Fridge for an Outbuilding

I need to replace a larder fridge which is kept in unheated accommodation. The old Electrolux running on R12 has given up.

Retailers tell me that modern fridges shouldn't be used in out-buildings. They say if I want to risk it I should go with the German makes as they use better quality refridgerants (R600a), yet some fridges running on R600a are also marked not for use in out-buildings.

It seems there is no official Climate Class that goes lower than 10°C (SN: sub-normal). (The old Electrolux was N: normal).

If the outside temperate is colder than 4°C then the fridge has nothing to do. Between 5 - 10°C I would like it to function normally, and above 10°C its working within spec.

The BP of R600a is -10°C at normal pressure, but I'm assuming that within the sealed system on the LP side the BP is going to be a bit higher. If the ambient temperate is below the BP pressumably I have a problem.

Could someone explain what the problem/risks are and offer advice please?

Thanks

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They say if I want to risk it I should go with the German makes as they use better quality refridgerants (R600a)

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Beware salesmen spouting rubbish.:eek:

Ask him what he knows about the quality of refrigerants and has he informed the manufacturers of these poor quality gases that they are below standard.

Would he also like to tell the rest of us which ones to avoid.:rolleyes:

The man is on commission, ignore stupid statements.

Brian

Thanks. Silly me - I should have thought of that!

But what's the problem with low ambient temperature for a straight fridge (ie not fridge / freezer)?

Hi,Nigel. You may face the problems when ambient temperature turns to -13 deg. C or below. It is vacuum inside your sistem in this case.It is possible that the ar (non-condensales) and moisture may come inside. I thinc i shouldn't continue than... :(

Not such a silly question after all.

I have two old R12 fridges in an unheated garage and there is a noticeable difference in their operation, summer and winter. But it’s nothing I’m concerned about because they are full of beer; but the temperature fluctuations I can tolerate for a bottle of beer may not be suitable for food.

So, you pays your money and you takes your choice.

There’s nothing to stop you putting your fridge in an igloo, if you want to, but it may not work as well as it would in a nice heated kitchen where it was intended to go..

But here are two plausible reasons why a minimum temperature limit is suggested by manufacturers and may affect the operation.

The first will be familiar to split air conditioning engineers as over condensing.
If the condenser is too cold there is a possibility of the refrigerant gaining too much sub-cooling, reduced condenser pressure and reduced flow through the capillary tubes feeding the evaporator. In other words, there will be a reduction in the machine’s capability to do its work. This may result in damage, long term.
Hydrocarbons (R-600 and the like) obey the same laws of thermodynamics as everything else. Their transport properties are selected to be close to the conventional CFC and HFC refrigerants.

The second reason will be familiar to people from the old school of refrigeration who worked on butcher’s cold rooms that were often outside the backs of shops in all weathers. It can affect some types of thermostats (not all, just some) where the temperature inside the fridge is warmer than the temperature outside in the winter. If parts of the stat, say its bellows, are mounted on the outside facia, the gas charge inside the stat can condense in the bellows section at low temperatures and cause it to give very erratic control. This is quite rare, but it can happen, even with a domestic fridge.

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Originally Posted by nigel_T

Brian

Thanks. Silly me - I should have thought of that!

But what's the problem with low ambient temperature for a straight fridge (ie not fridge / freezer)?

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Nigel a Fridge will work in any environment but the controls (thermostat) that control the temp will not.
Imagine how a fridge works.it pulls down to temp say 2degC and then cuts off. The fridge warms up then cuts in at say 5degC.
This is continuous forever.
The problem with fridges is when you put them out side and in the winter the out side temp does not rise above 5degC.
The fridge will sit there not running. With a fridge this does not matter but a fridge freezer is different.
If the fridge stat cuts off and the temp outside stays low the fridge will be ok but the freezer will warm up to 4degC and all the stock will be lost.
Modern fridge freezers with electronic controls do not work like this, they sense the temp across the evaporator and switch on and off the comp to control the temp.

