Condar Temp Probe vs. The Thermocouple...

[WES999]

Ok, here is the results everyone has been waiting for.

Pen sent me on of his Condar probe type thermometers.
This model is basically a by-metal spring type thermometer (like the magnetic ones that you would put on the stove top), with a metal rod that protrudes in to the flue.

One thing, the probe Pen sent me was the one that arrived to him damaged. Pen unbent the dial face but the pointer looks like it may be slightly bent. The pointer seems to be a bit toward the cooler side, so a undamaged one may possibly be less accurate than this one.

I installed the Condar right next to the thermocouple on the single wall pipe of my Fisher stove. I tried to have the temp stable on the controller to allow for the slower response of the Condar when I recorded my readings.

What I found was the Condar was reading 100 °F to 200 °F higher than the thermocouple.

Her are some readings:

Thermo Condar
600 700
650 800
750 900
800 1000

The Condar is more accurate at lower temp and gets less accurate as temp increases.

All in all, I would say for the price it's probably good enough to give a reasonable approximation of flue temp, but certainly not a substitute for a thermocouple type probe.

 

[Todd]

Thanks Wes. I knew these probes seemed to read high. I see you have an external there as well, was it pretty much reading half of what the probe was? Mine reads double til the temps get up over 800 then it seems to run away from my external.

 

[ggans]

Where did you get that alarm..

 

[WES999]

The one in the pic is from IMS co. , they are kind of expensive about $300 without a thermocouple.
I built my own for about half the cost.

 

[ggans]

Nice.. thanks..

 

[pen]

That is pretty much exactly what we figured it was doing.

Thanks for the conclusive test at high temps.

The needle on my other probe appears to be pointing straight towards the center of the probe (perpendicular) on the left side and tipped to the left on it's right side.

I hope condar gets back to me soon.

pen

 

[Peter B.]

Thanks pen and Wes for setting up the test...

Pretty much confirms the suspicions I had but couldn't prove.

I guess it's not 'definitive' since it was only a sample of one Condar probe, but a few other people have reported high readings with the FluGard, so there does appear to be a pattern.

Seems to me Condar must be aware of this... or you'd think they ought to be if they test an occasional probe that comes off the line.

I'm still curious to hear what they'll have to say.

Strikes me that there might be a market for <accurate> probes.

Peter B.

------

 

[pen]

Thanks pen and Wes for setting up the test...



I guess it's not 'definitive' since it was only a sample of one Condar probe, but a few other people have reported high readings with the FluGard, so there does appear to be a pattern.



Peter B.

------

No not definitive, but remember, the probe that Wes tested was the first damaged one that was sent to me. I received a replacement because of the squished face. Both thermometers read identically. Again, not conclusive, but I am confident that if I put my "pretty" probe in the same test that Wes did, it would read exactly the same.

pen

 

[Peter B.]

Thanks pen and Wes for setting up the test...



I guess it's not 'definitive' since it was only a sample of one Condar probe, but a few other people have reported high readings with the FluGard, so there does appear to be a pattern.



Peter B.

------

No not definitive, but remember, the probe that Wes tested was the first damaged one that was sent to me. I received a replacement because of the squished face. Both thermometers read identically. Again, not conclusive, but I am confident that if I put my "pretty" probe in the same test that Wes did, it would read exactly the same.

pen

pen:

I wasn't disputing or doubting...

On the contrary, I'm pretty much convinced my own FluGard reads 200* or more high at temps above 500*.

Wes' test and others reporting high readings all seem to bear out what I've observed myself.

Peter B.

-----

 

[pen]

Thanks pen and Wes for setting up the test...



I guess it's not 'definitive' since it was only a sample of one Condar probe, but a few other people have reported high readings with the FluGard, so there does appear to be a pattern.



Peter B.

------

No not definitive, but remember, the probe that Wes tested was the first damaged one that was sent to me. I received a replacement because of the squished face. Both thermometers read identically. Again, not conclusive, but I am confident that if I put my "pretty" probe in the same test that Wes did, it would read exactly the same.

pen

pen:

I wasn't disputing or doubting...

