Boiler settings help/advice needed.

My EFM has an adjustable feed rate, from 20k-200k BTU's. Right now I have it set at ~90k. My question is at what point should I raise the feed rate? The boiler is plumbed into a water/air heat exchanger which is rated at 140k BTU. When the thermostat calls for heat the circulator starts and then the stoker runs for a few minutes raising the temperature in the plenum and then the fan comes on heating the house. I was thinking that if I raised the feed rate the stoker would run for less time and make just as much heat, possibly using less coal. Also what should the fan stat be set at, I put it at 130 on, 80 off. I have good heat and my homemade system seems to be working well, I just don't know how to adjust it for maximum efficiency. I'm using about 100# of coal a day when the average temps are in the teens, about 80# when the temps are in the 20's, the other night it was down to 3 I used 150#. The only info I can find is from the outdoor boiler sites, they have the circulator running constantly and the thermostat controls the forced air fan, this doesn't seem right except for the fact that wood is "free" and they need the water flowing so it doesn't freeze up.

e.alleg wrote:The only info I can find is from the outdoor boiler sites, they have the circulator running constantly and the thermostat controls the forced air fan, this doesn't seem right except for the fact that wood is "free" and they need the water flowing so it doesn't freeze up.

I run a Modine fan off my boiler and I used a Honeywell L6006 to control the fan. When the boiler temperature gets to a certain point, the fan will start and when the boiler temp falls below a set point, the fan will go off. The circulator to the Modine is controlled by a B aquastat, which closes on temperature rise, and a relay.

The circulator won't start until the aquastat senses its set point and the Modine won't run until its set point.

Maybe this is how your house is set up. I don't know.

Thanks for the reply. Mine is setup a little different: a Honeywell 8124B aquastat controls the boiler temp and turns on the circulator pump when the t-stat calls for heat. A Honeywell L4064 B fan limit control turns the fan on once the duct temperature above the fan coil gets to 130 degrees. The "fan" is my forced air gas furnace's 3/4hp fan, the coil is a 3 row 19x20 heat exchanger mounted on top of the furnace. So basically the only difference is you use pipe temp to control the fan vs. I use duct temp.

e.alleg wrote:My EFM has an adjustable feed rate, from 20k-200k BTU's. Right now I have it set at ~90k. My question is at what point should I raise the feed rate? The boiler is plumbed into a water/air heat exchanger which is rated at 140k BTU. When the thermostat calls for heat the circulator starts and then the stoker runs for a few minutes raising the temperature in the plenum and then the fan comes on heating the house. I was thinking that if I raised the feed rate the stoker would run for less time and make just as much heat, possibly using less coal.

If you have too much feed and air you're going to start short-cycling. I would opt for the longer runtimes. Your coal is going to provide a certain amount of BTU per pound whether your stoker runs continuously or short-cycles.