Tjernlund AD-1 Draft Adjustments

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Post Thu. Nov. 17, 2011 8:53 pm

For those of us with short chimneys and low draft conditions in the shoulder months a draft inducer may be necessary. I am one of those people with an 18' chimney and trouble keeping a good draw on the stove in temps above 40º. I had purchased a Tjernlund AD-1 draft inducer at the end of last season but did not install it until the beginning of this season. Some things I've noticed about it are, that it does a very good job at creating draft. In fact, it's too good. Out of the box this thing creates a .13" of water draw on my chimney with a 200º fire set on the lowest setting. Too much.

I had purchased a new switch for it hoping it'd allow me a little more control. No go. The motor did not like the Lutron fan switch. So, being a curious person I decided to disassemble the factory switch that came with the blower. You'll notice that it's a cheap Chinese switch encased in a cheap plastic housing. There is a reason why the instructions tell you to keep it away from heat. It'll melt and be rendered useless. Which is why I decided to remove it from the box mounted on the side of the inducer and put it on a long cord and install it in a separate box close to the outlet. The second thing you'll notice is that the black housing has a back plate that is snapped into the sides of it. Using a small screw driver or a razor blade one can easily take the housing apart, exposing the guts of the switch.

Here is the interesting part. If you turn the switch over and look on the opposite side of it; wires should be pointing away from you. You'll see a small potentiometer or pot. It is set very high from the factory. Basically, it gives you "out-the-box" HIGHEST, [/i]HIGH[/b] and [/i]MEDIUM[/b]. So, even on low you are still going to pull well over your .06" of water target. If you turn the pot counter-clockwise you'll increase the speed of the inducer. Basically negating all adjustability with the switch as it would just give you the highest possible setting across the entire range. BUT, by turning it a little bit clockwise you slow the motor which gives you a proper [/i]HIGH[/b] and [/i]MEDIUM[/b] and [/i]LOW[/B].

The easiest way to adjust it is simple. Unplug the switch from the wall, take the switch apart LEAVE IT UNPLUGGED. Adjust the pot in small increments. Take one half of the cover and slide it back on the switch and hold it by the cover; pinch the sides. Plug it back in and turn it on. Make note of where the draft is. Fine tune as needed. Now, I readjusted mine without a fire in the stove. I had shut down, in fact when I was making my adjustments I was only burning some wood and Cowboy Charcoal. I'm not sure if the results will be different with a full blown coal fire. I'd imagine not, though.
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This is what you are looking for on the side of the switch. Turn counter-clockwise to increase motor speed (increase draft). Clockwise to decrease motor speed (decrease draft).


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Post Thu. Nov. 17, 2011 8:58 pm

Is this a 3 position/ 3 speed switch?? If so why not just use a infinite variable switch like those from KB Electronics?

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Post Thu. Nov. 17, 2011 9:06 pm

I'm afraid it might provide the same issues. I had one of the constant variable switches but at the time I was messing with the AD-1 I couldn't find it. In fact, I still can't find it. I may end up buying another one to try out as well; in fact I know I will because I like having spares of parts like these. In the meantime, the pot adjustment on the supplied switch seems to work fine.

*EDIT*

Actually, I was just looking on KB's site and I think one of those switches would work. I'd have to look closer on the housing supplied with the current switch to see what the amps are to see what would be compatible.

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Post Thu. Nov. 17, 2011 9:14 pm

I had a very similar issue

Put in a barometric damper to offset the artificial hi draft

or

put one or two fire brick in an available ( if available ) horizontal run while using the artificial draft

or

install am manual damper above the draft inducer to offset the overdraft

Your mileage and result may vary - side effects could include anal bleeding

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Post Thu. Nov. 17, 2011 9:22 pm

Sting, those were not options I had not considered. But, adjusting a little dial is a lot easier to do than shutting down a stove and disconnecting it to put a brick or a new damper in before/after the inducer. The baro "could" be installed with it running but I'd imagine you'd be a little "dizzy" afterwards.

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Post Fri. Nov. 18, 2011 7:53 pm

i'm on fire,

your adjustments worked good. on low setting my draft went from .11, and now to .04/.05 with a full fire burning. It took only 10 minutes to fix. thanks for the great info, hope it helps others also. Dennis

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Post Fri. Nov. 18, 2011 9:09 pm

So with your draft set at .04 - .05 at the vent pipe, what is your overfire draft? I've got a sort chimney also. I can get .04 at the vent before the baro but I can't get my over fire draft above .03. So I've adjusted ny vent draft down to .03.Seems to work fine.

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Post Sat. Nov. 19, 2011 8:03 am

Kirk,

I measure my draft after the flue outlet on the stove and before the mpd so with my inducer pulling .06" on low that is over the fire. Now that I just wrote that I could probably stand to turn it down a little more.


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Post Sat. Nov. 19, 2011 8:09 am

Dennis wrote:i'm on fire,

your adjustments worked good. on low setting my draft went from .11, and now to .04/.05 with a full fire burning. It took only 10 minutes to fix. thanks for the great info, hope it helps others also. Dennis
Glad it worked. It was bothering me that it wouldn't go lower than .13" in low. Hopefully others find it helpful too.

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Post Sat. Nov. 19, 2011 10:25 am

i'm on fire,

i turned the pot adj. all the way down,also I put foil tape on the 3" hole where the shaft goes into the blower assembly. I thought carbon monoxide would escape through that large hole( that might help lower the draft also,by not allowing so much air into the chimney pipe). My baro is set at .03,and on low it's .04/.05

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Post Sat. Nov. 19, 2011 5:23 pm

I have actually been meaning to cover that hole with a metal plate but haven't gotten around to it yet. Though I do like the foil tape idea. I'm gonna go cover mine now, actually.

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Post Sat. Nov. 19, 2011 5:54 pm

I'm on fire,

this spring when I shut down and clean the boiler out, i'm going to take the blower housing off and put a stainless patch then seal with high temp silicone. I do like your idea of installing the blower swicth elsewhere, iv'e already found the spot,but that will be for another day. Dennis

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Post Sun. Nov. 20, 2011 11:04 am

i'm on fire,

i took your advice and this morning I went down to shake and reload, the next thing I know I was relocating the draft inducer switch. I'm no electirial expert, but everything is working fine. thanks,i think it was only a matter of time before there was a melt down. Dennis
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Post Tue. Nov. 22, 2011 11:12 am

Looks good Dennis. A lot nicer than my relocation. Mine is in a switch box tossed on the floor about 3' away from the stove. I've been meaning to get a longer cord and put it in a nicer box near the mantle. But haven't gotten around to it.

On a related note, I readjusted my switch so that now on low it pulls .05" as opposed to .06-7" like it was. So, with a 250* fire it's reading .06".

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Post Tue. Nov. 22, 2011 2:51 pm

i'm on fire

thanks, it turned out good. The switch was only 4" away from the oil burner chamber(although I don't and most likely won't use the oil burner) a melt down was just a matter of time.Next I will be moving the brake line from the stove pipe(only 2" behind the AD-1) to the collar(witch will be 9" behind from the AD-1) When the combustion blower is on my draft is .03 and when the combustion blower and the AD-1 is on the draft is .05. I believe i'm getting a false reading with the brake line that close to the AD-1. Will having the brake line in the stove collar still have a good reading, or is that too close to the fire,as you will see in the pic. thanks Dennis
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