On the contrary, I'm pretty much convinced my own FluGard reads 200* or more high at temps above 500*.

Wes' test and others reporting high readings all seem to bear out what I've observed myself.

Peter B.

-----

I am truly disappointed I can tell you that. I really don't understand why they are so off. The mechanics are quite simple, but most importantly, consistent! I am consistently getting results that don't match the readings on the face, by the same amounts. This means that the error could be fixed by changing the scale on the dial.

Seems like a simple solution to me.

I really wish they'd respond as I am anxious to hear their explanation.

pen

 

[Peter B.]

I don't mean to be pouring gasoline on the flames, but...

The high reading tendency appears to be shared by Condar's (2009 issue, 4") cat probes as well... which are generally 'in agreement' with the FluGard.

I have a cat probe located immediately above the catalyst itself... and I don't get reliable light-off until the probe reads about 1000*... some 300-400 degrees higher than the presumed actual light-off temp.

And yeah, I'm disappointed too.

Since with my stove I can't see either the fire or the cat in operation, pretty much my only guide(s) for monitoring the stove are thermometers... so I tend to rely on them more than someone who has visual cues from the fire itself.

And constantly having to 'extrapolate' actual temps from inaccurate thermometer readings is pretty annoying, frankly.

I'd gladly pay twice what the Condars cost me if I could rely on the readings.

Peter B.

-----

 

[Highbeam]

We can play with percentages now.

So when the condar reads 1000 the actual temp is 800. This means the gauge reads 25% more than 800 or it is off by 25%. I suspect that when the internal temps really do approach 1000 that the error is even higher. The gauge should read accurately over the normal operating range of a flue which is room temp to 1000. After 1000 I could learn to live with an error since I hope to never go that high and once I do it is not too important what the actual temp is.

So perhaps it is a 30% error at 1000 true temp. That doesn't quite jive with the specified "less than 5% error" on the documents.

I am glad that the low end is more accurate since that is the creosote stage and the high end is conservative which may be intentional. The manner in which this meter is inaccurate reeks of a liability lawyer.

 

[pen]

The box says to add 6% to the value shown on the thermometer for horizontal installations, just to make matters even worse.

pen

 

[jasong]

I have a Condar flueguard probe and digital thermocouple alarms on stove and flue. What I have seen with the Condar is that it is extremely slow on how fast it registers on the dial. The digital one is pretty much instantaneous and can be several hundred degrees hotter than the condar when starting up. Once the fire is established and I close the air and the fire stabilizes the Condar will catch up and show what the digital thermometer shows. Even on a slow die down of the fire the Condar will register 30 or so degrees higher due to how slow it registers. When I got the Condar I stuck it in the oven to check its accuracy. It was off so I loosened the nut on the face and adjusted the dial to match the oven temperature.

 

[Highbeam]

"When I got the Condar I stuck it in the oven to check its accuracy. It was off so I loosened the nut on the face and adjusted the dial to match the oven temperature."

That's really too bad. It is not proper to adjust it that way since the condar is NOT an oven thermometer. However, using your thermocouple you could do a good job of adjusting it. Was it pretty easy to spin the face of the condar?

 

[jasong]

I needed a good steady heat source that I new the temperature of. It worked well. It was kind of a pain. when it's loosened you can match the dial to the actual temperature. It was a little hard to hold it in place while tightening it back down.

 

[pen]

Here is the response.

Wes, I am writing a reply now and will be using your readings also.

Dear Matt,



I’m sorry it’s taken a few extra days to get an answer to you, but I was out of town most of last week. Mike Whitt told me he did speak with you on the phone. I think I can answer most of your questions in both your emails.



First let me explain how our probe functions. The probe obviously is heated inside the fluepipe and the heat is conducted the length of the probe itself. The bimetallic coil is located outside the fluepipe, separated by the rivet collar and magnet (you should be using those). It’s obvious the highest temp is inside the flue and cooler outside the pipe. The coil measures the temp of the probe at its attachment point and the printed dial face is calibrated to match what is measured inside the heated chamber (fluepipe, with this model).



