Refrigerator monitor ideas?

We've got a 30 year old White-Westinghouse refrigerator/freezer in the
basement that's cosmetically shot, but still humming away, delivering
subzero temperatures in the icebox without major incident for years.

Several times in the past 10 years or so, the drain tube from the pan under
the freezer coils (it's an upright with a top freezer) has clogged, leading
the coils to become caked in ice. When this happens, the first clue is that
the freezer temperatures begin to rise. Other than placing a sight glass in
the freezer floor pan, what are some simple options to detect a coil
freeze-up condition. I had previously had this on a yearly inspection
schedule but the addition of a number of shedding dogs to the house in
recent months has made that too infrequent a cycle.

What I would really like to do is design something simple that can catch the
formation of serious ice long before the coil became caked. Simple
temperature sensing is inadequate because the self-defrosting feature causes
a sharp upward swing every night.

The conditions that occur during a "freeze-up" (in addition to an overall
increase of average freezer temperature each day it's building up) are that
very little water reaches the evaporation pan at the bottom of the fridge.
But checking that pan is about as inconvenient as unscrewing the drain tube
connector that runs from the center top of the refrigerator to the backwall
where it meets a drain tube that empties into the floor pan for evaporation.

One thought that had occurred was to modify the drain tube to include an
aspirin sensor between two spring loaded contacts at the top portion of the
tube. But I am not sure that would work because the typical mode of failure
is an ice dam that occurs at the drain hole. I would suspect that before
that happens, the entire drain tube in filled with water, but I can't say
for sure.

Probably the most convenient solution would be to stick a $12 CMOS board cam
in a baggie with some white LEDs to use as a video inspection port for the
evaporator tray on the floor. I'd only have to power it up during
inspection times, so it wouldn't require a device that consumed power 24/7.
Any monitoring of the temperature changes will likely involve a lot more
power consumption than a video inspection "port" would. On the other hand,
the video evaporator inspection method probably won't tell me the coils have
frozen until it's too late.

What I really want to know is when 5 on the freezer control no longer means
an average of X temperature in the freezer compartment.

--
Bobby G.

Robert,

A temperature monitor in the freezer itself will warn of problems from multiple causes. Additionally, consider placing a couple of
slow-release algaecide tablets in the pan. Algae is a common cause of clogged drains under fridges, freezers and A/C air handlers.
Our service drops a couple of tablets in the pan under each air handler several times a year and that seems to keep the pipes clear.

--

Regards,
Robert L Bass

=============================>
Bass Home Electronics
941-866-1100
4883 Fallcrest Circle
Sarasota · Florida · 34233
http://www.bassburglaralarms.com
=============================>

"Robert Green" <ROBERT_GREEN1963@YAH00.COM> wrote in message news:yZadnSuqcufcxl7YnZ2dnUVZ_qWvnZ2d@rcn.net...
> We've got a 30 year old White-Westinghouse refrigerator/freezer in the
> basement that's cosmetically shot, but still humming away, delivering
> subzero temperatures in the icebox without major incident for years.
>
> Several times in the past 10 years or so, the drain tube from the pan under
> the freezer coils (it's an upright with a top freezer) has clogged, leading
> the coils to become caked in ice. When this happens, the first clue is that
> the freezer temperatures begin to rise. Other than placing a sight glass in
> the freezer floor pan, what are some simple options to detect a coil
> freeze-up condition. I had previously had this on a yearly inspection
> schedule but the addition of a number of shedding dogs to the house in
> recent months has made that too infrequent a cycle.
>
> What I would really like to do is design something simple that can catch the
> formation of serious ice long before the coil became caked. Simple
> temperature sensing is inadequate because the self-defrosting feature causes
> a sharp upward swing every night.
>
> The conditions that occur during a "freeze-up" (in addition to an overall
> increase of average freezer temperature each day it's building up) are that
> very little water reaches the evaporation pan at the bottom of the fridge.
> But checking that pan is about as inconvenient as unscrewing the drain tube
> connector that runs from the center top of the refrigerator to the backwall
> where it meets a drain tube that empties into the floor pan for evaporation.
>
> One thought that had occurred was to modify the drain tube to include an
> aspirin sensor between two spring loaded contacts at the top portion of the
> tube. But I am not sure that would work because the typical mode of failure
> is an ice dam that occurs at the drain hole. I would suspect that before
> that happens, the entire drain tube in filled with water, but I can't say
> for sure.
>
> Probably the most convenient solution would be to stick a $12 CMOS board cam
> in a baggie with some white LEDs to use as a video inspection port for the
> evaporator tray on the floor. I'd only have to power it up during
> inspection times, so it wouldn't require a device that consumed power 24/7.
> Any monitoring of the temperature changes will likely involve a lot more
> power consumption than a video inspection "port" would. On the other hand,
> the video evaporator inspection method probably won't tell me the coils have
> frozen until it's too late.
>
> What I really want to know is when 5 on the freezer control no longer means
> an average of X temperature in the freezer compartment.
>
> --
> Bobby G.
>
>
>

