Refrigerator monitor ideas?

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.

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).

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

might be a good place to start. Maxim will send you samples free.

Or add a LM34/35/other analog sensor to your Ocelot (or whatever).

Or add a HA7E to your 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

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

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.

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.

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.

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. (-:

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.

with:

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.

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.

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.

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.

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.

Can you get a temperature probe on the coils?

snipped-for-privacy@yahoogroups.com

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.

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.

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.

end of the drain hose. Install a moisture detector in

water in the cup there's a problem.

That's a very good idea. The only problem I see is that the ice dam may be forming even though there's still flow to the pan on the floor. If that's true, and a mere reduction in flow is enough to cause a backup into the coil area, there would still be water in the cup and in the tray, but the volumes would likely be severely reduced.

In the meantime, I'm going to freeze down a CMOS camera and some white LEDs to see if they'll survive in the coil area. The box is still mostly empty and the panels are still unscrewed so I can get to the coils and run some tests.

I suspect that this will end up solved by using an easier to remove winged screw and inspecting the connecting elbow more frequently. But what's the fun in that? One hundred years from now, truly smart homes will take care of all of these issues without involving Rube Goldberg!

-- Bobby G.

Actually, I was thinking more of monitoring the condensor coil temperature which should rise steadily as the efficiency of the evaporator coil is degraded by the ice.

I would think that if the temperature stays above some (unknown) point for some (unknown) time it's a fairly strong indicator that something is amiss. You might even simulate this by leaving the door ajar for awhile to get a temperature profile to compare with a normal profile.

Then the logic is fairly simple. Measure the temperature every n minutes and increment a variable if its above some (unknown) level and reset the variable to zero if it's below that (unknown) level. If the variable reaches x, sound an alarm. You might be able to do this with the logic in an Ocelot (or CPU-XA) although I have to confess I'm not all that familiar with its variables and timers. You might get help on the ADI forum.

I realize this doesn't provide the early warning you desire but I doubt you are going to find any early warning methodology as the condensation will be affected by relative humidity.

snipped-for-privacy@yahoogroups.com

One hundred years from now truly smart homes will float. :(

snipped-for-privacy@yahoogroups.com

I was hoping for something a lot simpler than an Ocelot! The problem is complicated by the fact it's not frequently used for human food. It might take a week before a human would notice something was suddenly "too warm" or at least warmer than usual.

Since this is the dog/science fridge, only my food, my science projects and the dog's food live in there. The great "Active-Eye Cold-Soaking Battery Test" in the kitchen unit banished all science projects to the basement. By the time I drank a canned soda from the downstairs unit and noticed it was too warm, it was too late.

I think you're on the right track, though. What *may* work is a simple LCD thermo with a remote probe and a "max temp" alarm feature. I see them around for $10-15. If I placed the thermistor inside a jug of water at the back of the unit, its location and thermal mass should insulate it from all but the most severe open door or defrost cycle temperature swings. If I set it to just slightly warmer than what it reads as the MAX recorded temp after a few weeks, it should pick up coil anomalies quite fast. When those aluminum tubes and fins get covered with ice, their efficiency plummets.

That's a good point. The unit's in a position where I can easily extend the drain tube beyond the floor pan and into a floor drain. That might reduce the humidity in the summer and give me a visual indication of water flow but unless I armored it, the dogs would eat it. (-:

How do they detect wing icing on airplanes? I remember reading about one design that used an inflatable rubber wing surface that flexed and allowed the ice crack off but I don't recall how they determine wing icing depth. I do seem to recall that Palm 90 crashed here a while back because the pilots didn't know how badly iced they were at the moment of takeoff. I believe someone used diluted deicer that actually froze up on the wing surfaces.

If I really wanted to figure this out, I'd put a temp probe AND an intervalometer camera in the coil area and another temp probe in a water bottle and then correlate various bad events like a plugged drain or a propped open door with coil appearance.

-- Bobby G.

