rychw wrote:I have operated the boiler for 5 seasons on the factory settings and have had explosions (too many to count) during that time. That led me to make the changes to prevent the explosions. Yes, the explosions are a result of too much new coal being allowed to enter the burn chamber too fast. That is why slowing the rate of ash dumping will slow the rate of new coal allowed to enter the chamber. It is important to have the fire as high up the burn chamber, tube, as possible. I needed to lower the thermo ash dump temperature to accive that. The factory settings set by AHS are not correct, especially if you have a domestic hot water coil and thermo grate combo. Again, this is trial by error with no help from AHS.
I also had puffbacks for several seasons with factory settings. It was only when I came to understand the concept of fire height and searched for a SV that gave an appropriate fire height that my problem was resolved.
I know that one of the theories about the problem is that it is caused by the ashing running when the blower is not running. I don't have the data to conclusively accept or reject that theory. But I do know that my ashing does continue after the blower shuts down and for the past 1.5 years I haven't had a puffback.
I noted that both you and lsayre have your boilers set up so that the ashing cannot occur when the blower is not running.
I was only trying to suggest that you might try--if you haven't already--running the unit with ashing allowed when the boiler is not running but ensuring that the SV is set to maintain the appropriate fire height.