small stove temp swings

[ddug]

New and trying to get educated. Fire seemed such a simple affair until I got a wood stove.

Starting to get the hang of my VC Aspen, I bought one of those magnetic thermometers so I could monitor the pipe temperatures and get a more accurate idea of what is going on. If I get a real good burn going with the tubes on top firing away the stack temp. climbs to about 350, which is about the best I've managed thus far. The thermometer is 18 in. above the stove. With a nice full load of my most prime fuel it will hold the temp. at around 300 for maybe an hour, and then the temperature drops off quickly. Sometimes I have had it burning well and come back an hour later to find the temp. at 150. Fire seems to be burn well in the stove and responds when I close down the air intake to slow the burn. I am concerned about creosote buildup with the temps. often falling into the "creosote zone" on my gauge.

(1) the vent stack is 16 ft. single wall pipe into 6 ft. triple wall through and above the roof. It is a cathedral ceiling so the pipe doesn't pass through any floors or anything. I was not trying to be cheap (well maybe a little) but thought the single wall would be better inside to aid in releasing heat. Could this contribute to any problems?

(2) Would the fact that my place is of yet uninsulated and very leaky drastically affect the stoves ability to maintain temps?

(3) Is this just the nature of the beast ?

(4) I don't have a moisture meter but I'm pretty sure the wood is good and dry. Most was cut 2 years ago and although not split the average diameters were only 3 to 5 inches. The humidity is so low here that if you spill water it never makes it to the ground! Most is juniper, could the fuel be a problem? It does burn longer using the scrub oak I have here, but still no more than a hour or so at proper operating temps.

(5) Other?

Thanks for your patience.

 

[Todd]

As long as your firewood is dry you shouldn't have a problem with creosote. You flue temps sound about right for a small EPA stove. If you reload on a good bed of coals you may see some higher temps. Look outside at your chimney during the burn and see if you see any smoke. After you fire settles down and secondaries stop there isn't much creosote making particulates left so if your thermometer drops down to the creosote stage you should be fine.

16' of single wall is probably too much but if your stove seems to be drafting ok I'd leave it, it will radiate more heat into the space than double wall. Insulation always helps, you will burn less wood and be much warmer.

 

[ddug]

The only time I get smoke out of the stack if when I start it up or reload, otherwise it's nearly invisible. I guess I was under the wrong impression that the vent pipe reading should be between abut 300-500 degrees. The stove itself still seems pretty hot even after the vent pipe starts cooling down below 200.

Thanks.

 

[Backwoods Savage]

Do yourself a big favor and now that you have a thermometer on the flue, put one on the stove top.

Flue temperature of 350 is good but then, we don't even know if that thermometer is accurate and many of them are not. So that means the thermometers are guides and not necessarily a true temperature. For example, we've bought some that were 150 degrees off! You can do some quick checking by placing them in your oven and trying different temperature settings.

To give you an example of our temperatures, our flue usually is in the 300-350 range but does many times go below that. Remember than when the fire is almost done with the cycle there is not that much heat to go up the chimney until you reload. Our stove top temperature can range from 250-700 but during the cold of winter we usually run it in the 500-650 range and, of course, from there the temperature goes down as the fire completes the cycle. We typically reload around 300 degree stove top. Then typically after the reload our flue temperature will rise up to around 500 before we start closing off the draft. Then the stove top will rise quickly and the flue temperature will drop.

There is no worry about creosote at the end of the burn cycle. It is only on the reloads when there is more smoke and gasses going up the chimney when the creosote forms.

 

[ddug]

Good to know. Potential creosote buildup at the end of the burn cycle was my main concern. I'll get another thermometer for the stove top and see what that says.

Thanks.