Overdraft and barometric damper on a Napoleon HMF200 / Continental CHMF200

[Caydel]

Hi all!

Last summer, I had a Continental CHMF200 wood furnace installed. Continental is Napoleon's sister brand - this furnace is identical to the Napoleon HMF200 with the exception that some things are optional on the Continental instead of standard as on the Napoleon.

Anyways, last year, we went through a ton of wood, and I suspected I had a problem with the stove. My burn times were poor (2-3 hours), we went through a ton of wood, I had high chimney temps etc. Given the height of the chimney (probably 30-35' from the furnace vent to the top) and our high winds, I figured it was a draft issue.

This year, I installed a manometer (a Dwyer Mk II Model 25) to monitor my draft, and I definitely have a signifigant overdraft.

The manual for the stone calls for an operating draft between -0.04" and -0.06", with lots of warnings that draft should never exceed -0.06".

Now, I've been measuring the draft for the past week since I installed the manometer, and I'm seeing the following:

0C (32F) - still air - draft between -0.08 and -0.10. Flue temp ~400F
0C (32F) - slight breeze - draft between -0.10 and -0.13. Flue temp ~450F
-9C (15.8F) - still air - draft between -0.12 and -0.15. Flue temp ~525F (right now)

It gets a whole lot colder and a whole lot windier here as we get into winter proper.

Now, the manual does allow for a barometric damper, but with a list of warning including rapid creosote buildup and uncontrollable chimney fires

So, at this point, I'm looking for some advice. Should I install a barometric damper and just be prepared to check the chimney every few weeks? Should I just accept the loss of efficiency and high flu temps?

Does anyone have any rough idea how much a barometric damper will cool stack temps? I know my wood this year isn't *great*, so stack temps are cooler than they would be with 'proper' wood. However, I also ordered two pallets of ecologs, which will obviously burn *very* hot to mix with my less than stellar wood.

Seems that either way, I'm at risk of a chimney fire if I don't stay on top of the creosote buildup.

On another note - the only way to clean the chimney is from the bottom inside our utility room, which is a hugely messy proposition. I'd like to be able to keep to cleaning once per year. If the barometric damper means I need to clean several times per year due to cooled stack temps... I'd almost consider just eating the cost of extra wood!

 

[wood butcher]

I have a very simular set up and often wonder if I am loosing too much heat up the chimney. I haven't doen anything about it as overall I'm pleased with what I have but improvements are always welcome.
I'm in Perth county and we have high winds from Lake Huron so we never have a lack of draft.
I've just discovered cracks in the welds in the firebox on the part that takes air from the front of the furnace to the secondary tubes. Out of interest do you have anything that shields the corner welds, top left and right just inside the door?

 

[velvetfoot]

Now, hopefully someone will chime in that knows something.

You could put in a barometric damper and see how things shake out. If worst came to worst, you could maybe take it out and put a blank in its place, or otherwise deactivate it without doing a bunch more work.

Assuming you don't have the oil burner option?

There's no forced draft fan with this heater...just natural draft.

Do you have the outside air setup?

The manual seems to say that secondary air comes from inside the house, but maybe not.
(Note that secondary combustion air enters through two inlets on the front of the furnace either side of the ash lip tray and is not adjustable).

My personal opinion is that these things are designed for some norms, and regulations, and if you're outside of the norms, like high draft, it's not good. I found a way to limit the air intake on my wood stove to control the raging secondaries, and it works great now, but it's a wood stove, not a furnace.

Maybe contact the manufacturer?

Good luck!

 

[Caydel]

Now, hopefully someone will chime in that knows something.

You could put in a barometric damper and see how things shake out. If worst came to worst, you could maybe take it out and put a blank in its place, or otherwise deactivate it without doing a bunch more work.

Assuming you don't have the oil burner option?

There's no forced draft fan with this heater...just natural draft.

Do you have the outside air setup?

The manual seems to say that secondary air comes from inside the house, but maybe not.
(Note that secondary combustion air enters through two inlets on the front of the furnace either side of the ash lip tray and is not adjustable).

My personal opinion is that these things are designed for some norms, and regulations, and if you're outside of the norms, like high draft, it's not good. I found a way to limit the air intake on my wood stove to control the raging secondaries, and it works great now, but it's a wood stove, not a furnace.

Maybe contact the manufacturer?

Good luck!

I don't have the oil burner option, though I have a Continental propane furnace as the backup. My wood furnace is in the 'Add On' configuration.

Yes, I have the outside air kit installed. Secondary indeed comes from inside the house, via two ports in the front face of the stove that are not adjustable. The draft really is the thing that controls combustion on this stove, and it's way too high.

