Page 14 of 25
508133G01 / 31-5000715
Issue 2140
Thermostat Type
Indoor Unit Type
Qty. of
Wires to
NS18HMA Terminal
Strip Connections
Unit Operation
Field Wiring
Diagram
Conventional
24VAC 2-Stage
Cooling Thermostat
Any Furnace or Air
Handler
6
R, C, W1, O, Y1, Y2
Full Variable Capacity Operation
Controlled by NS18HMA Unitary
Control Using Suction Pressure
Figure 10
Conventional
24VAC Single-Stage
Cooling Thermostat
Any Furnace or Air
Handler
5
R, C, W1, O, Y1
(Jumper Y1 to Y2)
Full Variable Capacity Operation
Controlled by NS18HMA Unitary
Control Using Suction Pressure
Figure 9
Table 6. NS18HMA Thermostat Control Options
Size Circuit and Install Service Disconnect
Switch
Refer to the unit nameplate for minimum circuit ampacity,
and maximum fuse or circuit breaker (HACR per NEC).
Install power wiring and properly sized disconnect switch.
SERVICE
DISCONNECT
SWITCH
MAIN FUSE
BOX/BREAKER
PANEL
Figure 6.
NOTE:
Units are approved for use only with copper
conductors. Ground unit at disconnect switch or connect
to an earth ground.
Install Thermostat
Install room thermostat (ordered separately) on an inside
wall approximately in the center of the conditioned area
and 5 feet (1.5m) from the floor. It should not be installed
on an outside wall or where it can be affected by sunlight
or drafts.
THERMOSTAT
5 FEET
(1.5M)
Figure 7.
NOTE:
24VAC, Class II circuit connections are made in
the control panel.
