jerrybuilt wrote:

Bob Minchin wrote:
"D.M. Procida" wrote:
The instruction guide for our Bosch fridge tells us to press
a certain switch under two circumstances:

1: if the room temperature is below 18 degrees C
2: if we want to fast freeze stuff

What actually does this switch do? Why should the fridge need
a switch for different room temperatures? And why would the
switch for having a cold room (in which your fridge should
need to work less hard) be the same one for freezing stuff
quickly (for which it should work harder)?

I expect this is a single compressor fridge freezer. It is
widely know (especially in this NG) that this type of machine
has a design compromise whereby if the room temperature is
too low, the compressor does not switch on and the freezer
defrosts.

You can get freezers with two compressors? I didn't know. I am
considering buying a large chest freezer which will be sited
in an unheated outside garage. What should I look for?


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No Freezers only have one compressor. Some expensive, properly designed
fridge freezer have two but most FF have one compressor and arrange
through a design compromise to share the cooling circuit between one
cabinet at about +3 degrees and the other at -21 degrees .

If you are looking for a freezer for use in a garage I advise to make
sure the base (outside) is made of metal. Some have a form of foilcoated
cardboard for the base. This in time becomes saturated with condensation
from the garage floor which usually has no damp proof membrane and then
lets water into the foam.this decreases the insulation value hence more
condensation and starts rust on the cooling pipes buried in the foam.
after a few years, all the gas leaks out.

There are three ways chest freezers get rid of their excess heat.
1) Grill or plate with tubes welded on at the back of the freezer (no
specific name that I'm aware of)
2) By a fan blowing air though a little radiator (fan assisted)
3) through the front, ends and back surface of the cabinet (Skin cooled)

Type one is most common and works Ok

Fan assisted ones are good in the garage as they force some air
circulation.

The skin cooled ones are my favourite for garages as the outside of the
case is warmed regularly and this dries off the demon condensation which
the other two types do not and which tend to rust the outer casing. This
is only cosmetic but soon looks crap.
However, the running costs of skin types can be dearer or need thicker
insulation (less room inside for a given exterior size) as the inside of
the freezer is at -21 degrees and the outside can get to 50 or 60 degree
wehn the compressor runs.

Whichever type you buy, I suggest your stand it off the floor by a
couple of bricks height and dont push it back against a wall which
allows plenty of air to circulate around.

All based on 25 years plus of freezers in outbuildings.

Regards

Bob