On Fri, 2 Feb 2007 10:34:56 -0500, "Robert Green"
<ROBERT_GREEN1963@YAH00.COM> wrote in message
<yZadnSuqcufcxl7YnZ2dnUVZ_qWvnZ2d@rcn.net>:

>We've got a 30 year old White-Westinghouse refrigerator/freezer in the
>basement that's cosmetically shot, but still humming away, delivering
>subzero temperatures in the icebox without major incident for years.
>
>Several times in the past 10 years or so, the drain tube from the pan under
>the freezer coils (it's an upright with a top freezer) has clogged, leading
>the coils to become caked in ice. When this happens, the first clue is that
>the freezer temperatures begin to rise. Other than placing a sight glass in
>the freezer floor pan, what are some simple options to detect a coil
>freeze-up condition. I had previously had this on a yearly inspection
>schedule but the addition of a number of shedding dogs to the house in
>recent months has made that too infrequent a cycle.
>
>What I would really like to do is design something simple that can catch the
>formation of serious ice long before the coil became caked. Simple
>temperature sensing is inadequate because the self-defrosting feature causes
>a sharp upward swing every night.
>
>The conditions that occur during a "freeze-up" (in addition to an overall
>increase of average freezer temperature each day it's building up) are that
>very little water reaches the evaporation pan at the bottom of the fridge.
>But checking that pan is about as inconvenient as unscrewing the drain tube
>connector that runs from the center top of the refrigerator to the backwall
>where it meets a drain tube that empties into the floor pan for evaporation.
>
>One thought that had occurred was to modify the drain tube to include an
>aspirin sensor between two spring loaded contacts at the top portion of the
>tube. But I am not sure that would work because the typical mode of failure
>is an ice dam that occurs at the drain hole. I would suspect that before
>that happens, the entire drain tube in filled with water, but I can't say
>for sure.
>
>Probably the most convenient solution would be to stick a $12 CMOS board cam
>in a baggie with some white LEDs to use as a video inspection port for the
>evaporator tray on the floor. I'd only have to power it up during
>inspection times, so it wouldn't require a device that consumed power 24/7.
>Any monitoring of the temperature changes will likely involve a lot more
>power consumption than a video inspection "port" would. On the other hand,
>the video evaporator inspection method probably won't tell me the coils have
>frozen until it's too late.
>
>What I really want to know is when 5 on the freezer control no longer means
>an average of X temperature in the freezer compartment.

FWIW, a major effort nationwide by utilities is to encourage folks to
properly dispose of inefficient 'garage' refrigerators.

The power consumption for a modern monitoring system could trivially made to
be 1/1000 or less of what the fridge consumes so your concern for the power
consumption of the monitoring system is puzzling (to me).

<ROBERT_GREEN1963@YAH00.COM> BobbyG summarized/ended his post/question with:

"What I really want to know is when 5 on the freezer control
no longer means an average of X temperature in the freezer
compartment.

Why don't you do just that by leaving the dial set at 5 and measuring the
temperature with any of a bajillion different ways discussed in this
newsgroup?

