On 1/17/2015 9:21 PM, TimR wrote:


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 high limit switch shuts the heat off when the boiler water is at
temperature. If it cuts it prematurely, it won't heat the water enough
to heat the house. No reset required, that is how it is supposed to
work to make the burner cycle.

The water cools as it gives its heat to the rest of the hose. Once it
get down to the low limit, the burner is started again.

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.

Possible, unlikely. Check the flow as I suggested.