A sales rep told us you can use a catalytic stove as a non-catalytic by just leaving the bypass open...
Is that correct?
My gut feeling says no.
Is that correct?
My gut feeling says no.
What happens if a cat stove bypass is left open?
- Thread starter rpwalton
- Start date
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I doubt it will hurt the stove, but why? I'm only familiar with Blaze King cat stoves. Leaving the bypass open basically makes an old inefficient stove. There is no baffle or secondary burn tubes.
About the only way to hurt a Blaze King is by running it with the bypass open. Once it’s up to temperature the bypass needs to be closed so the thermostat can do its job.
kennyp2339
Minister of Fire
Well now... hold on here, I know the BK should not have the by-pass open due to stove running out of spec and damage that may occur on the by-pass retainers, but there are other stoves out there besides BK and I believe a few are hybrids which offer running the stove on secondary reburn and by-passing the cat, so OP, what stove were you looking at? Not all stoves are created equal.
I guess I have always been under the impression that the thermostat will control the air regardless of whether the bypass is open or closed. I have had really hot starts in the past where the cat wasn't to temp but the burn was really taking off. I just left the bypass open and turned down the thermostat until the cat was active. Realizing that an overburn can warp things, I just assumed that leaving the bypass open and controlling the air was just like operating the old models with no cat or bypass.
As long as you are there to turn the t-stat down, that’s the correct way to handle it. But leaving the bypass open unattended isn’t a good idea.
What stove is a hybrid that has a bypass and still utilizes the secondary burn in bypass mode? The only one I’m aware of is hearthstone. Which is shaping up to be a terrible design..
I don't know what stove you have. I have the VC in my signature and I've run it for years without closing the bypass and using the cat. It burns just fine but will obviously create more creosote in the chimney when you cut the air back for overnight burns. I can easily get an 8hr+ burn with the bypass open and the air turned down. I can get more heat out of my stove by not closing the bypass as I don't have to cut the air back as far to prevent the cat from overfiring. Yes, I will burn more wood but I will also get more heat out of my stove. yes, I will create more creosote but I clean my own chimney so it's just more work.
It depends on the stove and bypass design. On some, this is not a good idea and is discouraged. The Rockport's design makes this less of an issue, but allowing the flue gases directly up the liner for an extended time could compromise the liner integrity and shorten its life due to high temperature. It's also a waste of fuel as there will be little or no secondary combustion.
mdocod
Burning Hunk
The Lopi Rockport Hybrid-Fyre appears to have a fairly traditional secondary combustion setup, with preheated air being injected under a flame baffle through several cross-drilled pipes. When operated with the cat bypassed I would expect this stove to burn similarly to a modernish non-cat stove, but not as well as a stove whose design has been optimized around only having primary and secondary combustion. The most efficient clean burning non-cat stoves will have MORE secondary combustion than a hybrid stove. Hybrid stoves depend on both secondary and catalytic combustion to maximize efficiency and minimize emissions. Bypassing the cat in these designs will have a negative impact on the overall efficiency and emissions, however, it would not surprise me if most of these modern Hybrid stoves would still pass the 2020 emission standards with the cat disabled, but they would not show up near the top of the efficiency/emissions list the way many of them do with the cat engaged.
A Hyrbid stove should be operated with the cat engaged most of the time, however, most Hyrbid designs are designed to work with the cat bypassed without causing any harm to the stove or chimney system. This can be very useful if the cat is accidentally plugged or damaged by unforeseen burning conditions or fuel anomalies. You still have a functional, albeit, less efficient stove, if needed.
A Hyrbid stove should be operated with the cat engaged most of the time, however, most Hyrbid designs are designed to work with the cat bypassed without causing any harm to the stove or chimney system. This can be very useful if the cat is accidentally plugged or damaged by unforeseen burning conditions or fuel anomalies. You still have a functional, albeit, less efficient stove, if needed.
With the bypass open the smoke does not pass over the tubes and baffle, it goes straight up the flue. The net result being very incomplete combustion.
Correct.
To the OP, read the manual. Operate the stove as prescribed in the manual for the sake of emissions, efficiency, output, and preventing stove damage. The dealer quite often has no clue what he is talking about but may be more interested in making a sale to a customer that appears worried about cat failure leaving him without a stove. He's telling you what he thinks you need to hear to make the sale.
We are lucky enough to have some professional stove people on this site, some dealers, some manufacturers, and some servicemen that are smart and honest.
I only remember one stove, a VC, that actually directed the operator to choose to use the catalyst or not. It was in the manual.
mdocod
Burning Hunk
I was looking at a parts exploded view of the stove and saw what appeared to be bypass damper situated above the flame baffle. I now realize that the part I was looking at was the CAT itself, which appears to be in a good position to take a lot of direct flame, which is generally considered bad for cats.
No thanks... they can keep that stove design. On the hearthstones they can be safely operated with or without the cat engaged. If someone who isn't familiar with the cat control screws it up they aren't likely to cause any harm.
I just watched the cutaway video of this stove and checked the operational diagrams in the manual. You are absolutely correct there is no way to bypass cat while still using the baffle/secondaries in this stove design... The bypass looks more like a band-aid to fix the issue of the gap between the baffle and the front of the box being too tight and positioned such that it wants to direct smoke out the door, but then, seeing the cat right up there in the path above the baffle, yea the only way to bypass a cat in that position, which would be required for opening the door is around the back.
No thanks... they can keep that stove design. On the hearthstones they can be safely operated with or without the cat engaged. If someone who isn't familiar with the cat control screws it up they aren't likely to cause any harm.
Not being a cat stove owner/operator you answered some lurking questions i have had concerning the long burn times and what if my house is too cold with a long slow burn.
Coming from a Harman top loading stove to a Burn tube stove. I have just as long burn times with less fuel loss making sure the secondary stays lite. The Harman you could not operate with more than three or more pieces of wood with the bypass open without getting too hot.
The Rockport design is preferable IMO. The only time the bypass is intended to be open is when starting or reloading the stove. What's nice about this design is the ease of chimney cleaning with a straight shot up the flue. No parts to remove and it is ruggedly simple. The cat location is common to many cat stoves. It helps derive more heat from the cat before heading out the flue. Note that the Heritage also has the cats right above the baffle, with no flame shield.
The bypass handle should be closed once the catalytic combustor heats up to activation temperature, and remain closed whenever the stove is burning and in the active temperature range.
That needs qualification. Hearthstone seems to discourage open bypass burning in their docs for the Green Mountains. There are multiple designs depending on the Hearthstove stove model. Some of these designs are not so great for the opposite situation. With the bypass closed the flame heads right up the cat which sits directly below the flue collar. That ends up in less heat from the cat retained in the stove body and more up the flue. Additionally, the cat has no flame shield and users are reporting it can get ash plugged quickly.
The bypass handle should be closed once the catalytic combustor heats up to activation temperature, and remain closed whenever the stove is burning and in the active temperature range.
Sounds like you could benefit from a new stove. 😏
You don't have to burn a cat stove low and slow, you can open it up a bit for more output if needed.
Then open up the air more and let it cook.
Note that there are many cat stove designs. Some are better at heating at higher levels and not low and slow.
I may have misunderstood due to most of the comments by cat owners is to say how long their burn times are. I got the impression that was their only objective whether it kept their house warm enough or not. My bad. I'd love to have that long burn option in fall and spring though.
It is a bit less messing around than burning short loads in a non-cat to reduce output..
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