Filter
Top Products
VAV HEATING AND COOLING WITH ELECTRIC
CHANGEOVER — This application uses a CV control pack-
age along with a wall-mounted thermostat package (cooling/
heating) and an electric changeover package. The change-
over valve permits control of the unit to be switched between
the cooling and heating sides of a cooling/heating thermo-
stat. It is field-installed in-line between the volume control-
ler and the thermostat.
Refer to Fig. 70-73. In cooling operation, the NO port of
the valve opens the control circuit between the volume
controller and the cooling side of the thermostat. Because
the NC port is closed, the heating side of the thermostat is
locked out of the system. Upon changeover to heating, the
solenoid valve is energized. The NO port closes and the NC
port is opened, and the control circuit switches to the heat-
ing side of the thermostat. Typically, the solenoid valve is
wired to activate automatically when the heating system is
turned on, although it may be operated by a simple on/off
switch.
Fig. 70 — Heating/Cooling Unit — Cooling, Cold Air in Duct, Electric Changeover in Cooling,
Thermostat Open, Controller Shut Off, Unit Shut Off
66