Questions About Dual Combustion Fan Keystoker Boilers

dave brode · Post by **dave brode** » Tue. Feb. 14, 2012 7:06 pm

Hello All,

My little Kaa-2 has only one. I was curious as to how the larger units were setup. I looked at Keystoker's online manual, pics aren't very clear.

Do both fans just blow into the chamber under the grates? Is it a simple "on with the stoker feed" deal? Is the draft setting effected much when the part time fan kicks on with the stoker?

Anyone know of good pics here of the 4 and larger? I had a goofy thought about looking into making the Kaa2 a dual fan setup.

TIA

Dave

beatle78 · Post by **beatle78** » Tue. Feb. 14, 2012 7:47 pm

I have the KA-4(no longer in production). The small secondary fan runs 100% of the time. It was designed to help with outfires during the summer months, but I use it all the time. Then the main blower comes on during a call for heat.

dave brode · Post by **dave brode** » Wed. Feb. 15, 2012 7:57 pm

Thanks Beatle,

How much does the airflow increase with both on?

Anyone have pics, or links to pics of K4 or 6?

Dave

beatle78 · Post by **beatle78** » Thu. Feb. 16, 2012 9:13 am

The main blower does the real work. The small secondary fan keeps a small amount of air flowing to help keep the coal lit when the boiler is not calling for heat for extended periods of time.

I'll try to remember to snap a pic & post it when I get home tonight.

McGiever · Post by **McGiever** » Thu. Feb. 16, 2012 8:57 pm

Nice write up w/ pictures here...

Upgrading Older Keystoker Boiler With a Secondary Blower

Kungur · Post by **Kungur** » Fri. Feb. 17, 2012 7:28 am

OK. I am now officially confused!
I have a a KA-2. So why does the KA-2 not have a "2nd." blower to "do the work'? Is it possible to incorporate one into a KA-2?
Thanks!

dave brode · Post by **dave brode** » Sat. Feb. 18, 2012 9:32 am

Kunger,

Afaik, the KAA-2 has the same stoker unit as some stoves/furnaces. The pics at the link McGiever posted [thanks] show that the 2 is much different compared to the bigger units.

I am not aware of any kits to fit a 2nd fan on the 2. It looks to me that there is room to cut two new inlets in the front and mount a "left hand" and "right hand" fan on there. There are several smaller fans sold that are similar to our combustion fan. Another option would be compounding two fans, where one blows into the inlet of the other [think compound turbocharging setup]. Imo, the full time fan could be mounted downstream and pull air through the 2nd fan's body w/o any problem.

Although possibly more complex, I've also wondered about a setup with a single fan, where the inlet opening could be varied. Stoker on - more opening, idle - less opening.

I've also wondered about a "delay on" switch on the part time fan, so the stoker would have time to load the grate when ther triple 'stat called, prior to the 2nd fan coming on and blowing heat up the flue.

Dave

dave brode · Post by **dave brode** » Sat. Feb. 18, 2012 9:43 am

Here is an "opposite hand" fan, similar to our std fan.

http://www.grainger.com/product/DAYTON-PSC-Blower-1TDP3

picture two fans mounted, extreme left and right in the front plate of the stoker unit, inlets facing each other. This would, of course, require some welding and such.

Another option would be to mount a small axial fan on the std fan's inlet. It seems to me that the std fan should be able to draw sufficient air through said fan. When the axial fan would run, I suspect that it should increase the output of the std fan. I feel that the axial fan would not need to be a very high cfm output to markedly boost the std fan's output.

