VC Merrimack air intake?

[Boris]

Where are combustion air intakes on the VC Merrimack?

• There is primary air intake holes on the front/bottom, almost under door hinges which channel to the central "nozzle"
• There is a secondary "flap" intake on the top that closes when temperature rises

But how does the dampener work? Where does that air come from? Which opening in the stove?

Reason for question: Stove seems to burn faster than expected.

 

[therealdbeau]

We're in the same boat @Boris. I have a new Merrimack and have been burning it for about a week and have the same question.

I need to take mine apart again and try to study it a little more because I just can't seem to figure out how the damn thing works. The "primary air hole" is just fixed wide open. The "air control lever" adjusts some sort of damper in the upper part of the unit.

I think that by adjusting the air control lever we're actually closing the damper on the exhaust end of the equation.

I too would like to slow the thing down. I packed it as full as I could get it last night before bed with dry oak, turned it all the way down and woke up approx. 8 hours later to mostly ash with a few hot coals left hanging around. I don't know if this is par for the coarse but certainly not the 12 hours advertised.

 

[therealdbeau]

So if you look where the latch for the door slides in there is a channel that runs the whole width of the stove. This is where the ports open and close for the air control. This is also where the auto restart system opens up a port to take in extra air.

The automatic restart feature thingy appears to draw air from the top grate. The ports for the air control however I can't determine where they actually pull the air from. They seem to be contained in some type of manifold that runs to the back of the insert maybe.

The ports that open/close at the top are directed at the glass so this appears to function as the air wash as well. I suppose it makes sense that this air would come from the back of the stove so that it is heated to aid in cleaning the glass.

I may experiment with partially blocking those air inlets in the bottom of the unit that lead to the nozzle.

@Boris can you look inside that bottom grate behind the fan switch and tell me if your stove has a piece of white insulation tucked in there?

 

[Boris]

@therealdbeau
I've also taken the stove partially apart to figure it out but no luck yet.
- Yes, there is white ceramic insulation between the bottom of the cast-iron firebox and the sheetmetal that the fan mounts to. I actually removed the factory fan and re-routed the air intake (the non-combustion air).
- Yesterday, after the stove was up to temperature I put a magnet to cover one of the two primary air intake holes on the bottom front of the stove. That seemed to help a lot, nice slow burn but still no smoke or smoldering. Not sure if this is a viable solution.
- Have you taken the top sheetmetal cover off? I think that's my next step though might be a challenge since the insert is already installed.

I agree with you: I think I understand everything except for how the dampener works and where does the air for the secondary combustion tubes on the top comes from.
If taking the top sheetmetal off doesn't answer the questions, I might get a fog-machine, close off the main flue, pump it full of fog and see where it comes out from

Keep me posted if you find anything additional.

 

[begreen]

Before modifying a new insert is there anything that could change in the way that the stove is being run? Have you tried burning larger splits? Have you tried turning down the air supply much sooner?

 

[Boris]

@therealdbeau
I think I figured it out!
- Air for the secondary combustion (the tubes along the top) comes from manifold on the sides (top) of the stove. Manifolds get air from behind the side covers.


- The damper manifold also gets air from the the sides. See where the white zip tie is sticking out:


Few more pictures I took while it was partly apart:

 

[therealdbeau]

Nice work Boris! I suspected the air came from around the back (or sides) of the unit so as to heat the air.

I still don't quite understand why we have that intake nozzle in the bottom that we can't control the amount of air it feeds. I'm experimenting now with completely blocking those off.

I think insulating around the stove is definitely worth the effort so I'll work on that come spring time.

 

[therealdbeau]

Before modifying a new insert is there anything that could change in the way that the stove is being run? Have you tried burning larger splits? Have you tried turning down the air supply much sooner?

I get what you're saying begreen. For me, it's not so much that I'm displeased with the performance of the stove as much as I just like tinkering around.

You have a lot of experience with stoves, is it common that a stove has an unadjustable air intake separate from the adjustable damper air intake?