As it is, I hate the primary air control design as it's back asswards. It's run 100% by the thermostat - if the thermostat is calling for heat, the primary air is wide open. If the thermostat is *not* calling for heat, it's closed. So, in effect, you only get efficient secondary burn if the house is already hot enough. If you have a cold house, it will run the primary wide open until it's satisfied, which from my observation gives me no secondary burn, but 800 degree flue temps and a firebox burn down time of 1 hour. There is a high limit switch that shuts the primary air intake if plenum temps get above 250 degrees, but I've never seen that kick in, as the blower keeps the plenum sufficiently below that level.

In practice, I keep the thermostat low all the time so that the primary air intake wants to stay closed, then manually block it open long enough for the stove to get up to temperature before I let it close down to encourage secondary burn.

Now that I have numbers for the draft, I've contacted the contractor who installed the furnace to see about what we can do. It shouldn't have been installed in such a way that the draft runs 2-3X the maximum allowed in the manual.

I want to get the draft situation resolved before I complain too much about the rest of the design - it might be that everything I dislike about this furnace works better when it's not being run harder than designed.

 

[Caydel]

I have a very simular set up and often wonder if I am loosing too much heat up the chimney. I haven't doen anything about it as overall I'm pleased with what I have but improvements are always welcome.
I'm in Perth county and we have high winds from Lake Huron so we never have a lack of draft.
I've just discovered cracks in the welds in the firebox on the part that takes air from the front of the furnace to the secondary tubes. Out of interest do you have anything that shields the corner welds, top left and right just inside the door?

Looks like mine has a reinforcing plate of some sort added. I feel now like I need to unbolt it to look for cracks...

 

[brenndatomu]

Should I install a barometric damper and just be prepared to check the chimney every few weeks?

I would...in a heartbeat. You've got to get that draft under control, you are overfiring the furnace, and that leads to cracks, and poor efficiency, as you already know!
If they are so dangerous why do many manufacturers require them? Heck, some even come with them! Now it is true about the chimney fire thing, to some degree...but if you burn dry wood, and keep your chimney clean, very little risk of a fire.

n another note - the only way to clean the chimney is from the bottom inside our utility room, which is a hugely messy proposition. I'd like to be able to keep to cleaning once per year.

Buy a Sooteater...do a bottom up cleaning using the plastic over the cleanout hole, with a shopvac stuffed in a hole through the plastic...not messy at all.
Another neat trick I've seen is to cut the bottom off a milk jug, stuff the sooteater through the hole, again, shopvac taped into a hole in the milk jug.

Does anyone have any rough idea how much a barometric damper will cool stack temps?

Only enough to get the draft down to your preset #...in other words, the draft goes high, the baro opens, cools the gasses a bit, draft drops, baro closes...so on and so forth...only it happens so fast that the baro doesn't really open and close...just kinda flutters gently...more so when its windy.
In my opinion, you will get the most buildup right after the baro because that's where the air is the coldest...once it mixes with the hot gasses from the furnace, it will warm back up some.

As it is, I hate the primary air control design as it's back asswards. It's run 100% by the thermostat - if the thermostat is calling for heat, the primary air is wide open. If the thermostat is *not* calling for heat, it's closed. So, in effect, you only get efficient secondary burn if the house is already hot enough. If you have a cold house, it will run the primary wide open until it's satisfied, which from my observation gives me no secondary burn, but 800 degree flue temps and a firebox burn down time of 1 hour. There is a high limit switch that shuts the primary air intake if plenum temps get above 250 degrees, but I've never seen that kick in, as the blower keeps the plenum sufficiently below that level.

Many wood furnaces have this same issue...you need to visit the link at the bottom of my post...look through the glossary where it talks about the temp controller hack...go to the big Tundra thread and learn how to do it. It basically utilizes a programmable temp controller to overide the Tstats call for heat as long as the flue temps are within range...or you do as many of us have, not use a Tstat, just install a bath fan timer to call for heat long enough to get the firebox up to full temp, then just let it go...kinda like a manually operated stove. It works really well as long as you have dry wood!

 

[Caydel]

Ok, the Sooteater looks amazing! Of course, I've already spent the same amount on a manual brush and rods... but the milk jug idea seems like the trick to do it much cleaner.

 

[wood butcher]

Looks like mine has a reinforcing plate of some sort added. I feel now like I need to unbolt it to look for cracks...

Thanks for the picture.
I think that is what I am getting sent from Napoleon. I don't see how that will seal a cracked weld but I will see what I get. If it wasn't for the warranty I would grind and reweld it then put the plate on.

