When to engage/close the bypass

[Hunter8282]

So basically, you want to close the bypass as soon as the gauge is showing the cat is in the active zone correct? On either a cold start or reload.

Regardless of what you do with the thermostat, close they bypass once it's active, and you don't want to have the door cracked open at all once the bypass is closed correct?

Do I have that right?

 

[stoveliker]

All Correct.

 

[stoveliker]

One minor detail, upon a hit reload (i.e. cat still reads active) I do let the box burn a 30 seconds to a minute with the bypass open after the door is closed. This exhausts some of the cold (room ) air that came in upon reloading and provides some heat to the wood before the gases are routed through the cat when one closes the bypass. Possibly better for the cat imo.

 

[Woody Stover]

With the digital thermometer and thermocouple/probe setup that Todd gave me, I burn in the load until the temp gets to about 500 (the temp at which they say catalytic burning begins,) then I close the bypass. The flame heat/smoke is then routed to the cat, and the temp takes off, jumping by 4-6* every couple of seconds. The cat generally will begin glowing at about 900, but that can vary. At that point, you can decided to run with a little flame in the box, or none at all, and the cat will remain active.
The only thing I'd add is that if the cat is still active but you want to add more wood, open the bypass for a couple minutes before opening the door, to avoid thermal shock to the cat. This won't cause a steel cat to crack, as it would a ceramic, but I would still avoid it nonetheless.

 

[stoveliker]

The steel cat (and the ceramic one) also can suffer from cold air by having the oxide coating (onto which the active metal atoms have been deposited) spall off of the (metal or ceramic) substrate.
Possibly even more so on the metal one (thermal expansion differences) - I guess.