System Installation Guide
14
69-2490—05
Prestige THX9321 or EIM:
Using universal relays to control heating or cooling
Powering universal relay with separate
heating transformer (THX9321 shown)
Powering universal relay with system
transformer (THX9321 shown)
1
2
3
U1/U2/U3 terminals are normally open dry contacts when set up for a stage of heating or cooling.
You must install a field jumper if the stage of heating or cooling is powered by system transformer. Do NOT install a field
jumper if the stage of heating has its own transformer.
U1/U2/U3 terminals are assigned to a stage of heating or cooling in the Installer Setup. Options are:
THX9321 Thermostat (U1 and U2)
•
Cool Stage 3 (ISU 2080 - commercial only)
•
Cool Stage 4 (ISU 2090 - commercial only)
•
Conventional Heat Stage 3 (ISU 2100, 2140)
•
Backup Heat Stage 2 for Heat Pumps (ISU 2170)
•
Geothermal Radiant Heat (see wiring guide on pages 12-13)
THX9421 Thermostat with EIM (U1, U2 and U3)
•
Cool Stage 3 (ISU 2080 - commercial only)
•
Cool Stage 4 (ISU 2090 - commercial only)
•
Geothermal Radiant Heat (see wiring guide on pages 12-13)
HEAT STAGE 3 or
COOL STAGE 3 or
COOL STAGE 4
120
VAC
C
Rc
R
U1
U1
U2
U2
24
VAC
Transformer
Thermostat
C
R
1
1
2
3
MCR32952A
HEAT STAGE 3
120
VAC
C
Rc
R
U1
U1
U2
U2
24
VAC
Transformer
120
VAC
24
VAC
Transformer
Thermostat
C
R
C
R
1
1
2
3
MCR32953
Dry Contact Alerts
If you are not using the S1 and S2
terminals on the EIM, you can con-
nect them to a dry contact device to
display an alert. Dry contact alerts
include Full Drain Pan, Dirty Filter,
Water Leak, System Shutdown,
Service Needed, Fan Failure and
Custom Alert (ISU 6000).
You can connect multiple Dry Contact devices in parallel to the S1 or S2 terminals.
The dry contact device must be rated for low voltage.
EQUIPMENT DAMAGE HAZARD.
Do not apply power to S1 or S2 terminals.
MULTIPLE DRY CONTACT DEVICES
ON ONE SET OF TERMINALS
EIM
M31488
ONE DRY CONTACT DEVICE
