Upgrading Older Keystoker Boiler With a Secondary Blower

For those of us with older Keystoker boilers we are aware of the problem that has plagued these boilers for years while trying to keep fire during the summer. You had fires go out, or as you try to make adjustments to the maintenance timer to keep it going you had a very hot or overheated boiler resulting in headaches and wasted coal.

A few years back Keystoker made a change in their stoker. A small blower was added to continuously blow a small amount of air under the grate in order to keep your small “pilot fire”, if you wish to call it that, going. For people who have an older Keystoker without this feature Keystoker has come up with an adapter that can be placed on the existing stoker body. To attach this motor a hole must first be cut into the lower portion of the stoker fan shrouding before attaching.

I was advised by a local plumber to update my used 1984 manufactured KA-6 before I installed it. I decided not to. I wanted to see how it would work without it. It worked fine until the warm weather of May 30th or the 31st and then a fire out. After adding time to the timer it went until July 15th the fire went out and then again on the 17th. Each time the run time was increased and by then the boiler was holding about 170 degrees on maintenance alone and the aquastat was set at 140.

The boiler was shut down July 21 thru 28 while on vacation. When I came back I put on the additional blower before lighting fire again. I purchased the small blower and fabricated adapter directly from Keystoker earlier in the year for $150 plus tax. Anyone should be able to get one directly, if you live near the factory, or through a dealer.

This is the small blower to be added and the adapter bracket. This is the stoker, less motor and fan, before modification A hole must first be cut into the stoker body fan shrouding behind and below the stoker fan to permit the air from the secondary blower to flow under the grates. The sides of the stoker body are quite heavy at this point, about ¼” steel plate, but the metal between the two heavy plates where the hole must be cut is just a heavy gauge of sheet metal. Several methods can be used to cut this hole. With the stoker motor and fan removed it can be cut with a plasma cuter, a cutting wheel on a die grinder or drilling holes at the corners and using a reciprocating saw with a metal cutting blade. The adapter made by Keystoker fits over top of the stoker body and is secured by 4 self tapping metal screws. The gaps along the edge are sealed with furnace cement or high temperature silicone. NOTE: the stoker can be modified without removing from the boiler. I had other reasons to pull the stoker. This makes better pictures too!

The stoker body after cutting a hole to allow the small blower to blow air under the grates. Notice the air comes in off center, a small flaw in the overall design in my opinion. Test fit, stoker body shown upside down.
Job done and mounted to boiler. The small blower will run continuously 24/7 and should be wired to a constant hot wire but one that is turned off with the furnace switch. There should be a fused shutoff mounted on or near the boiler that will turn off ALL motors, blowers, circulators or anything else connected to the boiler. Keystoker recommends installing as shown with the shutter about ½ closed on the small blower and leaving the air settings for the main blower as they were before. Gaps around adapter bracket must be sealed. Set timer to minimum, (for older adjustable notch timers, newer pin type timers contact Keystoker) my stoker runs 45 seconds on and about 14 minutes off.

No more out fires! Until you lose power…

After installing this second blower I turned the timer to minimum run time and have not lost fire ever since. We have had some hot, humid days with no breeze since then and at no time did the fire ever look as if it were about to go out. If you have an older boiler that you wish to run through the summer or you have the opportunity to pick one up cheap and wish to use it year round I would highly recommend updating it with this second blower. You should not be disappointed.

Thanks Gary, very nice photos and explaination.

Greg L

Great pictures Gary, lots of detail too. I'm curious how low your able to get this boiler to fire during the warm weather. I have the Harman boiler which is similar in size, and have it running at about 160 deg in pilot mode. This gives me plenty of hot water for 4 teenagers.

I've been monitoring my coal usage pretty religiously and have it down to about 12# per day or a half pound per hour. I keep the combustion blower running constantly, the small ribbon of fire would not keep going without the extra air supply.

One thing I found very helpful was to add some fiberglass insulation under the sheetmetal, the boiler water went up about 10 to 15 deg after I added the insulation and the basement was quite a bit cooler.

Highlander wrote:I'm curious how low your able to get this boiler to fire during the warm weather. I have the Harman boiler which is similar in size, and have it running at about 160 deg in pilot mode.....

...I've been monitoring my coal usage pretty religiously and have it down to about 12# per day or a half pound per hour.

I am averaging 13 1/2 pounds per day for hot water and "pilot fire" I do not know if it can be cut back any more than that or not. I am burning buckwheat coal, I could also burn rice or a mixture of both. I don't know if using rice or a mixture would affect coal usage or not.

Highlander wrote:One thing I found very helpful was to add some fiberglass insulation under the sheetmetal, the boiler water went up about 10 to 15 deg after I added the insulation and the basement was quite a bit cooler.

My sides are insulated, the top is not. I may try adding insulation on the top. Right now boiler temps are at 150 most of the time, aquastat set for 140, basement temps not too warm either but adding some insulation to the top of the boiler can't hurt.