A Dallas/maxim 1-wire-wire interface from www.PHAnderson.com might be a good
place to start. Maxim will send you samples free.

http://para.maxim-ic.com/index.mvp?tree=1wire


Or add a LM34/35/other analog sensor to your Ocelot (or whatever).
http://catalog.national.com/Cat/jsp/national.jsp?i=71

Or add a HA7E to your www.Homeseer.com setup and have the computer email you
the temperature or call you on your cell phone.

There was a post a while back in comp.home.automation by an Australian feller
who wanted to hook up his beer still to his refrigerator and then (based on
the tenor of his posts) directly to a gastric feeding tube -- or something
like that ;-) IIRC, there was some useful discussion in those threads about
1-wire temperature measurement.

.... Marc
Marc_F_Hult
www.ECOntrol.org

"Robert L Bass" <no-sales-spam@bassburglaralarms> wrote in message
news:89-dnWxAS6TJD17YnZ2dnUVZ_uCinZ2d@comcast.com...
> Robert,
>
> A temperature monitor in the freezer itself will warn of problems from
multiple causes.

By time a temperature monitor alerts me, the coil is usually a solid block
of ice. That means the solution is not just unplugging the unit for a few
hours, it's pulling the floor of the freezer compartment and pouring hot
water over the coils until the ice melts. I've even made a hot water
"enema" out of a soda bottle and some surgical tubing to insert into the
frozen drain hole to clear it. It's very messy, though. To catch the
beginning of an "ice up" via temp. monitor I would have to be able to
calculate the average daily temperature (when running correctly) and then
look for upward trends. That gets complicated very quickly and has two
problems. One is that it will likely take a PC to process the data. The
other is that any change of the freezer control dial will affect the
system's balance. I'd also have to account for the brief upward temperature
bursts each time the door is opened.

The most critical place to look is the connector from the bottom of the
freezer pan that goes to the drain hose at the back. It has a little
plastic tab in the center of the hole designed to keep large items from
going into the drain tube. That's where all the dog hair matted together
and formed a blockage. A sensor there might be able to tell me when a clog
had formed. When the clog does form, water no longer reaches the rear hose
nor the evaporator pan on the floor. That's a condition that's probably
easier to check.

Since reefer condensate lines are gravity-operated, there's not much hope of
using a filter on the existing small diameter hose unless I can find a
filter that's got two small openings and a huge filter compartment.
Cosmetics are not a great issue in this particular icebox. With a large
filter area, there's a lot less chance of a clog forming

> Additionally, consider placing a couple of slow-release algaecide tablets
in the pan.
> Algae is a common cause of clogged drains under fridges, freezers and A/C
air
> handlers.

The freeze-up is occurring very high up in the system, right where the
freezer drain empties into the connector at the top of the refrigeration
compartment. That connector goes from the drain at the bottom of the
freezer pan to the drain hose that runs down the back of the unit.

I'm assuming when dog hair builds up at the tab in the connector (as it's
designed to do) it eventually causes the condensate water to back up into
the freezer drain plug where it freezes. When that happens, each defrost
cycle adds more and more ice to the frozen coils. I want to detect when the
ice dam at the drain *first* appears when treatment involves just removing
the freezer pan-to-drain tube connector and cleaning it. The solution
might just be to increase inspection rates, but I'd rather have some sort of
warning system.

> Our service drops a couple of tablets in the pan under each air handler
several times
> a year and that seems to keep the pipes clear.

This problem, as I said, is far upstream of the pan on the floor. It used
to occur every few years and yearly inspection took care of it. Now that my
wife's in the dog rescue business (and business is booming now that all the
Christmas puppies are being taken to the pound!) there's lots and lots of
dog hair around that didn't used to be. Couple that with the location in
the basement and our house's proximity to a major thoroughfare and you can
see why I am pretty confident algaecide won't be helpful although improved
air cleaning near the box might. The big problem with the floor evaporator
pan is all the calcium that builds up over time, but a little vinegar clears
that right up.

--
Bobby G.

> We've got a 30 year old White-Westinghouse refrigerator/freezer in the
> basement

Dude, with the time you've wasted already you could've just bought a
replacement fridge or at least had an AC professional come out and fix it.

