KAA-2 Combustion Fan

Why does Keystokers instructions say combustion motor will run all the time, when everything I have read here says only when calling for heat? Which way do in wire it???

COMBUSTION MOTOR: Combustion motor will run all the time to force air
through holes in grate to burn coal hotter. The constant running of motor will
assure the maximum amount of heat is gained and will aid in a more complete
burning of coal. The motor has an adjustable air shutter for regulating air flow
through fire.

My kaa-4 has a rheostat that runs the fan at a lower voltage anytime the fan is not running from the timer or a call for heat (when it runs at full voltage, bypassing the rheostat.)

KAA-2 only has one combustion fan, and they want it to run continuous.

My kaa-4 only has one fan too. That is why they use the rheostat to cut the voltage so it runs on low "continuously". It runs at full voltage during timer and heat calls but at reduced voltage all other times

The Kaa-2 combustion fan does run continuously on high. The second little fan you see on the Kaa-2 stoker is for cooling the stoker motor. It is not a combustion fan.

The bigger KEYSTOKER models use the older style stokers. They added a second smaller combustion fan to help prevent "Out Fires" when no call for heat. EXAMPLE: Summer months / hot water

Apparently, the Kaa-4 combustion motor slows down when no call for heat.

So do I wire my combustion fan to start when the B1 terminal starts the push bar, or does it run all the time?

It runs all the time on the Kaa-2. If not, the fire would go out. Running all the time doesn't hurt a thing. As a matter of fact, in a gas / oil furnace, where they have the same style fan (used for circulation), it is recommended that they do run all the time. It is said, the life span of the motor is about the same. That is why the fan on some higher end central heating system is made to slow down, not stop. It slows down for noise purposes. Others are run on low 24 / 7. Must be that same technology has slid over to the Kaa-4.

I've never had a problem with the fan on my Kaa-2. A few drops of light oil every now, and then is all you need.

Oliver,
Yes, the KAA-4 I purchased new last April had a rheostat in between the timer and fan to make the fan run at a lower voltage continuously unless the timer, thermostat, or hot water had a call which bypassed the rheostat an then ran at full power.

Tryingitout wrote:So do I wire my combustion fan to start when the B1 terminal starts the push bar, or does it run all the time?

No.

Is this not factory wired already?

I do not know why they changed the fan side of things on the KAA-4.

My 2 year old KAA-4-1 dual fuel stoker has a single combustion fan that
runs on a heat call or when the hold fire timer activates it.
My timer runs the stoker and fan for 3 minutes every 15 minutes and
it works very well.

Oliver, I am still having a hard time understanding the operation of the boiler, and combustion fan. I value everyone advise on the forum and I am not trying argue, I am trying to makes sense of the sequence. The aqua stat tells the B1 terminal to start the push bar, the bar moves coal across the grate, the combustion fan forges the fire hotter than heck. When the water temp. is reached, the B1 terminal stops the bar, but the blower continues to forge the fire. Then every 10 minutes or so the timer pushes coal, and the blower forges that. It does not seem like there is ever any down fire time. When is the water not getting heat?
Thanks Garey

Mcgiever, I bought this boiler used, the previous owner had things pretty screwy. I have it wire per the manual from Keystoker, just trying to make sense of its operation!

Tryingitout wrote:Oliver, I am still having a hard time understanding the operation of the boiler, and combustion fan. I value everyone advise on the forum and I am not trying argue, I am trying to makes sense of the sequence. The aqua stat tells the B1 terminal to start the push bar, the bar moves coal across the grate, the combustion fan forges the fire hotter than heck. When the water temp. is reached, the B1 terminal stops the bar, but the blower continues to forge the fire. Then every 10 minutes or so the timer pushes coal, and the blower forges that. It does not seem like there is ever any down fire time. When is the water not getting heat?
Thanks Garey

You are correct. NEVER any down fire time. There is NEVER down fire time with any solid fuel appliance. The water is always getting heat. At the same time, you're always using heat. If you're not using heat, you might just as well shut her down. EXAMPLE: Summer time.

I will try running per the instructions, I have a feeling it might over heat. My system has less than 30' of pipe, supply and return. If the thermostat is not calling for heat, the blower on the furnace is not going to be removing heat through the coil.( For what it is worth, by down time I was speaking fire at idle, not super heated by the blower.) Thank you for the input.

If that is the case, and it does dump a lot, you can probably just add the rheostat. I'm sure Keystoker has them in stock. Mine was prewired and had power wires coming out each end. One end was labeled "to timer" and the other end was labeled " to stoker". My KAA-4 idled all last summer and did not activate the dump zone once. It just ran up to about 190 or so and provided unlimited hot water!