HAI Omnistat RC-120 User manual

O M N I S T A T
ELECTRONIC COMMUNICATING THERMOSTAT
Installation Manual
RC-120 Two Stage Heat/Cool
2 Stage Heat / 2 Stage Cool
Document Number 13I00-7
January, 1997

Copyright © 1997 Home Automation, Inc.
All Rights Reserved

CONTENTS
DESCRIPTION ....................................1
INSTALLATION ...................................1
LOCATION ......................................2
REMOVING AN EXISTING THERMOSTAT ..................2
MOUNTING ......................................3
TYPICAL WIRING DIAGRAMS ........................6
POWER UP .......................................8
DISABLE KEYS ...................................9
INSTALLER SETUP ................................9
OWNER'S MANUAL ................................14
QUICK REFERENCE SETUP GUIDE ....................15
REMOTE SYSTEM WIRING DIAGRAMS ................16
TROUBLESHOOTING TIPS ..........................18

DESCRIPTION
The RC-120 is a precision digital thermostat designed for 24 VAC
two stage heating and cooling systems. It has the capability of being
controlled both locally and by remote control. It offers
programmability, stand alone operation, and robust, optically isolated
communications with automation systems, utility control systems,
and personal computers.
Electrical rating: 24 V; 3 A; 50/60 Hz
Maximum current: 2 A on any circuit, 3 A total
Thermostat operating current: less than 15 mA
The following requirements must be observed for installation in
Europe: CE
1.This equipment must be installed in accordance with National
wiring rules for the country in which it is installed.
2.Fuses must be replaced only with IEC rated components.
3.All product labels, instructions and markings relating to safety
must be translated to a language which is acceptable in the
country in which this equipment is to be installed.
INSTALLATION
Before installing this thermostat:
1.Read all of the installation instructions carefully.
2.Read the Owner's Manual carefully.
3.Ensure that this product is suitable for your application.
4.Ensure that wiring complies with all codes and ordinances.
5.Disconnect power to the control transformer to prevent electrical
shock and damage to equipment.
6.Select an appropriate location to ensure an accurate temperature
reading.
1

LOCATION
When replacing an existing thermostat, install the RC-120 in the
same location. If the existing location doesn't meet the following
criteria, choose a new location to mount the RC-120.
When choosing a location for the thermostat:
1.Ensure that the thermostat is mounted about 5 feet above the
floor and is at least 2 feet from an outdoor wall.
2.Ensure that the thermostat is located in an area where there is
adequate air circulation.
3.Do not mount in the path of direct sunlight or of radiant heat
generated by appliances.
4.Do not mount behind an outdoor wall, near a fireplace, or in the
path of any air ducts.
REMOVING AN EXISTING THERMOSTAT
1.Disconnect the power to the control transformer.
2.Remove the cover to the existing thermostat.
3.Disconnect the wires going to each terminal on the thermostat.
Label each wire with the letter or number at the terminal.
4.Remove the existing plate or base from the wall.
2

MOUNTING
When mounting the RC-120, grasp the thermostat by the sides,
avoiding the keys, and unsnap the base from the face.
Holding the base to the wall so that the word "TOP" is upright and
facing you:
1.Mark the two mounting holes on the wall using a pencil.
2.Drill a hole using a 3/16" bit at each mounting hole marking.
3.Install the two wall anchors supplied.
4.Slide the system wires through the opening in the base.
5.Mount the base to the wall using the two #6 x 1/2" self-tapping
screws supplied - See Figure 1.
Figure 1 - Mounting thermostat base
3

Connect each wire to the terminal strip on the thermostat base per the
wiring diagram for your system application - See Figures 4 - 5.
Form the thermostat wiring so that the cable lies flat between the
terminal strip and the center of the thermostat base - See Figure 2.
Figure 2 - Forming thermostat wiring
If a remote system is being used with the thermostat, connect the
remote system wiring to the supplied cable using the wire splices per
the diagram for your remote system application - See Figures 7 - 8.
Insert the cable into the connector on the thermostat circuit board
marked "COMM".
Upon completion of wiring the thermostat, push all excess wiring
into the hole in the wall. Plug the hole with the supplied insulating
foam to ensure an accurate temperature reading by the thermostat.
4

Align the tabs of the thermostat face with the slots of the thermostat
base. Gently push the thermostat face into the thermostat base
locking it into place - See Figure 3.
Figure 3 - Mounting thermostat face to thermostat base
Note:
Be sure that the thermostat temperature sensor is standing up, and
that it has not been damaged during installation.
SLOT TAB
WALL BASE
FACE
TEMPERATURE
SENSOR
5

TYPICAL WIRING DIAGRAMS
CAUTION
1. Be sure to disconnect the power to the control
transformer before removing or installing thermostat.
2. Do not short cooling or heating relays, or fan relay...
even momentarily. This will blow a non-replaceable
fuse.
3. Do not attempt to hook up to live circuits. An accidental
connection to a component on the thermostat circuit
board could cause damage to the thermostat.
Figure 4 - Thermostat power-up for test or demonstration purposes
6

FIGURE 5
7
2ND STAGE
COOLING
RELAY
FAN
R
Y2
C G
HEATING
1ST STAGE
TRANSFORMER
24VAC
1
2 3
4
5
6
7 8
W1
Y1
COOLING
1ST STAGE
24VAC "HOT" 24VAC "COMMON"
TWO STAGE HVAC SYSTEMRC-120
W1
Y1
C
Y2
G R
24VAC "HOT" FAN
24VAC "COMMON" 1ST STAGE
NOT USED COOLING COOLING
2ND STAGE
HEATING
1ST STAGE
W2
2ND STAGE
HEATING
W2
HEATING
2ND STAGE