Seriously, I have to wonder how inefficient that thing is as well. The
money wasted just running it is probably more than it'd cost to get a new
one.

"Marc_F_Hult" <MFHult@nothydrologistnot.com> wrote in message
news:ea37s2dv2rfvuerdu9oetv2daa6mouai86@4ax.com...
>
>
> On Fri, 2 Feb 2007 10:34:56 -0500, "Robert Green"
> <ROBERT_GREEN1963@YAH00.COM> wrote in message
> <yZadnSuqcufcxl7YnZ2dnUVZ_qWvnZ2d@rcn.net>:
>
> >We've got a 30 year old White-Westinghouse refrigerator/freezer in the
> >basement that's cosmetically shot, but still humming away, delivering
> >subzero temperatures in the icebox without major incident for years.
> >
> >Several times in the past 10 years or so, the drain tube from the pan
under
> >the freezer coils (it's an upright with a top freezer) has clogged,
leading
> >the coils to become caked in ice. When this happens, the first clue is
that
> >the freezer temperatures begin to rise. Other than placing a sight glass
in
> >the freezer floor pan, what are some simple options to detect a coil
> >freeze-up condition. I had previously had this on a yearly inspection
> >schedule but the addition of a number of shedding dogs to the house in
> >recent months has made that too infrequent a cycle.
> >
> >What I would really like to do is design something simple that can catch
the
> >formation of serious ice long before the coil became caked. Simple
> >temperature sensing is inadequate because the self-defrosting feature
causes
> >a sharp upward swing every night.
> >
> >The conditions that occur during a "freeze-up" (in addition to an overall
> >increase of average freezer temperature each day it's building up) are
that
> >very little water reaches the evaporation pan at the bottom of the
fridge.
> >But checking that pan is about as inconvenient as unscrewing the drain
tube
> >connector that runs from the center top of the refrigerator to the
backwall
> >where it meets a drain tube that empties into the floor pan for
evaporation.
> >
> >One thought that had occurred was to modify the drain tube to include an
> >aspirin sensor between two spring loaded contacts at the top portion of
the
> >tube. But I am not sure that would work because the typical mode of
failure
> >is an ice dam that occurs at the drain hole. I would suspect that before
> >that happens, the entire drain tube in filled with water, but I can't say
> >for sure.
> >
> >Probably the most convenient solution would be to stick a $12 CMOS board
cam
> >in a baggie with some white LEDs to use as a video inspection port for
the
> >evaporator tray on the floor. I'd only have to power it up during
> >inspection times, so it wouldn't require a device that consumed power
24/7.
> >Any monitoring of the temperature changes will likely involve a lot more
> >power consumption than a video inspection "port" would. On the other
hand,
> >the video evaporator inspection method probably won't tell me the coils
have
> >frozen until it's too late.
> >
> >What I really want to know is when 5 on the freezer control no longer
means
> >an average of X temperature in the freezer compartment.
>
> FWIW, a major effort nationwide by utilities is to encourage folks to
> properly dispose of inefficient 'garage' refrigerators.

Oh yeah, my utility is my friend and *always* wants the best for me. Arf
arf! You and Bill are always so quick to spend MY money. (-:

> The power consumption for a modern monitoring system could trivially made
to
> be 1/1000 or less of what the fridge consumes so your concern for the
power
> consumption of the monitoring system is puzzling (to me).

Monitoring system? You've completely missed the main points of the original
specs. I want to know when the starts freezing up. 112W divided by 1000 is
about 1/10 of a watt? What kind of temperature montoring AND evaluation
system are you proposing that consumes less that 1/10 of a watt? Or are you
leaving out what I need to do with the temperature information to make it
useful in the context of the original question?

Further, assuming the box only draws 112 watts when the compressor is
running, you probably need to divide your 1/1000 number by another 10 to
give 1/100 of a watt. How does this 1/100 watt device render useful
information about impending coil-freezeups? Keep in mind, Marc, my original
spec called for something *simple*!

I want to know when the coil has frozen and/or water is not draining into
the pan beneath the unit.

