About
Legacy Steam + Hydronic Controls
A small set of field calculators for the systems that were already in the building — one-pipe steam venting, and the reset and mixing controls that get retrofitted alongside it.
Where the numbers come from
Every capacity, volume, and coefficient on this site is transcribed from a published source and cited on the page that uses it. Pipe volumes are computed from Schedule 40 internal diameters. Vent capacities come from the instrumented Gill & Pajek test data. Valve Cv values are the ones printed in Taco's own sizing guides.
Where a figure has never been published — several Gorton vents have no measured CFM rating anywhere — the calculator shows a gap and the documents to chase, rather than an interpolation dressed up as data.
What it does not do
No boiler selection from connected EDR, no common vent sizing, no orifice work, no heat loss calculation. Those need a site survey and a load calculation. These tools give you a defensible starting point; the system still has to be timed and adjusted.
Results here are estimates. They are not a substitute for licensed HVAC design.
The calculators
- 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.
- Radiator vent sizer — Size a one-pipe radiator vent from EDR and runout, then adjust for where the radiator sits in the building.
- Outdoor reset curve — Turn four setpoints into a reset ratio, a target supply temperature, and a curve you can read off in the field.
- Injection mixing — Design injection flow rate for a mixed loop, and the valve Cv that goes with it.