Frost free / Auto defrost?

[Terry Pinnell]

As our current unit is plainly struggling, I'm about to buy a new
frost-free combination fridge/frezer. But I'm confused about one
feature that is offered on some models and not others, namely
'Automatic defrost'. If the product is frost-free, then why would I
ever need to 'defrost' it? And I've seen posts which seem to imply
this feature is undesirable, and that manual defrosting is preferable.
The more I read, the more hazy the issue becomes!

Any crisp and clear advice on this would be greatly appreciated
please, as I need to place an order fast.

 

[Don Pearce]

As our current unit is plainly struggling, I'm about to buy a new
frost-free combination fridge/frezer. But I'm confused about one
feature that is offered on some models and not others, namely
'Automatic defrost'. If the product is frost-free, then why would I
ever need to 'defrost' it? And I've seen posts which seem to imply
this feature is undesirable, and that manual defrosting is preferable.
The more I read, the more hazy the issue becomes!

Any crisp and clear advice on this would be greatly appreciated
please, as I need to place an order fast.

Frost free and automatic defrost are as far as I know the same thing.
I have one of these, and the freezer element is a flat vertical plate
at the back of the top cabinet. During the non-cooling phase the ice
melts to allow any excess to drip away through a pipe onto the
condenser bulb at the bottom, from which it evaporates into the room.

Mine has been working fine for many years.

The actual freezer bit at the bottom enjoys no such features, but it
only gathers frost when I have the thing too full and the door fails
to close properly. There is nothing for frost like a 1mm gap in the
door seal.

d

Pearce Consulting
http://www.pearce.uk.com

 

[Ken Weitzel]

As our current unit is plainly struggling, I'm about to buy a new
frost-free combination fridge/frezer. But I'm confused about one
feature that is offered on some models and not others, namely
'Automatic defrost'. If the product is frost-free, then why would I
ever need to 'defrost' it? And I've seen posts which seem to imply
this feature is undesirable, and that manual defrosting is preferable.
The more I read, the more hazy the issue becomes!

Any crisp and clear advice on this would be greatly appreciated
please, as I need to place an order fast.

Hi...

It's frost free because it auto defrosts

The upside is that you never have frost problems...

The downside is that energy consumption is slightly
increased (the fridge shuts down two or three times a
day and turns on a little electric heater to melt the
ice for a few minutes)

Ken

 

[Terry Pinnell]

Hi...

It's frost free because it auto defrosts

The upside is that you never have frost problems...

The downside is that energy consumption is slightly
increased (the fridge shuts down two or three times a
day and turns on a little electric heater to melt the
ice for a few minutes)

Don, Ken: Thanks both. Apprecaite the fast replies. But I don't see
how to square that with the fact that all the products I've researched
today seem to show these as two *independent* features. That's the
cause of my confusion.

For example, the HOTPOINT FFA70P at
http://www.comet.co.uk/comet/html/cache/30_823026.html
has Frost Free AND Automatic fridge defrost.

But the Bosch BOSCH KGU34124GB at
http://www.comet.co.uk/comet/html/cache/30_202096.html
has Frost Free but NOT Automatic fridge defrost.

 

[Derelict]

Don, Ken: Thanks both. Apprecaite the fast replies. But I don't see
how to square that with the fact that all the products I've researched
today seem to show these as two *independent* features. That's the
cause of my confusion.

For example, the HOTPOINT FFA70P at
http://www.comet.co.uk/comet/html/cache/30_823026.html
has Frost Free AND Automatic fridge defrost.

But the Bosch BOSCH KGU34124GB at
http://www.comet.co.uk/comet/html/cache/30_202096.html
has Frost Free but NOT Automatic fridge defrost.

I have seen two systems at work in modern fridges. One is the heated
defrost (auto defrost). The other is sucking the humid air out of a
freezer every time you close the door (frost free). Make sense?

 

[Don Pearce]

I have seen two systems at work in modern fridges. One is the heated
defrost (auto defrost). The other is sucking the humid air out of a
freezer every time you close the door (frost free). Make sense?

How do they do that? The air sucked out must be replaced by -
presumably - dry air. Where would that come from?

d

Pearce Consulting
http://www.pearce.uk.com

 

[Julie]

How do they do that? The air sucked out must be replaced by -
presumably - dry air. Where would that come from?

No, it creates a partial vacuum. The sound of these freezers is very
distictive -- you hear a sucking sound when you close the door.

 

[Don Pearce]

No, it creates a partial vacuum. The sound of these freezers is very
distictive -- you hear a sucking sound when you close the door.

Are you sure? To be of any use, a partial vacuum would have to be at
least, what? 4psi below atmospheric? Now my fridge door is about 20
inches by 30. That is 600 square inches. Multiply that by 4psi, and it
would take a pull of 2,400 pounds to open the door.

No.

d

Pearce Consulting
http://www.pearce.uk.com

 

[Ken Weitzel]

Are you sure? To be of any use, a partial vacuum would have to be at
least, what? 4psi below atmospheric? Now my fridge door is about 20
inches by 30. That is 600 square inches. Multiply that by 4psi, and it
would take a pull of 2,400 pounds to open the door.

