My KA-2 and my bit of a challenge

Ok ,this is season #2 for heating with my KA-2. It along with the radiant floor heat has been very comfortable. The challenge I face is when we get these tempature drops into single digits I cannot seem to get the boiler temp up. It runs about 150-160F and provides me with DHW and the right temp to the floor loops with out overshooting. But when it gets REALLY cold the temp drops to about 140F.
The other day I decided to play with it and turned the screw on the stoker to increase it. But it seemed just to burn more coal and not really increase the boiler temp. I guess I am still on the learning curve.
Any thoughts as to what I might try?

Sounds like my situation. You are essentially maxing out the boiler on those extreme cold days. That's not a bad thing. It means you are running efficiently 99% of the time. And 140 degree water probably does the job for you. Show me a coal boiler that can maintain the 180* water temp under extreme weather and I'll show you an oversized boiler wasting fuel.

Kungur wrote:The challenge I face is when we get these tempature drops into single digits I cannot seem to get the boiler temp up. It runs about 150-160F and provides me with DHW and the right temp to the floor loops with out overshooting. But when it gets REALLY cold the temp drops to about 140F.

It sounds like your boiler meets its match on the really cold days. If the house is comfortable and you have enough DHW...I don't see a problem. Does it ever get below zero in your area? Can you reduce the room temperature in certain zones?

Kungur wrote:The other day I decided to play with it and turned the screw on the stoker to increase it. But it seemed just to burn more coal and not really increase the boiler temp. I guess I am still on the learning curve.

How long did you let it run with the increased feed rate? With a high-mass radiant system and your boiler already running at 100% capacity it might take HOURS to see any difference.

coalkirk wrote:Show me a coal boiler that can maintain the 180* water temp under extreme weather and I'll show you an oversized boiler wasting fuel.

That is the beauty of a stoker with an adjustable feed rate.

Can you increase the air rate, or could something be blocked ? How did it respond last year ?

AA130FIREMAN,
I was tyhinking about the airflow on the combustion blower. I have not yet taken it apart and vaccumed out the fines underneath. Maybe this week as we are suppose to be in the 40's.

Kunger,

I'm heating 3500 ft2 with a KAA-2, and it struggles some when it's really cold, but I'd probably choose it over the 6 if I was picking today.

I'm really not even close to being an authority on these boilers, but I agree with AA130, a higher feed rate might need more air to get more heat. More waste up the flue, perhaps, but I REALY don't like the idea of the boiler getting below 150 [condensating issues - bad]. On cleaning below the grate, I have to do it fairly often. I can usually tell when it's time, fire burns in a peaked shape, as corners are full of fines. I clean mine by removing the combustion fan. I can do it w/o loosing the fire by using a piece of small tubing taped into a small vac cleaner hose...

Also, I'll assume that you have a mixing valve on the floor heat. So, you should be able to run the boiler at a higher temp. Doing so would allow it to have more heat stored [water at higher temp] while the house isn't pulling heat from it. I have found that mine seems to work better running it at 180* or so, although spring and fall, I set it a bit lower.

Also, when it gets to single digit temps, and the boiler struggles, I have on occasion closed my domestic water loop off, and switch my elec tank back on. A day or two here and there....

Dave

If you haven't cleaned out the fines, does this also mean that you have never tried to clean out the combustion chamber or the heated surfaces?

The thin layer of ash on the inside of the boiler surfaces does act as an insulator, a quick wipe down with a wire brush should improve the heat transfer to the water.

A few minutes of maintenance might help your boiler maintain temperatures.

Greg L