Anyone have a Harman with the auto draft?

Robby, I forgot to answer your question regarding whether my furnace has a switch or control to control how hot it can get. It has a basic honeywell fan switch that controls the furnace fan and also a high temp limit switch. I plan on using the limit contacts to shut the draft when the stove gets so hot. I also am planning on installing a snap type limit switch of some sort for some redundency. I want the system to be as safe as possible.

No problem, I will do all of above tomorrow. The hinge is the most interesting part. It is a door hinge, I'll measure it, but just an ordinary door hinge. The bolts, where it bolts to main box are slightly slotted so you can adjust to make damper door fit exactly flat against opening. If you look carefully at the pictures you will see a short 1/4" bolt with a wing nut. This can be screwed in/out to set the maximum damper door opening. I put the wing nut on and painted one wing red so easy to count turns. At maximum i think about 6 turns out lets door open max. I never use more than 4. With coal I use 2 turns, with wood 2 to 4 depending on dryness. The little flat plate in middle is to set idle air so it is not completly shut off. As you can see I don't have it open much.

The wheel (with many holes around the perimiter) attached to damper motor just has a bolt through one hole and the damper door over laps opening by 1/2 to 3/4". Head of bolt sits behind and opens door.

Yes the main box that bolts to cast door is beveled so gravity closes damper. In three years I have never had any ashes or material in box that would hinder damper closing. I did have creosote build up on opening in cast door (where damper box bolts on) but so slowly I noticed before restricted air any.

Take pictures and some measurments tomorrow.



Robby

The draft opening (the exterior box) is 4"x4".
The door overhangs side by about 1/2"
Idle inlet holes are 1/2", there are two and rotary slide opens both the same amount at the same time. As you can see I have them set at minimum. Thats where I set them initially, thinking I would need to open more later. Never changed it.
Yes the bolt (on wheel of motor) contacts the door maybe just lower than 1/2 way down.
The back side of cast door, that damper assembly bolts to, the opening is about 3.5" x 3.5" with the bolting mechanism in the middle. Seems to be lots of draft. The wood I burn is poplar and pine, pretty dry.

The reason I asked about overfiring. My electronic controls have built in overheat (opens up a zone) and controls damper door etc. I don't completly trust electronics, so I took old fashioned snap switches, put one right on top of boiler. If temp excedes 210F , cuts power to damper. Second one took some trial and error. A second one at 220F bypasses electronics, powers up pump and dumps heat all zones.

Any more info, let me know.
Robby

Robby, Thanks so much again for the pictures and the measurements. I think I'll be able to get an assembly put together fairly easy. Its simplier than it looks initially. I am like you, I don't trust electronics totally either. I've had too many electrical things fry or quit working without warning. We just had our two week old computer fry yesterday. I also plan on using a snap disc type thermostat switch for a safety.My stove is a hot air furnace type. I think I'll put a snap disc switch in the hot air plenum and I think I'll also put one on the stack. Do you burn any coal then? I burned a little wood when we first got the furnace but had trouble keeping the chimney clean. If I burned the stove hot enough to keep the creosote burned away, the house was too hot. A neighbor burns coal so I decided to give it a try and its really nice. We don't have anthracite coal around here. I've been burning sub-bituminous/bituminous from the Decker, MT/Sheridan, WY area. It seems to be good coal. I buy lump and then break it to my desired size. I've found that stove size works best for the stove. If I want to bank it for a long time, I'll throw on some small "fines" leftover from breaking it up. When its good and cold, I put a 5 gallon bucket full in the morning and then again at evening. I really appreciate your willingness to help me and the work put forth to do so. I'll take some pictures of my setup when I get it built.

Thanks!
Ben

I have this same setup on my Harman SF 1500. When I bought this stove second-hand, someone had rewired everything badly. I've been able to troubleshoot most everything and get it working correctly. But...

You see on the right the bolt that's on the wheel that moves the draft door? Mine was like that, with the bolt at the top of the wheel. But when my thermostat called for more heat, the wheel would turn counter-clockwise, closing the damper. So I moved the bolt to the bottom of the wheel, and now it works correctly. Except...

When the power is shut off (or I turn the furnace off with my kill switch), the draft door opens! I don't think this is the safe action for it to take, I would rather that it closed if the power is lost. It would get darn hot with the door open and no fan to suck the heat out of the plenum!

So I now that I see these photos, I'm thinking that the motor that spins the wheel is turning backwards. I did try swapping the hot and the ground on the motor itself, but that did not reverse the action (and I didn't think it would, but had to try anyway).

Can anyone solve this puzzle? I'll be happy to scan the schematics if you really think you'd have a shot at solving it.