Field calculators for old buildings
The steam system was here first.Size the controls to match it.
Four calculators for the work that keeps legacy systems running: venting a one-pipe steam main and its radiators, and setting up the reset curve and injection loop on the hydronic side.
Every vent capacity, pipe volume, and valve Cv used here is transcribed from a published source and cited on the page. Where no measurement has been published — the Gorton Big Mouth, for one — the calculator says so instead of printing a number.
Direct answer
This site calculates one-pipe steam main and radiator vent counts from Schedule 40 volume and published Gill & Pajek CFM (Gorton #1/#2, C/D, etc.), plus hydronic outdoor-reset ratio/curve and injection-mixing GPM→Cv. Every capacity is cited; unpublished figures stay blank. Estimate only — time the system and adjust.
- Schedule 40 volumes from ASME B36.10M
- Vent CFM from Gill & Pajek test data
- Valve Cv from Taco iSeries guides
- Unmeasured figures left as gaps
Four field calculators
Jump straight to the tool you need. Each page cites its pipe volumes, vent capacities, and valve Cvs to a published source.
One-pipe steam
Main vent sizer
Add up the air in a one-pipe steam main and work out how much venting it takes to clear it in the time you want.
Open calculator
One-pipe steam
Radiator vent sizer
Size a one-pipe radiator vent from EDR and runout, then adjust for where the radiator sits in the building.
Open calculator
Hydronic controls
Outdoor reset curve
Turn four setpoints into a reset ratio, a target supply temperature, and a curve you can read off in the field.
Open calculator
Hydronic controls
Injection mixing
Design injection flow rate for a mixed loop, and the valve Cv that goes with it.
Open calculator
How these numbers are produced
Nothing here is a house rule of thumb dressed up as data.
- Pipe volume is computed from ASME B36.10M Schedule 40 internal diameters, not read off a chart — and cross-checked against the published cubic-feet-per-foot table.
- Vent capacities come from the instrumented Gill & Pajek test data published by HeatingHelp. Gorton itself publishes no CFM ratings, only relative comparisons, which we quote but never convert.
- Valve Cv values are the ones printed in Taco's own iSeries sizing guides.
- Unpublished figures stay unpublished. A missing capacity shows as a gap with the sources to chase, not an interpolation.
Sources
- Gill & Pajek, "Balancing Steam Systems Using a Venting Capacity Chart" (2005), HeatingHelp.com
- Gorton Valve Corp. — product listings
- Gorton Air Valve Chart (hosted by NY Radiant Plumbing Corp.)
- Taco — OVERVIEW iSeries-R (Outdoor Reset) Mixing Valve (PA04)
- Taco — Radiant Made Easy Application Guide, iSeries-S Mixing Valve (PA06)
Free quick tools
One question, one answer.
Mixing valve calculator — Load + supply/return temps → injection GPM → closest published Taco iSeries 2-way Cv.
Radiator vent speed calculator — Minutes to vent one radiator with each Gorton radiator vent and a Hoffman 1A at max, from published CFM.
Gorton #2 main vent calculator — One steam main → required CFM → how many Gorton #2 (or #1) eliminators, checked against the tapping.
FAQ
What this site calculates — and what it does not.
What does this site calculate?
Four field tools: one-pipe steam main vent count (/main-vent), radiator vent pick (/radiator-vent), hydronic outdoor-reset ratio and curve (/outdoor-reset), and injection-mixing GPM→Cv (/injection-mixing). Short guides deepen the same math with Direct Answers and cited sources.
Where do the steam vent CFM numbers come from?
Instrumented Gill & Pajek capacity charts (HeatingHelp PDF) at 1 / 2 / 3 oz. Gorton publishes relative ratings only — we quote those but never convert them into CFM. Pipe volume uses ASME B36.10M Schedule 40 IDs.
Does this size common vents, orifices, or boilers from EDR?
No. No common vent sizing, no orifice drilling, no boiler selection from connected EDR. Those need a survey and a load calculation. Use these results as a starting point, then time the system and adjust.
Which page should I open first for one-pipe steam?
Start with main vents (/main-vent / /guides/gorton-2-how-many), then radiator vents (/radiator-vent / /guides/gorton-c-or-d). Keep the thermostat-room vent small (/guides/dont-oversize-thermostat-vent).
What this tool does not do
No common vent sizing, no orifice drilling, no boiler selection from connected EDR. Those need a survey and a load calculation, and a calculator that pretends otherwise does more harm than good. Use these results as a starting point, then time the system and adjust.