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Frost free / Auto defrost?

F

Frank Bemelman

Jan 1, 1970
0
Fred Bloggs said:
No refrigerator in the world will operate without frost if you block the
drain for the frost water with debris and/or scum formation:) Those UK
refrigerators you cited would be considered miniature doll-house
accessories in the US- absolutely tiny. How cramped are the quarters in
that country anyway?

I have a second refrigerator in my hobby workshop. I runs on a peltier
cooler, and can hold 6 cans of coke.

You don't see many double door refrigerators in Europe. The average
kitchen is too small and it's easier to go to the shop and get it fresh,
instead of piling it all up in your fridge. Or borrow what you need
from the neighbours ;)
 
J

Jeff

Jan 1, 1970
0
See if this makes any sense:

Frost Free - means frost does not grow around the doors, due to small
heating elements embedded around the door frame.

Auto defrost - operates on a timer, or counter that shuts down the
compressor and turns on a heating element (350 - 500 W) that heats up the
evaporator to melt any accumulated frost. The time frame for the timer is
around a few days to a week, and the system uses a counter, it's operated by
the number of times the door is opened.
 
F

Fred Bloggs

Jan 1, 1970
0
Frank said:
I have a second refrigerator in my hobby workshop. I runs on a peltier
cooler, and can hold 6 cans of coke.

You don't see many double door refrigerators in Europe. The average
kitchen is too small and it's easier to go to the shop and get it fresh,
instead of piling it all up in your fridge. Or borrow what you need
from the neighbours ;)

It is a bad habit to drink Coke at home. I do drink it at work because
the water is extracted from a well bored through a former toxic chemical
refuse dump and the "old timers" have advised against drinking it-)-
not to mention the recent e.coli contamination bulletin.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Sam Goldwasser
So you heat your food when the compressor isn't running?
'Heat' is a big word. It's about a 5 W heater embedded in the cooling
coil plate.
That forms an
oscillator with a frequency dependant on ambient temperature and the
quality of the fridge's insulation. :) I guess what you mean is that it
defrosts until another thermostat says there isn't any more ice.

No, just the one thermostat. It opens at about 0 C, stopping the
compressor, and the heater then warms up the plate to about 5 C, when
the thermostat closes again and cuts off the heat. I won't go to law on
the precise temperatures.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Fred Bloggs <[email protected]>
How cramped are the quarters in
that country anyway?

The floor plan of my bungalow is 40 ft by 20 ft. Individual rooms in
quite modest US houses are bigger than that.
 
S

Sam Goldwasser

Jan 1, 1970
0
John Woodgate said:
The floor plan of my bungalow is 40 ft by 20 ft. Individual rooms in
quite modest US houses are bigger than that.

Maybe in McMansions. Not most of the more than modest homes
around where we live. :)

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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R

Roger Hamlett

Jan 1, 1970
0
John Woodgate said:
I read in sci.electronics.design that Sam Goldwasser

'Heat' is a big word. It's about a 5 W heater embedded in the cooling
coil plate.
These systems normally also have a fan from the cooler module. This is
switched off, when the cooler is being defrosted. So the main freezer
contents only 'warm', by perhaps half a degree in the entire cycle.
No, just the one thermostat. It opens at about 0 C, stopping the
compressor, and the heater then warms up the plate to about 5 C, when
the thermostat closes again and cuts off the heat. I won't go to law on
the precise temperatures.
It is worth making a comment here about the 'Hotpoint' units, that have
had some significant bad reports here. I have one. A few months from new,
it developed the sort of problem being discussed. The engineer who came
said it was a known problem with the module, and replaced it with a new
design. The original system was a fairly basic mechanical timer, and
thermostat. The new module was a solid state system, with a temperature
pickup that had to be attached to the cooler assembly. I have had this now
for over eighteen months, without any problems at all. Hopefully new units
would have this design.

Best Wishes
 
R

Rich Grise

Jan 1, 1970
0
Sam said:
Maybe in McMansions. Not most of the more than modest homes
around where we live. :)

True. I've never seen a single room that big. But one time I moved
from a relatively small rooming house to an apartment, and my Dad
remarked, "The bathroom is bigger than the room you used to live in!"

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
John said:
I read in sci.electronics.design that Sam Goldwasser

'Heat' is a big word. It's about a 5 W heater embedded in the cooling
coil plate.


No, just the one thermostat. It opens at about 0 C, stopping the
compressor, and the heater then warms up the plate to about 5 C, when
the thermostat closes again and cuts off the heat. I won't go to law on
the precise temperatures.

John, would it be possible to humor me and take some actual temp.
measurements? I can't imagine a freezer with a chill plate at only
0 C doing much freezing of stuff at all.

Thanks,
Rich
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Rich Grise <[email protected]>
wrote (in said:
John, would it be possible to humor me and take some actual temp.
measurements? I can't imagine a freezer with a chill plate at only 0 C
doing much freezing of stuff at all.

