Zanussi ZNB3240, came with the house and probably from 2007 and has never auto-defrosted. It gets to a point, after ~ 3 months, where the fridge is ok but the freezer is only at -10c.
Left off overnight and used separate containers to catch the water from the pipes at the back. Freezer supplied 1.8L, nothing from the fridge pipe.
I can see that the fridge defrosts by looking at the back of the fridge where it is sometimes frosted up and other times small water droplets and the exit drain is clear.
The unit is in a tight space modern fridge/freezers seem to be larger but with less capacity. This one suits if it wasn't for the 4 or 5 times per year faff of defrosting manually.
The paper test is fine though I don't see why that would cause the freezer outlet pipe to be full of ice (presumably). The freezer will be fine now for several weeks working at -20c or thereabouts and then it'll start to drift down and eventually after 2-3 months end up at
-10c. The fridge generally remains at around 5c plus or minus depending on the kitchen temperature and thermostat setting.
I was thinking more about the general build up of excessive frost/ice in the whole compartment caused by a faulty door seal. Much the same as you would get if you left the door open for a few hours. The moisture in the "new" air freezes.
Perhaps the freezer drain pipe is partially blocked with mould and air-bourn debris/dust etc.. During a defrost cycle not enough water can escape through a restricted hole during the defrost cycle and pipe above the blockage ends up being still full with water at the end of the cycle. This water now freezes meaning that during the next defrost cycle the drainage is delayed as the water in the pipe has to thaw first before any water can flow out, and then at a very slow rate. If the pipe was not partially blocked there would be nothing to freeze and during a defrost cycle would give an unrestricted passage for any water immediately.
If you are turning off the freezer overnight then you may not see the difference between a full flow of water or a restricted flow of water from the drain pipe. Overnight gives the chance of draining a few litres at a slow drip rate.
Poke something down the full length of the drain pipe. In the past I've used things like the spiral plastic coated wire for hanging net curtains up at a window but anything similar that has some flexibility will work. You may be surprised what is in the drain pipe.
If that was me, I'd take the airflow adjustment off "ice cream rock hard", and use a lesser setting. Maybe -20C is just too much for it, and frost is forming behind the panels somewhere. Sometimes, so much ice forms in places it's not supposed to, the plastic panels inside bulge.
+1 . My Liebherr fridge freezer seems to manage about -16C and any colder makes ice-cream rock hard. Also helps to buy decent quality icecream like Judes Cornish Clotted-cream icecream which has more animal fat.
Well as you know, I have opposite problem as its the fridge that does not defrost, but my fridge definitely does not have drain anywhere, and it kind of makes one wonder how it was supposed to work. The defrost works it just comes out the door at times when its opened. In the case of the original query, does the freezer actually look coated in ice? From your description it sounds like its only in the pipe. In that case perhaps the pipe is supposed to be insulated from the cold and the insulation has gone and hence its freezing up. Normally you would expect freezer insulation to prevent this problem as the air is supposedly warmed as it exisxits with its water vapour by going near the hot end of the heat pump. Brian
How does auto-defrost of a fridge or freezer work? Does it run the compressor "in reverse" (or use a heating element near the heat exchanger inside the fridge/freezer cabinet) to make the accumulated ice melt?
I ask because we've recently started monitoring the power consumption of our freezers minute-by-minute (*), using TPLink HS110 remote controlled/monitored sockets, and we've noticed that every day or so the power consumption increases from a normal 30-60 W to about 200 W for maybe
10 minutes, in amongst the normal 20 minutes on / 40 minutes off cycle. This suggests that a) the compressor motor has current control, in addition to simple off/on of a thermostat, and b) that something is triggering it into the higher power state occasionally.
What typically fails when a freezer maintains a constant temperature and looks to have no ice on the heat exchanger, but then suddenly ices up and starts to warm up, needing manual de-icing with pans of warm water before it will get down to -18 again? That's happened several times over the last year with another freezer (kept indoors) and it's unlikely that on every occasion we might have left the door slightly ajar. It's as if the frost-free mechanism works perfectly most of the time but occasionally fails.
(*) Partly to watch for equipment failure: we had a freezer outside in the garage (yes, a Beko, rated down to -15 deg C ambient temperature) and the other day I noticed that the food was a bit soft so it had failed sometime in the last day. There followed a day of frantically cooking all the joints of meat that my wife had bought when they are only on sale at Christmas, for us to eat throughout the year, and then we re-froze them. The freezer seems to be completely dead: the last junction point before the motor is getting power, and any thermostat is beyond that point in the sealed motor unit.
They put a drain tray down at the very bottom of the fridge.
Some fridges have a grillwork at the base of the fridge, and this decorative detail hides the tray behind it.
