Adding a stove top temperature controlled blower switch

[velvetfoot]

My insert has a two speed blower. (See diagram below).
The blower motor has, I guess, two winding taps for high and low speeds.

Ideally, what I'd like to do is control the blower speed based on the stove top temperature. Say, if greater than 300, then run blower on low, greater than 500, run blower on high. less than 300, turn blower off. Something like that. And also have a digital stove top temperature display.

The stove already has a snap switch to turn on the blower when the stove (bottom) reaches a certain temperature. That works fine. If I could just add the high speed function I'd be happy.

If both windings were to receive power at the same time, what would happen? Would the motor burn out? An on/off control of the high side feed might be easier (for me) to incorporate. Plus it could be safer, inasmuch if the controller I'd inevitably get craps out, it'd still be blowing on low.

Then, there's the finding of the controller. I imagine it'd have to have some kind of thermocouple, and have a range to over a 1000F. Plus the digital display.

 

[black smoke signals]

Only problem I see is where wood you place wires on top of stove? I really like this idea!

 

[cableman]

Would def love this feature!

 

[velvetfoot]

I poked around and found that when current goes to the high power connection, no current goes to low side. So, I guess it won't be as simple as interrupting the high side wire. I looked up the switch, and it's called an spdt type. single pole double throw.

Only problem I see is where wood you place wires on top of stove? I really like this idea!

The only wire to the top of the stove would be the thermocouple wire. The controller could be on the hearth, close to the other wires.

 

[WES999]

If both windings were to receive power at the same time, what would happen? Would the motor burn out?

Um, Yes, I did that to the blower on on my Regency. Make sure that both high and low speed are not energized at the same time.

My previous stove, Regency and current BK have a temp controller to turn on the blower when the stove reaches a set temp.
(Mine is set to turn on at 675)

I usually just run the blower on low so the blower is only on or off.

I bonded the TC to the top of the stove with stove gasket cement mixed with copper filings.

I think you could us a controller like this, https://www.auberins.com/images/Manual/SYL-2362 instruction 1.6.pdf
It has 2 relay outputs, one to turn on the blower, and the other to switch the blower from low to high.

 

[velvetfoot]

Um, Yes, I did that to the blower on on my Regency. Make sure that both high and low speed are not energized at the same time.

Sure, now you tell me. I did try energizing both at the same time for a very short while, and the fan seemed to just run on low. I didn't pursue it, thankfully.

Thanks for the great info.

 

[velvetfoot]

I think you could us a controller like this, https://www.auberins.com/images/Manual/SYL-2362 instruction 1.6.pdf

Oh yeah, just a little light reading there.

 

[velvetfoot]

Maybe using that controller with the spdt relay below could do the trick. Snap switch would supply power to normally closed terminal on relay through controller and to low speed winding when stove gets warm, and when controller hits setpoint, turns on normally open relay contact to high speed and drops the n.c. low speed.

Maybe could get away with a cheaper controller.

Still have to buy the k type thermocouple and box to put it in.

https://www.auberins.com/index.php?main_page=product_info&cPath=2_31&products_id=250

 

[velvetfoot]

It looks like that controller can switch 3A. The fan on high draws .85 amps, so it should be okay even with the motor startup current So that could save a relay. It'd be nice if it came in a package though.

 

[brenndatomu]

Maybe using that controller with the spdt relay below could do the trick. Snap switch would supply power to normally closed terminal on relay through controller and to low speed winding when stove gets warm, and when controller hits setpoint, turns on normally open relay contact to high speed and drops the n.c. low speed.

Maybe could get away with a cheaper controller.

Still have to buy the k type thermocouple and box to put it in.

https://www.auberins.com/index.php?main_page=product_info&cPath=2_31&products_id=250

Just what I was going to suggest. Wire low to the NC side of a relay, the NO gets the high speed wires, when the temp switch trips, activates the relay, BAM, high speed! No risk of powering both windings this way

 

[velvetfoot]

Just what I was going to suggest. Wire low to the NC side of a relay, the NO gets the high speed wires, when the temp switch trips, activates the relay, BAM, high speed! No risk of powering both windings this way

But I don't think you'd even need an external relay...just use the one that's built in since it can handle 3 amps.

 

[velvetfoot]

I bonded the TC to the top of the stove with stove gasket cement mixed with copper filings.

Can you please tell me what the stove end of the thermocouple was like? Was it shaped like a bolt? Is that why the stove gasket cement and copper filings, or was the end of the thermocouple flat? Thanks.

 

[WES999]

I started with a TC with a a ring terminal like this:

I removed the ring so it now looks like this

Then I used the cement to bond it to the stove top. BTW adding copper filings seem to make the
bond more durable, without it, the cement wound tend to crack after a while.

With the 2 relay controller I don't think would need an additional relay,
The relays are double throw so you could wire it so only the high or low winding
could be energized at one time.

 

[velvetfoot]

Nice! Can I ask how high a temp it goes to? The cheopos go to 400C but I'd like to go higher, but they usually have a bolt end.

I wonder if mixing in some copper anti seize would work?

On a side note, I'm seeing maybe 150F less with the new Rutland magnetic thermometer on the stove top compared with the IR gun.