No.

d

Hi Don...

And that would most likely require seals made by NASA - else
the vacuum would leak down quite rapidly anyway...

I have a stand alone chest freezer in the basement... if
you open it to get something, close it, change your mind
and try to open it again - you can't. For a very few
minutes.

In my humble opinion, just a sales gimmick...

Take care.

Ken

 

[Joerg]

Hi Ken,

...(the fridge shuts down two or three times a day and turns on a
little electric heater to melt the
ice for a few minutes)

And that is often done with a lowly electro-mechanical timer. Probably
because it is still a few cents cheaper than electronics. After all, a
CD4060 costs north of 10 cents which would put a dent in the profit
margin on a $1000 fridge/freezer

Regards, Joerg

 

[Terry Pinnell]

Any crisp and clear advice on this would be greatly appreciated
please, as I need to place an order fast.

Still hoping to get that!

 

[Gareth]

Hi Don...

And that would most likely require seals made by NASA - else
the vacuum would leak down quite rapidly anyway...

I have a stand alone chest freezer in the basement... if
you open it to get something, close it, change your mind
and try to open it again - you can't. For a very few
minutes.

In my humble opinion, just a sales gimmick...

My freezer (which is not frost free) does that as well. I think it's
just the warm air which entered the freezer cooling down and contracting.


--

 

[John Woodgate]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp

Hi Ken,


And that is often done with a lowly electro-mechanical timer. Probably
because it is still a few cents cheaper than electronics. After all, a
CD4060 costs north of 10 cents which would put a dent in the profit
margin on a $1000 fridge/freezer

In mine, the heater is just wired across the thermostat contacts: COOL
XOR HEAT at zero cost.

 

[Julie]

Are you sure? To be of any use, a partial vacuum would have to be at
least, what? 4psi below atmospheric? Now my fridge door is about 20
inches by 30. That is 600 square inches. Multiply that by 4psi, and it
would take a pull of 2,400 pounds to open the door.

I was speaking empirically, and not technically, my bad. It looks like I'm
wrong on my assumptions -- I retract my statements.

 

[Tony Williams]

As our current unit is plainly struggling, I'm about to buy a new
frost-free combination fridge/frezer. But I'm confused about one
feature that is offered on some models and not others, namely
'Automatic defrost'. If the product is frost-free, then why would
I ever need to 'defrost' it? And I've seen posts which seem to
imply this feature is undesirable, and that manual defrosting is
preferable. The more I read, the more hazy the issue becomes!

We have three fridge/freezers Terry (don't ask why,
because I don't know).

Two of them are Hotpoint "frost free", and really not
worth the extra money and running costs. Overload
them just slightly, (which hampers the internal air
circulation), and the fridge compartment freezes up
(literally, a solid block of ice), whilst at the same
time everything in the freezer section starts to melt.

Don't bother with frost free.

The third is a Bosch auto-defrost, which works very well.

However I should have bought the more expensive Bosch,
which has separate compressors and thermostats for the
fridge and freezer compartments. That type works better
over a wider range of ambient temperatures.

 

[Terry Pinnell]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp


In mine, the heater is just wired across the thermostat contacts: COOL
XOR HEAT at zero cost.

But unless I've missed something, I've still not had answers to my
original questions. To recap:

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?

 

[Terry Pinnell]

We have three fridge/freezers Terry (don't ask why,
because I don't know).

Two of them are Hotpoint "frost free", and really not
worth the extra money and running costs. Overload
them just slightly, (which hampers the internal air
circulation), and the fridge compartment freezes up
(literally, a solid block of ice), whilst at the same
time everything in the freezer section starts to melt.

Don't bother with frost free.

The third is a Bosch auto-defrost, which works very well.

However I should have bought the more expensive Bosch,
which has separate compressors and thermostats for the
fridge and freezer compartments. That type works better
over a wider range of ambient temperatures.

Thanks, Tony. On the basis of that, plus the fact that our current
ailing Hotpointo suffered identical problems to those you describe,
I've just ordered a Bosch.

 

[John Miller]

But unless I've missed something, I've still not had answers to my
original questions. To recap:

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?

Yes.

Terry --
While I cannot answer your first two exact questions authoritatively, I
would be willing to wager almost any amount that no refrigerator will be
frost free without use of an auto defrost feature.

--
John Miller
Email address: domain, n4vu.com; username, jsm

He is not only dull himself, he is the cause of dullness in others.
-Samuel Johnson

 

[Sam Goldwasser]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp

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.

In mine, the heater is just wired across the thermostat contacts: COOL
XOR HEAT at zero cost.

So you heat your food when the compressor isn't running? 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.

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[Fred Bloggs]

As our current unit is plainly struggling, I'm about to buy a new
frost-free combination fridge/frezer. But I'm confused about one
feature that is offered on some models and not others, namely
'Automatic defrost'. If the product is frost-free, then why would I
ever need to 'defrost' it? And I've seen posts which seem to imply
this feature is undesirable, and that manual defrosting is preferable.
The more I read, the more hazy the issue becomes!

Any crisp and clear advice on this would be greatly appreciated
please, as I need to place an order fast.

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?