 

[Caydel]

I just wanted to circle around on this, in case the experience is useful for anyone else.

The barometric damper has completely transformed this furnace.

• It's throwing out significantly more heat per load. Maybe 30-50% more - it's hard to measure, but I'm definitely burning less wood.
• I'm getting a good, stable, long secondary burn.
• it's keeping hot coals for hours longer than it was previously.

The main downside is that stack temperatures are low - I have a probe thermometer in the pipe that isn't getting above 215 degrees, and I have to have a good fire burning to get it even that high. Obviously, this is terrible from a creosote buildup perspective. I'll need to monitor my chimney - while the stove is burning very clean when it gets up to temperature, it takes longer to get there with the lower draft. I'm going to give it a good cleaning at the next opportunity so that I'm starting from a fresh base to monitor it how quickly it builds up. Some experience from others online suggests that the buildup is pretty manageable if you are very good about getting the operating temperature up quickly to get that 'clean' burn, but we'll see.

I've played with the damper setting - regardless of where I set the draft, it doesn't impact the stack temperature in a meaningful way. I think my natural draft is so strong that every setting leaves way too much room temperature air going up the stack. However, the stove itself clearly performs best at 0.05" of draft, right in the middle of the range set in the manual.

 

[Toe]

In 2018 we had a Continental CHMF 200 combination wood/propane installed. (by Napolean) For the first few year it worked well. It held a fire for up to 8 hours. Last winter and this there is fine ash escaping into the plenum and duct work. The filters clog up quickly. Anyone else having this difficulty. A local neighbour and qualified installer contacted Napolean and they are not making tis furnace nor replacement fire boxes.

 

[Rockstar1346]

In 2018 we had a Continental CHMF 200 combination wood/propane installed. (by Napolean) For the first few year it worked well. It held a fire for up to 8 hours. Last winter and this there is fine ash escaping into the plenum and duct work. The filters clog up quickly. Anyone else having this difficulty. A local neighbour and qualified installer contacted Napolean and they are not making tis furnace nor replacement fire boxes.

Sounds like you have some cracking in your firebox.

 

[Rockstar1346]

I just wanted to circle around on this, in case the experience is useful for anyone else.

The barometric damper has completely transformed this furnace.

• It's throwing out significantly more heat per load. Maybe 30-50% more - it's hard to measure, but I'm definitely burning less wood.
• I'm getting a good, stable, long secondary burn.
• it's keeping hot coals for hours longer than it was previously.

The main downside is that stack temperatures are low - I have a probe thermometer in the pipe that isn't getting above 215 degrees, and I have to have a good fire burning to get it even that high. Obviously, this is terrible from a creosote buildup perspective. I'll need to monitor my chimney - while the stove is burning very clean when it gets up to temperature, it takes longer to get there with the lower draft. I'm going to give it a good cleaning at the next opportunity so that I'm starting from a fresh base to monitor it how quickly it builds up. Some experience from others online suggests that the buildup is pretty manageable if you are very good about getting the operating temperature up quickly to get that 'clean' burn, but we'll see.

I've played with the damper setting - regardless of where I set the draft, it doesn't impact the stack temperature in a meaningful way. I think my natural draft is so strong that every setting leaves way too much room temperature air going up the stack. However, the stove itself clearly performs best at 0.05" of draft, right in the middle of the range set in the manual.

Did a barometric damper really change the stove that drastically? I feel like I have real high draft right now with no way to measure just seems my wood consumption is a little higher than normal.

 

[brenndatomu]

I feel like I have real high draft right now with no way to measure just seems my wood consumption is a little higher than normal.

With the colder temps, I almost guarantee it.

 

[laynes69]

Did a barometric damper really change the stove that drastically? I feel like I have real high draft right now with no way to measure just seems my wood consumption is a little higher than normal.

Didn't your furnace come with a baro? Baro's allow for proper operation and heat exchange. Too much draft and you get an influx of cooler air in the firebox and you'll flush heat up the flue. A baro will allow for the proper exchange of heat and help produce a longer burn.

 

[Rockstar1346]

Didn't your furnace come with a baro? Baro's allow for proper operation and heat exchange. Too much draft and you get an influx of cooler air in the firebox and you'll flush heat up the flue. A baro will allow for the proper exchange of heat and help produce a longer burn.

No it didn’t the manual says you can use one if you have drafting issues but hasn’t seemed that bad until we got down into the -35s lately and just seems to burn up quick. I’m very intrigued now I’ll have to pick one up this week to try see if it makes a difference.

 

[brenndatomu]

I’ll have to pick one up this week to try see if it makes a difference.

