How Long to Bypass on Reload

[Garrin]

Howdy All,

First season running a Bk Princess Insert (or woodstove at all, for that matter).

I reached out to BK about this but haven't heard back.

On a hot reload, how long should I leave the cat bypassed? I've heard mixed information on here.

Some are in favor of leaving the bypass open for 5-10 to let moisture cook off before engaging the cat- which supposedly means longer cat life as you're not shocking it with water vapor.

Others say that you're good to go as soon as you've got the loading door closed, so long as the car is in the active range.

Any definitive answer on this one?

Thanks all.

 

[NHWS]

The stock cat gauge is slow. It tells you the cat temp several minutes ago. I've heard estimates between 5 and 10 minutes. If you just closed the door after a hot reload, you don't know the *current* state of the cat.

In my Copious Free Time(tm), I'm looking into a digital cat gauge to get quicker info. Check the VC Owners threads - there are some discussions about it for VC stoves. AFAIK the very experienced BK owners here are not using digital cat gauges. Not sure why not.

What I've been doing instead is using a digital flue temp gauge as a proxy for the state of the cat. Once the flue gas gets to 600 dF, I close the bypass. Sometimes that's just a few minutes, sometimes it takes 10+ minutes, depending on the coal bed and the kind of reload. The flue gas usually drops 50 to 75 dF when the bypass is closed, and then starts slowly going back up.

I leave the air all the way up for 15 minutes after that to reduce the remaining MC of the wood, then start slowing it down.

Not sure if what I'm doing is right, but there are at least a few other people here doing similar things.

 

[DonTee]

On my PE32 Princess I close the bypass after the flue temp is 600-700 degrees. That’s assuming the cat is in the active zone by then. If it’s not, I turn down the stove temp knob a little to keep the temp under 700 until the cat is in the active zone, then I close the bypass and turn the temp back to max.

After the bypass is closed I let the temp get back up to 600-700 before turning down the temp to my desired setting.

 

[kennyp2339]

Princess owner here, I have a wood stack next to my stove, so the wood is usually room temp, I open by-pass load and close the by-pass all in one shot, if the wood is coming directly from outside and cold, I'll leave the by-pass open for like 5 min, my splits are never wet or snow covered since its stored in a woodshed or inside on the rack.

 

[Dieselhead]

Same as Kenny, as long as temp gage is in active zone.

 

[Highbeam]

Kinda splitting hairs. Doesn’t really matter? Assuming the cat meter is active and the new dry wood ignites quickly as it should, send it!

 

[Garrin]

Thanks all.

Based on replies, I probably should have tried to install a flue temp probe when I installed the unit, but that's alright.

From what I have gathered generally, so long as I've got dry wood and don't keep the bypass open indefinitely or open the loading door without opening the bypass, I should be fine.

My big "wonder" is whether those little procedural differences can affect cat lifespan as I've heard some folks claim.

I suppose another thread of "how to maximize cat life" might be a better question.

Again, thanks for the replies!

 

[Tron]

I probably should have tried to install a flue temp probe when I installed the unit, but that's alright.

You still can. All you need is to drill a 1/4" hole into the flue about 2' above the stovetop and insert a Condar or something.

To your initial question, when the cat is still in active range, I usually leave the bypass open until I see that all splits have caught fire and it's raging in there. With coals left, that usually takes 5 Minutes, tops. Then I close the bypass and turn down the thermostat in one go.

 

[NHWS]

I've found that leaving the air full open for around 15 minutes reduces smoke from the chimney.

 

[Garrin]

You still can. All you need is to drill a 1/4" hole into the flue about 2' above the stovetop and insert a Condar or something.

To your initial question, when the cat is still in active range, I usually leave the bypass open until I see that all splits have caught fire and it's raging in there. With coals left, that usually takes 5 Minutes, tops. Then I close the bypass and turn down the thermostat in one go.

I didn't realize installing a probe is so easy. I imagine with the negative pressure there's no need to seal it or anything?