Hi Robert,

I monitor our freezer in the attached garage. I use an Ademco TS300 with a optional remote probe which is inside the freezer. This is a self defrost freezer and so it has a warm period of about 20 minutes each day. I allow for this in my Elk M1G by starting a timer for 30 minutes when the zone alarms. At the end of 30 minutes if the zone is still faulted it beeps the keypads and displays a message and logs the event.

These TS300 sensors show up on eBay every so often (be sure it includes the optional remote probe) and seem to be quite accurate and can be programmed. The have both hi and low alarm setpoints. See link below.

How do they detect wing icing on airplanes?

Simple: They cease to fly. Indicators are all over the cockpit.

Bobby, Bobby, Bobby ...

One of the reasons that it's so hard to help you is that you indulge in hippospeak -- hypothetical hyperbole.

Do you understand that you now claim that your refrigerator uses only (115 x

1/10th time on) = 11.5 watts = 101 kWh/yr ?

There have been several exhaustive studies on energy use of refrigerators. For example, the calculator here:

indicates that a 24-year-old refrigerator (yours is about 30, but the calculator doesn't go that high) used in a heated space as in your case averages about 1,540 kWh/yr. This is 15 times your claimed usage.

And that even a very efficient US Department of Energy 2004 rated top-mount, no through-door ice uses 532kWh/yr (5 times your claim)?

And that your claim that the duty cycle on your refrigerator is 1:9 (ON:OFF) is at odds with (eg) the study by the utility in my metro region that measured in-use performance of about 5,000 actual refrigerators and cit as typical a 20-min ON, 20 minute OFF --> (1:1) duty cycle ?

Because you already have an Ocelot running 24x7, the power needed to do this is less than 1/1000th of what the refrigerator uses even without optimization despite your claim/implication to the contrary. By shutting down power to the sensors when not measuring, you could likely get it down to 1/100,000th. Use reality-based data and the figures will fall into place.

So you are off again into your hypothetical world where few care to follow.

But I'll stick with you long enough to follow through with what is intended to be a useful answer to your question. Conceivably others may benefit even if you don't.

First, since *you* stated that: "... the first clue is that the freezer temperatures begin to rise, and

*you* summarized and ended your long original post 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,

it seems to me that a responsive answer to the question you pose would include temperature measurement despite your rude and incorrect comments. I also suggest that you measure compressor "ON" time and calculate as fraction total time, i.e, duty cycle.

So consider this:

1) Measure the temperature of the freezer compartment (as per your summary) 2) Measure the temperature of the coil 3) Determine fraction "ON" time and duty cycle by detecting power to the compressor in one or more of several possible ways. 4) Use your Ocelot (and therefore analog Lm34/5-style sensors, not 1-wire) for the temperature and duty cycle measurements. 5) Ask your wife to stop fiddling with the thermostat. If she _has_ to turn it up, its probably time to clean/unclog. End of experiment. 6) Make your measurements between 3AM and the earliest anyone uses the fridge each day (say 7AM) to avoid perturbations. The problem presumably takes at least several days to develop. You should be able to figger out how to program your Ocelot in CMAX to do this. If not, ask in the ADI user group.

In brief:

1) manually monitor the temperature for a few of days to get the general range of values for your calculations. This will depend in part on how clean the coils/filter/clog/ is at that time.

2) Program the Ocelot to compute a 'running average' of n measurements by measuring a new T_FreezerNow and computing:

T_NewFreezerAve = (T_FreezerNow + (n-1)*T_FreezerRunAve)/n T_FreezerRunAve = T_NewFreezerAve

3)Determine the duty cycle and(or) percent "ON" time. A study by my utility of 5000 in-use household fridges states that this is typically 20 minutes on, 20 min off, --> 50% duty cycle = 0.50 "ON" fraction.

Trigger whatever you want to trigger (Gong, LED, email, mousetrap) when duty cycle and average temp indicate a problem,

eg: T_NewFreezerAve > 5 degreesF AND Fraction_ON > 0.65

Additionally, if you measure the temperature of the coil that is supposed to be defrosted by melting, if it stays below 32F for an extended period of time, (say 48 hours) it is frosted. That's another condition that you can use to improve your notification algorithm.

