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Typical layout with analog heating and cooling:
N.C.
N.O.
M
M
AO - Mixed air dampers
OA
DA
M
BO - Fan low speed
BO - Fan high speed
(optional)
AI - Discharge air temp
(optional)
DX
BO - Cooling stage 1
BO - Cooling stage 2
T
AI - Zone temp
AI - Zone setpoint adjust
BI - Zone override
T
T
BI - Freezestat
(optional)
AI - Outside air temp
(optional)
AO - Heating valve
HWR HWS
HW
T
Typical layout with staged heating and cooling:
N.C.
N.O.
M
M
AO - Mixed air dampers
OA
DA
M
BO - Fan low speed
BO - Fan high speed
(optional)
AI - Discharge air temp
(optional)
DX
BO - Cooling stage 1
BO - Cooling stage 2
T
AI - Zone temp
AI - Zone setpoint adjust
BI - Zone override
T
T
BI - Freezestat
(optional)
AI - Outside air temp
(optional)
Elec
BO - Heating stage 1
BO - Heating stage 2
T
#12: Unit ventilator - 2-speed fan
Control schematics