Thermostatically Controlled AD-1 Draft Inducer

Lightning · By: **Lightning** On: Thu Nov 22, 2012 1:11 pm

Well, I've been contemplating this project for a while. What I did here is wired the thermostat in my living room to turn on and off my AD-1 draft inducer to cause my furnace to produce more heat automatically.. For those of you unfamiliar with the AD-1, its a motor installed on the flue pipe that pushes flue gas up the chimney with a variable speed control switch on it.

I harvested a relay from the old electric heat system no longer in use. I added a snap switch to the pipe so my furnace won't over fire in the event of a prolonged call for heat. During a call for heat, the snap switch on the flue pipe will open (turning off the draft inducer) at 230 degrees. Then when the pipe cools to 190, it will close turning the inducer back on, as long is there is still a call for heat.

I'm currently in my first run of this set up. The thermostat is set at 72 degrees and calling for heat. My flue pipe is at 187 degrees and rising slowly. I also put a screw in the baro damper to stop it from opening completely while the inducer is running since the inducer is after the baro.

Lightning · By: **Lightning** On: Thu Nov 22, 2012 1:32 pm

Successful first run!! The pipe ran up to 194 degrees and the furnace over the load door got up to 259 when the thermostat reached 72 and shut the inducer off

Lightning · By: **Lightning** On: Fri Nov 23, 2012 9:28 am

Last night the furnace held the temperature up, being controlled by the thermostat while it got colder outside. The only tweak I had to make so far was setting the thermostat to notice a .5 degree of change instead of a full degree. Whats happening is that when the thermostat is satisfied and shuts the inducer off, the furnace needs time to cool and return to its "cruising" temperature which of course causes the temperature in the living room to come up a couple more degrees over set point. SO at a set point of 70 degrees it continues to rise to 72 after shutting the inducer off. Which I guess I can live with that. Maybe having the thermostat set to notice a smaller degree of change will close the gap some on the temperature over shooting, we shall see

Dennis · By: **Dennis** On: Fri Nov 23, 2012 6:15 pm

Lightning wrote:Well, I've been contemplating this project for a while. What I did here is wired the thermostat in my living room to turn on and off my AD-1 draft inducer to cause my furnace to produce more heat automatically.. For those of you unfamiliar with the AD-1, its a motor installed on the flue pipe that pushes flue gas up the chimney with a variable speed control switch on it.

Just a thought.
Isn't the draft inducer designed to pull the air out of the stove and doing this are you pushing your heat out of the furnace and up the chimney and just making your coal bed hotter,thus more heat in the plenum. Just asking,don't know if i'm right or not,your thoughts please.

Lightning · By: **Lightning** On: Fri Nov 23, 2012 10:01 pm

Since I have the furnace pretty tight, my thought is that turning on the inducer is absolutely no different than opening combustion air feed on the ash pan door OR turning on a combustion blower.. It doesn't matter how hard the chimney is pulling. If a gallon of air goes in the furnace, then only a gallon of air plus/with coal exhaust will exit the furnace. NOW, if I have the load door cracked OR the gasket around it is letting air in, that would be a different ball game. Then, air sneaking in this way would serve no combustion purpose, and would be carrying heat with it up the chimney.

You are absolutely right, running the inducer is pulling air out of the furnace, which is causing more air to come in at the ash pan door without changing my combustion air feeding the fire. Since there is more negative pressure in the fire box with the inducer on, more air will get thru the same size hole.

This is my logic on the whole system..

My point is, I don't think it matters if combustion air is being pulled in OR if its being pushed in.. :idea:

Maybe its wrong, but so far I don't think it is :lol:

Its been working pretty dam good!

I'm On Fire · By: **I'm On Fire** On: Fri Nov 23, 2012 10:13 pm

Dennis wrote:
Lightning wrote:Well, I've been contemplating this project for a while. What I did here is wired the thermostat in my living room to turn on and off my AD-1 draft inducer to cause my furnace to produce more heat automatically.. For those of you unfamiliar with the AD-1, its a motor installed on the flue pipe that pushes flue gas up the chimney with a variable speed control switch on it.

Just a thought.
Isn't the draft inducer designed to pull the air out of the stove and doing this are you pushing your heat out of the furnace and up the chimney and just making your coal bed hotter,thus more heat in the plenum. Just asking,don't know if i'm right or not,your thoughts please.

The draft inducer is supposed to keep the draft at a certain point. It especially helps if you chimney can't maintain a proper draft.

