Over-draft situation?

Quick history- house is designed like a walk-out basement but with a solid concrete roof. Almost no air infiltration. I have tried Fresh air hooked up and just open. First wood stove I installed once I got a 12’ class A chimney installed was a Summers Heat 2k. Decent little heater especially for the price paid. I did have some trouble with going through the wood. Now I have a WS Ideal Steel Stove and am having trouble with a hot cat. I am in talks with WS and they are very helpful with my unique house.

I have found if in 50+ degrees F I will get some smoke rollout and slow starts on a 12’ chimney. I added 4’ and this resolved the problem but made the cat go way Hot at times. When temp gets lower near freezing the cat gets even hotter. On the 3rd notch from closed it was running just fine then out of nowhere it started to rise; the cat needle was past pointing straight down! I would have to cut air all off and eventually it would go down but I would also soot up the glass.

Talking to WS I started monitoring the draft and installed a damper. For now I removed the 4’ section back down to 12’ class A. In a week or two I will have to add 8’ for a total of 20’ of class A.

currently with draft fully closed, air at 1/4 mark, 350* stove top next to top flue exit, 440* pipe probe, 1600* cat probe, 28* outdoor, 74* indoor, I have a 0.65 inWC on a less than half load. This is maybe 2 hours into loading. Cat is still slowly climbing. I do have secondaries and some flame up off of wood.

Anyone have suggestions for what to try or monitor?

 

I've only had my IS installed for 2 weeks but come to the conclusion i cant trust the cat probe, one morning stove was stone cold and it was reading about 500 degrees. Even a small fire and it reads way hot. Going to order a condar and try that.
Will be interested in the comments you get, I'm just using flue temps and stove top temps as my guide lines now, some dont even have a cat probe.
I will add one person at Woodstock told me to just go by stove top temps.

 

There is a electronic option for the probe also, not sure what i will get after thinking about it.

 

So you have a outside air kit hooked up? With concrete roof does your chimney go through wall then up? If it’s 50 degrees outside I have trouble with draft and I have 24’ of pipe. Through the wall set ups are known for these type of problems.

 

WS did say the cat probe isn’t the best to have but is required for regulations. Going by STT it will get hot after a time (around 500+) and you can smell the hot metal. The hot metal smell is what caught WS’s attention and had them ask for more details.

chimney goes straight up. It is clay tile going up so we ran class A up it. With my Fieldpiece digital manometer I was reading a draft of -.12 at times. I rigged up the Dwyer b/c it is a pain to use the digital like this. Also much easier to reference.

Fresh air intake is now hooked up again as of last night. Seems to work a bit better. I do have a vented dehumidifier that can slightly pressurize the house.

The grille on wall is just a cross-over to a utility room; it is not a return.

With the 12’ Class A and damper is seems controllable but I worry about when I add 8’ (because we are adding a roof) and it drops closer to 0*. Am I going to have an out of control draft?

 

So, pretty much an in ground bunker?

 

Yep. Solid as can be. I have had tractors on top of it to remove dirt with no problems. After new roof is done I’ll make a carport/garage out of it and park my vehicles on top.

 

The damper will reduce the draft. I say better too much draft and a damper than not enough.

 

I would normally agree but today on lunch I loaded up stove about 3/4 or just less full. All going good and well when I left house 1.5 hours later. Draft was closed all the way and my air supply a bit less than 1/4 open. Stopped by a few hours later after picking up kids from school and found a 650* stove top, almost 700 pipe probe, cat probe was past point straight down, and about -0.10 draft out of stove. Damper is between draft port and pipe thermometer. Turned air down and box fan on high and it cooled back down fairly quickly.

 

By box fan, do you mean a standard box fan blowing air on the stove?

 

Yes, standard 20” cheap box fan. It is set in the opposite corner blowing air towards the stove. Normally have it on low.

 

Fan is in the opposite corner of the stove room, or of the house? I assume those temperatures are unusual for your stove? Do you attribute that happening to the weather today, or what?

 

corner of room. I have attached a picture of my house and the ductwork layout I designed for it. Assume top is N. Wood stove sits in NE corner of LR. Box fan is at SE corner (exterior wall). I will if needed put a fan at the end of hall (NW corner) and have it blow down the hall to the kitchen. Kitchen and dining room are fairly open to LR. Family complains about fan in the way when I do that so only if it is stupid cold for a long period. Otherwise the bedrooms are on their own zone and I let the HP/propane furnace handle it.

I have been having trouble with this thing running hot and am in talks with WS about it. I am collecting data to help. I will say adding the damper has helped a lot but I am a bit concerned about adding the 8’ of class A pipe. Picture is taken near LR windows looking back to kitchen and dining room. Hall is left of dining room.

I’m wondering if the soil and chimney chase are retaining a bunch of heat and it causes the draft to just build after heating up? I even have the outside air hooked up just in case my house becomes pressurized.

 

Regarding your ductwork design....

I'm having a hard time understanding just how this is configured. Are the red supply air and the yellow return air?

 

Different color rooms are the specific zones for the system (I have 3). The ductwork color corresponds to the zone(s) they are serving. There is a return duct on there (green) but it is just for sizing purposes.

 

This looks like underground duct system?

 

It is in a fur down/soffit. Here is a picture of us tearing out the soffit to gain access to ductwork and electrical. This chase goes the length of the house.

 

For a basement, we would install supply air outlets near the outside walls in ceiling and the return air inlets near the inside wall but down low near the floor. that way, the conditioned air you introduce into the room has to migrate across the room from high to low before it is retuned to the heating unit. This is typical in a northern climate.

If your returns are on inside walls, your room air exchange may be short cycled and leave pockets of unconditioned air between the supply outlet and the outside wall as the air will migrate to the return air inlets from the supply air outlets.

 

Thank you for the input. That is certainly a common and good way to do the ductwork but not necessarily always the best or possible. A few bits that might have failed to explain: I am an HVAC contractor by trade, not one part of the ductwork is original and it keeps most of the house even on temperature as designed, this house isn’t exactly a basement (it is designed like a walkout basement but there is only one floor), with concrete load bearing walls and ceiling it limits the placement and size of ductwork.

I am a fan of sidewall termination blowing along ceiling towards outside wall. Not only does this reduce the amount of ductwork but airflow will actually cling to the ceiling so to speak for a distant; we can figure that distance based on velocity and such and this helps the air travel further into the room. This is a design I had to utilize in the house and it works great. Really only problem with comfort is due to not being able to fit the designed size pipe to an area, the exposed outside wall having only 1” foam board for insulation, and a child who keeps opening the 40 year old windows that won’t close back very well. Couldn’t really have a 6’ ceiling to fit ductwork so until I add insulation somehow I will have one room that gets a bit cold in the winter and a bit warm in the summer. Still not uncomfortable though.

 

I'm not convinced that cat probe is accurate.
Try putting a Rutland burn indicator right here. This is the hottest spot on the stove.