Defiant Encore 1986 - Correct operation of the secondary air intake?

[cwpates]

I have a Defiant Encore 1986 and am confused about the correct operation of the secondary air intake. It makes some sense that this flap should be open at startup and close down to regulate heat as the stove warms up. Lots of comments in the forums to this effect, but there are also a lot of comments that say it should be shut on startup, and the shut position seems to be the correct setting in the rebuild instructions (Serv_Encore_0028_2140) see quote below:

Has anyone a definitive answer on this, or can explain the technical operation of this secondary intake? Thanks in advance..


"secondary STEP 31: Assemble and install the secondary inlet assembly. Holding the secondary

air probe and thermostat assembly with the probe facing away from you

and the mounting tab at 12 o’clock, the tab on the end of the thermostat

coil should be at 4 o’clock position, loosen the lock nuts on the probe shaft

and adjust the coil tab and the mounting tab to the 4 o’clock and 12

STEP 31 Cont: o’clock positions respectively and re-tighten the lock nuts. Insert the

double bent end of the secondary air link through the hole in the tab end of

the thermostat coil. Insert the single bent end of the secondary air link

through the hole in the tab on the secondary air flap. Insert the secondary

air probe through the drilling in the stove back and secure with 1 each,

Phillips pan head machine screw (10-20x ¼”). Secure the secondary air

flap to the stove back with 1 each, Phillips pan head machine screw (10-

24x ¼”) and 1 each, shim ring. Tighten the screw securing the air flap

until snug and back off ¼ turn. Insure that the secondary air flap moves

up and down freely and that the flap rests at or near the closed position.

See figure A-8.

Fig. A-8 Positioning of Secondary Air Probe & Flap"

 

[defiant3]

Gate should be OPEN when the stove is cold then as the probe heats up and the coil expands it should CLOSE the gate. The catalyst needs that extra bit of air for a time. Why? No bloody idea. But I guess it does. When the probe deteriorates, then the gate willNOT close as the stove heats and the gate will never close likely resulting in a prematurely dead catalyst. No one will ever tell you but it's very important to replace the probe at the same time as you replace a combustor.

 

[cwpates]

Hi defiant 3, thanks for the info on the probe. Again, it makes sense that the gate should be open, but why should the technical manual say the opposite? It just seems odd...

 

[Eman85]

I have an older Encore and I pulled the cover over the secondary air flap while cleaning the stove. Noticed mine is closed when cold just like the OP's. What is correct?

 

[Defiant 3]

Tech manual is just wrong. Gate open when cold. That said, if the catalytic combustor functions as it should with the secondary gate always closed then maybe just go with it!?!?!

 

[Eman85]

I'd like to understand the theory behind the secondary air. I have no problem with buying and replacing the probe/coil.

 

[Defiant 3]

Indeed, so would we all.

 

[Eman85]

@Defiant 3 I emailed VC and asked about the secondary air flap control, here's their response...As for the for "thermost spring/sensor". Arriving at an accurate diagnosis can be challenging by phone or email. We rely on our network of factory trained authorized dealers to diagnose and repair products. Your local dealer can provide the proper equipment to form a diagnosis as well as parts if needed. If further assistance is needed to resolve your issue, we encourage your dealer to reach out to us.
I guess it's too challenging to describe. Hard to believe a flat piece of sheet metal and a bi-metallic spring is that challenging to describe.

 

[Eman85]

In looking to purchase a new secondary air flap probe I ended up on Amazon. I asked the question on Amazon and 2 people responded that the flap should be open approx 1/4" when cold. Amazon also had a good price on the probe.

 

[Kevin Weis]

If this secondary is similar to the newer Encore's of which I had one' the manual is probably correct. The secondary opens when the primary is closed down in an effort to prevent a draft stall at the lowest primary air settings. This is a sort of standard set up with all the VC stoves albeit with different mechanical setups. In some of the newer models the secondary air is not even mentioned. Guess it's considered a safety mechanism of sorts. IMO it detracts from the responsiveness of the primary air control.

 

[Eman85]

If this secondary is similar to the newer Encore's of which I had one' the manual is probably correct. The secondary opens when the primary is closed down in an effort to prevent a draft stall at the lowest primary air settings. This is a sort of standard set up with all the VC stoves albeit with different mechanical setups. In some of the newer models the secondary air is not even mentioned. Guess it's considered a safety mechanism of sorts. IMO it detracts from the responsiveness of the primary air control.

I ordered the probe and I'm running the stove and not activating the cat by keeping the damper open. I've had the cat start to run away and it was climbing into the high 1600's and the flue temp went high. Also started making a whooshing noise in the cat chamber. I never had this problem in the past but was running without using the cat the last year or so as it didn't seem like it was active. Bought the replacement cat and the Auber probe this year. After I install the prob/coil for the secondary I'll see how it reacts.

 

[Eman85]

Update, I removed the old probe/coil and the end of it was burnt off quite a bit. Installed the new probe/coil and the secondary air is open just like the drawing posted above. With the stove burning but the cat not engaged the secondary air closed. I engaged the cat and it ran up to 900's and the secondary air styed shut. I left the cover off so I could observe it especially after seeing the post @Malarky112 has about the secondary opening back up.
The probe/coil I purchased from Amazon came from Home & Hearth and looked like the original and fit fine.

 

[Kevin Weis]

I'm in a different camp on this secondary air intake stuff. I belive cold, the secondary is designed to be open. How far I don’t know and I'm sure that is not going to be in any manual. VC dealer will have to get intouch with HHT to get the specs on that. As I've stated on other threads on this on the Intrepid flexburn the secondary airflap is a bypass directly to the flue to pre ent a draft stall in the event the primary is set to low. Strictly a safety issue but it's effect is supposed to make it impossible for the draft to the stove to be cut off completely. I don't believe VC has the secondary flap serve a different purpose on they're other stoves. Maybe the misnomer here is that the secondary air flap controls the secondary combustion in the combuster directly but it does not. The secondary combustion as the same source of air from the primary that's also routed to the airwash. If this is not true I'd like to see the schematic from VC that shows the specific routing of the airflow in both the primary and secondary airflaps. With respect to replacing secondary air bi-metal thermostat, it looks for sure that replacement was needed. Hopefully a dealer can get the specs on how the placement and adjustment should be on the installation of it.

 

[Eman85]

VC pretty much blew me off. If you call for technical assistance you get transferred to a dealer. I emailed and they sent me some mumbo jumbo about it being complicated and I should contact a dealer. I spoke to my closest dealer and he was knowledgeable but didn't really know or understand the purpose of that secondary air shutter. Called a few other dealers and they knew nothing about it at all. One dealer did give me an email of their repairman and I'm waiting to hear back.