Pump Over-run stat for Kerosene Boiler

Andy From Sligo

Hello - this is just to whet my curiosity and for no other reason. We had an LPG indoor boiler and it had a built in Pump Over-run thermostat, reading in the instruction manual it said something like running the pump because its not good to have hot water sitting in the cast iron heat exchanger - however we have a firebird outside kerosene boiler (in metal case) with an RDB2 burner in it and it has a frost-stat, a normal stat (set to 55'c) but from what i can see no Pump Over-run thermostat. Just wondering/curious at to why the LPG gas boiler needed a Pump Over-run thermostat but the Firebird boiler dont need one? - no worries if I dont get any answers to this post, as i say its just one thing i have always wondered about.

DGOBS

Most gas boilers have low water contents heat-exchangers these days. Unlike older gas boilers and oil boilers where there was a large heat exchanger that is a natural heat-sink used to absorb the heat still transferring into the water jacket when the boiler demand is terminated.

A low water content ones would not be able to deal with that, would cause overheats, and calcification in the heat-exchanger, so originally fan overrun was employed to run cool air through the boiler until the heat load was dissipated, later in the day manufacturers used pump overrun as it was more effective.

I have pump over run on my oil boiler, using a pipe stat to control the pump, as why waste the useful heat in the boiler when it turns off, shunt it to the house or the cylinder if possible (but shut down at 55ºC to avoid condensation in the combustion chamber)

Andy From Sligo

DGOBS wrote: »

Most gas boilers have low water contents heat-exchangers these days. Unlike older gas boilers and oil boilers where there was a large heat exchanger that is a natural heat-sink used to absorb the heat still transferring into the water jacket when the boiler demand is terminated.

A low water content ones would not be able to deal with that, would cause overheats, and calcification in the heat-exchanger, so originally fan overrun was employed to run cool air through the boiler until the heat load was dissipated, later in the day manufacturers used pump overrun as it was more effective.

I have pump over run on my oil boiler, using a pipe stat to control the pump, as why waste the useful heat in the boiler when it turns off, shunt it to the house or the cylinder if possible (but shut down at 55ºC to avoid condensation in the combustion chamber)

ah right many thanks for that now it becomes clear to me, yes our wall hung potterton gas boiler had just a small cast iron heat exchanger in it.