The grill can be adhered by plastic posts sticking out the moulded piece of grillwork and plugging into holes in the steel fridge chassis. You pull the grill away from the chassis, to expose the tray. Then, using a flashlight, visually examine the tray for water content.
If a drain somewhere in the system plugs up, water comes out somewhere else, and the tray will remain dry. Depending on whether the fridge is leveled via the leveling legs, determines whether any water residue is in the front or the back of the tray. A person attempting to stick a finger in the tray, might not find any water, if the tray happens to tip backwards a bit and all the water is at the back.
The rising warm air movement up the back of the fridge, pulls air through the front grill, and that dry air passes over the tray. The tray is gently dried by that quite-small airflow.
Like all exceptional plastic items in our lives, the tray can crack, leading to the floor underneath rotting out in sympathy. Consequently, for the lazy homeowner, it pays to occasionally remove the fridge from it's resting spot and inspect the tray and/or flooring for damage. I have a "plastic rail kit" which allows the fridge (not having wheels), to be slid out on the plastic rails without damaging the floor. This allows cleaning of any accumulated dust behind the unit, but also allows the flooring to be checked. I have to pull it out typically, when the stupid defrost timer needs to be replaced yet again.
There are two pipes at the back, about 3/4" dia, one from the fridge and one from the freezer. They go between the unit body and the condenser so they should not get cold, and then rest in a plastic tray which sits on the motor, so presumably any condensate would then evaporate from the heat of the motor.
Neither the fridge (upper half) nor freezer (lower half) are frosted up.
The freezer part has a fan which blows the cold air around. This is fine until towards when a defrost is required and it seems to be choking up.
Anth>Well as you know, I have opposite problem as its the fridge that does not
I'm assuming not a heating element. At most the fridge has a thin layer of frost on the back before a defrost takes effect and if the drain hole is ever blocked (wife stuffing too much into the space) then the bottom of the fridge will be wet. She is slowly learning!
Interesting but I don't have a ready way of monitoring the power consumption.
I'm guessing if there was no auto-defrost the freezer would normally require defrosting every 3 months? In which case it is as if the freezer auto-defrost was not working at all but the fridge is.
I have to pull the whole unit out every time to defrost otherwise the tray, which sits on top of the motor, will overfill. I put the pipes into a bucket and that is how I know there is 1.8L of water coming out of the freezer pipe.
Thanks but that relates to the fridge part which is not a problem and as mentioned in other posts that drain hole is clear except when SWMBO pushes the veggies to the back blocking the path.
I had an old appliance which developed bad contacts on the mechanical time switch for the defrost cycle. For a while it was fixable by tweaking the contacts, but eventually it needed replacement.
As designed, every 24-36 hours, it stopped the compressor, energised a small heater element near the cooling coils inside the fridge/freezer (and possibly a smaller one to ensure the water doesn't freeze again on its way out.). After a delay, ,just long enough for the accumulated ice to melt off and the water to run away, the heater is turned off and the compressor restarted.
I guess the controls may be solid-state these days.
There are usually two rotary adjustments of some sort.
One is a true thermostat. That's what turns the compressor on and off.
The second control, while maybe giving the impression it is the same as the other, is not. It can be a knob, with an airflow vane behind it. It's a valve in the airstream, and as you rotate the knob, it changes the amount of air that flows in that path. This knob is likely to be much closer to the freezer.
By changing how much air flows down to the milk section, that adjusts how quickly the milk section cools off. If you set the knob on "ice cream rock hard", then hardly any air flows down to the milk section, and it might take an hour before the milk section hits the target temperature.
The temperature in the freezer section is only "roughly controlled". If the machine is on for an hour, the freezer might hit -20C. If the machine was on for ten minutes, maybe the freezer gets to -7C. That knob, which is not a thermostat, provides a rough adjustment. And so "ice cream rock hard" is an approximation to the temperature the machine expects to hit there. If you warm up the freezer section by leaving the door open on just the freezer section for five minutes, the machine doesn't have to start up again... until the milk section also warms up because of it.
If the pathway that channels the air down to the milk were to be clogged, then the machine might need to stay on for an hour trying to get the thermostat in the milk section to trip. And in the process, the freezer box (and the co-located coils nearby), become iced up.
You want to adjust the airflow knob (not a thermostat) so that the machine stays on for less time, and then the defrost mechanism has a chance to keep up. Or, you want to verify that places expected to have airflow, have airflow. My milk section has two vents, which shoot down from above. and the airflow there is pitiful. Not exactly a blast of air. But I was unable to debug the airflow path and show it was all clear. Ice might not freeze in there, but mould can grow there.
While the airflow knob near or in the freezer icebox may give the appearance of control, if the airflow paths happened to be blocked for some reason, then the box could end up trying to do "ice cream rock hard" as a side effect of the blockage.
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