In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Boilermate trouble code has me stumped!
Did the control have one button or three? If it has one button, there is a pre programmed post purge. The burner will be turned off before the setpoint then the circ will continue to run to draw residual heat from the boiler. However if this happens during a call for heat, the burner will continue to run and you may be overheating the tank. If there are three buttons, the post purge is programmable. Try setting it to 0 for the winter months and see if that helps. If the homeowners are always mixing cold with it anyway, you may be able to drop the setpoint 5 or 10 degrees without affecting their comfort and give some extra room before the 155 degrees.
The aquastat on the boiler keeps the boiler from making steam when there is a call for hot water but not for heat. If there is a call for heat, it is overriden by the tstat.
Hope this helps.