Carrier 42C Series - Controls

14
Use the Control Selection Guide table to make sure that all
necessary components are provided for and that the com-
ponents are compatible with the required control system.
NOTE: When thermostatic fan control is selected or when
unit outside-air dampers are used, unit-mounted thermo-
stats are not recommended as their use will result in poor
room temperature sensing.
CONTROL SELECTION GUIDE
LEGEND
*If system is HEATING-ONLY or COOLING-ONLY, no changeover or bypass is required.
NOTE: Unit-mounted thermostats are not recommended with either fan-cycle control or applications with outside-air dampers.
SYSTEM DESCRIPTION THERMOSTAT
CHANGEOVER
ON
SUPPLY PIPE
VALVE
FAN
SWITCH
NOTES
2-PIPE HEATING-COOLING*
Fan
Control
(2-pipe)
Fan manually cycled None None None 3-Speed switch Not recommended for
high humidity applica-
tion
Two-
Position
Electric
Valves
(2-pipe)
Thermostat cycles valve
open or closed.
Wall or unit
mounted includes
heat-cool switch.
None Motorized (N.C.)
3-way or 2-way,
no bypass
required.
Thermostat has
integral 3-speed
switch
Valve packages with
belled end(s) for field
soldering to coil.
Thermostat cycles valve
open or closed. Mode auto-
matically switched by
changeover sensing water
temp.
Wall or unit
mounted.
Heating/cooling
Thermostat
Yes Motorized (N.C.)
3-way or 2-way
Thermostat has
integral 3-speed
switch
ELECTRIC HEAT
Two-
Position
Electric
Valve with
Auxiliary
Electric
Heat
(2-pipe)
Thermostat cycles valve
open or closed. Thermostat
activates electric heater.
Heater cannot turn on if hot
water is in coil.
Wall or unit
mounted.
Sequenced heating
and cooling.
Ye s.
Two Required.
Motorized 3-way
or 2-way
Thermostat has
integral 3-speed
switch
Valve packages with
belled end(s) for field
soldering to coil.
Two-
Position
Electric
Valve with
Total
Electric
Heat
(2-pipe)
Thermostat cycles valve
open or closed.Thermostat
activates electric heater.
Wall or unit
mounted.
Sequenced heating
and cooling.
None Motorized (N.C.)
3-way or 2-way,
no bypass
required
Thermostat has
integral 3-speed
switch
Valve packages with
belled end(s) for field
soldering to coil.
4-PIPE
Two-
Position
Electric
Valves
(4-pipe)
Thermostat cycles cooling
valve open or closed. Ther-
mostat cycles heating valve
open or closed.
Wall or unit
mounted.
Sequenced heating
and cooling.
None Motorized (N.C.)
3-way or 2-way
(requires 2
valves)
Thermostat has
integral 3-speed
switch
Valve packages with
belled end(s) for field
soldering to coil.
N.C. — Normally Closed
Controls