Cheers taz

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Originally Posted by taz24

Nigel a Fridge will work in any environment but the controls (thermostat) that control the temp will not.
Imagine how a fridge works.it pulls down to temp say 2degC and then cuts off. The fridge warms up then cuts in at say 5degC.
This is continuous forever.
The problem with fridges is when you put them out side and in the winter the out side temp does not rise above 5degC.
The fridge will sit there not running. With a fridge this does not matter but a fridge freezer is different.
If the fridge stat cuts off and the temp outside stays low the fridge will be ok but the freezer will warm up to 4degC and all the stock will be lost.
Modern fridge freezers with electronic controls do not work like this, they sense the temp across the evaporator and switch on and off the comp to control the temp.

Cheers taz

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bear in mind that I live somewhere that never goes below 0C ambient. But what you're saying sounds weird to me because all domestic fridge/freezers have the entire thermostat inside the cabinet.
The only ones I've seen with the actual thermostat (with a bit of the capillary) mounted to the outside are stand alone freezers.
Also, you'd have to try hard to find any with the capillary t/stat in them anymore, most of them are thermistors.

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Originally Posted by paul_h

bear in mind that I live somewhere that never goes below 0C ambient. But what you're saying sounds weird to me because all domestic fridge/freezers have the entire thermostat inside the cabinet.
The only ones I've seen with the actual thermostat (with a bit of the capillary) mounted to the outside are stand alone freezers.
Also, you'd have to try hard to find any with the capillary t/stat in them anymore, most of them are thermistors.

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Yes thats the type I mean (internal thermostat)
but if you imagine where the heat is coming from then the position of the stat inside the case is affected by outside temp.
When the stat cuts out the fridge at say 2degC because of the differential that is built into the stat it will not cut in untill about 5degC.
apart from the product in the fridge the only other source of heat is the out side ambient temp.
If the ambient temp is lowere than 4degC then there will be no increase in temp inside the fridge so the stat remains open (off).

Cheers taz.

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Originally Posted by taz24

apart from the product in the fridge the only other source of heat is the out side ambient temp.
If the ambient temp is lowere than 4degC then there will be no increase in temp inside the fridge so the stat remains open (off).

Cheers taz.

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Iv'e seen fridges with the bulb wired to the off position on the stat.
When the fridge cuts off down to temp it brings on the bulb which slowly warms the inside of the fridge.

taz.

Taz is exctly right , we used to do this with the internal light to give some off cycle load. this only happens on self defrosting fridges that are part of a fridge freezer arrangement, which have what we call constant cut in stats and they work on evap temp and wont cut in till +5 evap temp so evap is clear of ice

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Originally Posted by taz24

Yes thats the type I mean (internal thermostat)
but if you imagine where the heat is coming from then the position of the stat inside the case is affected by outside temp.
When the stat cuts out the fridge at say 2degC because of the differential that is built into the stat it will not cut in untill about 5degC.
apart from the product in the fridge the only other source of heat is the out side ambient temp.
If the ambient temp is lowere than 4degC then there will be no increase in temp inside the fridge so the stat remains open (off).

Cheers taz.

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Wait, I get you now. You're saying that if a fridge/freezer runs off a thermostat in the fridge, the freezer won't work.
I can't see that being a problem with modern fridges, as most frost free fridge/freezers have the themostat in the freezer, The fridge is cooled by air ducted from the freezer using a damper and has a different thermostat that just controls that damper.
edit:At least that's how all mechanical thermostat samsung frost free fridges work.

edit2:
They also have electric heaters for defrost, electronic or klixon controlled so defrost only terminates at postive temperatures to ensure full defrost)

They also have the condenser inside the cabinet insulation for a bit of heat load.

That's why I was confused, as I look at them all day so when I think of a domestic fridge, I think of how samsungs work.
I couldn't see anything that would stop them working in low ambients, but like I said, I'm not in a country that has ever tested that theory.

As mentioned the problem is mainly down to the type of stat fitted, where the body of the stat is mounted and the lack of heat load to cycle / operate the stat and defrost the unit

I've had a problem with two units (Derby/Esta) that used bottle cooler type stats (2 - 12 deg) with the bellows mounted outside the cabinet. Overcame the problem by fitting stats that sensed the evaporator rather than the air, thus capillary colder than bellows.

An electronic control would also be unaffected by the low ambient.

The lack of heat load would only tend to affect the units ability to defrost properly. Some fridge/freezers do have an evaporator heater fitted to overcome this problem.

I think you need to analyse the exact location and possibly suggest a small coldroom with positive defrost. Less ongoing hassle when the units don't work properly due to the low ambient!