Using universal relays to control heating or cooling
1
U1/U2/U3 terminals are normally open dry contacts when set up for a stage of
heating or cooling.
2
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.
Dry contact alerts
EQUIPMENT DAMAGE HAZARD. Do not apply power to S1–S4 terminals. Do
not connect a temperature sensor to the S1–S4 terminals if set for a dry contact
device.
NOTE:
The dry contact device must be rated for low voltage.
If you are not using the S1–S4 terminals on the EIM, you can connect 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. Dry contact device can be normally open (shown in diagram) or normally
closed.
NOTE:
You can connect multiple Dry Contact devices in parallel to the S1–S4
terminals.
ONE DRY CONTACT DEVICE
MULTIPLE DRY CONTACT DEVICES
ON ONE SET OF TERMINALS
U3
U3
U2
HEAT STAGE 3,
U2
COOL STAGE 3,
COOL STAGE 4 OR
U1
GEOTHERMAL
1
RADIANT HEAT
U1
2
RH
RC
R
24
VAC
C
EIM
S4
S4
S3
S3
TRANSFORMER
24
VAC
EIM
MULTIPLE DRY CONTACT DEVICES
9
120
VAC
ONE DRY CONTACT DEVICE
ON ONE SET OF TERMINALS