Setting freezer temperature.

[ericmark]

I was sure my mothers freezer was faulty but major problem was to measure -18°C. At the same time I wanted to control my fermenting beer temperature so decided to combine the two and buy a temperature controller which would also double as a simple thermometer. I settled on one of these units and also a new thermostat.

Still waiting on the thermostat for freezer but the temperature controller has arrived. I was a little disappointed as I want one with two sets of contacts one for cool and one for heat but that was my mistake.

Job one was build it into a socket box to make it save to use and second was to test freezers, fridges and weather stations with temperature read outs to verify it was giving reasonable accurate readings and it was.

My guess was confirmed my mothers freezer just keep going down in temperature so turned it off again. But then I thought why not use the temperature controller at least on a temporary basis to control the freezer. Well one reason is it's then not controlling my beer temperature.

But although I can measure my freezers they both have inverter drives so switching on and off with little gap between is no problem. My mothers however is rather basic and it will need time to allow pressure to drop before switching back on again.

The instructions I put on my web site mainly so I will not lose them but it gives some options as to settings. "Slewing range of temperature" is one default is 2°C and I suppose this will alter the time before it switches back on. But also there is a delayed start up to 10 minutes I am guessing this is what I need to set to protect the motor.

But question is how long does it take for the pressure to drop what should be the settings?

Idea is simply tape the sensor onto roof of freezer compartment and run wire out of door until correct part arrives. But don't want to damage cut out by trying to restart while pressure is still in the pipes so any idea of delay required or temperature range with a non inverter freezer?

 

[big-all]

you need a perfect seal to stop air being drawn in a wire will prevent this

 

[Steve]

Don't fasten the sensor to the freezer lid. This is the warmest part of the freezer and you'll use more energy cooling it. The sensor should be in the middle of the freezer so it takes an average.

 

[ericmark]

Sorry it's this freezer I have ordered a thermostat which should fit up the pocket which would seem to place the sensing tip at centre back top.

However attempts so source local have failed and internet seems slow so idea was to use a thermostat really bought to brew beer to work freezer until the correct one arrives.

The sensor I have will work heat or cold -40ºC~120ºC so well within the range but it is the "slewing range of temperature : it could be adjusted in the range of 1-30ºC" which raises the question. I don't have an old style freezer to test and copy. Both mine are inverter control.

If the slewing range is too small then it may try to start the motor before pressure has dropped from last run and if too big the food shelf life is reduced.

If I had a working old style freezer I could just monitor but I don't.

 

[big-all]

if its frost free i wouldnt worry to much as occasionally it will go into defrost cycle this involves stopping the freezing heating the void to melt ice so will bring the internal temperature far closer to zero than a wrongly set up thermostat

 

[ericmark]

Well gave it a go. Set to minus 18 and with 0.5 between on/off it hunted. So increased to 1 degree between on/off and hit minus 16 before restart so settled at minus 19 with 1.5 degrees between on/off and it was doing whole cycle in around 25 minutes which seemed reasonable this is with a full freezer.

It's not a frost free.

It will be interesting when the correct part arrives to see how that performs.

 

[big-all]

i borrowed my brothers temperature probe last year
the freezer was stopping around 15 degrees and the control knob[a small coin turn sort]wouldn't turn

defrosted and it operated correctly at 17-19 so an ice buildup was insulating the probe now wether this reduced the cycle time or increased i don't know but it played havock with the temperature
now nothing will be in the freezer for more than a year whilst the average will be nearer about 6-8 months

i just wonder how many people don't bother defrosting 2 times a year and have a higher ice coating and a higher say -10 degrees without suffering any harm??

 

[ericmark]

I think this is a big problem. We never check how the freezer is working.

We had one old chest freezer which we realised never switched off. The insulation had gone. From that point I started to use an energy meter, and on a regular basis, around twice a year, monitor energy used, although when I calculated the running costs not really worth changing if slight fault with the insulation, but I would suspect there would be also warm spots.

It was during one of these routine tests I found my mothers freezer was running all the time. However I could not find a thermometer local for sale to work out if an insulation fault or a thermostat fault.

However I then found an interesting fact. Minus 18°C is the freezing point of brine. So boiled up some water and salt to make a saturated solution then put it in the freezer and it froze solid so clearly a thermostat fault.

Phoned around to get it repaired call out charge around £45 before any parts added and freezer was less than £100 to buy.

So internet search for parts and found the part for around £4 so worth swapping a thermostat. But the unit is marked Off 1, 2, 3, 4, 5 which does not really help setting temperature.

So I had wanted a temperature controller for my beer so idea was to also order one of them so I could use it to set the temperature. I selected one which would read down to -40°C.

