Single-pipe woes

Fizz

Thanks Bob. My cape is small, 1150sf, and downstairs has one door only-the bathroom. Front door opens to living room and steps to 2nd floor; so not a lot of wiggle room. Basement has a lot of fiberglass shoved between joists, tho can probably shove it higher. When inspected by my guy he said we don't need more insulation in attic area, but I'm going to go-up and see for myself.
Does your heat satisfy thermostat or does v-stat come-into-play?

BobC

My v-stat comes into play before the t-stat is satisfied because the boiler is a bit large 270EDR vs 210 for the rads, The v-stat cycles once or twice before the t-stat is satisfied and I have huge main venting - a bigmouth and MOM1 on about a 14ft 2" main.

Bob

Fizz

I 354 EDR for roughly 220 for rads. T-stat is Honeywell mercury T822D and pressuretrol. I have Big mouth and MOM 1 on one main of about 30'11/2" and MOM 1 on other same length 2". Also have a have dry return on each of appoximateliy 28'11/2" which fills with steam.

Fred

Fizz said:

I 354 EDR for roughly 220 for rads. T-stat is Honeywell mercury T822D and pressuretrol. I have Big mouth and MOM 1 on one main of about 30'11/2" and MOM 1 on other same length 2". Also have a have dry return on each of appoximateliy 28'11/2" which fills with steam.

If this is a one pipe system and that 28' of dry return is actually an extension of the main, after the last radiator run-out, they will fill with steam, especially if the main vents are at the end. That is normal. It just needs to drop below the boiler water line at some point and if it ties to another dry return, that connection needs to be below the water line.

Fizz

Yes it is Fred, and the vents are at the end, then line drops below water line.