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SkyWalker
11-10-2008, 02:28 PM
does anyone have a basic pipe layout of a domestic fridge freezer, and can anyone explain to me how they work, i have wondered how i can get 2 compartments running different temps with only one compressor?

what happens when only one compartment requires cooling?

Does one side have the evap and side have the condensor, if so plz explain more temps ect, thanks you

n00b question i know but i have no experience in this field!

paul_h
11-10-2008, 03:22 PM
Normally in modern frost free systems only the freezer has the evap, and the fridge thermostat operates a duct, allowing freezer air to blow into the fridge.
The compressor runs until the freezer is satified, the thermostat powering the compressor is only connected to the freezer. If the fridge requires cooling but not the freezer, there's plenty of freezer air to circulate into the fridge after the compressor has turned off. Eventually the cmpressor will start again when the freezer temp gets too high.

On twin evap models, the fridge fan motor cuts out when the fridge gets to it's setpoint, so no air circulation through the fridge evap, though liquid refrigerant flows through it to the freezer evap. Likewise, if the fridge needs cooling but not the freezer, then the compressor will start but the freezer fan motor will not run.

Old school cyclic defrost systems had the thermostat in the fridge, and the freezer kept running until the fridge coil was low enough to make the fridge cabinet down to temp.

SkyWalker
11-10-2008, 04:43 PM
this makes perfect sense! i didn't think for a minute it would be ducted off but i can see how this would work and still be practical, thanks for the quick reply Paul

the twin evap model has raised a few questions mind, what would the pipe schematic be for this? when you say refrigerant runs through both evaps i take it the refrigerant goes through the freezer coil first?

in that case the fridge would still get its cooling even though the refrigerant has absorbed heat already from the freezer?

paul_h
11-10-2008, 05:16 PM
I'v only worked on samsung twin evap side by sides, not many others make them anyway. But its the fridge first, once the temp setting has been reached in the fridge, the fan shuts off, liquid refrigerant flows through the fridge evap and into the freezer evap.
While the freezer is getting down the temp, the fridge fan starts and stops (edit: or runs at very low speed) as needed to cool the fridge.
The fridge coil icing up is not a big deal because it will melt off when the fan starts or when the control system calls for a defrost.
It would be a bigger problem if it went through the freezer first, freezers don't have that great a usage (ie opening of the door and 'browsing' ), plus harder to naturally defrost as they run below 0*C, and thy are normally stocked with food that is already frozen. So the evap in the freezer would ice up more trying the keep the fridge cool if the refrigerant went into the freezer evap first as the liquid refrierant would be constantly flowing into a -30*C coil first.
It's more likely that feeding the freezer first would cause more problems in a fan controlled frost free system just because of the product in there, and the usage the owners give browsing the fridge, so the system I am familiar with feeds the fridge coil first.

icecube51
12-10-2008, 09:54 AM
in European fridges there is no fan, so they work whit two capillary and a thermostat for the freezer compartment. this is normally basic school.

Ice

icecube51
12-10-2008, 09:57 AM
by the way, looking for a manufacturer of fridges ......have some ideas for the door of the fridge.why it has to turn left or right???? if it slides out,more handy....no??

all comment welcome.;)

Ice

nike123
12-10-2008, 10:34 AM
in European fridges there is no fan, so they work whit two capillary and a thermostat for the freezer compartment. this is normally basic school.

Ice

In my home I have the simplest model who has evaporator in freezer compartment, only one capillary tube and thermostat is placed in fridge part, not in freezer. No automatic defrost.
Evaporator (plate) is in shape of leter U and in horizontal position.
Frozen food is placed directly at evaporator surface, and evaporator is separated from the rest of fridge with drip tray who at back side has hole for air circulation.
Evaporator at upper side is distanced from housing about 2 cm for air circulation. Front of Freezer compartment has thin plastic doors.
Air is circulated naturally from top of evaporator to bottom of fridge compartment thru space leaved above evaporator and thru hole in drip tray.

As you see, temperature in freezer compartment is not controlled at all. Its lowest temperature is controlled by thermostat of fridge compartment and construction details.

This is most omnipresent type of fridge freezer in Europe till last 10-15 years.

SkyWalker
12-10-2008, 11:29 AM
this is normally basic school.

Ice
thanks for your input guys. i appreciate it

ice cube i appreciate your comments but i think you should understand that many of us work in different areas of refrigeration and although i know the principles i have never known how a domestic fridge freezer works.

i currently have nvq 2 and studied in the evenings, there simply wasn't enough time to go through all the different appliances in the fridge trade, hence we learnt the principles!

im sorry but "get off ya high horse" springs to mind.

i am going to start studying level 3 next September which will hopefully be day release, more time to learn hopefully.


i have just taken taken delivery of modern refrigeration and air con by Althouse and turnquist and there's a great chapter explaining this subject.

icecube51
12-10-2008, 12:32 PM
this has nothing to do whit" high horses" , but if you are looking for things like that, just pointing out the direction to go for in your searches.

Ice

SkyWalker
12-10-2008, 03:28 PM
o.k dude, thought you were "looking down ya nose at me" that's all.