> <ROBERT_GREEN1963@YAH00.COM> BobbyG summarized/ended his post/question
with:
>
> "What I really want to know is when 5 on the freezer control
> no longer means an average of X temperature in the freezer
> compartment.
>
> Why don't you do just that by leaving the dial set at 5 and measuring the
> temperature with any of a bajillion different ways discussed in this
> newsgroup?

And what mechanism correlates temperature to dial to tell me if my wife has
turned up the control as opposed to the temperature rising as a result of a
coil freezeup? Simple temperature readout can be achieved with a $10 LCD
thermometer pasted to the side but it requires continuous inspection AND
interpretation. Those sytems probably consume 1/100 of watt but they don't
tell me if my wife's changed the dial, if the dog's opened the door, if the
machine's in a defrost cycle, the compressor has failed or if the coil froze
up. Remember my original specs. I want to know when the automatic defrost
system has been compromised by dirt in the drain tube. I'd like to do it
automatically, but it seems that the best I can do it to inspect and clean
it with a greater frequency. That consumes zero watts. Well, maybe just a
few if I keep the door open too long when I disconnect the tube.

> A Dallas/maxim 1-wire-wire interface from www.PHAnderson.com might be a
good
> place to start. Maxim will send you samples free.
>
> http://para.maxim-ic.com/index.mvp?tree=1wire

I'm well aware of that option. What that *doesn't* provide is anything more
than a $10 LCD thermometer with a remote probe would. It's not necessarily
useful to solving the problem I outlined in my OP.

> Or add a LM34/35/other analog sensor to your Ocelot (or whatever).
> http://catalog.national.com/Cat/jsp/national.jsp?i=71
>
> Or add a HA7E to your www.Homeseer.com setup and have the computer email
you
> the temperature or call you on your cell phone.

No, not what I want. I only want to know when ice has formed on the coil.
As I mentioned in the OP, that occurs when the drain tube gets plugged.
Your suggestions would lead to an enormous number of false alarms and would
require an awful lot of intelligent processing to meaningfully indicate a
simple coil freezeup or stuck drain tube.

> There was a post a while back in comp.home.automation by an Australian
feller
> who wanted to hook up his beer still to his refrigerator and then (based
on
> the tenor of his posts) directly to a gastric feeding tube -- or something
> like that ;-) IIRC, there was some useful discussion in those threads
about
> 1-wire temperature measurement.

Crikey, mate, you're not poking a mullock at our Bazzaland brethren, are
you? Careful, seppo! (-:

You've settled on temperature measurment as the cure but it's neither simple
nor cheap and it's eventually not very useful in detecting coil freezeups.
The temperature of a frost-free freezer compartment can vary wildly and yet
still be operating without any problems like coil freeze-up. That makes
temperature monitoring not nearly as useful as some of the other options I
have.

The $20 microcam with some white LED's located so that it can reveal whether
there's water in the floor level evaporator pan or not would take an hour or
so to fabricate and install and could be plugged into a spare MUX input.
The camera solution, while cheap and easy is still not what I really want.

The best solution would be something that tells me either the drain line is
plugged or the coil is frozen by sounding a sonalert or closing alarm
contacts when either condition is detected. There's probably a commericial
solution somewhere because we had plenum AC at work that overflowed in the
same way and ruined a ton of IT equipment. The replacement unit had both an
extra "catch tray" and a system of failure alarms including a dialout
warning system.

--
Bobby G.

> When the clog does form, water no
> longer reaches the rear hose nor the
> evaporator pan on the floor...

Bingo! Here's a simple solution. Rig a small, loosely covered cup to the end of the drain hose. Install a moisture detector in
the cup and another in the pan. Any time there is water in the pan but no water in the cup there's a problem.

--

Regards,
Robert L Bass

=============================>
Bass Home Electronics
941-866-1100
4883 Fallcrest Circle
Sarasota · Florida · 34233
http://www.bassburglaralarms.com
=============================>

"Robert Green" <ROBERT_GREEN1963@YAH00.COM> wrote:

>What I would really like to do is design something simple that can catch the
>formation of serious ice long before the coil became caked. Simple
>temperature sensing is inadequate because the self-defrosting feature causes
>a sharp upward swing every night.

