Why did Hearthstone stop using the Bi-Metallic Coil Primary Intake control?

I bought my first stove, a Heritage back in the mid 80's. It had the Bi-metallic coil on the back of the stove that controlled the amount of air that entered the primary. Basically it's a big heavy duty thermostat coil, with a wire hooked on one end. The other end of the wire is hooked to the intake flapper. As the coil gets heated up, it opens, closing the air intake, then again as it cools opens it back up. It was along time ago, but I don't remember having any issues with it at all. Fast forward to a few years ago when I bought my used and abused H1 off CL. It was missing a bunch of parts including the Bi-metallic coil. While talking back & forth with Jim Casavant at Hearthstone he told me that they stopped using the coil and replaced it it a all manual control. At the time I didn't think too much about it and had my work cut out re-building the beast.

Well, Once I fired it up and started using it I realized that the all manual control is kind of a pain in the arse requiring much more user adjustment. So after a almost 3 year search, Defiant here(THANKS AGAIN DEFIANT!) shipped me a proper coil he took off a parts stove. The fire does not get more air as it burns down with manual input unless you are monitoring it all the time, which in turn means more coals. With the coil, it opens up and gives those coals more air which has given me a noticeable more complete burn. Once adjusted correctly the coil controls the air intake perfectly. I can load it up and walk away for 8-10 hrs. Every time I look at the flue temp monitor it's running at optimum temps(usually between 425 and 500), and I have not touched the coil or intake flapper since I installed it over a month ago.

So the question is why would Hearthstone abandon a very simple air intake system that works better(in my opinion) then an all manual one? It can't be cost, the thing could not cost Hearthstone more then $20. Do y'all think it was because of user error....idiots unable to figure out how to set it up right? Or something else?

This is what one looks like for those that have never seen a Bi-Metallic coil:

I just sent Jim a update on the stove after the re-build 3 years ago. I asked him the same question, so maybe he has the answer.

Well Rick I am glad it worked out for you

Well, I should have asked Jim the question first & here is the answer:

"The bi-coil is one of those items that 50% of the users loved, and the other 50% requested a manual air control. When we started making the EPA certified stoves, the concern was that the bi-coil would start to shut the stove down before it got hot enough to start the secondary combustion (in the catalytic combustor originally – now via secondary air pipes). Secondary burn requires fuel (smoke), temperature from the wood burn, and air supplied through the tubes. If any of the three are missing, there will be no secondary combustion and therefore no certification."

I had not thought about CAT operation but it looks like I was right about user error. I wonder how long it will be before we see digital & servo controlled air intakes on CAT stoves...or does that exist already?

Yep there were a couple threads on those subjects