Flue temp conundrum!

[Todd]

But you should care because you don't want to wreck your liner with a continuous burn over 1000 degrees internal which would be about 500 for your external thermometer.

Todd, I do believe the continuous 1000ºF UL safety rating is for the actual temperature of the metal, not the gas temps. I had the same single-wall black pipe for my old stove for almost twenty years, and I'm sure I consistently ran it in the 500-600ºF range all that time. That's because I was advised to by every expert I ever spoke to. It was in fine shape when I finally hauled it to the recyclers when I needed a larger capacity flue for the new stove. Exposure to 1000ºF is nothing for steel, especially stainless. The metal parts on the inside of your stove exposed to temps a hell of a lot hotter than that.

Oldspark, I'm certainly not attempting to show scorn for your concern, just poking you a little. I thought you knew me well enough by now I didn't have to put silly emoticons in there to let you know. I think you are showing a lot of intelligence for pursuing this the way you are, I just don't have the inclination to go back over all those posts to rehash it all. You've been at this long enough that I'm sure you'll figure out what you need to know sooner than later and all will be fine.

Yep, your partly right, it's 1000 flue temps for factory built fireplaces, but I think they go by internal flue temps not external, could be wrong tho? Can't find the UL rating for liners.

 

[begreen]

1 Scope

1.1 These requirements cover factory-built chimneys intended for venting gas, liquid, and solid-fuel fired residential-type appliances and building heating appliances in which the maximum continuous flue-gas outlet temperatures do not exceed 1000°F (538°C). Factory-built chimneys are intended for installation in accordance with the Standard for Chimneys, Fireplaces, Vents, and Solid-Fuel Burning Appliances, NFPA 211, and in accordance with codes such as the International Mechanical Code, the International Residential Code, and the Uniform Mechanical Code. They are intended for installation inside or outside of buildings or both, in a manner that provides a vertical (30 degree maximum offset) conduit or passageway to transport flue gases to the outside.

1.2 The chimneys covered by these requirements comply with either a limited duration 1700°F (927°C) flue-gas temperature test or a limited duration 2100°F (1149°C) flue-gas temperature test, at the manufacturer's option.

1.3 These requirements cover dual purpose residential type and building heating appliance type chimneys, and single purpose building heating appliance type chimneys. Dual purpose residential type and building heating appliance type chimneys are tested enclosed and intended to be installed unenclosed or enclosed with combustible construction. Single purpose building heating appliance type chimneys are tested unenclosed and intended to be installed unenclosed or enclosed in a noncombustible chase.

(broken link removed to http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0103.html)

 

[BrotherBart]

Yeah I have never seen any combustion testing spec from flue pipe to jet engine exhaust that didn't test to the gas temp being contained, not the material temp.

 

[Battenkiller]

Well, there ya go. Another day, another bit of useful information. Gotta love this board. ;-)

I wrote that and then started to think about it. 1000ºF temp of the metal itself and it would be glowing continuously. That can't be healthy. I wanted to go back and edit it, but we were watching an Italian movie and I couldn't duck out and still listen because I'm an Italian that doesn't understand Italian. :cheese:


I've never actually read the standard before, just assumed it had to be for the metal itself. Thanks for the link, BG. I've been told for over 20 years to run my flue temps between 400º and 650º, but I never had a thermometer so I just ran the stove as open as I dared. Never seen it glow, but it must have been close at times. :roll:

I'm a bit confused by the phrase "maximum continuous flue-gas outlet temperatures". Where are they to be measured, right at the collar? That is the outlet to me. Things can get pretty dang hot at that point.

Of course, continuous is continuous. No one can maintain 600ºF pipe temps continually. There will be a spike, and then a slow drop to more moderate temps, maybe around 400-500º, then a cooling off as the coaling stage progresses. Now that I am using a thermometer, I only deliberately run flue temps that high for about 30 minutes to an hour, just to warm up the flue tiles and dry up any gunk that may have formed the night before. I try to keep them at about 400º in down draft mode, but rarely can keep them much above 300º. So even at double the pipe temp, I probably can run the thing as hot as I've been without coming close to exceeding the UL test standard.