---
title: Terminal Heating Units
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electrical rooms, entries, and perimeter spaces.
Not intended for: Central air-handling units, packaged rooftop equipment, fan-coil units
− serving multiple modes (see [[syncs/fan-coil-units]]), VAV terminals, radiant panel and
+ serving multiple modes (see [[sync/fan-coil-units]]), VAV terminals, radiant panel and
in-floor radiant systems, gas-fired make-up air units, and infrared heaters. Hydronic and
− steam distribution piping serving these units is covered by [[syncs/hydronic-piping]].
+ steam distribution piping serving these units is covered by [[sync/hydronic-piping]].
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- Central station air handlers, packaged rooftop units, VAV terminal boxes, and gas-fired make-up air units
−- Multi-mode fan-coil units (see [[syncs/fan-coil-units]])
+- Multi-mode fan-coil units (see [[sync/fan-coil-units]])
- Radiant panels and in-floor radiant systems
−- Hydronic supply, return, and condensate piping upstream of each unit's connection (see [[syncs/hydronic-piping]]); this standard governs the unit, its control valve, and its terminal connections
+- Hydronic supply, return, and condensate piping upstream of each unit's connection (see [[sync/hydronic-piping]]); this standard governs the unit, its control valve, and its terminal connections
# Definitions {toc}
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## A line-voltage single-setpoint thermostat cannot provide the scheduled setback and programmability that current energy-code editions require; in jurisdictions enforcing ASHRAE 90.1-2019 or later it fails the control requirement and a programmable or BAS-integrated thermostat is required instead. {note}
−## Units integrated with the building automation system shall interface with the controls specified in [[syncs/building-automation-system]].
+## Units integrated with the building automation system shall interface with the controls specified in [[sync/building-automation-system]].
## Hydronic units shall be provided with a two-way or two-position control valve with an end switch that interlocks the fan to valve position, so the fan does not run when the coil is cold.
## A fan that runs while the control valve is closed blows unheated air into the space, which feels like a draft and wastes fan energy; the end-switch interlock prevents cold-blow by holding the fan off until the valve opens. {note}
−## Modulating units served by a variable-speed plant shall be provided with a 0-10 V modulating valve actuator compatible with the BAS, as coordinated with [[syncs/hvac-variable-frequency-drives]] where applicable. {note}
+## Modulating units served by a variable-speed plant shall be provided with a 0-10 V modulating valve actuator compatible with the BAS, as coordinated with [[sync/hvac-variable-frequency-drives]] where applicable. {note}
# Freeze Protection {toc}
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## Manufacturer technical data was mined for facts only and written in manufacturer-agnostic language; no proprietary guide-form specification text was copied or adapted. {note}