Where Can I Buy a Bi-Metal Draft Regulator?

Ok so I determined the "spring loaded thermo" device is cheaper than every comination of PID controller and other vent device I've concocted. The 'other vent device' possibilites being motorized ball valve, linear actuator, hvac damper actuator, solenoid, the aforementioned draft inducer, and hydronic zone valve. Ambient operating temperature is a big constraint on cost and availability of parts. And, while proportional control of an on/off vent is far more fun to tinker with and tune, the simplicity of mechanical pull chain and my local county's propensity for winter power outages wins out. Adding battery backup to an electronic solution is easy but only drives the cost up further. And most importantly, my manager of domestic operations advised me that new tile in the kitchen was more important to the fiscal plan! Sounds like some bass akwards Obamacare logic to me... But anyway, she said I could get a welder if I cut some of the cost of it out of my solution. And a welder is just so cool to have around!

So I ordered the Daka 412 furnace auto damper version. $64. It looks like a good one and since rberq indicated he'd have used a different one had he done it all over again, I figured I'd branch out and try something different. (Sorry to Fred and any Hitzer fans here).

Now all that's left for big decisions is how to fabricate the vent or draft box portion of the design.

Unless you just want a welder and have other work for it this is just an excuse to buy one.

You will just make a mess of the installation. You still have to fashion the box to the curvature of the stove.

Take a piece of string and a pencil, tie a nail on one end and a pencil on the other 9 inches apart or whatever the radius of the stove barrel is. Make two arcs the length of the box on a piece of letter paper. Cut with a scissor and glue to the box. Rough out with hack saw, grinder file,etc. to the pencil marks. There really is not that much.

Place box on stove and mark around it. Around an inch in from both edges drill a half inch hole in the stove. File the edge of that hole in the direction of the box edge a square flat surface. Using a hack saw blade in a holder or taped for a handle cut two slots one half inch apart toward the inner edge of the box. Heat the tab you just made red hot and bend it out at right angles to the stove. This is to mount the box with using 10/24 screws and nuts after drilling through both box sides and the tabs you just made. Finish with a narrow bead of furnace cement and should look very neat.

franco b wrote:Place box on stove and mark around it. Around an inch in from both edges drill a half inch hole in the stove. File the edge of that hole in the direction of the box edge a square flat surface. Using a hack saw blade in a holder or taped for a handle cut two slots one half inch apart toward the inner edge of the box. Heat the tab you just made red hot and bend it out at right angles to the stove. This is to mount the box with using 10/24 screws and nuts after drilling through both box sides and the tabs you just made. Finish with a barrow bead of furnace cement and should look very neat.

Having trouble visualizing it, do you have a picture of the concept?

Edit:...wait I got it now! Good thinking. I guess furnace cement is needed to get airtight.

I do think it is a mistake to not buy the bi metal sensor and the damper assembly meant for each other.

The bi metal spring should be calibrated for the weight of the flapper door. To fashion a flapper assembly and box with hinge yourself would be a lot of work and might not work well with the bi metal spring.

franco b wrote:I do think it is a mistake to not buy the bi metal sensor and the damper assembly meant for each other.

The bi metal spring should be calibrated for the weight of the flapper door. To fashion a flapper assembly and box with hinge yourself would be a lot of work and might not work well with the bi metal spring.

Interesting point. I thought the weight of the door would be nominal and spring would not be affected much by the presence of something pulling on it. A pretty tight coil so to speak. Maybe I'll need to engineer around that.

Maybe calibrating it means controlling the size of the opening in the stove wall inside the draft box. How about a spin draft on the stove inside the box? It'd directly damp the air intake relative to the size of the opening of the flapper.

And/or make a light flapper and add weight as needed. Anyone that has one approximate how heavy the flap is? 1/4 inch steel, or thinner sheet metal?

JRLearned wrote:So I ordered the Daka 412 furnace auto damper version. $64. It looks like a good one and since rberq indicated he'd have used a different one had he done it all over again, I figured I'd branch out and try something different.

Looks like this Thermo damper uses no chain for linkage, but is directly mounted over where the inlet hole is cut into the stove.
Depending on where the hole is cut/located will determine how much the bi-metal coil will react to changes in temps.
Coal needs it's air from below the grates...but the temps in that area may not act on the bi-metal as may be desired in this case...but I may be wrong.

Hitzer's design is a time tested solution...no?

Also, looking at the DAKA...the bi-metal damper could interchange with an electric blower at the same cut-out hole location...so, this reinforces the no chain design application...Sorry

McGiever wrote:

JRLearned wrote:So I ordered the Daka 412 furnace auto damper version. $64. It looks like a good one and since rberq indicated he'd have used a different one had he done it all over again, I figured I'd branch out and try something different.

Looks like this Thermo damper uses no chain for linkage, but is directly mounted over where the inlet hole is cut into the stove.
Depending on where the hole is cut/located will determine how much the bi-metal coil will react to changes in temps.
Coal needs it's air from below the grates...but the temps in that area may not act on the bi-metal as may be desired in this case...but I may be wrong.

Hitzer's design is a time tested solution...no?

Good point. I did not realize that. Looking at the Daka it says mounted on the furnace door. It might be all in one which will not work for you.

But it also defeats the "no electric" concept--time will tell on this one. Let's remember---the proof is in the pudding ---McGievers 2nd post above

McGiever wrote: Looks like this Thermo damper uses no chain for linkage, but is directly mounted over where the inlet hole is cut into the stove

Yes, it looks mounted on the over fire air hole, but check out this component that's in there.
http://store.dakacorp.com/product_p/32205.htm
It has a chain, albeit a short one. Seems pretty adaptable.

McGiever wrote: Hitzer's design is a time tested solution...no?

You may be right and I may have to limp on back to Hitzer. we'll see when it arrives.

Hell JR, that's not limping---nothing ventured, nothing gained---or not

freetown fred wrote:Hell JR, that's not limping---nothing ventured, nothing gained---or not

Right. Limping would be telling you I'm sorry for calling you rude!

There's return shipping costs I guess if it doesn't work.

JRLearned wrote:There's return shipping costs I guess if it doesn't work.

Telephone, maybe it is not shipped yet.

Whatever you decide to do, please take pictures of all the steps and post them on here. It would be a good read.

warminmn wrote:Whatever you decide to do, please take pictures of all the steps and post them on here. It would be a good read.

Will do. I decided to get my Chubby's body sandblasted because of problems with paint adhesion, as documented in one of my other threads. I should be getting it back this week.