micky;
3101115 Wrote:
>
> There was no fan blowing air out of the freezer. That didn't start
> afaik until "frost-free" was invented, and iiuc, it's the fan that
> makes it frost-free.
No, it's not the fan that makes the fridge "frost free".
It's the fact that the place where the refrigerant gets injected as a
high pressure liquid and evaporates into a vapour, absorbing heat as it
does, was moved from channels molded into the freezer compartment to a
special "evaporator coil" typically located in the back wall of the
freezer compartment.
And, that evaporator coil was accompanied by a defrost heater, defrost
termination switch, defrost timer, defrost pan with drain and a hose
that carried the melt water down to the bottom of the fridge where it
would re-evaporate into the ambient air. Together, all those parts
would automatically defrost the evaporator coil once a day or so so the
homeowner didn't have to defrost it.
And, of course, they added an evaporator fan to suck cold air through
that evaporator coil and blow it into the freezer compartment, and from
there some of the cold air would get sucked back over the evaporator
coil and some would get blown down into the fresh food section of the
fridge, keeping that space cool, too.
So, a frost free fridge operates on the same thermodynamic cycle that a
regular manual defrost fridge does... it's just that it's equipped with
all of the necessary equipment to defrost itself every 10 to 20 hours or
so. And that defrost cycle is governed by the defrost "timer", which is
the "Brains" of a frost free fridge.
Keep this in mind:
All frost free fridges that I know of have the compressor and evaporator
fan in parallel, with both in series with the thermostat. The other
circuit in the fridge will have the defrost heater in series with the
defrost thermostat (aka: defrost termination switch). The defrost timer
DIVERTS power from the thermostat to the defrost heater for about 20
minutes once every 20 hours or so. That means that when the defrost
timer is in defrost mode, power won't be going to the thermostat, and
hence not the compressor and evaporator fan either. So, when the fridge
is in defrost mode, you should NOT hear the compressor running nor feel
a breeze in the freezer compartment. When the defrost cycle is over,
then BOTH the compressor and evaporator fan will always come on and go
off simultaneously. So, if you hear the compressor running, but there's
no breeze in the freezer compartment, there's something wrong with the
evaporator fan. Similarily, if you feel a breeze in the freezer
compartment, but you can't hear the compressor running, there's
something wrong with the compressor.
If the fridge appears to be spending too much time in defrost mode,
it could be that the defrost timer is stuck in defrost mode. Defrost
timers will be equipped with an exposed output shaft that can be turned
to advance the timer manually, putting the fridge back into "run" mode.
That shaft will be designed so that it can only be turned in one
direction with a slot screw driver. That's because turning that shaft
backward can wreck the defrost timer. Unfortunately, the defrost timer
will be located in different places on each fridge, so you have to know
where yours is before you can turn that output shaft and advance the
timer to get the fridge out of defrost mode.
--
nestork