 

[DonTee]

I didn’t seal mine with anything. I remove it whenever I clean the stove pipe.

 

[Garrin]

I've got the princess insert. Other than checking it being a bit annoying, does that present any other problems with the flue probe?

 

[Sandy Alan]

Know I'm late to the party, but I find this interesting. I've been burning a Princess for 20 odd years. I have always, on reload, turned up the thermostat, opened the bypass, waited a minute or two, slowly open the door, add wood, close the door, and immediately shut the bypass (assuming cat thermometer is in active zone), wait ten minutes or so, or until cat thermometer is near upper end of active zone, and start turning down the thermostat. I usually run it about midway (2).
But I do notice smoke billowing out of chimney for about an hour (hour and a half) or so after that. Always figured that to be normal until everything settled down. I burn exclusively pine, as that's all you are going to get around here. It's aged minimum a year, often two or three. Wonder if leaving bypass open longer would mitigate that? Though I do worry about hot embers going out the chimney when the bypass is open.

 

[stoveliker]

I think your smoke is due to you burning so long wide open - with wood that gets going fast.
Then, from wide open to closed bypass and decreasing thermostat, you're likely sending too much combustibles through the cat too quickly (hot flue = high draft; long wide open burn of pine = much, much off gassing) so that the residence time of the gases in teh cat is insuffiicient for it to fully combust everything.

 

[Sandy Alan]

We usually shut the bypass and wait awhile before turning the thermostat to 3, then wait awhile longer before turning it to 2. We don't go directly to 2. We have found that if we turn the thermostat down before the needle on the thermometer is near the highest point in the "active" area we will get a very strong smokey smell in the house (same thing if we turn the thermostat too fast all the way to 2 without stopping awhile on 3), so much so that it can even water your eyes a bit. Don't see any smoke, nor does the nearby smoke/co detector go off, but it is very noticeable. That's why we let it get really hot first. Probably has to do with the pine that goes up so fast (sometimes the needle on the thermometer will "bury" or go nearly all the way around to collect $200.00 😂 if we get distracted for a few minutes), but we are in Montana in the middle of a pine forest! It's all you are going to get! We do still manage 12 hour burns though!

 

[stoveliker]

I have pine too, but anything I say is not comparable, as I'm at sea level, have a different flue, etc.
So what works for you works. (How old is the cat?)

I quite agree that air quality indoors is more important than air quality outdoors.

Finally, maybe @Highbeam has useful things to say, as I believe he mostly burns pitchy "softwood" too.

 

[Tron]

. Don't see any smoke, nor does the nearby smoke/co detector go off, but it is very noticeable. That's why we let it get really hot first

Strange. I, too, burn mostly pine, and on a reload I keep the bypass open and the thermostat on WOT until I see the wood has caught (2-3min tops), then I close the bypass and directly dial down to where I want it. That is if the cat is still in the active zone.
No strange smell. I only get that if I wait too long with that and the flue temperature gets above 1000F. THEN I clearly notice a burnt smell.

 

[Highbeam]

We usually shut the bypass and wait awhile before turning the thermostat to 3, then wait awhile longer before turning it to 2. We don't go directly to 2. We have found that if we turn the thermostat down before the needle on the thermometer is near the highest point in the "active" area we will get a very strong smokey smell in the house (same thing if we turn the thermostat too fast all the way to 2 without stopping awhile on 3), so much so that it can even water your eyes a bit. Don't see any smoke, nor does the nearby smoke/co detector go off, but it is very noticeable. That's why we let it get really hot first. Probably has to do with the pine that goes up so fast (sometimes the needle on the thermometer will "bury" or go nearly all the way around to collect $200.00 😂 if we get distracted for a few minutes), but we are in Montana in the middle of a pine forest! It's all you are going to get! We do still manage 12 hour burns though!

I burn lots of softwoods and do it like you. I even have numbers on my thermostat dial like you!

