Fly Ash plugging up Cat

[Rob_Red]

Hey everyone long time lurker but new to the forum.

I have a Hearthstone Green Mountain 40. This is my first epa stove and so far we love it with one exception... The cats keep plugging up with fly ash. Over about a month and a half time frame the cats will get so plugged up when I engage them it will basically put the fire out. My fix has been to cool down the stove and gently brush the cats with a soft paint brush to unplug them. Works like a charm but I'd rather not have to do it with such frequency because we burn every day and I don't like to let the stove cool down!

I have a clay lined flu which seems to draft really well (it will blow out a lighter if held up to the flu pipe) and the stove seems to operate perfectly when the cats are clean. My wood is primarily red oak at 20-23% moisture content (per my General tester on room temp splits) and has been seasoning for about a year, I know this could be better but we just moved to this house a year ago and I'm still building up my wood program. I do not burn paper (or anything but wood) in the stove, I split thin kindling and light with a propane torch.

Is this avoidable? Is it because my wood is only a year seasoned? Is this normal for a HearthStone? Any advice would be appreciated!

 

[begreen]

What is the ash removal process with the stove?

 

[Rob_Red]

What is the ash removal process with the stove?

Generally in the morning, I scoop out excess ash before loading more wood. The ash is still quite hot and yes lots of fine particulate goes flying. I never connected the dots that the fine stuff is going up into the cat! It's also flying into the room which is not so nice.

Think that could be the problem? If so what is the solution? We burn a lot and sometimes build the ash to the point where we can fit wood into the stove.

 

[begreen]

First, be sure the bypass is open. Then turn off the blower if it is running. Remove the ash slowly.

 

[Nigel459]

Yes, I hope you are using that bypass!

I have the GM40 as well. Second season now. I love it too and have not had this issue.

Clogged cats typically happen when draft is too high. I’ve also heard that engaging the cat too early can gunk them up with ash. I do use a flue damper for my setup so maybe that’s a difference? I find it an easy breathing stove otherwise, a bit too easy to achieve the long burns without a damper for me.

I used the paintbrush after last season and my cat had some ash built up but was nothing like yours. So pretty sure was not inhibiting draft.

Different wood species can produce more or less ash as well. I burn white ash and black locust with some pine occasionally for starting. Maybe it’syour oak?

 

[Nigel459]

What is the ash removal process with the stove?

If you meant cat ash removal: Remove the baffle (kinda finicky but easy, no tubes) and voila, cats are right there.

 

[Rob_Red]

First, be sure the bypass is open. Then turn off the blower if it is running. Remove the ash slowly.

no blower on the stove

I'm pretty good with regularly opening the by pass but I will be extra sure in the future, also I will try to jostle the ash less when removing. I assume same goes for raking coals and for reloading and opening the door in general?

 

[Rob_Red]

Yes, I hope you are using that bypass!

I have the GM40 as well. Second season now. I love it too and have not had this issue.

Clogged cats typically happen when draft is too high. I’ve also heard that engaging the cat too early can gunk them up with ash. I do use a flue damper for my setup so maybe that’s a difference? I find it an easy breathing stove otherwise, a bit too easy to achieve the long burns without a damper for me.

I used the paintbrush after last season and my cat had some ash built up but was nothing like yours. So pretty sure was not inhibiting draft.

Different wood species can produce more or less ash as well. I burn white ash and black locust with some pine occasionally for starting. Maybe it’syour oak?

One thing I do is leave the door cracked to get the fire going quickly. This creates a very strong draft (fire makes a jet sound) and gets the fire ripping. Do you think this may be contributing?

 

[begreen]

One thing I do is leave the door cracked to get the fire going quickly. This creates a very strong draft (fire makes a jet sound) and gets the fire ripping. Do you think this may be contributing?

It might be, but the daily cleaning is probably the main contributor. This may be the wood being burned if it creates a lot of ash. I clean out the stove about once every 4-6 weeks, but that is when burning douglas fir.

 

[Nigel459]

One thing I do is leave the door cracked to get the fire going quickly. This creates a very strong draft (fire makes a jet sound) and gets the fire ripping. Do you think this may be contributing?

I assume you do that with the bypass open only, right? Even if yes, I guess anything is possible and jet-sound draft (pretty strong) might be swirling ash up and be so strong that some air gets pulled through the cat. I don't need to crack the door with my dry ash so I don't. If I were trying to start a fire with my black locust I sure would though, even though it's dry. It's dense like your oak. Maybe try to find another source of and easier starting wood to get things going... even 2x4s chopped up and split for kindling could work.

 

[Highbeam]

All too common with these fine steel cats and their tiny holes. Brushing the face of the cat doesn't clean out the cells though, are you able to vacuum those cells clean? Like any filter, the more it plugs up the faster it plugs up.

The stove design is based on a specified draft strength. If you exceed the specification, then things like this can happen. Being over or under the specified draft is something worth fixing.

 

[Rob_Red]

All too common with these fine steel cats and their tiny holes. Brushing the face of the cat doesn't clean out the cells though, are you able to vacuum those cells clean? Like any filter, the more it plugs up the faster it plugs up.

The stove design is based on a specified draft strength. If you exceed the specification, then things like this can happen. Being over or under the specified draft is something worth fixing.

I am able to vacuum and usually do, however all of the buildup is on the outside face of the cat only, the interior of the cells stay clear. I verified this the first time I had the issue by brushing that powdery fly ash off and then pulling the cat out and sighting through it to make sure it was flowing.

How does one adjust the draft to make sure it is within the specs of the stove? Also I don't see a specified draft for this stove anywhere in the manual, would I need to contact the stove company to figure that out? Non of the chimney companies around here seem to be very helpful all they want to do is cleanings and pass the buck and say its the stoves problem. When I contact the stove dealer they say its a chimney problem..

 

[Highbeam]

Most stoves specify 0.04” to 0.06” of vacuum in the chimney at high burn. The professional installers should have a device called a manometer to measure the draft strength but honestly it’s not usually done unless there’s a problem.

If draft is below spec you can add chimney height or insulate the flue to increase it. If draft too strong as you seem to have the common solution is a key damper.