Double wall pipe flue temp vs outside surface temp

[bag of hammers]

Got a cheap IR gun and pointed it at the black pipe this weekend just for kicks. Temp read 200 deg. Meanwhile the flue probe reading was 400 deg Either there's a 200 deg difference inside vs outside the double wall or one of the gauges is fubar. Any thoughts?

 

[DanCorcoran]

Normal readings. I get big differences, even on single-wall.

 

[pen]

I've yet to read someone post where they saw a direct relationship between probe and external temps on double wall pipe. The air gap kinda screws that up.

With single wall pipe, the way I have my probe and magnetic setup, when one hits the "it's real hot" zone, so does the other.

How hot was the stove top when you had the 400 degree probe reading? Was the stove cruising? Early in the burn with active flaming? Later in the burn? Coaling stage?

What kind of probe are you using?

Keep playing around at different stages in the burn and see what you find.

pen

 

[bag of hammers]

thanks Dan, Pen...

Not sure what the stove top temp was (I don't have a stove top thermo) - I suppose I could have just lifted the trivet and pointed the gadget down at the top of the stove, but I didn't even think of doing so to be honest . It was probably about an hour after I last loaded it and it was cruising along pretty well. The probe is an Osburn brand (not sure if it's actually made by someone else and just branded by SBI - they sell for @ $16 at the stove dealer).

I was just curious more than anything - I picked up the IR on sale for 1/3 price so I figured I might as well point the gadget at a few objects just to see what it would do (a new toy - gotta play a bit). Just didn't expect such a wide temperature gap at the pipe. But I will play around more with different stages of the fire and see what happens.

 

[Jags]

I think it would be a difficult thing to relate double wall outside temps to internal temps of the pipe. Where you are at in the burn cycle could have everything to do with the double wall temp and almost not correlation to the internal temps of the pipe.

Example: Start up - 20 min into the burn, your internal pipe temp might be reaching 600-700F and the outside of that double wall is at 150-170. Maintain the same internal pipe temp for the next 2 hours and your external is probably at 220-240. No correlation. (these are just example numbers, please don't bust my hump if that do not relate to the number anyone else gets).

 

[bag of hammers]

Thanks Jags. Seems like that relates to Pen's point around measuring at different times in the burn cycle. I think you guys are right - there's probably no correlation - just seems kinda interesting to me to see how it behaves. I must be a fire geek...

 

[DanCorcoran]

I have a probe and a stove-top thermometer. I like to watch the interplay between the two, as I open or close the primary air or use the blower. You can really see some dramatic temperature changes, with the probe/flue gas measurements responding almost immediately and the top of the cast iron stove taking much longer to adjust.