If there is no natural cooling of the coil at its attachment point, then the measurement won’t be as accurate. Your test set-up on your cooking stove shows the probe inside a pan with the radiant heat rising up from the burner; I’d suspect the reading to be higher in that test compared to your digital monitor.



Your description of the operation of your woodstove at its optimum setting with it “cruising” would indicate our reading to be just at the top end of the BEST ZONE. I would question the infrared reading just short of 300F as that temp is well short of the 400F at the beginning of BEST ZONE. That would indicate you need more wood or air or both. The BEST ZONE is a guideline for the operation of most woodstoves. In other words, based on the operating status of your woodstove at that point in time, the infrared is reading too low.



The infrared meter is measuring the outside of the fluepipe and the FlueGard is measuring the flue gas temps. Without an extensive study of the hot gases and how they flow up and out, I can’t really offer a reasonable answer as to why there is such a large gap between the infrared and FlueGard. It does seem from the description of the operation of your stove during these tests, you have it operating as efficiently as possible. From our experience the FlueGard is more closely measuring the true temps one would expect to see inside a fluepipe as compared to the surface temp you’re measuring with the infrared. It’s reasonable to expect the outside shell of the fluepipe could be the temps showing on your infrared, but that’s not what the Condar meter is measuring.



If after all of this, you’re not completely satisfied, you may return the FlueGard for a full refund.



I thank you for your business. (I see that the first unit received was damaged in transit. Do you mind describing the damage so that I can design better packaging if needed?)



Best regards,



Tim Pope

VP

 

[Peter B.]

Call me less than charitable, but that seems like less than a meaningful or direct response.

At least he offered you a refund.

Peter B.

-----

 

[pen]

My Response

Tim,

Thank you so much for getting back to me.

It is truly refreshing to ask a question of a company and receive an earnest response!

Here is a picture of the damaged probe. It works fine, but is cosmetically trashed. I believe that the postal service simply decided that this small package be placed under a very large one. Here is a picture of the damage after straightening out the probe.

I am using the rivet collar and magnet as your directions recommend.

I operate an Englander 30 wood stove burning well seasoned (at least 1.5 years since splitting) hardwoods (maple, ash, cherry). The stove is 1 year old, the baffle boards are in tact and the stove operates w/out fuss.

What I raise question to is the claim on the back of the package that the fluegard will read approximately 50% higher than the external flue pipe temperatures.

I have checked this Rutlands accuracy against my IR thermometer and the two read virtually identical across the board. The IR has been tested against another I have at work and both read quite similarly. Essentially, I trust the IR’s temp readings on the single wall stove pipe’s black surface. As such, when taking this picture (seen below) and the external stove pipe is reading 350, I would expect 350 + 50% to result in a temperature of 525 on the fluegard, not 1000! This picture was taken about 1 hour after startup so there is no rapid change in flue gas temp as the stove had its primary air adjusted a solid 45 minutes prior and is “cruising.”

During this time the highest temperature recorded on the stove top is 625 degrees F.

I had a friend with 2 digital probe thermometers perform a test on his wood stove to compare results.

Here is my damaged fluegard with one digital probe that he has

And the second probe he used for comparison

Using both probes in the setup (for comparison) on the horizontal pipe found in the picture, the following results were recorded.

Thermo Condar
600 700
650 800
750 900
800 1000

In all, it appears that the Condar fluegard seems to be reading consistently higher than expected by 100 to 200 degrees.

If I maintain a temperature (at 18 inches above the flue collar) in the Normal zone on the Flue Gard (below 1000 degrees) my stove’s primary air needs to be completely closed and I need to keep the stove top below 450 degrees. Any stove top temp above 450 and the fluegard will be in the “too hot” zone.

My concern is that if this unit truly is reading too high, that a novice burner, who is reading this thermometer as though it is the gospel, may be running his stove at too cool an operating temp and thus actually making a condition that could lead to excessive creosote formation in his chimney / flue liner.

