Replaced rope gaskets, now creosote? (pics)

[spuldup]

This is our first year running this wood furnace, a Brunco WC190 installed in the basement of a new-to-us ~2800sqft 2 story cathedral ceiling home. About 32' of new 8" duravent up the side. After speculation that the rope gaskets on the load and ash doors had lost their seal (hard), I replaced them yesterday. Instantly noticed it was using about 3 times less wood to hold the same temperature. Also has a much smoother operation profile. It used to ramp up quickly, even with low intake air shutter and inducer off.
I just burned all night on 6 barkless, white oak slabs. These are from a veneer plant, cut and split for 3 years, reading 14-16% moisture on a fresh split, at room temperature (stored inside about a week now). So they are dry. Normally I burn veneer blocking or cut, split wood overnight, but this was an experiment using the thinner, hotter pieces.

Normally in these outdoor conditions (low wind, 35F overnight), the 1st floor temperature would ramp from 72F to 76F in 2 hours, then die in about 2 more hours, and that s with about 3 times as much wood in. Last night it held 70F for 7 hours and had a good few coals left, but I noticed the door was covered in fresh creosote, the bad, wet looking kind. I spent an hour with wire wheels on the doors yesterday, so I know they were clean.

I really like the way this operates now but do I have to open the intake back up and increase the thermostat to the blower to keep the creosote in check? Just have a hot burn everyday? Any alternatives are appreciated!

First photo shows burning with the old gasket. 2nd is temp just after adding new splits this morning, next inside of load door, next is load deck where creosote dripped. Blurry because I didn't think to take them until a bit after adding and smoke was coming out.

Thanks all.

 

[St. Coemgen]

Old gaskets leak air. So your burns were getting a lot more air to fully combust with the leaky gaskets. So no creosote. But also shorter burns, with maybe a lot of heat going up the chimney rather than being ducted into the house.

Now that things are tightened up. You may need to manually regulate the air to the fire till you find the sweet spot of burn long, ideal heat capture, but without creosote buildup.

Anyway, that is only IMHO. No expert on Brunco WC190 or anything similar....

 

[begreen]

The flue gas temp is about twice what can be measured by a surface thermometer. So in this case about 400º. By the time the flue gases get to the top of that long chimney, they have significantly cooled down. Once the flue gases drop below about 250º they start condensing on the colder chimney flue surfaces. This condensation is creosote. With each fire the creosote builds up layers, setting up conditions for a potential chimney fire. Try to keep the Rutland flue temp around 300º to avoid this.

Also, the stove pipe is installed upside down. The crimp should be pointed downward, toward the furnace.

 

[Boil&Toil]

Yup - new gaskets mean less air intake by leaky seals, which means you need to open up the actual vent and adjust your flue temp to a safe zone when burning fresh wood (it can drop back when you've only got coals left, as the creosote in that load of wood has burned off by that point.)

 

[spuldup]

The flue gas temp is about twice what can be measured by a surface thermometer. So in this case about 400º. By the time the flue gases get to the top of that long chimney, they have significantly cooled down. Once the flue gases drop below about 250º they start condensing on the colder chimney flue surfaces. This condensation is creosote. With each fire the creosote builds up layers, setting up conditions for a potential chimney fire. Try to keep the Rutland flue temp around 300º to avoid this.

Also, the stove pipe is installed upside down. The crimp should be pointed downward, toward the furnace.

I assumed actual flue gas temp was more than the exterior, but did not think it'd be twice. I've been thinking of a probe type thermometer.

The company that installed the new all-fuel chimney installed that stove pipe. I told them it was upside down but they said there isn't room for the adapter fitting due to the clerance to the all fuel adapter. Seemed like BS. What is interesting that if creosote were formed in the pipe it outta drip out of those backwards fittings, but it is only on the burn door. Before the new 8" vent it would form on the ash door. I wheeled about 1/16" of shiny creosote off the whole thing.

 

[begreen]

Can you post a picture of the whole stove pipe from furnace to chimney thimble?

 

[spuldup]

@begreen Here are 4, one showing the side with thermometer and damper, 2 showing from the opposite side where I can get a camera in, and one of the furnace nameplate. You can see there is just enough distance from wall for the 2 elbows.
The main problem seems to be that the adapter should be a male fitting. So an adapter that goes over the female fitting and necks down to a male to make the pipe right was not made (if it can be?). Curious because they did crimp the lower elbow into a male-male. I know the 90 was standard started because the installer did not bring the stove pipe parts (miscommunication) so I ran to the HW store and bought them.

When I added the damper about 2 weeks after they installed the system, I noticed some dried up creosote in the bottom elbow, but nothing looking shiny in any of the pipe. Added damper because the fire was burning so fast with a taller 8" vs 6" vent. Now I understand that was also due to the old gaskets.

 

[cahaak]

If your unit does not have a very good air wash system, it can be difficult to not get deposits on the glass. Normally on a newer EPA stove, you have secondary air injection which greatly help to minimize creosote formation once the primary air is reduced (assuming that the firebox is hot). Not clear if your unit has any of these modern stove type features.

 

[spuldup]

@cahaak This furnace has no glass, but I understand what you are saying. This has a cast iron spinner in the center of the load door. It is meant to take in secondary air. The main inducer is also baffled to induce 50/50 air above and below the grates. But this is a 1984 unit so it's not perfect (not that 2022 is ;-))

 

[brenndatomu]

The main inducer is also baffled to induce 50/50 air above and below the grates. But this is a 1984 unit so it's not perfect (not that 2022 is ;-))

If you can cut off the under grate air, do so for burning wood...its not needed and just costs you efficiency...most wood/coal stove/furnaces have the ability to do so. The only time under grate air is nice is for starting a new fire.
I've BTDT with the 70's/80's wood burning technology...I'll take a modern firebox every time.
Don't miss the whole dance between hot n "clean" and slow n dirty one single bit...

 

[spuldup]

If you can cut off the under grate air, do so for burning wood...its not needed and just costs you efficiency...most wood/coal stove/furnaces have the ability to do so. The only time under grate air is nice is for starting a new fire.
I've BTDT with the 70's/80's wood burning technology...I'll take a modern firebox every time.
Don't miss the whole dance between hot n "clean" and slow n dirty one single bit...

We do burn bit coal in it as well. Honestly it is better at coal than wood. Ran out of coal and all the trucking guys are off for the holidays right now. Stocking up in 2023.

Upgrading the old furnace is on the list. It is in really good shape, having been unused at least 20 years of its life.