running and high air temp points to been low in gas or very bad air infiltration

thanks joe-ice,
as the fans are in use the entire chest seems to be around the same temp (now -11C) but overall temp seem to be decreasing (ie. getting warmer). Compressor area is clean and as mentioned in another post I have placed a fan in front of the heat exchanger to increase airflow for cooling ... this has had little effect.
My thoughts all along have been a suspicion about the gas.

[Rapserv]

Evaporator plate only services 1/2 the box suggesting this is a 2 temperature cabinet. 40% or so fridge space.

thanks mikeref,
thats right... normally about 40% freezer and 60% fridge, however the chest can be used entirely as a fridge or freezer by removing the divider and adjusting the thermostat accordingly.
I have been using it as a freezer for the last 2 years now without any major issues. It has only been recently that the inside temp has been gradually decreasing (getting warmer). The compressor area is clean and free of dust and airflow seems good through heat exchanger.
Is it possible that their is a blockage of some sort??

[mikeref]

G'day Rapserv." The Evaporator (the aluminium item that freezes you goods) is really only sized to freeze a specific volume. The divider is there to separate frozen and chilled zones as you know. It requires far less energy to keep goods above 0 degrees C then it does to maintain -18C.
If this cabinet were designed to store the full 110 litre at -18 degrees C then the evaporator would cover all 4 walls.
Basically, your two temp cabinet isn't meant to be used entirely as a freezer and the 50*C temperature you measured at the condenser outlet is way too high. What you have is an overloaded system.
I suggest you start reducing your cabinet volume and only fill to the recommended freezer volume.
Hope this comment helps.

[mikeref]

thanks mikeref,thats right... normally about 40% freezer and 60% fridge, however the chest can be used entirely as a fridge or freezer by removing the divider and adjusting the thermostat accordingly.(Quote)
Entirely as a fridge? Yes. Entirely as a freezer? No, not how i see it.

Edit: Currently New Years Eve and just a few hours until 2014. Seasons greetings to you and yours, Mike :-)

[Rapserv]

G'day Rapserv." The Evaporator (the aluminium item that freezes you goods) is really only sized to freeze a specific volume. The divider is there to separate frozen and chilled zones as you know. It requires far less energy to keep goods above 0 degrees C then it does to maintain -18C.
If this cabinet were designed to store the full 110 litre at -18 degrees C then the evaporator would cover all 4 walls.
Basically, your two temp cabinet isn't meant to be used entirely as a freezer and the 50*C temperature you measured at the condenser outlet is way too high. What you have is an overloaded system.
I suggest you start reducing your cabinet volume and only fill to the recommended freezer volume.
Hope this comment helps.

hello again mikeref,
I understand what you say however, the manufacturers specs state that this chest as a freezer can maintain a temp of -19C with an ambient temp of 43C and not only is this stated in their specs, but I have for the last 2 years been doing just that. It is only in the last couple of weeks that something has changed and I am now having this problem. I am also of the understanding that the freezer (once frozen) is more efficient when full or close to it.

[mikeref]

Rapserv, are you saying you've previously had this freezer running at 90% full in similar conditions.....and at -18*C? Without the baffle?

[install monkey]

yep when the freezer is as full as possible with dingo burgers and road kill it holds temperature better than air so it doesnt run as much,once it has cut out on temperature- is the freezer covered ie out of direct sulight?- even if your running low on grub then add anything to displace the air in the freezer - bonza!

[Rapserv]

yes ... absolutely!! its my normal configuration.

[Rapserv]

exactly!! I have always found the freezer to be very stable and efficient when full. In fact, I used to have a couple of styrofoam blocks that I used to place in the freezer to displace the air when frozen goods got down a bit. :-)

[Rapserv]

whoops!!

sorry, I meant to reply using quotes in my last 2 messages to mikeref and install monkey respectively.

[install monkey]

re reading the previous posts- you modified the divider (partition) by sticking 2 pc style fans to circulate the air - then this will req gaps for air to circulate - usual suspects for poor freezing is the 5 kilo bag of chips

[Rapserv]

Rapserv, are you saying you've previously had this freezer running at 90% full in similar conditions.....and at -18*C? Without the baffle?

sorry mikeref,
just to clarify, I have run the entire unit as a freezer and maintained the temps as stated.
However, without the baffle it took much longer to get the temp down to the required level, especially when something new like a fresh chook was put in and the compressor was cycling considerably more often.
The baffle is used only because it gave me the ability to mount a couple of fans in it to rapidly circulate the frigid air. Above stated 'chook' would take 2-3 days to solidify as opposed to overnight with the fans.

[install monkey]

freezers are designed to hold frozen meat/rodent chooks(im guessing chicken type bird) u need a blast freezer or co2 injection to freeze stock before you store it

[install monkey]

aussies are renown for tinkering and modifying kit
http://youtu.be/XG5bZWWFk2M

[mikeref]

O.K...I still believe you are overloaded.The evaporator size is far too small to do the job.
For starters, throw out your road kill as the Hawks and Dingo's have already staked their claim and will hunt you down while you sleep.
Nah seriously, check the evaporator and make sure it is fully frosted over. If it ain't completely coated in frost then there is an issue with circulation or your new thermostat isn't doing it's job, Or.... your 240 to 12/24 Volt transformer is cutting out on thermal overload due to the heat.

Just trying out options here as my Crystal ball is currently down town getting a polish :-)

[mikeref]

aussies are renown for tinkering and modifying kit
http://youtu.be/XG5bZWWFk2M

Damn! Conditions are strict these days. FYI, Aussies can be caught for DUI while riding a horse on a public street. Go figure.

[install monkey]

fit an endocube!
http://www.refrigeration-engineer.co...-Science/page3

[mikeref]

Damn. Another link lost.

[Rapserv]

O.K...I still believe you are overloaded.The evaporator size is far too small to do the job.
For starters, throw out your road kill as the Hawks and Dingo's have already staked their claim and will hunt you down while you sleep.
Nah seriously, check the evaporator and make sure it is fully frosted over. If it ain't completely coated in frost then there is an issue with circulation or your new thermostat isn't doing it's job, Or.... your 240 to 12/24 Volt transformer is cutting out on thermal overload due to the heat.

Just trying out options here as my Crystal ball is currently down town getting a polish :-)

I know what you mean by the size of the element compared to the chest size, however, as mentioned it has done the job for the last 2 years really well.
The reason I have defrosted to chest at regular intervals is that the element is covered in frost/ice and my concern has been that this in itself may be acting as an insulator.

[Rapserv]

thanks to everbody for your replies.
I think that I will see about getting the unit regassed, as the chest is not cooling as it used to. I have tried 3 new identical thermostats which all operate the same and the most telling point is that the internal temp is not decreasing (currently -12.6C) and the compressor is not switching off ... obviously because it is not reaching its selected temperature. It has been running non stop now for over a week!!

[Gary]

The most telling point is that you changed the thermostat 3 times. If it's running non stop and doesn't get down to temperature, that isn't the thermostat's fault. The thermostat just tells it when to start and stop.

Did you get this problem sorted out?

[Gary]

Recently I had an issue with the freezer struggling to maintain it's set temperature (-15-to -18 C) and upon inspection found that the cap tube from the thermostat had failed due to metal fatigue near where it enters the chest freezer wall. I obtained an exact replacement and installed without any issues. The week prior to the thermostat replacement saw the freezer running non-stop ... no doubt as a consequence of the thermostat failure.

When the cap tube on a thermostat fails, the system stays off, not on.