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View Full Version : Liebherr fridge-freezer using too much electicity







garycoombs
23-07-2015, 07:38 PM
Apologies for the somewhat cryptic title.

I have a KGNves3846 fridge/freezer that has been trundling away pretty much fine for 10 years. Indeed I have 3 fridge-freezers (don't ask) which are all fine except for one thing - energy use on the 3846.

I am trying to be energy efficient (I know 3 fridge-freezers don't help) and bought an energy monitor. Stuck it on the 1988 unit in the garage for a month as I thought such an old unit would be a gas guzzler and it suggested about 30 per annum - obviously hot summers will use more and cold winter less but the annual extrapolation was better than I expected for a 27 year old Liebherr. Did the same on the Miele in the utility and it came out with a similar expected cost.

Stuck it on the 3846 in the same ambient space as the Miele and it seems to be sucking about 1.8kWh per day or about 70 per annum - ouch. Temperatures are fine at 5 and -18 degrees. Tried defrosting (not a lot of ice so probably not necessary) and cleaned the back (hardly any dust anyway) but no change.

Looking at the leccy monitor it looks as though the unit takes about 2.5W when just sitting there nice and cold. When the compressor turns on it goes up to about 120W just like the others but after about the same time that the others would be switching back to 2.5W or so, the 3846 throttles back to about 80W and the motor/compressor is still whirring and is hot, but not scorching, to touch. This goes on for a very long time but eventually it does turn off and leccy use drops back to 2.5W. If you were to sit and watch I reckon it could be 30-40 minutes in this mode but life is too short to do that.

I assume a thermostat, thermometer, switch, sensor or something is kaput. Anyone have any ideas please?

thanks

Gary

nike123
23-07-2015, 10:11 PM
Looks like you have faulty compressor valve (after some time is passed and compressor valve has heated up) or maybe some moisture in refrigerant circuit.

garycoombs
25-07-2015, 02:15 PM
Thanks. These two issues would seem to be quite separate surely. Wouldn't moisture indicate a leak of some sort? And if the compressor valve is sticking would that not be sporadic/intermittent or permanently on?

Clearly moisture in the coolant is not something I could check myself but how about the compressor valve, how could one diagnose if that is indeed the issue - and is it visible anyway?

Glenn Moore
26-07-2015, 10:21 PM
Hi Gary
I don't know this model but the drop in current draw maybe due to the unit having a solenoid valve in the evaporator circuits, between the freezer and the fridge evaporators. Many of the European manufacturers started to fit these valves to try to make the unit more efficient. So the thermostat switches the solenoid valve depending on what part of the unit is satisfied ie cut out on temperature. On the standard fridge /freezers with one compressor the gas circuit starts by freezing the freezer department then carries on into the fridge area in which the thermostat is fitted on the exit of the evaporator. So at all times both evaporators are working. To try to make the FF more efficient they fitted a 3 way solenoid valve between the 2 section of the cabinet. So whichever part of the cabinet is satisfied first, the thermostat switches the solenoid off to that section so that all the compressor capacity is then switched onto the section still calling for duty. This would cause the suction pressure at the compressor to drop and hence reduce the power consumption. These models have been discontinued due to the solenoid valves failing. So it maybe something of this nature, or the other thing it might be is that the unit has a compressor that is speed controlled and again when part of the cabinet is satisfied the compressor slows down due to the reduction in capacity required.
Danfoss supplied a series of black compressors called SLV's which could be speed controlled to several manufacturers so that maybe another possibility for you to check.
The other thing that you can check is the integrity of the cabinets insulation, especially in the freezer side. Look at the cabinet to see if the sides has bowed and especially at the back behind the condenser to see if it feels wet at all Best regards

garycoombs
03-08-2015, 07:26 AM
Hi, Glenn,

Thanks for your thoughts. I've been otherwise busy and not had a chance to look at this but will do so properly when I get a chance. I know the insulation looks fine as I defrosted the unit before starting this thread, so was having a good look inside to clean it.

Interestingly, there monitor has now been connected for 22 days and suggests we are now back down at about 1.5kWh per day, which is about 50 per year. It's almost as if the unit has to "settle down" after it is powered back on. All very odd.

I'll report back when I get a chance to pull it out and look behind it properly to see the compressor etc.