Liebherr 7082 defrost cycle drainage issue

[BrianFWombat]

Firstly, I am a DIYer, but reasonably competent in this area as I have some knowledge of refrigeration obtained whilst tweaking a domestic fridge for the storage of hibernating reptiles (!) using Eliwell controllers!

My problem lies with the home fridge freezer… It has worked for many years but now has developed a problem in that the drainage channel at the rear is filling up with ice and subsequently water builds up in the base/salad tray of the fridge.

I tried the obvious… I defrosted the channel and then cleaned the drainage channel and hole and flushed the plastic tube with water. It seems there is a good flow when conditions are right and that the defrost water should simply flow away and then evaporate later on the compressor tray.

… but the ice returned.

I levelled the fridge using a spirit level but the problem recurs.

What could be causing the water to freeze before having a chance to run away? Could I have a different problem and the ice in the drain is a symptom?

Thanks in advance,
BfW

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

CNes 3866 Index 20B/147
Service-Nr/No.Service: 0974506-02
Gerate-Nr/appliance-no 22.103.490.7

[kwatt]

Re: Liebherr 7082 defrost cycle drainage issue

Is it too cold in the fridge?

Roughly how old, a rough guess?

K.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

We think it is approx 6 years old.

After your reply I measured the temperatures in the fridge as best I could… although the fridge is set to 4C the fridge compartment seems to have a significant temperature gradient (although it is after breakfast so there has been a good degree of door opening recently)… currently the lower part with the salad trays is 2.4C with a gradient across the shelves 4.2, 6.1, 8.3, 9.4, 11.0 at the top. These are all air readings. I can only assume the back is much colder as otherwise the water in the drainage channel would not be ice.

In anycase having 11C at the top doesn’t sound very healthy.

Perhaps in the first instance I should empty and completely defrost the fridge/freezer?

Thanks
BfW

[kwatt]

Re: Liebherr 7082 defrost cycle drainage issue

Hi Brian,

It’s an air driven fridge so the temperature should remain pretty stable throughout the cabinet. You’ll get variations of course but they shouldn’t be as large as that.

The cold air is drawn from the freezer through a channel at the back, if that’s blocked or obstructed then you get a reduction in cool air.

If the fridge thermistor is wonky then you will get incorrect temperatures reported to the electronics and it won’t draw cool air into the fridge.

If the fan is faulty, same.

If the freezer evaporator is blocked, same.

Freezer thermistor, possibly the same.

I’ve attached a blowout of the fridge freezer, the thermistors are items 260 and 270 both should show a constant and linear resistance as heat is applied or they are cooled, in the opposite direction of course.

The electronics in Liebherr machines are very robust and give very, very few problems so that’d be the last thing I’d look at.

Other than that, it’s detective work.

HTH

K.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

K

Thanks alot. That diagram will really help.

I left two digital thermometers in the fridge and just returned to them. The top reads 11C and the bottom reads -0.7C. I guess the previous readings were distorted due to the breakfast door opening.

The -0.7C at the bottom possibly explains the freezing occurring in the drainage channel.

As you pointed out there are many potential causes… I was initially thinking about a fan failure… but following your diagram I opening the freezer section took out the drawer and saw the lower fan spin down and hear it spin up when the door was closed so that appears OK.

We normally do not have the ‘Ventilation’ feature enabled… I guess it is not on by default, but if I do press that button, close the door and then open the door I see the top fan blades spin down. So both fans seem OK.

I do not quite understand the air flow in this fridge. Where does cold air from the freezer enter/exit the fridge?

Thanks in advance
BfW

[kwatt]

Re: Liebherr 7082 defrost cycle drainage issue

I’m not 100{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} sure where the air channel is as you now have as much info as I have or many engineers do when we see the fridge freezers for the first time. It really is a case of just sitting and working it out.

K.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

Thanks. I’m guessing a blockage or a problem with the flap that controls air flow between the compartments.

Will eat the contents and then defrost!

Thanks
BfW

[johnsdad]

Re: Liebherr 7082 defrost cycle drainage issue

Its not a ducted fridge, its a “wet wall”, hence the need for a drain hole. The fan in the fridge simply keeps the air moving, if selected. It will help in reducing temperature stratification. The sensor fixed to the back wall is a common source of problems with Liebherr, but other faults are possible.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

I assumed that it was ducted… i.e. cold air would be allowed to circulate from the freezer compartment into the fridge to regulate temperature.

Please can you point me to a definition of “wet wall”.

… and excuse the ignorance.

Or does the fridge have its own evaporator?

Thanks in advance
BfW

[kwatt]

Re: Liebherr 7082 defrost cycle drainage issue

Not having seen one in person, I can only go on what info I have. The drawing for the machine shows and, lists for that model, a fridge fan mounted at the top. I believe Liebherr call it cool control or something like that.

But, when you think about it, a drain hole is a thing normally only found on a wet wall evaporator fridge so what Johnsdad says makes sense to me.

I was sure that I’d written an article on wet wall fridges but I can’t seem to find it.

Basically, the fridge evaporator is foamed in behind the rear wall of the fridge. Water freezes on the rear wall, defrosts on a defrost cycle, runs down the plastic rear wall and drains through a drain channel.

K.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

Thanks for the info re: ‘Wet Wall’.

I will check out the thermistor when I defrost the whole thing sometime over the next few weeks; hopefully it is that simple.

My only remaining worry is that since the lower section is cold (sub-zero at the drainage channel) but the upper part is warm this suggests that the bottom of the wet-wall evaporator is cold but the top is not.. I imagine that would be a refrigerant issue.

Regards
BfW

[kwatt]

Re: Liebherr 7082 defrost cycle drainage issue

Highly doubtful on the refrigerant.

They are a sealed system, they don’t leak. If they leak they just don’t work and as they are sealed there has to be physical damage or pipe degradation to allow that to happen, you can imaging how long it takes a copper pipe to degrade to the point where it will leak.

In all the time I’ve been doing this I’ve seen leaking systems from new that weren’t sealed up properly but none that I can think of that magically sprung a leak after a few years. I have seen many however that have been labelled as having a refrigerant leak, almost all incorrectly.

I think it’s due to large refrigerant and AC plants where leaks are common but on small systems like a domestic fridge freezer has, a gas leak just kills the machine stone dead within days due to the small volume of gas in it,

If there is a domestic refrigerant system issue that presented those symptoms it’d most likely be the compressor pumping weak as the internal seals had gone or it was otherwise internally faulty. But on a Liebherr I certainly wouldn’t think it was and it sure wouldn’t be my first port of call looking for the problem.

HTH

K.

[BrianFWombat]

Re: Liebherr 7082 defrost cycle drainage issue

>>> Highly doubtful on the refrigerant.

Thanks. That is reassuring.

Regards
BfW

[SAMURI]

Re: Liebherr 7082 defrost cycle drainage issue

The fridge evaporator sensor on a liebherr can sometimes fail due to water leaking into the sensor.
You can purchase a fridge evaporator sensor kit from liebherr.
It comes with the instructions how to fit. You no longer have to take the sensor back to the pcb/ Module and comes supplied with a connector to join the new sensor to the old sensor wireing.This is the most likly fault with temporature problems.

[Author]

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