Get a Fields, not one of those Vogelzang POS.
I've dealt with these guys plenty of times, they have good prices and ship fast!

6-RC - Field Controls 6-RC - 6" Draft Regulator for Wood, Oil, or Coal

Field Controls 6-RC - 6" Draft Regulator for Wood, Oil, or Coal - The Field RC is furnished as standard equipment on many leading brands of oil or coal-fired heating equipment. It is calibrated to allow for easy adjustment to the furnace or boiler manufacturer?s specifications. Designed for...

www.supplyhouse.com

 

[Rockstar1346]

Get a Fields, not one of those Vogelzang POS.
I've dealt with these guys plenty of times, they have good prices and ship fast!

6-RC - Field Controls 6-RC - 6" Draft Regulator for Wood, Oil, or Coal

Field Controls 6-RC - 6" Draft Regulator for Wood, Oil, or Coal - The Field RC is furnished as standard equipment on many leading brands of oil or coal-fired heating equipment. It is calibrated to allow for easy adjustment to the furnace or boiler manufacturer?s specifications. Designed for...

www.supplyhouse.com

Only problem with the link is it only ships to USA. What about this would it be close? https://www.grainger.ca/en/product/DRAFT-CONTROL,28-3-NOMINAL-CAPCTY,SILVER/p/WWG45DX71

 

[brenndatomu]

Only problem with the link is it only ships to USA. What about this would it be close? https://www.grainger.ca/en/product/DRAFT-CONTROL,28-3-NOMINAL-CAPCTY,SILVER/p/WWG45DX71

Oops, sorry I didn't realize, or forgot, you were in Canada...your location (without clicking on your info) says your location is "Fredericton, New..." and I assumed (there's that word again) that it was New Jersey
Yes, that looks to be the same damper.

 

[salecker]

get your self a gauge for measuring draft then you can keep it in the sweet spot

 

[HMF 200]

I just wanted to circle around on this, in case the experience is useful for anyone else.

The barometric damper has completely transformed this furnace.

• It's throwing out significantly more heat per load. Maybe 30-50% more - it's hard to measure, but I'm definitely burning less wood.
• I'm getting a good, stable, long secondary burn.
• it's keeping hot coals for hours longer than it was previously.

The main downside is that stack temperatures are low - I have a probe thermometer in the pipe that isn't getting above 215 degrees, and I have to have a good fire burning to get it even that high. Obviously, this is terrible from a creosote buildup perspective. I'll need to monitor my chimney - while the stove is burning very clean when it gets up to temperature, it takes longer to get there with the lower draft. I'm going to give it a good cleaning at the next opportunity so that I'm starting from a fresh base to monitor it how quickly it builds up. Some experience from others online suggests that the buildup is pretty manageable if you are very good about getting the operating temperature up quickly to get that 'clean' burn, but we'll see.

I've played with the damper setting - regardless of where I set the draft, it doesn't impact the stack temperature in a meaningful way. I think my natural draft is so strong that every setting leaves way too much room temperature air going up the stack. However, the stove itself clearly performs best at 0.05" of draft, right in the middle of the range set in the manual.

Hi Caydel, Napoleon Home Comfort in Barrie spent the last 2 and a half years installing an HMF 200 for me. I also have the draft issue and a barometric damper but I'm thinking they did not install it correctly. Would love to have a telephone conversation with you. New to this forum so don't know if you are allowed to provide phone #s or how to PM.

 

[brenndatomu]

how to PM

Click on the other persons name and then click "start conversation" at the bottom of the pop up.

It took 2.5 years for them to install your furnace?!

 

[HMF 200]

Click on the other persons name and then click "start conversation" at the bottom of the pop up.

It took 2.5 years for them to install your furnace?!

I paid my deposit Aug 2020. They said they would have it installed for Aug. 2020. took 4 installs of the stainless chimney, at least 5 of the DSP chimney and 9 times for the air intake. They walked away from my install in Dec. 2022 refusing to do the WC test.

 

[Caydel]

Hi Caydel, Napoleon Home Comfort in Barrie spent the last 2 and a half years installing an HMF 200 for me. I also have the draft issue and a barometric damper but I'm thinking they did not install it correctly. Would love to have a telephone conversation with you. New to this forum so don't know if you are allowed to provide phone #s or how to PM.

Reached out via PM with some contact info!

 

[brenndatomu]

I paid my deposit Aug 2020. They said they would have it installed for Aug. 2020. took 4 installs of the stainless chimney, at least 5 of the DSP chimney and 9 times for the air intake. They walked away from my install in Dec. 2022 refusing to do the WC test.

Hole E Crap!