These stoves smoke. Much more than a noncat. I also get smoke from the stack, blue smoke when cat is active, until things settle in but I don’t get any smoke smell in the house. The huge majority of the burn is with no visible smoke from the stack.

 

[Sandy Alan]

So last night, just for jollies, I tried adding wood (thermometer indicated active cat throughout), closing the door, leaving bypass open three or four minutes until it was burning good, closing bypass and started slowly turning down the thermostat right away. I turned it to 2 1/2, waited 5 minutes and turned it to 2 1/4. Waited a few minutes and went to 2. Everything seemed good. Cat temp moved up from about 25% into active to about 75% into active. Then about 1 1/2 hours into the burn we got a strong smoke smell in the house. I opened all the windows and doors. I looked out at the chimney and it was billowing smoke that was trailing across the valley in the night sky as far as I could see putting my tactical flashlight on it. Never saw it so bad. Came back in and turned thermostat back to wide open. Left it until the thermostat moved past the active zone into the black on the right side (very hot), then I again turned it down over a period of ten minutes or so. During this period smoke continued billowing. After I got it down to 2 I rechecked and smoke reduced to puffs that dissipated about 10-15 feet from the chimney. Smoke smell inside was clear, so I left a window cracked in the room with the stove and we went to bed.
As for the cat, someone asked, it was brand new from Blaze King at the start of the 2023-24 burning season. The previous one lasted 9 years. Should last longer than one and a half burning seasons for $450.00!

 

[stoveliker]

Is the smell in the home coming in from outside?

This behavior is not what most people see. 🤷‍♂️

 

[Sandy Alan]

If I use the old super sniffer it is strongest just above the stove. Is less so the further you move away from the stove. Also, fyi, I did my midwinter chimney sweep 2 1/2 weeks ago. Got only about 1/2 a cup of crusty creosote, about average for my midwinter sweep. Usually more on the chimney cap than in the chimney. I cleaned that off really well.

 

[Tron]

Then about 1 1/2 hours into the burn we got a strong smoke smell in the house. I opened all the windows and doors. I looked out at the chimney and it was billowing smoke that was trailing across the valley

Now that is really strange. At that point in the burn I don't see any smoke at all, even turned down.

 

[Sandy Alan]

So I am testing the cat right now. Turned it down to 1.5 about two hours ago. See if it goes out. So far so good. Thermometer about 20% into active zone. Smell completely went away after turning it down. No smoke. I added wood this morning, letting it get really hot before turning it down. It took 4 hours before smoke stopped at chimney, though it wasn't bad. Just a puff going out about 10 feet and dissipating.
I just ordered a hand held c02 detector to help pinpoint odor (hopefully), though we have not had an alarm, either c02 or smoke go off. We have them all over the house including a few feet from the stove. At this point I am starting to suspect leaking bypass gasket, at least regarding the smoke. Door gasket was replaced this fall and passes dollar bill test to the point of tearing all the way around.

 

[Tron]

I just ordered a hand held c02 detector to help pinpoint odor (hopefully), though we have not had an alarm, either c02 or smoke go off.

I suppose you mean a CO (=Carbon Monoxide) detector?
That's what a smoldering fire emits, the cat turns that with excess oxygen into carbon dioxide (and heat).

My money is not on the bypass gasket, at least not for the smoke IN the home.

 

[Highbeam]

Forget about the bypass gasket, it's not the problem.

Tell us about this fuel. Is it stored outside in the snow? How many years cut split and stacked in the shed? How big are the splits?

I would suggest that you buy your next cat online for about 250$ shipped but this one should still have plenty of life left. I am also on a cat that was installed in november of 23 and it's working great still.

Is it really cold there where cars and folks burning natural gas have huge plumes of steam from their exhaust pipes? Wood burning can steam if conditions are right.

Is the plume of smoke with a very active cat white smoke? If so, that's mostly water. Blue smoke is mostly unburned fuel.