Here are some Dayton axial fans. There are all sorts on ebay, Dayton and other, as low as 30 cfm, less money.

http://www.electricmotorwarehouse.com/Dayton/axia ... n_menu.htm

Some ebay search results, but I'm not sure how long the links will work. Anyone finding them dead in the future can go to ebay home page and search axial fan, or axial fan Dayton. Make sure to click the "us only" box, or you get sellers from asia.

http://www.ebay.com/sch/i.html?_nkw=ac+axial+fan+ ... m270.l1313
http://www.ebay.com/sch/i.html?_nkw=ac+axial+fan+ ... m270.l1313

Kungur · Post by **Kungur** » Sat. Feb. 18, 2012 4:10 pm

If the idea of mounting a 2nd. fan is workable. How would it be wired?

dave brode · Post by **dave brode** » Sat. Feb. 18, 2012 4:35 pm

Kunger,

[ note that I was editing the post above when you replied]

I'm no wiring expert, but afaik, the least compicated way to control a part time 'booster" fan would be to parallel wire it into the stoker feed motor circuit. It would run whenever the stoker fed.

Let's say that it took the stoker 3 minutes to load the stoker bed with coal after the triple 'stat called for heat in the boiler. Assuming for a moment that it would be good to delay the booster fan, a "delay on" timer could be used. This would also prevent the booster fan from running when the keep fire timer ran the stoker. I don't believe extra air would be a benefit during those short feed cycles.

Here are some delay timers;

http://www.ebay.com/sch/i.html?_nkw=delay+on+time ... m270.l1313

In case of dead link, go to ebay, search "delay on timer", click us only box.

You can find all sorts. The smallest will handle only an amp or maybe 1.5, but a small axial fan might not pull even that much. You can find timers that'll handle bigger loads, but they are pricey.

This all said, it does seem to me that for hard running, the bigger fire likes a tad more air than it needs on idle [watching the draft signal on my water gauge tells me so too]. The bigger Keystokers are set up as such. I am surprised that someone hasn't already tried this on a Kaa-2.

A real goofball could also use another timer to limit the time the booster fan runs. Once the bed of coal is "roared up", the extra air might not be needed. One could also rig up a temp switch to cut the booster fan if the flue gas temp exceeded a certain point, etc.

Dave

CSCPeter · Post by **CSCPeter** » Thu. Feb. 23, 2012 8:01 pm

Even the new furnaces and boilers do not come with the correct wiring diagram to hook up both the little fan and the main feed motor and combustion fan. I have re-done the wiring diagram to the way that I have been wiring them up and it seems to work pretty well. I have to find the file and post it on here. Basically you run the little fan off of the Normally open switch in the timer box so that when it doesn't call for heat or the timer is not calling then the little fan kicks on.

dave brode · Post by **dave brode** » Thu. Feb. 23, 2012 8:32 pm

Peter,

Interesting. I hadn't thought about two fans, but only one running at any given time.

On the subject, for anyone looking at the subject of 2 stage air;

I have dinked around blowing air [via another small fan] into the inlet on the single fan on the Kaa-2. It doesn't take much extra air to increase the output. No direct connection, just air blowing on the fan's inlet, which causes a little positive pressure there, and increase output.

It would not take a very big fan.

Dave

staybolt · Post by **staybolt** » Fri. Feb. 24, 2012 6:35 am

I have a k2 boiler and have the the small dayton axial fan attached to the inlet of the main combustion fan. had it on there for 6years now with no problems. I wired it to run ALL the time with main fan in the burner circut. I just attached fan with some rtv to the inlet of combustion fan and let dry. maybe will up load some pics. let me know. Guy

staybolt · Post by **staybolt** » Fri. Feb. 24, 2012 6:40 am

not to confuse, combustion blower only cycles with call for heat but axial fan runs all the time even when combustion blower is running. Guy

dave brode · Post by **dave brode** » Fri. Feb. 24, 2012 9:37 am

Hi Guy,

Interesting. I thought of setting the normal fan at a little less than normal "one fan only" output, and boost it with the extra fan when the stoker runs. I can see how your way would be another option. Pics of yours would be nice.

Do you have a flue draft [manometer] gauge? How does the levels of fan output effect the draft signal?

Thanks.
Dave