boiler on/off in cycling

Big Ed

.....If you would use a voltage meter..Why guess ?

sidney r. bray

boiler on/off when cycling

My he 5 series III wm cast iron boiler has been turning itself off after a few minutes when it calls for heat, then after 30-45 seconds (as the blower motor stays on) the igniter kicks in and the flame starts back up again, only to turn off after an even shorter time heating the block...of course it seems more noticeable in colder weather as the boiler cycles more...we've replaced the flame sensor, ignition control module and checked for any obstructions in the vent pipe...it seems the only other part (according to the manual) would be the pressure switch...any other ideas out there would be appreciated, thanks.

Unknown

This may sound dumb,,

but I had a simple thermostats heat-anticipator setting send me on a similar "wild goose chase" once.

Dave

sidney r. bray

dave-
Did check the heat anticipator, it should be at .40 for that particular boiler and that's where it's set.

Glenn Sossin_2

A few other ideas

Try jumping out the pressure switch temporarily - while your there to observe - see if that changes things. If not, how about checking the the aquastat? What type? Try swapping that out. Is there conductive grease in the well? When it does turn off, what is the water temp ? Is it always the same or different?

Just some things to ponder. Will be waiting to see what the answer is.