Do cat stoves use secondary air?

[EddyKilowatt]

The thread that's running about add-on catalysts got me to wondering where the oxygen to catalytically "burn" the smoke comes from.

Do purpose-built catalytic stoves all have some arrangement to heat and mix secondary air into the smoke stream before it goes into the cat? Or do they just rely on leftover oxygen from the primary air?



ever curious,
Eddy

 

[Backwoods Savage]

The cat needs no flame at all. All it needs is smoke or rather, the gasses. Many times when the cat is working nicely, there is no flame to see in our stove and sometimes you can't even see a red coal, yet, the cat is glowing red. It also just uses the same air; no secondary air there.

 

[sparklow]

My Dutchwest A-Plus Cat from 1990 most definately uses secondary air for the converter. It is an adjustable air source and probably one of the reasons that Cat equiped stoves earned a reputation for being harder to use than non-cats. That said, mine works great, but then I've had eighteen years to learn how to use it.

 

[FireWalker]

On my Dutchwest Cat stove, When cat was engaged and working you could look up thru the glass and see the bottom of the combustor (the round ceramic can thing) glowing red hot. the combustor rests in a chamber just below/inside the stove top. The combustor is surrounded by this thing called the air distributor:

(broken link removed to http://www.blackswanhome.com/product/air-distributor-various-dutchwest-models)

On the side of the stove, there is a threaded thumb screw device used to allow more or less air directly into the air distributor inside the combustion chamber. Open a couple of turns, only a quarter turn or closed tight this secondary air adjustment made no change to the heat output, heat duration or chamber temprature as indicated on the stock thermometer. It even said in the manual it was nothing short of an art to get setting just right.

So, yes some stoves have an adjustable secondary air supply.

 

[FireWalker]

My Dutchwest A-Plus Cat from 1990 most definately uses secondary air for the converter. It is an adjustable air source and probably one of the reasons that Cat equiped stoves earned a reputation for being harder to use than non-cats. That said, mine works great, but then I've had eighteen years to learn how to use it.

Was 1/4 turn open the setting you used most often? I believed this to be my sweet spot but it was hard to tell.

 

[VTSR5]

Do purpose-built catalytic stoves all have some arrangement to heat and mix secondary air into the smoke stream before it goes into the cat? Eddy

My VC Winter Warm catalytic insert definitely uses secondary air to feed the cat. This air is metered by a guillotine-type gate on the back of the insert, operated by a bimetallic coil. The coil has a probe which pierces the refractory package and sits in the exhaust one inch downstream from the cat. No user input possible on the secondary air.

Complicated, but sophisticated.

 

[elmoleaf]

My VC Intrepid II also uses secondary air. There's a bimetallic coil with probe into the secondary combustion area that's connected to metal flapper over a secondary air entry.
As the secondary combustion area heats up, the thermostat automatically cuts down on the amount of secondary combustion air entering the chamber.

This system is separate and distinct from the primary air thermostat that's adjustable by the stove operator.