Sorry, my numbers refer to the *fridge* section defroster. I don't know
how the freezer defrosts. I'll ask someone who knows, but he often
doesn't answer.
 
J

Joerg

Jan 1, 1970
0
Hi Terry,
1. Are 'Frost Free' and 'Auto Fridge Defrost' independent features
(not 'the same thing' as Ken and Don both said)? The evidence of my
research, as per the examples I gave, appear to imply that they are.

2. Why is 'defrost' necessary, if the unit is frost free? Is it just
an admission that the Frost Free thing doesn't always work?

3. Is 'Auto Fridge Defrost' a worthwhile feature?
I'd side with John. Whenever you open a freezer or fridge door some air
will enter. That air has a certain humidity. Now some of that humidity
will condense on the walls and freeze there. That is inevitable. Same if
you don't open the door, just slower. That is because no door seal is
going to be 100% tight.

I have yet to see a frost free unit that doesn't have an auto-defrost
feature.

In the olden days the defroster was a human. We had to turn off the
fridge, leave the door cracked and then take the little container of
water out. And clean whatever had spilled. Then came the auto-defrosters
where you still had to remember to check that container in there or
it'll spill over. The amount of water in there depended on the weather
and all. The current state of the art appears to be the auto-defroster
that has a little hose which guides the water outside into a little
tray. In ours that tray is within the outside blower airflow so it
evaporates enough that we hardly have to worry about it overflowing. But
it still needs to be scrubbed regularly or molds might grow.

Regards, Joerg
 
J

Joerg

Jan 1, 1970
0
Hi Sam,
It's not only the cost of a CD4060. Add in the power supply and other
low power components for it (a few cents) and the power relays needed to
switch the compressor circuit and heater circuit.
No need for a compressor relay since that is already handled by the
thermostat. The defroster only receives power when the compressor is
off. So that only leaves a tiny triac or so to turn on that little
heater loop. Ok, the triac would add a few cents here. But the whole
thing wouldn't break so often anymore.

Our fancy combo had cost way over $1000 yet it has broken down twice in
five year. The ol' Bosch in the basement is from 1958, never broke down,
can't even remember whether it ever asked for a new light bulb.

Regards, Joerg
 
S

Sam Goldwasser

Jan 1, 1970
0
Joerg said:
Hi Sam,

No need for a compressor relay since that is already handled by the
thermostat. The defroster only receives power when the compressor is
off. So that only leaves a tiny triac or so to turn on that little
heater loop. Ok, the triac would add a few cents here. But the whole
thing wouldn't break so often anymore.

In the systems I've seen, the timer also turns off the compressor
if it is on since it's possible for the compressor to be running 24/7 in
very extreme conditions and then there would be no defrost.

Typical circuit from GE Frost Free:

Black (4)
Gray (3) /o---------o Normal position - Compressor, evaporator fan.
H* o-----+------/
| o---o Blue (2)
Timer | Defrost heater Defrost Thermostat
Motor (3180 o------------/\/\/\------------o/o----------+
| ohms) 31 ohms 32 F |
| |
| Orange (1) |
o---------------------------------------------------------+--o Common

* H is the Hot wire after passing through the main thermostat (cold control)
in the fresh food compartment.

The contacts switching the black and blue wires is controlled by the timer.
Our fancy combo had cost way over $1000 yet it has broken down twice
in five year. The ol' Bosch in the basement is from 1958, never broke
down, can't even remember whether it ever asked for a new light bulb.

Yep! :)

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
F

Fred Bloggs

Jan 1, 1970
0
John said:
I read in sci.electronics.design that Fred Bloggs <[email protected]>
wrote (in <[email protected]>) about 'Frost free / Auto
defrost?', on Tue, 10 Aug 2004:




The floor plan of my bungalow is 40 ft by 20 ft. Individual rooms in
quite modest US houses are bigger than that.

I live in a 650 sq ft space and still have a 14 cu ft refrigerator, in
addition to every other appliance known to mankind. It feels bigger than
it sounds because of the cathedral ceilings, skylights, and floor plan.
This area is rightly pursuing high density housing in an attempt to
staunch the so-called urban sprawl and all the damaging and wasteful
aftermath associated with it. The 650 sq ft is quite large when you
consider that it is situated in a 20 acre park setting with two pools,
tennis courts, jogging trails, 24-hour fitness center, indoor handball
courts, private parking, sound barrier, immaculately maintained grounds
and infrastructure, and centrally located within urban neighborhood
requiring no travel whatsoever- not 1/2 mile direct from a choice of two
mega-supermarkets for example. It was either this place or a townhouse,
but when I took the tour, I was immediately sold on the efficiency of
the compactness- and fully intend to buy the place once I save up about
five million dollars.
 
T

Terry Pinnell

Jan 1, 1970
0
Fred Bloggs said:
I live in a 650 sq ft space and still have a 14 cu ft refrigerator, in
addition to every other appliance known to mankind. It feels bigger than
it sounds because of the cathedral ceilings, skylights, and floor plan.

Now those *are* features we just don't get in our fridges here...
 
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