Gravity Return \"B\" Dimension

Steamhead (in transit)

Pressuretrols usually aren't that accurate. Get the Vaporstat that cannot go higher than 1 PSI. Mount it on a brass pigtail above the waterline.

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Meowschmidt

Cut-out Pressure

I'm sort of a novice at this stuff, so please bear with me. I have a gravity return 2-pipe system in my house. I was calculating my "B" dimension recently and have a little concern. My lowest steam-carrying pipe is at 78" and my boiler water line is at 30". I understand that this gives me a "B" dimension of 48". LAOSH tells me I need 30" of vertical height for each psig of boiler pressure to get my condensate back into the boiler. My calculations (48/30)tell me that I can have a max. cut-out of 1.6 psig on my pressuretrol. I have a classic honeywell additive pressuretrol with a low limit of 0.5 and an upper limit of 9 psig (lowest differential is 1). Can I rely on this pressuretrol to control between 0.5 and 1.5? Are they that accurate? Are there units that have more control at the low end? I usually get spitting from my main vents (dry return) at the end of the cycle. Thanks for any suggestions!

Meowschmidt

Thanks for the suggestion. Who makes a good Vaporstat? Won't I need one with a higher max (than 1 psig) to get enough differential for the heat cycle or do they work differently than a pressuretrol?

Unknown

Honeywell has,,,,,,,,,,,,,,,

the one you need. It`s an L408A1132. The max. pressure you can set this at is 1 psi. That should be all you need as you said the main vents "spit", and that usually goes along with running too high a pressure anyway. Like Steamhead said, make sure it has a brass pigtail.

Jamie_6

why a brass pigtail?

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Unknown

Jamie.........

I guess it doesn`t really have to be, just a matter of "personal preference" for corrosion reasons.

Ken_40

Brass?

Steel is fine as well.

The crud that builds up inside the pigtail (or hard piped in steel nipps. and ftgs.) is NOT rust based from internal pigtail corrosion. It is the impurities and temperature changes within the "siphon" (the correct mis-nomer for a pigtail)...

Steamhead (in transit)

Brass pigtails

don't rust up inside though. And some codes and inspectors call for brass ones now. So we have standardized on them.

"Steamhead"

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