How do I size a heating hot water control valve?

Heating hot water control valves follow the same Cv sizing formula as chilled water valves (Cv = Q × √(SG/ΔP)), but the design typically uses a lower ΔP because heating coils operate with higher water temperatures (160–200°F vs 42–45°F for chilled water) and therefore need less flow for the same heat transfer. A key difference is that heating valves must be selected for close-off against the higher system pressures in heating loops (often 40–60 PSI at the pump, compared to 25–40 PSI for chilled water), and valve bodies must be rated for continuous 200°F+ operation with appropriate EPDM or PTFE seats. Per ASHRAE guidance, heating valves on VAV reheat coils should be line-sized or one size smaller than the coil connection, with an authority of 0.3–0.5 for stable temperature control at the typically low loads where reheat operates. Belimo CCV valves with equal-percentage characteristics work particularly well for heating because they linearize the inherently logarithmic heat output of coils.