Flue Temp Question... I'm Confused

[Zzyk]

I'm posting this as recently I have seen a few flue temperature threads and I think I've been mistaken in my understanding of the measurement.
I've been using a cheap Rutland magnetic thermometer about 18 inches up the stack. Usually I load the stove, run the flue up to about 500-600 on the dial, then start to shut it down.
The stove will then usually cruise with the dial at 350-450 for awhile.

Now the question....

It the actual temperature twice what the thermometer reads? If so it would appear I'm running hot and should back off a bit, but I fear the creosote monster.
He haunts me in my sleep...

Thanks
Chris

 

[Todd]

Sounds about right to me. You may want to stick that thermometer in your oven and test it. Every Rutland I've had read about 50-100 degrees on the hot side.

 

[Zzyk]

Thanks Todd!

The thermometer reads about 50 degrees high as best I can tell (from putting it in the oven). I was just concerned I was running the flue too hot.

 

[oconnor]

The descriptions on them are based on where they are intended to be mounted - if you compare a flue mount surface and a flue mount probe, the descriptions use the correct temp of what they measure - lower temp on a surface than a probe, but same description as to what the effect is - normal, low, or overheat.

The descriptions are quite general, and can be debated - I use the thermometer as a trend indicator - mostly it tells me when things change from what I'm used to seeing. Last week, I noticed that my start up temps seemed to be taking longer to achieve, and sure enough, when I stuck my moisture meter into my wood, I had found some less dry wood in the pile. When you do things the same way, you should see the same results - if the results differ, then look for what has changed - draft, wood, blocked intake (a few Jotul Kennebec folks have found that out), etc.

Unless I climb up on my roof two storeys up in the winter wiht 30cm of snow on it, I suspect that my temp guage will be my first indicator of a creosote clog, as it will heat up more slowly on startup if my screen gets clogged.

 

[MontanaBob]

My Rutland is 175 degrees on the high side - based on an oven test.

 

[jebatty]

Is the actual temperature [interior flue, probe thermometer reading] twice what the thermometer [surface thermometer 18" above the top of the stove] reads?

This is a fair approximation with a 6" black stovepipe. I have the surface thermometer on my wood stove and the probe thermometer on my gasification boiler. When I put the surface therm right next to the probe, the surface therm reading was a pretty close to twice. I don't think any of these therms are exactly accurate, except by chance, but their purpose is to be somewhat close and be a good guide to stove-burn performance and danger.

My stove really purrs when the surface stovepipe therm reads 300-400, and I do not intentionally burn the stove any hotter than that.

Correction: Surface therm approx 1/2 of probe therm.

 

[carp]

I have an industrial thermometer made for measuring the outside surface temp of pipe. It reads way lower than the magnetic ones. It was explained to me that it is more of a reflection of inside flu temp for the magnetic thermometers which is the temp that really matters.