I recently swaped out a leaking exspansion tank on the castiron Peerless Propane fired Forced Hot Watter boiler wioth two zones on a two story 1,500 sq. ft colonial. It was fine fater I purged all the air and the air reducers did there job. But now when the boiler first fires up to heat the first floor I hear a bang/rumble from the boiler? I am running 20 psi in the system and it shuts off at 190, and turns on at 140?;)

Sounds like 20 PSI is high. How many storys is your house (how tall)

The spread on 140 and off 190 is a bit too much also.

Try to check for more air in the system.
Try to close the gap on the temps. Ttry 160 190 instead.

What kind of radiation do you have? Fan coil,baseboard, or radiators?

Report back

The house is two finshed stories. But the boiler is in walk out basement which has 8 foot ceilings, Two fished floors above that and there is a tird floor I am finishing soon.;) It has baseboard finned radiators.

Did you do these?


The spread on 140 and off 190 is a bit too much also.

Try to check for more air in the system.
Try to close the gap on the temps. Try 160 190 instead.

This might also be a burner light off problem. Have someone activate the thermostat while you are watching the boiler fire up. See if you can tell where it is coming from.

Did you do these?


The spread on 140 and off 190 is a bit to much also.

Try to check for more air in the system.
Try to close the gap on the temps. Try 160 190 instead.

This might also be a burner light off problem. Have someone activate the thermostat while you are watching the boiler fire up. See if you can tell where it is coming from.


I did but when it first lights off the flame is yellow then quickly turns a good blue? The high temp is adjustable cool is not it is a cold staart system only keeps 140-190 during heating season goes down to 0 when no demand for heat.

So where did the noise come from when you watched the boiler?