 

[WES999]

I think the one I have was from ppe.com, they don't list a max temp, 400 is probably OK
for a stove top TC.

https://www.auberins.com/index.php?main_page=product_info&products_id=307
This one is rated to 900, this would be a good one to use.

I would not use anti-sieze, it has grease in it. I think I actually used brass filings,
just take a old brass fitting and a file and make some.

The magnetic thermos seem to be a bit hit or miss, some are reasonably accurate and others are not,
the Condars seem to be better. The Condar I have is pretty good for what it is.

 

[shoot-straight]

I have the outlet my blower hooked up to a switch across the room. I wventually intend to put a cheap stat on it as well. So the blower on my Bk will kick in when heat is needed.

In the meantime, I use a cheap timer and it works great. I can cycle the blower on and off on an hourly basis if needed. I can also delay it to turn on later in the night as it gets colder and we need more heat.

 

[velvetfoot]

The blaze king with its catalytic converter and thermostat seems to be able to handle higher draft situations better than the tube stoves. I wish I could have a long, clean burn.

 

[velvetfoot]

I ordered this:
1 x 1/16 DIN PID Temperature Controller (For Relay) (SYL-2342) = $46.50
1 x Type K Thermocouple, Bare Tip (TC-K5) = $6.44
1 x K type Thermocouple, Washer Probe (TC-K-WS) = $13.95
Sensor Cable Length Option 6 ft Cable with spade connector
------------------------------------------------------
Sub-Total: $66.89
United States Postal Service (USPS First-Class Mail): $5.16
Total: $72.05

The relay has more switching capacity, but no ssr capability, I guess. I figure I'll try the bare thermocouple first.

 

[jatoxico]

Sounds like a cool idea. Hoping you can get it to work.

 

[velvetfoot]

Any suggestions on adhesive? I've seen epoxies so far to 550F, and I'm not sure stove cement would work, long term.

 

[WES999]

This is what I used:

Mixed with brass filings. I just looked at my stove, so far it seems to be holding up fine.
I don't think an epoxy will work, 550 is much too low for a stove top, my stove top can reach 800.

Autozone has something called thermosteel, rated for 2400
I tried it in the past, it worked OK for a few months and then became un-bonded form the stove.

A few other parts you may need, (I purchased them form PPE.com) Male plug for the bare tip TC 14002-M-K,

Female panel jack RPM-K, some type K TC wire to go from the controller to the panel jack.

Box to put the controller in, I got mine from E bay. You could probably use a smaller one than I used.

Having the TC plug into the box instead wiring it direct, will make life easier if any changes need to be made.

Just a thought, while you are at it you could add another controller with an alarm, (could be a cheap $20 one) to monitor your flue temp,

put it all in one box similar to what I did.

Good luck

 

[velvetfoot]

Thanks. Good to know the Rutland stuff + brass filings is holding up.

I think I'll see how it works before I buy the box, jacks, plugs, etc. The jacks and plugs would make it nice, I guess.

I think I'll stick with just the stove top tc for now. The controller I ordered has provision for two alarms plus the spdt 10 amp (120v) relay. So, an alarm could go off if the stove top got too hot, not that there's too much that could be done about it at that point since the fan would be running on high. Maybe try opening the door (I've read of it). Plus, this is an insert with more difficult access to flue pipe.

It would be nice to have complete manual override even with controller failure, but I don't see how I can do this with the non-option of possibly supplying power to both high and low sides at the same time.

It'll be nice, at a minimum, to have a stove top temperature that's more trustworthy.

Then, I'll have to figure out what to set it at.

Do you use any PID functions of your controller, or just with hysterisis, if I'm using the right terms, lol.

 

[velvetfoot]

Replacement glass came in so I'm looking at this again.
Set the controller up, but not sure what to set the "turn fan to high" setting.
I thought I'd start at 500, but might bump that up. Will see how stove responds.
I guess running it will tell. It is an insert, after all. Fan more important than with free standing stove.

 

[velvetfoot]

I put the sensor about 6" from the front of the stove flue outlet. I held the eye down with a ferrite magnet I had. Waiting on an Alnico magnet from eBay, but will run current magnet for as long as possible-doesn't take much to hold the thermocouple down. Plus, there's not that much room to work with, and even the 1/2" diameter Alnico magnet I ordered might be too tall.

I've settled on a setpoint of 750F to turn the fan to high, with a 10 deg. +/- (hysteresis)

With a not packed stove, it peaks at about 860 and stays there a while, until it drops to 740, and then the fan switches to low speed. I've had the fan cycle around the set point on the last burn, but not this one.

The thermocouple is probably at the spot on the stovetop that gets hottest, but I didn't notice any glowing.

The controller can be overridden by existing switches.

What's nice is that I can go to bed with the fan on high, and it gets turned down automatically.

The constant readout of stove top temperature is also something I've never had-it's nice.

 

[velvetfoot]

This setup has been working great. I've got it at 700F now.
Being able to cut down on the air supply has really made it more controllable.
The fan comes on an off to keep it at 700F, plus or minus 10 at the peak of the burn.
Dancing, not raging, secondaries.
Previously, without the additional air supply control, the fan on high would not be able to keep the temp from rising to 850, or whatever.
I open it up once things have died down.