ECM Overview and Setup
86
UNT-SVX07E-EN
Customer Supplied Thermostat
Interface
Customer Supplied Thermostat Interface (CSTI) is a
control interface intended to be used with a field-supplied,
low-voltage thermostat or controller. The control box
contains a relay board which includes a line voltage to 24-
volt transformer and disconnect switch (for non-electric
heat units). All end devices are wired to a low-voltage
terminal block and are run-tested, so the only a power
connection and thermostat connection is needed to
commission the unit. Changeover sensors and controls
are provided whenever a change-over coil is selected.
When N.O. valves are selected, inverting relays are
provided for use with standard thermostats.
The CSTI adapter board provides all the hookups of the
standard adapter board, but in addition, provides hookups
for valve control (main and auxiliary coils), electric heat
control, and damper control. Screw terminal blocks
provide convenient access to fan controls and to end
device control. In addition, a courtesy 10-Vdc supply is
provided for use with an external potentiometer or
rheostat. The 10-Vdc supply supports up to 10 mA draw.
TB3 (right 13 positions) is normally used to provide:
•
24 Vac supply to a wall fan speed switch or
•
24 Vac supply to a field-installed unit-mounted
controller, or a wall-mounted controller or thermostat
•
Inputs (returns) for thermostatic fan control: High,
Medium, and Low
•
Inputs (returns) for cooling/heating requests
•
Inputs (returns) for electric heat requests
•
Inputs (returns) for damper operation requests
TB4 (left three positions) is normally used to control the
system with a 0–10 Vdc input from a thermostat/controller
with a variable speed output, or a fan control rheostat.
The terminal block functional assignments and polarity
are shown for reference only, and the schematics that ship
with each unit should be consulted before wiring. Wiring
assignments are configured for each unit.
Installation and Initial Setup
Figure 76.
CSTI adapter board and field connections
1.
VSP 10V (TB4)
2.
VSP 0–10V (TB4)
3.
VSP DC COM (TB4)
1.
24 VAC B (hot) (TB3)
2.
24 VAC Y (gnd) (TB3)
3.
Fan High (TB3)
4.
Fan Medium (TB3)
5.
Fan Low (TB3)
6.
V1 Open (Cooling) (TB3)
7.
V1 Close (Modulating Cooling) (TB3)
8.
Freezestat (TB3)
9.
Freezestat (TB3)
10. V2 Open/EH Stage 1 (Heating) (TB3)
11. V2 Close/EH Stage 2 (Heating) (TB3)
12. Damper Open/Condensate Overflow (TB3)
13. Damper Close/Condensate Overflow (TB3)
Customer low-voltage
interface for fan speeds,
variable fan speed, and
24 Vac supply, valve control,
EH control, damper control,
condensate overflow status
Valve(s), electric heat, and
changeover configuration
switches (factory-set)
3 2 1 13 12 11 10 9 8 7 6 5 4 3 2 1
WARNING
Hazardous Voltage w/Capacitors!
Failure to disconnect power and discharge capacitors
before servicing could result in death or serious injury.
Disconnect all electric power, including remote
disconnects and discharge all motor start/run
capacitors before servicing. Follow proper lockout/
tagout procedures to ensure the power cannot be
inadvertently energized. Verify with an appropriate
voltmeter that all capacitors have discharged.
For additional information regarding the safe discharge
of capacitors, see PROD-SVB06A-EN
