Need ideas for keeping cat active while minimizing heat output

[HarvestMan]

I have a Hearthstone Harvest soapstone stove built in 1990. The flue gases are drawn into the cat chamber at the rear bottom of the firebox when the bypass damper is engaged. I think this old design makes it more difficult to maintain an active cat on reloads.

The problem is that if I reload while the coal bed is still quite hot, I can reload and close the bypass damper in a minute or so and still have the cat lit. Over time, the temps rise in my house to where it is too hot.

If I let the coal bed burn down and then rake to front and reload, I need to wait quite a bit longer to engage the bypass damper (up to 45 minutes).

I just replaced the cat this year and really like not producing any smoke, but I just can't take the heat after a few reloads.

Also, a cold start takes a good 60 to 90 minutes before I can engage cat and get confirmed light off (cat probe temps over 500)

Any owners of older cat stoves similar to mine have this problem?

Any suggestions on how I can keep the cat active and maintain reasonable temperatures?

Thanks.

 

[pen]

Are you putting full loads of wood in the stove? A cat can help you keep things down lower for a longer period of time on a good sized stove (which this is) better than a non-cat, but at the end of the day, the more fuel you put in, the more heat you are going to put out.

Sounds like this is in either a smaller home or one that is very well insulated? Regardless, the only solution might be smaller loads / loading less often. This may mean starting a cold start (no or little coals) once a day, but such is the beast. In general, think loading in cycles... If you are too warm, loading on a coal bed that is still quite hot, is not the thing to do.

I grew up with a friend having one of these stoves in his home. They heated a 2500 sq ft house with it. It was a storm trooper. After his parents divorced, he asked me if I wanted the stove as his mother didn't. What I didn't know was it sat outside under a tarp for about 8 months Couldn't save the stove, but did tear it down and save the soapstone. They are a good heater, as you mentioned, the design is a bit different and probably a good reason for why hearthstone really didn't keep up with the line...... I just don't think they idle down as well as some other designs of cat stoves.

 

[HarvestMan]

Our home is about 2500 sf 2 story. We did insulation upgrades several years ago and I use the 3M window insulation kits for the windows.

Up until last year, we would only burn in the evenings and let the furnace kick in as needed in the morning. When propane spiked last winter, I shut off the furnace and burned exclusively with wood. At that time, I had an old cat and no cat probe in the stove. This spring I installed a new cat and probe and recently patched some leaks in the stove I didn't realize were there and now this thing is like a new stove and really puts out the heat after a few hours. After saving so much money not buying propane and since wood heat is so much "warmer" than forced air, I wanted to burn 24/7 this year. This is a very nice problem to have; its kind of funny that after 24 years with this stove I'm still learning how to use it.

I'm going to try letting the coals burn way down and then reload using several smaller splits on the coals and larger splits on top. Perhaps this will allow me to get back up to temp quicker so that I can re-engage the cat quicker while extending my burn cycles. I am also going to experiment with using different flue damper settings (or throttle control as Hearthstone calls it) to extend my burning cycle.

 

[begreen]

Here's an idea to keep the cat active.

 

[HarvestMan]

What an interesting day. I burned the entire day without using the cat. Only controlled the burn using air intake and flue damper. Checked chimney for smoke several times during the day and was quite amazed at how little smoke is produced. Starting to wonder why I was such a slave to using the darn thing. Burned all last winter without using the cat, hmmm. Perhaps I'll only use it on the super cold days.

Makes me wonder how many older model cat stoves out there are burning without the use of the cat engaged.

 

[pen]

What an interesting day. I burned the entire day without using the cat. Only controlled the burn using air intake and flue damper. Checked chimney for smoke several times during the day and was quite amazed at how little smoke is produced. Starting to wonder why I was such a slave to using the darn thing. Burned all last winter without using the cat, hmmm. Perhaps I'll only use it on the super cold days.

Makes me wonder how many older model cat stoves out there are burning without the use of the cat engaged.

Were you sacrificing with the practice though? The cat is there to burn what doesn't happen in the stove and help release heat that way.

Point is, what did you do differently today other than not engaging the cat?

Not engaging the cat should mean a less efficient burn. You can do that with an old or a new catalyst. I'd try and focus on how to make best use of that new catalyst. In the meantime, if doing so damages the cat, then you are back to running it with the cat unengaged.

In other words, with this many years of service out of the stove, and a new cat now to work with, keep experimenting!

pen

 

[HarvestMan]

Were you sacrificing with the practice though? The cat is there to burn what doesn't happen in the stove and help release heat that way.

Point is, what did you do differently today other than not engaging the cat?

Not engaging the cat should mean a less efficient burn. You can do that with an old or a new catalyst. I'd try and focus on how to make best use of that new catalyst. In the meantime, if doing so damages the cat, then you are back to running it with the cat unengaged.

In other words, with this many years of service out of the stove, and a new cat now to work with, keep experimenting!

pen

I agree with everything you wrote. I didn't express myself very well in my last post.

Yesterday the outside temps were around 32 throughout the day. I was able to burn the entire day maintaining a steady comfortable temperature by varying the load size, air supply and flue collar damper. I had been trying to accomplish this same goal while having the cat engaged nearly constantly after coming up to temperature from the cold start. I became enslaved to keeping the cat active and the result was too much heat output. I just don't think it is possible to keep the cat active and maintain lower heat output with this design of stove. Perhaps the newer stoves with their top mounted cats can do this.

Today, I awoke to 1 degree temperatures and am very glad to have the stove cranking away with the cat engaged. I think on these kinds of days, keeping the cat active won't be a big problem and the heat output is noticeably greater. When the cat is engaged, it really damps the firebox and burns way hotter than if the cat is bypassed; it is a very mellow pleasing burn. I am quite pleased with this performance with the new cat.

For the warmer days, I'm just going to focus on maintaining the temps I want and in the process run the cat as much as possible.

One question: what did you mean by? "if doing so damages the cat". I know I can't throw wet/cold wood and immediately re-engage as there is risk to thermal shock. With this stoves design, I think it is very difficult to get flame impingement as the gases get drawn down, then under the cat tray and then finally enter the cat for burning. So, any other things I need to worry about? I also don't want the gases just being pulled through the cat if the temps are not hot enough to light it.

Thanks.

 

[pen]

I also don't want the gases just being pulled through the cat if the temps are not hot enough to light it.

Yep, that would be the concern. Enough smouldering fires and the cat can get plugged up.

Sounds like you have a good plan. Keeping the cat in the active zone 100% of the time would mean a ton of heat. Towards the end of a burn cycle (the last several hours) most of what the cat would have to consume is going to be taken care of already (at the charcoal stage) and it is fine to let the temp drop then until you are ready to reload.

This design certainly has it's challenges. Have fun.