While I may not be a professional in the heating / thermodynamics industry, I do have a degree in science (which at least makes me mildly competent) and have been burning wood for my entire life. Been doing it in open fire places, 2 styles of fisher wood stoves, fisher stove imitators such as the timberline, a modern Jotel, an old style convection stove, a Kalamazoo cookstove, this Englander 30, hell even use a double barrel stove in a cabin I frequent! Point is I am well aware of the problems associated with overfiring as well as problems from burning a stove too cool. I know how to operate a stove and that is why I was so concerned by how high this fluegard is reading. I am using the fluegard to satisfy my inner nerd, I do not need it to burn safely. I just hope that my results are an isolated anomaly.

I appreciate your offer for a refund, but that is not necessary. I have now have the fluegard installed about 28 inches above my stove top directly into a 90 degree elbow. At this level, the temperatures displayed on the fluegard stay within the “normal” range while the stove is also cruising at “normal” surface temperatures (600 to 650 MAX). I enjoy it’s responsiveness in comparison to external thermometers and it has worked well to show my wife why she needs to be careful leaving the primary air open upon startup as the flue gas temps rise much quicker than the external pipe temps! But again, my concern is that I believe it reads higher than it ought to at 18 inches above the stove collar.

Thank you again for listening and considering my concerns,

Any suggestions or criticisms of the results I have gathered would be welcome,

Best regards,

 

[Todd]

Sounds to me like he thinks your trying to compare your external IR temps to the internal probe and your wondering why it's so much higher? The main question I'd like to know is why they state their probe reads 50% higher than the external temps when in fact supported by everyone here, it reads 100% or double the external temps. Even their painted burn zones coincide with doubling the temps not 50%. Also as the temps climb up over 800 it seems to run away further.

 

[pen]

Sounds to me like he thinks your trying to compare your external IR temps to the internal probe and your wondering why it's so much higher? The main question I'd like to know is why they state their probe reads 50% higher than the external temps when in fact supported by everyone here, it reads 100% or double the external temps. Even their painted burn zones coincide with doubling the temps not 50%. Also as the temps climb up over 800 it seems to run away further.

I too think he misunderstood my interpretation. I am hoping my response makes clearer what my concerns are. I hope to hear from him again but don't know.

While I am not convinced their product is right, and am surprised that he doubted my IR thermometer even when it agrees with the rutland, I am pleased to see that he even gave me the time of day! Not many companies are willing to do that. Now if they would just get their product to read correctly I'd want to buy stock in them!

pen

 

[pen]

Newest Reply:


Dear Matt,



Youre welcome; we aim to please here at Condar!



It sure looks like the postal service did a number on the first FlueGard we shipped youwow! They must have driven a postal truck on top of it.



I cant disagree with your analysis and comparisons and am glad to know you found that positioning the FlueGard a little higher on the pipe helped. I guess it best that it read a little high because I think most folks tend to burn too hot rather than too cool, so the indication is protecting the high heat burners.



Im glad to know that your friends in-flue thermocouple test was a close match, though I do wonder if the readings would have been even a little closer match had he reversed the positions of the FlueGard and the thermocouple (that is the thermocouple is downstream by 3 or 4 of the FlueGard and would naturally read a little lowerI think). Whats your friends stove brand and model?



I see one of our really old white surface meters. How does it compare with the Rutland?



Your results are valuable to us in evaluating field use by consumers. We appreciate that very much.



Regards,

Tim

 

[Highbeam]

Thank you pen, your efforts are great.

Thanks also to condar for lying to us and delivering a product meant to trick us into burning our stoves the way you want us to.

 

[pen]

I am surprised that they feel people generally burn too hot. I would have assumed the opposite.

I am at least impressed that they are addressing my questions / concerns and being candid in their responses.

I too wish that they readings weren't skewed. But, it is what it is.

pen

 

[mikepinto65]

Great job pen, thanks for doing this for everyone.