Lightning,

I'm not sure what you're trying to do. On my stove my AD-1 doesn't control the burn rate. It just helps my stove maintain a .04" draft. The burn rate is controlled by the bimetallic thermostat at the base of the stove. My stack temp is 145° and my draft is being held at .05" by my AD-1 the stove is 398° and my bimetallic thermostat is closed. The stove just finished a call for heat as I recharged it an hour ago.

Lightning · By: **Lightning** On: Fri Nov 23, 2012 10:25 pm

Yeah, I understand your confusion. Let me explain.. I have no bi metallic thermostat on my furnace. It has no automatic regulation of heat output. Once I set the air feeding the fire, it maintains the same heat output until its changed or burns out. SO, this is my attempt to increase the draft, to create more heat output at the call of my thermostat in the living room. The draft inducer is doing quite the same thing as your bi metallic mechanism.. Its letting (thru pulling) in more combustion air to rev up the fire

Instead of using the draft inducer to maintain a draft, I'm using it to make a stronger draft at the will of my thermostat. :idea:

I'm On Fire · By: **I'm On Fire** On: Fri Nov 23, 2012 10:35 pm

Ok, now it makes sense. Once my stove drops back down to 320° my draft will drop back to .04" as my stack temp drops. Then the stove will just sit there with those temp and draft setting.

The draft might fluctuate a bit with a wind gust or a call for heat but it'll always drop back to .04". If I were to turn the inducer off it'd go to .01".

Lightning · By: **Lightning** On: Sun Nov 25, 2012 4:51 pm

So far, this set up is doing a fine job. Another hurdle I had was that my snap switch on the flue was waiting too long to shut the inducer off. The pipe was going to 300 degrees instead of the 230 that the switch is suppose to open at. I discarded the mounting bracket and moved the snap switch to the top of the pipe and wrapped some insulation and foil tape around it. Now during a heat call, the pipe is running up to 252 degrees and shutting the inducer off till it falls to 212. Over the load door is going up to 375. This break (about 20 minutes) during the heat call gives the furnace time to scrub heat to the room and keep it from over heating

Lightning · By: **Lightning** On: Fri Nov 30, 2012 8:09 am

I recently discovered an added benefit to this arrangement. The coal I'm burning this year has a HUGE amount of fines in it. So much so, that I was prepared to start screening it. It turns out that the calls for heat which add draft under the fire, are forcing the furnace to burn thru the fines

Some are still making it to the ash pan, but its nice not needing to screen them out.

Without the added draft from the calls for heat, I most definitely would be having a miserable time dealing with the fines.. I do agree that the fines are causing more calls for heat, but thats cool with me. Its no where near the point of the furnace not being able to produce the heat needed to satisfy the thermostat. Let em burn!

Dennis · By: **Dennis** On: Fri Nov 30, 2012 8:14 pm

Lightning wrote:I most definitely would be having a miserable time dealing with the fines..

You bought the fines also,so you might as well use them.I always dig deep into the coal bin with the first shovel and purposely
get some fines,so at the end of the season there won't be any left.

Lightning · By: **Lightning** On: Fri Nov 30, 2012 9:52 pm

Dennis wrote:You bought the fines also,so you might as well use them.I always dig deep into the coal bin with the first shovel and purposely
get some fines,so at the end of the season there won't be any left.

Ya know, I've been trying to scoop up more fines instead of avoiding them in hopes that I don't end up with several hundred pounds of just fines when I get towards the end of the heating season. Towards the end of last heating season, I got into some fines and had to screen them since they were cooling the fire down too much. I'm glad now that I'm able to burn thru them with the added draft on demand of the thermostat

Lightning · By: **Lightning** On: Wed Dec 19, 2012 4:35 pm

Since I've been using the thermostat for a few weeks now, I thought I would share some observations that I thought was interesting. I sketched up a graph of a typical call for heat cycle. The furnace is in a stable cruise state, just under the amount needed to maintain 72 in the house on a cold day, when the thermostat kicks the inducer on.

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During the call for heat, I have a snap switch shut the inducer off at 250 on the pipe then turn the inducer back on at 210. During a prolonged call, it may do this a few times. The first time the furnace climbs up to around 320. By the second time, the furnace will reach its ceiling (ceiling dictated by the snap switch) at around 380 with about 125 degree air thru the duct work to the house. When the thermostat is satisfied, it all returns to its stable cruising state again. But in the meantime, I may see 73 on the thermostat before it calms down.

This has served me well since the coal I got is sized inconsistently and would otherwise need a varying adjustment for combustion air to maintain desired temperature in the house :lol:

Thermostatically Controlled AD-1 Draft Inducer

Thermostatically Controlled AD-1 Draft Inducer

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