The timer and full-time fan keeps a minimum amount of coal on the bed and the fire going between fires. It's not like an oil or gas boiler that shuts down and re-ignites when there is a call for heat.n0useforaname wrote:Ok.. so I did some more research.. the Aquastat will call for coal. I guess the timer is basically for the spring/summer when nothing is calling for heat at all. Fine tuning this thing has been a task, but I'll eventually find my solid ground : )
The aquastat and water temp question...
In many (most?) coal systems, the load is cyclical. When you have a call for heat, the distribution system (radiators, baseboard, tubing, etc) has higher BTU output with higher water temps. As zones continue to call for heat, the boiler is firing and the water temp is increasing, so is the output of the distribution system. It is "ramping up" and the BTUs sent to the zone(s) are increasing until the zone(s) are satisfied.
But what happens when your boiler takes 15 mins to ramp up to max temp, then the zones are satisfied and here you are left with all those BTUs in standby mode with nothing to do?
Targeting those temps and adjusting the LO, HI, and maybe MID (see my other thread where we're discussing that: Scottscoaled @ Aquastat With Post-Burn Purge? ) is the adjusting and tweaking we all strive to achieve maximum efficiency.
A modulating gas boiler would be simple to hold a given temp all the time. A coal is a bit more challenging. Of course, for the reasons above and some others (rooms at 85F!), you likely don't want your water to be at max temp ALL the time.
