In ,
Ed Pawlowski typed:
On 1/15/2015 3:01 PM, TomR wrote:


I was definitely wondering what may be causing the short cycling
where his heater keeps cuttin gout and then restarting before
getting the radiators hot. I don't know if a bad circulator pump
could cause that or if something else is being detected by a sensor
of some type that keeps telling the heater to stop and then re-start.

Few possible things.

There is a high limit switch that will cut the burner at a pre-set
temperature. That would make the boiler cycle more if it is set too
low or defective. If the circulator is not moving the water to the
rest of the house it will shut down the burner. If the boiler cycles
for just a couple of seconds, I'd first feelt he pipes and see if the
water is moving. If not, replace the pump. If yes, check the limit
switches.
There are other potential problems but not enough information to
discuss. Since the boiler is 2 years old, I have to assume it worked
OK last year. If so, that removes speculation about the size of the
boiler. It is probably smaller in output, but that is because it is
more efficient. If the old boiler was 60% and dumping 40% up the
stack, an 85% boiler does not have to be as big.

All good points, IMO. In the alt.hvac group the OP did write back that his
"new" heating system did work last year and that the recent developments
where it kept short cycling and won't heat the house properly were new. So,
IMO, that ruled out the possibility that the heating system was undersized
for the house (which he says is small -- 810 sq. ft.), or that the piping
system was designed incorrectly (it's the same piping system that the old
heater used).