Vaporstat Question

EdwinD

Have Weil MClain EG-55 with 2 pipe radiators. Finished install on brand new Vaporstat (Steam), 0 to 16 oz and Pressuretrol PA404A control.

Settings:
Vaporstat 8 differential / 12 main
Pressuretrol .05 cut-in / 1 differential

Conducted a test lasting 75 minutes with the boiler fired the entired time - before cut-out.

After 60 minutes the pressure gauge registered flat with pressure gradually rising after 60 minutes:


Vaporstrat 12 oz cut-out occurred around 75 minutes burn time


Consistent with a visual observation of pressure guage, cut-in occured at around 4 psi

My question is whether this is desirable/expected behavior? I'm mostly concerned about the cut-out time of 75 minutes, should it happen later as in short cycling - or is that about right? Comments appreciated. Thanks

Note: yesterday I put 1 1/2 Steammster tablets into the boiler. Pressure was erratic at first but seems to have stabilized.

Jamie Hall

From what you describe, it seems to me that you have a pretty good match between your boiler size and firing rate and load -- since it is that, not the existence of the vapourstat, which determines how long it takes before the pressure starts to rise (which you said was 60 minutes). The only comment I'd make is that if your radiators are pretty well hot across at that point, I'd seriously consider dropping the cutout pressure to 8 ounces, with a 4 ounce differential, as the additional run time bringing you up to 12 ounces isn't doing much to heat the building.

EdwinD

@Jamie Hall Ok - will do. That makes a lot of sense. Thank you!

Fred

In reality, this test does show that you are very well matched, boiler output to radiation. I'm not sure it matters that you make any adjustment to the Vaporstat, cut-in or cut-out. That boiler isn't going to run a full 60 minute heating cycle during the winter to maintain thermostat settings. It will likely run maybe 15 minute cycles and never even get to an 8 ounce cut-out.

EBEBRATT-Ed

What @fred & @jamie hall mentioned is true. You don't have to have measureable steam pressure for the system to work

EdwinD

@Jamie Hall @Fred @EBEBRATT-Ed I'll tell you this, you guys are awesome. So much great advice being shared is truly a blessing. I've never been this excited enterng into a winter heating season - a BIG thank you!

JUGHNE

You have another posting about your single main vent hissing?
I wonder what the others think if you should increase the venting capacity, if it would speed up the steam delivery?

EdwinD

JUGHNE said:

You have another posting about your single main vent hissing?
I wonder what the others think if you should increase the venting capacity, if it would speed up the steam delivery?

@JUGHNE Thanks. Just curious, how do you increase the venting capacity?

EBEBRATT-Ed

Add more vents. If you cant put a larger vent on due to pipe size add a tee and a second vent. Measure the size of you steam mains to determine the correct vent size.

nicholas bonham-carter

I would think that the pressure would rise during the venting phase, if the venting were inadequate. Your initial test was with dead cold pipes and water, so it took longer. Do you have crossover traps?
Are all the rads getting hot at the same time? Pats of butter on identical plates should melt at the same time-and you can have toast afterwards!—NBC

EdwinD

@nicholas bonham-carter No crossover traps. No, all the rads are not getting hot at the same time. Upstairs rads are warm when downstairs are hot. But upstairs rads eventually catch up, in about 5 min or so.

Jamie Hall

Do you have adequate venting on your dry returns? In a two pipe system, that's critical -- and often overlooked.

EdwinD

EBEBRATT-Ed said:

Add more vents. If you cant put a larger vent on due to pipe size add a tee and a second vent. Measure the size of you steam mains to determine the correct vent size.

@EBEBRATT-Ed Thanks