OT: Freezer energy usage

[Pancho]

I recently put a power meter on my kitchen freezer.

The freezer hadn't been defrosted for a while, and was heavily iced. The on off power cycles were something like on for 20 minutes/ off for 20 minutes. Daily energy use was about 1.13 KW/h (It's old).

So I defrosted it, expecting the efficiency to improve. Sure enough, the power cycling was much more frequent, approximately 5 minutes on/ 5 minutes off. However, the energy usage went up to 1.25 KW/h.

Would anyone like to hazard a guess as to why the freezer gets less efficient after defrosting. This happens even if the freezer door is closed all day.

Maybe the internal temperature is different, colder after defrosting? I suppose I need a thermometer for next time I try the test.

[Brian]

What is the condition of the door/lid seal? If it is poor, it could be being frosted helped seal the door/ lid.

[Andrew]

Could it be that the junction between the ice and the casing is at a higher temperature than -20C ?, whereas without the ice the inner casing is at -20C, so more heat is lost through the insulation ?. Could be time for a new one.

[Robin]

I suggest because ice is a better insulator than whatever else is now in its place

[newshound]

+1

[Chris Hogg]

And ice has a greater thermal capacity than the air which replaces it after a defrost, so the fridge will 'hold the cold' better when heavily iced up.

[Pancho]

It's a jolly good idea, well argued. I would be convinced, but...

The ice was largely on the metal cooling pipes and fins, which don't touch the plastic sides. There are two horizontal layers. One about 2 cm below the top and one about 15 cm lower, making a shelf. It's front opening, under cabinet.

So the only ice touching the case/frame of the freezer is at the very top, even then it is patchy.

The internal plastic sides (and seal) of the freezer, are pretty much always frost free. I'll need to check next time it is frosted, but I'm pretty sure.

I reckon a new one would take half the electricity, so save about £40-£50 pounds a year.

Is frost free worth it? Some people say they can be noisy.

[Pancho]

Yes, but ice is a relatively small volume percentage. And the effect occurs even if the door remains closed.

[Martin Brown]

The fluffy ice surface of the interior frost behaves like an insulator and the volume of ice in the freezer acts to provide thermal inertia. Freezers are at their most efficient when they are close to full.

The thermostat will certainly be a lot more responsive to the interior temperature now that it isn't under 1cm of thick ice.

[Andy Burns]

I wouldn't say it's noisy as such, just that it makes the occasional wheeze or groan type noise as it alters the ducts/flaps that let air between different compartments.

I don't find that it's totally frost free, just goes longer between times when the freezer section does need defrosting, maybe that doesn't happen on the more expensive ones with dual-compressors?

[Andrew]

Alternatively, by increasing the internal volume (by removing ice) you have increased internal air movement. I read somewhere that freezers that are more empty than full should have screwed up newspaper stuffed in to occupy the empty space.

[lkpo]

That is likely true, but its less clear why that should see it consume more electricity.

I read somewhere that

It would be easy to test if that reduces the power consumption.

[Animal]

Frost frees are well worth avoiding. They turn the occasional planned hour's defrost into a less often unplanned, unavoidable defrost lasting days.

[alan_m]

It could also depend on how full the freezer.

After a recommendation on this group a few years ago I purchased one of these.

Note 1: example only - this example is a Chinese supplier and I purchased from a UK supplier with UK stock for a couple of quid more.

I have one sensor in the fridge and the other in the freezer. It monitors the real time temperature as well as recording the max and min temperatures between display resets.

Note 2: I also found the sensors/transmitters worked a lot better when fitted with Energiser AA Lithium ultimate batteries which are rated to

-40C operational. (Alkaline is typically -18 to +50C)

[Andrew]

Maybe go skip diving and get some 'celotex' offcuts and stick them to the outside of the freezer with double sided tape ?.

The thickness of celotex now mandated by building regs is far thicker than the wall of a domestic freezer.

[Steve Walker]

Don't give them ideas - you'll have them mandating far thicker insulation, but people will only have the same space (often 600mm) to fit the freezer in so the space left for contents will be useless!

[Brian Gaff (Sofa]

AS I've said here before my frost free certainly still is, but at times, totally random, we get a puddle in the bottom of the fridge bit at the bottom. There is no drain hole to the tray underneath that the freezer defrost pipe comes out in, so I'm not totally surprised, but after a good manual defrost and all of that stuff, it was fine again for three months, now we ar back with the occasional flood. Despite advice here, the underlying advice seems to be that its on its way out. They don't make em like they used to, but then if they did, nobody would sell any more fridges!

Brian

[RJH]

When I defrosted mine the temperature dropped from -17 to -22 at the same setting. So maybe check the temperature/setting . . . as you say:

[Animal]

Rod the retard strikes again. Frostfrees aren't as reliable, hence the unplanned downtime.

[Animal]

how does rodtard propose to freeze air yet not need to cyclically defrost the freezing element?