Field guides
Steam and hydronic field guides
Short walkthroughs for the questions that come up on the job: how much air is in the main, what the ounce columns and clear-time minutes mean, how many main vents to hang, whether a radiator wants a Gorton C or a D, why the thermostat-room vent should stay small, how outdoor-reset four setpoints and ratio work, and how injection GPM maps to valve Cv. Numbers stay in the calculators — these pages explain the method and point you there.
One-pipe steam
How many Gorton #2 main vents?
Measure the main, convert pipe volume to a venting rate, then decide how many #2 (or #1) eliminators you need.
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One-pipe steam
Gorton C or D on a radiator?
Is D faster than C? About 1.2× at 1 oz (0.33 vs 0.27 CFM). Size from EDR + runout, then geography — never fatten the thermostat radiator.
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One-pipe steam
Hoffman 1A vs Gorton C
Is C faster than a Hoffman 1A? Compare published CFM, check mains before the orifice, then upsize a late rad — never fatten the thermostat radiator.
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One-pipe steam
Don't oversize the thermostat radiator vent
Keep the thermostat-room radiator vent small so that room does not heat first and shut the boiler off while far rooms are still cold.
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One-pipe steam
Cold third-floor / upstairs radiator
Cold upstairs rad on one-pipe steam? Clear end-of-main vents first (Gorton #2 cited), then step the late rad Hoffman 1A → C → careful D — never fatten the thermostat rad.
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One-pipe steam
Steam main air volume
Measure main ID and length, convert Schedule 40 internal volume to cubic feet of air, then feed that volume into main-vent sizing.
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One-pipe steam
Vent ounces and minutes
What the 1 / 2 / 3 oz pressure columns mean, why ~3 minutes is a common clear-time target, and how both feed the vent calculators.
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Hydronic
Outdoor reset curve: four setpoints and ratio
How OUTDR START / BOIL START / OUTDR DSGN / BOIL DSGN and the reset ratio define the supply curve — then run the four points in the calculator.
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Hydronic
Injection mixing: GPM → Cv
When to inject hot water into a cooler loop, how load and Ti−Tr become injection GPM, and how to read that flow into a closest-Cv valve pick.
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