On Saturday, January 17, 2015 at 3:20:32 PM UTC-5, Ed Pawlowski wrote:
On 1/17/2015 12:29 PM, TimR wrote:
If the boiler is starting up, getting hot, and shutting off before the house gets warm, one likely cause would be something is stopping the hot boiler water from getting to the radiators.

It could be as simple as an air lock. Or, a bad pump somewhere. Or, bad controller for that pump.

If that were the case, I would expect the thermostat to keep calling for heat, and the boiler to be maintaining its setpoint, whatever that is, and coming on and off just enough to keep the boiler water from getting cold.


I think we pretty much narrowed it down to that. What we don't know is
what was actually checked. You can feel the pipes around the house to
see if they are hot. Most systems will allow some gravity circulation,
but not enough to heat the house properly. Depending on the pump, you
may see, hear, or feel the motor running
Assuming it is ok, the high limit switch would be my next step.

I'm not seeing why you suspect the high limit switch. Wouldn't that require hitting the reset, if tripped? This boiler short cycles during the day without tripping any safeties.


The old boiler was 50 years old. The boiler was replaced but not any of the pipes or radiators, so they are all 50 years old. They might have worked fine the first year then a chunk of something came loose and there's a blockage somewhere.