Well the temperature controller arrived but as yet no thermostat, so while waiting for correct part (I hope) using the temperature controller. It runs about 50% of the time, so dread to think how cold the freezer was getting running all the time.

Before putting it in my mothers freezer I put it in both of my own freezers and the display was near always showing -18°C it never seemed to vary. The display on the freezer doors also always shows -18°C so I set the temperature controller to 0.5°C between on/off but it started to switch back on immediately after switching off so changed that to 1.5°C.

I will guess three reasons why my freezer stays bang on temperature.
1) Bigger.
2) Frost Free.
3) Inverter motor control.

To me the problem has been internet. Before internet there were shops which sold parts for freezers, washing machines, vacuum cleaners and many other domestic items. I could have walked in with old part in my hand and walked out with a new part that I could have fitted that day.

These shops have gone. Only option is internet. Which means one your guessing as to if ordering correct part and two you have to wait for ages for it to arrive. Cheap yes but been without the second freezer for nearly 3 weeks before I got parts.

Every shop has to test their freezers and I thought I could have bought a thermometer in any good cook shop. Wrong. Maplin have them listed but shops had no stock not due back in until after Christmas.

 

[JohnW2]

Well the temperature controller arrived but as yet no thermostat, so while waiting for correct part (I hope) using the temperature controller. It runs about 50% of the time, so dread to think how cold the freezer was getting running all the time.

It might not be as bad as you think/fear. My (old) chest freezer has a so-called 'quick freeze' switch which bypasses the thermostat, so that it runs continuously. We rarely use it but when we do, we often forget to switch off the 'quick freeze' for a few days (one of the main reasons we don't use it much!), so that the freezer runs continuously for that period. However, although it usually (with thermostat working) runs at close to -18° (per my thermometers!), when it is left running continuously for a few days, it doesn't get a lot colder than about -21°.

One thing one has to remember is that the freezer will not continue getting 'colder and colder' so long as it is running. The refrigeration system can only extract heat from the cavity of the freezer whilst the coolant is cooler than the cavity - so if the coolant can't get much below, say, -21°, then nor can the cavity of the freezer ever get any colder than that, even if it is running continuously.

Kind Regards, John

 

[ericmark]

The problem was my mother uses the instructions on the ready meals so when it was too cold the centre of ready meal was still cold.

 

[JohnW2]

The problem was my mother uses the instructions on the ready meals so when it was too cold the centre of ready meal was still cold.

I don't think that you should necessarily be too quick to blame the freezer for that. IME, that is very common when one follows the "cook from frozen" instructions on food products, even if the food comes out of the freezer at -18° - quite probably due to the inevitable variations between ovens.

Kind Regards, John

 

[ericmark]

I hope tomorrow to be able to turn the second freezer off. But the recorded measurements have been an eye opener. A+ rated but costs twice as much to run as a 70 litre freezer per litre also A+ rating.

The main freezer has about an 2 hours cycle time maybe longer to maintain -17 to -19 degrees C but this small unit has just 20 minuets cycle time.

OK I knew running two freezers was more expensive than running one large one but did not realise that a A+ 32 litre would cost twice as much per litre as a 70 litre A+ freezer.

I looked at A+ and though OK it will not cost much to run.

At the moment I am looking at my beer stock and thinking I want my beer temperature controller back ASAP.

Problem is once ordered one has to just wait I hope each day the replacement thermostat will arrive.

 

[big-all]

the trouble you have is they will set standard tests or requirement to fit within a or a+ ect
i dont think they have to go to a centralised test center
i think its more self certification so open to bias

 

[big-all]

well thats me wrong again
http://en.wikipedia.org/wiki/European_Union_energy_label

suggest its consumption rather than efficiency ??

A+++ <22
A++-- <30
A+ <42/44
A -----<55
B------<75
D -----<95
E ----<110 -----
F-----<150
G---->150

 

[JohnW2]

well thats me wrong again
http://en.wikipedia.org/wiki/European_Union_energy_label
suggest its consumption rather than efficiency ??
A+++ A++-- A+ --A ----------=B--------- C ---D ------ E -----F G
<22---- <30 ---<42/44 -<55 <75 ---<95 <110 <125 <150 >150

Not really. You omitted to include the title of that table, which read:

Refrigerating appliances, as EEI

...and the accompanying text which explains what "EEI" is ...

For refrigerating appliances, such as refrigerators, freezers, wine-storage appliances, and combined appliances, the labelling is specified in terms of an energy efficiency index EEI, which is an indication of the annual power consumption relative to a reference consumption that is based on the storage volume and the type of appliance (refrigerator or freezer).

... so, it seems, a fairly crude attempt to relate to efficiency.

Kind Regards, John