Can you get a temperature probe on the coils?

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-subscribe@yahoogroups.com

"Bill Kearney" <wkearney-99@hot-mail-com> wrote in message
news:SeudnWXgAvd_J17YnZ2dnUVZ_qOpnZ2d@speakeasy.ne t...
> > We've got a 30 year old White-Westinghouse refrigerator/freezer in the
> > basement
>
> Dude, with the time you've wasted already you could've just bought a
> replacement fridge or at least had an AC professional come out and fix it.

Geez, dude. I *did* have a professional come out to look at it when we
first moved in. He absolutely assured me the compressor was shot and I
needed either a new compressor or a new refrigerator. I was going to scrap
it at that point, but I took it apart, noticed the coil freezeup, cleaned
the stuck drain tube and let it sit. When I started it up again a day later
it was fine. So much for the advice of "professionals."

I'm also not quite sure how you assume I've *wasted* $600-$800 doing an
occasional cleanout but I can assure you it's not a valid estimate. It's a
hour long project and I've had to do it perhaps four times in ten years. If
I had checked the drain tube more frequently, I would never have had to do
it at all. Hence, I am looking for a way to build a *simple* sensor that
would alert me to a drain tube failure. I wouldn't be surprised if other
pet owners had similar problems with refrigerators of ANY vintage. It's
endemic to narrow tubing, gravity feed water systems and airborne dust and
hair.

I may sound harsh, but I think you've missed the entire gist of my message.
I *know* what causes the problem. I also believe that a new $6-800 box
would be just as susceptible to the clogging problem as the old one and end
up as an *entire* waste of my money. I would also be adding a perfectly
serviceable machine to the growing junkpile of the world, and that's an
insult to the environment. Would the energy saving offset the cost to the
environment of making another refrigerator? All of those "savings analyses"
seem to conveniently ignore that it takes an *awful* lot of industrial plant
electricity to make that second, high EER refrigerator you want me to buy.

I'm always astounded at how many purely technical questions get responses
that either end up as lifestyle critiques or miss the point of the original
post completely. This is how *I* choose to spend my time. It really
shouldn't become a subject in a purely technical request for input and
ideas.

Let's exit this excursion from the original specifications by restating my
requirements. I am looking for a way to detect an "out of normal"
coil-freeze condition that indicates a problem is occurring. The same coil
"freeze-up" problem, BTW, can be induced in even modern refrigerators by
simply leaving the freezer door open long enough. While it may seem that
throwing money at this problem will fix it, I'm pretty sure it won't have
any effect other than to make me poorer and the world's junkpile a little
bigger.

My choices appear to be:

1) to eliminate the dog hair that eventually clogs the drain tube,

2) detect a dirt or ice dam forming in the condensate pathway or

3) take the increased airborne hair load into account and revise my
maintenance cycle.

> Seriously, I have to wonder how inefficient that thing is as well. The
> money wasted just running it is probably more than it'd cost to get a new
> one.

You buy, you bring it and YOU install it and I'd be happy to keep my dog
food and frozen dinners in it. (-: In the meantime, I hope other
respondents stick to the requirements document, i.e. my original post. I
posted with the hope of entertaining possible *simple* technical solutions
to a simple, well-known problem before it occurs, not a analysis of my
choice to wring as much life out of something as I can before I deadline it.
I guess that's old school, but that's my choice.

My wattmeter tells me it draws 112 watts when running. That's far less that
the total of all my automation gear. I've always been suspicious of how
much money a new, more energy efficient *anything* will save me. Why?
Because I've seen the "funny math" that CF bulb makers use to show how much
money CF's save. I *know* those claims have proved wildly inaccurate in my
house. More importantly I have absolutely *no* faith that any new
refrigerator I bought today would *last* 30 years. My personal experience
with newer vintage major appliances is that they fail far more frequently
and catastrophically than older ones. So I'm assuming in 5 to 10 years I'll
be either buying a replacement unit or spending hundreds for a new
compressor. All that money and effort to cure a problem that likely effects
every refrigerator/freezer unit ever made. No thanks!

