Deep freeze temperature varying over several hours

We have an Arctis freezer - not sure what model, but it's a tall one about 5 feet high, which was left by the previous owners of the house.
The temperature on the display used to be constant at -18 degrees C, but over the past couple of weeks it's started fluctuating between -18 and -12 over the course of several hours. The times when it is showing a warmer temperature are not necessarily when it has been opened; nor are they times when the room is warmer, either because of sunlight or daily variations in the temperature of the Aga (which also came with the house). There are times when it's showing -12 but the compressor isn't running, so it's not as if the refrigeration mechanism is struggling to achieve the temperature that the thermostat is set at.
Do freezers tend to show a higher temperature on the display when they are going through a periodic "frost free" thawing stage? How frequently do freezers typically do a frost-free cycle - daily, weekly?
I've not checked with a thermometer to see if the actual internal temperature (in a consistent location) varies - ie whether it's the display or the cooling which are varying.
I've never noticed our own Samsung freezer which we brought with us displaying a temperature which varies by more than +/- 1 deg C from the -18 that it is set at.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
NY wrote:

As far as I remember a frost free will go on defrost cycle every ? hours and the temperature will go up in the cabinet. The increase in temperature is only to be expected. Don't get paranoid.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Older freezers were not as well insulated and insulation can go leaky over time due to ingress of damp or any kind of seal issue. I'd have thought that -12 if confirmed is probably just the self defrosting. Mine does this and nothing has poisoned me as yet. Brian
--
----- --
This newsgroup posting comes to you directly from...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I too work on the basis of "I've not been poisoned yet so it must be OK". The fact that the temperature returns to -18 after a hour or so and that it isn't worse when the kitchen ambient temperature is warmer, suggests that it's not leaky seals. Ice cream shows no sign of large ice crystals that you get if it's partly thawed.
Odd that we've only started noticing it recently, when I presume its been doing its self-defrosting cycles for the past 2 months since we've lived here. Perhaps we're just not very observant...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I’ve never noticed an auto defrost cycle other then when it failed- the heated was on too long. That was caused by a timer that got stuck - at least that was Whirlpool’s diagnosis (it was under warranty). It was troublesome before it failed so dramatically and defrosted everything.
The timer was just a simple mechanical device which turned on a small heater every for a set time periodically. I don’t think it even sensed the ice build up.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 13/08/2019 21:21, NY wrote:

Could be because the voltage is varying more than it used to.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thursday, 15 August 2019 17:38:31 UTC+1, Andrew wrote:

d

rge

it could not.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 13 August 2019 15:17:24 UTC+1, NY wrote:

If it's a frost free, this behaviour is normal, it's doing a defrost cycle.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That’s not frost free, that’s cyclic defrost. Frost free pumps very cold air into the freezer and never have a thawing stage. That’s where the name comes from, there never is any frost to thaw.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Rod Speed wrote:

Really?
"Frost-Free" refrigerator/freezer units usually use a heating element to defrost their evaporators, a pan to collect and evaporate water from the frost that melts from the cold plate and/or evaporator coil, a timer which turns off the compressor and turns on the defrost element usually from once to 4 times a day for ...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


Nope, that’s cyclic defrost, as I said.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, 14 August 2019 05:07:01 UTC+1, Rod Speed wrote:

out

t

-12

e).

so

are

pumps very

wrong as always. What's new.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The latest in the saga of the freezer...
We noticed that it was spending longer and longer at around -14 to -12, and less and less time at -18. Then last night the alarm went off because the temperature had reached -11.
So we hastily moved everything into other freezers (including starting up one that we used to use only in the summer for freezing all the veg and fruit that we grew) and turned the misbehaving one off. When I investigated behind a bit of trim I found that the cooling pipes in the freezer compartment were surrounded by a large block of ice. So much for frost free ;-)
Having left the freezer off overnight, about a litre of water collected in the vessel where it normally collects during the thaw cycle and then evaporates in the heat of the compressor.
It looks as if the freeze/thaw cycles had stopped working properly and the freezer was never defrosting properly before the thermostat started another freeze cycle.
It's cooling down again now (it's gone from +21 to +8 so far) so I'll see whether it gets to -18 and stays there. And if it starts doing it again in the future, at least I'll know what to check.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 20 August 2019 09:32:27 UTC+1, NY wrote:

It typically takes more than overnight to defrost it all, so expect a repeat soon
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ah... The cooling pipes that were visible in a heat exchanger at the top of the freezer compartment looked completely clear of ice, and no more water was dripping down the drain pipe into the heated vessel above the compressor. I wonder if I should have left it a bit longer. I thought that about 12 hours at 20 deg C would have melted all the ice.
So far, the freezer is at about fridge temperature, so it's got a long way to go.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 20 August 2019 10:05:07 UTC+1, NY wrote:

Maybe you're right in this case. In frost frees where the ice builds up is normally insulated. But if it stopped melting... fairy nuff.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.