The whole deal for a basement wood furnace

Good evening all.

I have a question about insulating a ss chimney liner. Since my chimney is located in the middle of my home and is heated with the homes heat except the last 15ft or so I was wondering if I need to insulate the whole length of the chimney? Approximately 30' or so. I'm installing a Drolet Tundra in my basement. Thanks for your input.

Dave..

Well, a couple reason why that's not a good idea...
1. The duct work will have to go down from the tundra meaning if there is a power outage you have ton of trapped hot (and getting hotter) air in the ducts...tundra not getting any cooling...need I go on?
2. The blower motor of the furnace is made to take in cool air, hot air will shorten the motor life greatly...
It could be done buts it's really not a good idea

If I understand the drawing right then that should be fine

You don't want to put the backdraft damper on your electric furnace inlet? That seemed like the least invasive of your options. That's equivalent to your drawing above, so to answer your question, that's what I vote would be the most efficient first solution.

After thinking more about your earlier idea of putting the damper down in the filter housing, I think it is better being above the furnace somewhere. Reason being is that blowers don't do too well with much if any restriction on the low pressure side (filter, or "vacuum" side) and pulling the damper open would cause some restriction. So I like your current plan the best

brenndatomu said:

blowers don't do too well with much if any restriction on the low pressure side

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Hard to argue with that. I had wondered that too, but convinced myself that I was getting confused with a check valve before a water pump, where cavitation is a concern. If you say it's a concern with blowers, then I believe you.

DoubleB said:

Hard to argue with that. I had wondered that too, but convinced myself that I was getting confused with a check valve before a water pump, where cavitation is a concern. If you say it's a concern with blowers, then I believe you.

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Water pump or air pump, many of the same principals apply

brenndatomu said:

After thinking more about your earlier idea of putting the damper down in the filter housing, I think it is better being above the furnace somewhere. Reason being is that blowers don't do too well with much if any restriction on the low pressure side (filter, or "vacuum" side) and pulling the damper open would cause some restriction. So I like your current plan the best

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Agreed. I think what you have sketched out above is a better way to go but I would still test the theory by blocking off the filter in the electric furnace so you can see if it's going to cure you woes. That way you will know if you need to make other mods before you rework your duct work and can get it all done in one shot.

One other thought, if you plan to use the wood furnace for your primary heat source you may want to consider using manual dampers in the two 8" pipes coming from the Tundra. In case of a power failure the heat from the wood burner may not be able to push the back draft dampers open so it would be best if they just stay open. Then you would just close the manual dampers if you need to run the electric back up.

Smoke Signals said:

One other thought, if you plan to use the wood furnace for your primary heat source you may want to consider using manual dampers in the two 8" pipes coming from the Tundra. In case of a power failure the heat from the wood burner may not be able to push the back draft dampers open so it would be best if they just stay open. Then you would just close the manual dampers if you need to run the electric back up.

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Or another suggestion I have seen in the past is to install powered close/spring open dampers, that way if power is lost it can still gravity flow

I have a barometric, and can tell you it's nearly impossible for these flues to leak hot air into the house. Keep in mind what's happening in the chimney: there's a strong draw, or negative pressure (or at least there better be). Any non-sealed portions of the flue will leak cold room air into the flue before they'll allow any out......

I like options so I personally have both a manual and barometric damper on my stove pipe. I have had creosote issues with my baro, but I also am not running a Tundra, so take that for what it's worth. I normally control the draft with the manual (or key) damper leaving the baro opening covered with HD alum foil. But I use the baro on real windy days where the draft is really erratic or really cold/windy days where neither damper is enough to get the draft reading down to normal operating levels. (I have a 28' high draft chimney) Also the baro is used when I use the oil burner. I am planning on putting both types of dampers on my sisters Tundra when I install it too.

I would say that Drolet emphasizes the use of a baro to satisfy the lawyers, it adds one more layer of "idiot proof" to running the furnace, and this furnace is marketed toward the masses, so...
I personally would put a lot more emphasis on their statement that the draft must be controlled to the range of -.04" WC to -.08" WC, maybe not as much on how it's controlled.

If your stove pipe is that hot (I can't remember, did you ever give us flue temps?) then you definitely are losing heat up the flue and are in need of a damper...adjusted properly using a manometer.

As joe said, the chimney and flue provide negative pressure to the firebox so there should never be any smoke coming out. There is normally a little air being drawn into every pipe joint and about the only way I can think of that smoke will come out is if you get "backpuffing" or have a plugged chimney. If you do have smoke coming out the joints it is nearly impossible to seal everything to the point of not getting smoke in the house, but like I said, when everything is right, the chimney provides "suction" that only pulls air in, but lets none out.
And that brings up a point, the chimney is the "engine" that powers the stove/furnace so to speak. The stove/furnace is kinda like a car, without an engine it is just a body, and the car can only work as good as it's engine is "tuned", that's why it is so important to get the draft set correctly.

roofyroo said:

I have two 8" backdraft dampers coming this week so will see what difference this makes.

On the subject of dampers, I've read here that some people are using a manual damper on the exhaust, which contradicts page 36 of the manual which states "WARNING: DO NOT INSTALL A MANUAL DAMPER ON THIS FURNACE" (bold text, underlined and boxed). I understand the damper is installed to keep the hot air in the furnace, but it seems an extreme choice for such an extreme warning from Drolet.
I'm mentioning this as my exhaust is VERY hot, so I'm worried about the amount of heat I'm losing. I have a barometric damper to install along with a manometer and in-flue rod. I'm concerned that with this extreme heat, hot air will escape out of the T where the barometric damper is. Do you guys have a barometric damper installed, or a manual damper, or nothing at all on the exhaust?

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Roofyroo,

What kind of 8" dampers are you using for the outlets on the Tundra? And are you using any backdraft damper on the return side of the Tundra?

Thanks Dave

With all gravity backdraft dampers, how will you account for proper firebox heat dissipation in the event of a power outage? You will not have gravity flow....?

I have a gravity damper in the bonnet of the LP furnace and a powered damper in the supply duct of the wood furnace. It's wired in such a way utilizing a relay where the ONLY time it's closed is when fan on the LP furnace/AC is the only one running. This gives backdraft protection in all scenarios (also allows for both the LP and wood blowers to run at the same time) and also allows for gravity flow in case of a power outage.

JRHAWK9

Where did you order your motorized damper from? Any input would be appreciated

Thanks Dave

The46Zone said:

JRHAWK9

Where did you order your motorized damper from? Any input would be appreciated

Thanks Dave

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I got it from Retrozone (Google them). They were very helpful as well. I went with one of their better models and also got the Belimo motor.

JRHAWK9 said:

I got it from Retrozone (Google them). They were very helpful as well. I went with one of their better models and also got the Belimo motor.

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Thanks for the input. Dave