New reefers as large as the one in the basement are from $600 to $800+. I'd
also have to remove a door and the basement handrails to exchange it and
drag it up the stairs and a new one down the stairs. No thanks! It would
also be naive to think that a new box will run trouble-free.

One reason I am happy to keep this old basement unit running is that stuff
made 30 years ago was made with lots of metal in the mechanicals and not
with cheap plastic that becomes brittle over time. Older appliances were
over-engineered and built to last. The fact that my White-Westinghouse is
running and still able to generate subzero temps is a testament to that
fact.

The dogs don't seem to mind that the plastic interior is cracked. I don't,
either. It keeps the dog food cold and the long term frozen stuff
well-frozen and that's all I ask of it. I'm going to attach the Kill-o-Watt
to it and run it for a week. That will give me some idea of where the
breakpoint in KwH's v. new box cost lies.

But all that's pretty much irrelevant to the question I was asking: I want
a simple way to be warned when the drain tube connector clogs with dog hair
and dust. That's a pretty simple *technical* request. It might even
produce a useful idea for others who've had drain tube clogs even in the
high efficiency, $1000 boxes. My furnace filter whistles when it gets
clogged. I want my refrigerator condensate "filter" to chirp or close a set
of contacts when *it* is clogged.

--
Bobby G.

"Dave Houston" <nobody@whocares.com> wrote in message
news:45c40e48.1182409093@nntp.fuse.net...
> "Robert Green" <ROBERT_GREEN1963@YAH00.COM> wrote:
>
> >What I would really like to do is design something simple that can catch
the
> >formation of serious ice long before the coil became caked. Simple
> >temperature sensing is inadequate because the self-defrosting feature
causes
> >a sharp upward swing every night.
>
> Can you get a temperature probe on the coils?

Yes. I thought of that but the problem there is I would have to probably
artificially freeze the coil once or twice to make sure the readings
corresponded to a freeze-up event! I've monitored unit once upon a time
with Ratshack multimeter with an RS232 port (one of the most useful analysis
tools around considering the cost) and a thermistor taken from an LCD
thermometer whose display went flaky.

Anyway, IIRC there were lots of variations in coil temperature due to door
openings, defrost cycles, power blips and more. I'm assuming that your idea
is to look for constant 32F readings on the coil indicating that it's a
block of ice. That implies a control system of some complexity, doesn't it?
If I could find a cheap used pen recorder I'll bet that coil freeze-ups
would appear distinctly differently after a few days of icing but that's
still too late. The ideal time to stop it is before an ice dam forms.

I may be stuck on the wrong vector, but I think the simplest system to
implement is one that detects a change in the water flow in the tube. Since
it's gravity fed, that makes sensing flow pretty delicate. Worse, still,
there are times when the tube is full (towards the end of the defrost cycle)
and times when it's dry. But the heart of the problem is reduced flow
through the drain tube that causes an ice dam to build up at the bottom of
the freezer pan and that seems the best place to direct my detection
efforts.

Now that I think about it, the coil is the right place to look but the probe
should be a videocam, not a thermistor. With a small board cam and LED I
could actually see the condition of the coils! The question is whether the
electronics will work when frozen but that's easy enough to test.

If they don't, the cheap CMOS camera and some white LEDs in a baggie will
help. The real problem is that inspecting both the floor tray and the drain
tube "shuttle" connector requires a lot of bending that an old back injury
finds particularly loathsome. If I put an ugly winged screw instead of the
Phillips head screw that now secures the shuttle piece, I can probably
remove, inspect and clean it without have to bend too awkwardly to reach it.
To their credit, they designed the connector so that it WOULD clog first by
inserting a "snag" in the center of the tube. They could have just used an
elbow or buried the whole thing in the walls of the unit and then clogs
would likely form wherever the tube bent the most.

I think I need to detach the shuttle connector and photograph it so people
can see what I am talking about. If the water always trickles out and never
reaches the top of the shuttle trough, an immersion-type water sensor might
do the trick.

Gee, George, ain't ya gonna lecture me about how bad I am for wanting to
keep that smelly old thing? (Apologies to J. Steinbeck) (-:

--
Bobby G.