Past experience suggests that you will say that you can't/don't/won't know how to do this because of umpteen convoluted reasons including, as you wrote earlier, that the dogs open the refrigerator!

So don't.

Just like you have umpteen convoluted and specious reasons why HA PC's running 24x7 don't work dependably despite not actually having one, and despite extended testimony by those that have been successful that they are dependable.

... Marc Marc_F_Hult

| 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."

Some years ago I made the mistake of replacing a 1959-vintage stainless Tappan with a (supposedly) "top of the line" efficient KitchenAid. The first things I noticed were that the compressor ran almost all the time and the temperature in the refrigerator section varied wildly. It was necessary to tweak the controls depending on ambient temperature and even if you got it right for a particular pattern of use, leaving it for a few days without opening the door would result in things freezing. The repair folks claimed that this was all normal and a result of the high efficiency, achieved in part by sizing the cooling system with minimal capacity required for steady-state operation.

I can buy the efficiency argument, but I'd rather sacrifice a little efficiency to have the reserve capacity to bring the temperature back down quickly. Moreover, the poor temperature regulation was not mainly a function of the "efficient" design. The real problem was that cooling of the refrigerator section was achieved by a constantly running fan that blew cold air from the freezer section through a manually adjusted baffle. The compressor cooled only the freezer directly and was controlled by a thermostat in the refrigerator. Lack of active control of the fan and baffle was bad enough, but to top things off the thermostat was right in the path of the cold air entering the refrigerator from the freezer. All of this struck me more as cost-reduction and poor design than efficiency improvement. That refrigerator lasted about seven years during which an extended service contract (unusually) paid for itself. Every major part (including the compressor at least? once) had to be replaced.

I replaced the KitchenAid with a SubZero which was very expensive but which has entirely separate cooling systems for the refrigerator and freezer sections. In retrospect the Tappan must have been a very clever design. It had only one compressor but there was no air path between (bottom) freezer refrigerator sections. I'm pretty sure that it had coils in both sections, though people keep telling me I must have imagined this. However it worked, it worked well...

Getting back to your problem, I might be inclined to try an electromechanical solution. Could you arrange a slow-moving arm (motor geared way down) in the area where the ice dam forms? When the arm ices up the motor stalls (or a clutch slips) and this can be detected. As a bonus it might help slow the formation of a blockage in the first place.

Dan Lanciani ddl@danlan.*com

Oh give it a rest already.

Do a better job of keeping your house clean. Avoid the crud getting in their entirely. What better non-technical solution could be devised to stave off the dirt collecing in the first place? Or altering the drain setup such that it better handles the crud.

Frankly I'd just get rid of the dog and solve the whole problem.

If you're as suspicious as you claim to be then you wouldn't trust that meter.

I thought you were claiming in the good old days they made stuff that didn't crack?

Your furnace can do this because it's already moving air and can detect the blockage. A passive drain doesn't afford the same option. I think Bass made a good suggestion, a pair of moisture sensors, one at the top and the other at the bottom of the drain tube. If there's water at the top and not at the bottom then you've got a problem. And if the water's below a certain temperature it'd be a sign there's possible freezing developing. Is water not moving or is it too cold? If either of those conditions is true then you'd got a problem. I'd think a threshold on the temperature could likewise be an early warning indicator but then I don't know how fast it freezes up.

Yeah, there's probably a grain of truth to the notion of continuing to use an existing device instead of a new one. But I doubt it. Besides, if you keep using that same one you're depriving the industries and all their employees of work. Gotta keep those wheels turning, right?

-Bill Kearney

Even if the original poster doesn't have a full automated system, your "window to ignore the sensor" approach could be useful. Just set up a timer that ignores the temperature alarm for a window or even that only looks at it for a short time each day.

However, the poster said that this problem has happened several times in the last 10 years. Would not an occasional inspection and cleaning work for a lot less hassle?