Robertshaw 9420 User manual

DIGITAL
NON-PROGRAMMABLE
THERMOSTAT
9420
HEAT PUMP
H
NeW
2 Heat / 2 Cool
User's Manual
Quick Start
Installation
Application
The Robertshaw 9420 is a multi-stage thermostat designed to control
24 VAC heat pump systems.
Features
•Summer and winter setpoints
•Large back lit display
•Adjustable 1st stage temperature differential: 0.5°F to 3.0°F
(0.5°C to 1.5°C)
•Adjustable 2nd stage temperature differential: 1°F to 6°F
(0.5°C to 3.0°C)
•Adjustable 2nd stage delay (10-40 min.)
•Compressor short cycle protection
•Accuracy within ±1°
•Zone system compatible as a master thermostat
•Permanent memory retention
•Fahrenheit/Celsius display option
•Adjustable from 45°F to 90°F (7°C - 32°C)
•Quick wire terminal block
•Automatic heating shutdown if temperature exceeds 94°F (34°C)
1
110-1044B

IMPORTANT SAFETY INFORMATION WARNING:
•Always turn off power at main fuse or circuit breaker panel before
installing, removing, cleaning, or servicing thermostat.
•Read all the information in this manual before installing this
thermostat.
•This is a 24 VAC low-voltage thermostat. Do not install on voltages
higher than 30 VAC.
•All wiring must conform to local and national building and electrical
codes and ordinances.
•Do not short (jumper) across terminals on the gas valve or at the
system control to test installation. This will damage the thermostat
and void the warranty.
•Do not connect ground to any terminal in this unit.
Step 1: Replacing Existing Thermostat
1. Turn off power to heating and cooling system.
2. Remove cover from old thermostat to expose wires (Figure 1).
3. Disconnect wires one at a time from existing terminals. Use enclosed labels
to mark existing wires. Refer to cross references in Table 1 if existing wiring
does not directly match the labels.
4. Remove existing thermostat base from wall.
Old Terminal New Label Description
R, V-VR or VR-R R 24 VAC, Return
Y, Y1 or M Y1 Compressor Relay (Stage 1)
O or R O Reversing Valve (Cool Active)
BBReversing Valve (Heat Active)
F or G G Fan Control Relay
Y2 Y2 2nd Stage Cooling Circuit
W2 or W-U W2 2nd Stage Heating Control
C, X or B C 24 VAC, Transformer Common Side
L or X L System Monitor
EEEmergency Heating Circuit
NOTE: THIS THERMOSTAT REQUIRES A 24V COMMON WIRE FOR PROPER OPERATION.
Table 1
2
Figure 1
!

Recycling Thermostat
If this thermostat is replacing a thermostat that contains mercury
in a sealed tube, do not place your old thermostat in the garbage.
Contact your local waste management authority for instructions
regarding proper disposal of the thermostat. If you have any ques-
tions, call Robertshaw technical support at 1-800-445-8299.
Step 2: Installing Model 9420 Thermostat
NOTE: FOR NEW INSTALLATIONS, MOUNT THERMOSTAT ON
INSIDE WALL, FIVE FEET ABOVE THE FLOOR. DO NOT
INSTALL BEHIND A DOOR, IN A CORNER, NEAR AIR
VENTS, IN DIRECT SUNLIGHT, OR NEAR ANY HEAT OR
STEAM GENERATING FIXTURES. INSTALLATION AT THESE
LOCATIONS WILL AFFECT THERMOSTAT OPERATION.
1. Turn power off to the heating and cooling systems.
2. Place EMER-HEAT-OFF-COOL in OFF position (Figure 2).
3. Place -ON-AUTO switch into AUTO position (Figure 2).
4. Remove the cover using a coin or screwdriver (Figure 3). Set aside.
3
Figure 3
SETTING OR CHANGING THE SETPOINT TEMPERATURE:
1. Press or button. Display will show SET and the current
temperature setpoint.
2. Press or button to adjust temperature setpoint.
3. After completing the change, the display will return to the current
room temperature after a few seconds.
CHANGING THE TEMPERATURE DIFFERENTIAL,
DEAD BAND, AND RESIDUAL COOL:
The temperature differentials are factory set at 1˚F and 2˚F for
1ST and 2ND stages respectively. The dead band for Auto-
changeover is set at 3˚F.To change settings:
1. Press the and buttons at the same time and hold for 1
second. Display will indicate: DIFFERENTIAL 1ST.
2. Press either the or button to adjust the 1st stage differ-
ential between 0.5˚F – 3˚F (0.5˚C - 1.5˚C).
3. Either wait five seconds or press the button. The display
will indicate: DIFFERENTIAL 2ND.
4. Press either the or button to adjust 2nd stage differen-
tial between 1˚F – 6˚F (1˚C - 3˚C).
5. Either wait five seconds or press the button. The display
will indicate: DEADBAND.
6. Press either the or button to adjust the dead band
between 3˚F – 6˚F (1.5˚C - 3˚C).
7. Either wait five seconds or press the button. The fan
icon and ON will be displayed.
8. Press either the or button to adjust the Residual Cool
fan delay between 0, 30, 60, or 90 seconds.
9. The display will return to the current room temperature after
a few seconds.
Item
9555
120-1523
Maple Chase Company
www.maplechase.com
Tech Service: 1-800-445-8299
M-F 7:30 a.m. - 5:30 p.m. CST
MADE IN MEXICO
TM
Figure 2

5. Place thermostat against the wall at desired location. Make sure wires
will feed through opening (Figure 4) on base of thermostat.
6. Mark placement of mounting holes (Figure 4). Set base aside.
7. If mounting on drywall, tap plastic anchors into wall.
NOTE: ENCLOSED PLASTIC ANCHORS DO NOT REQUIRE A
DRILLED HOLE FOR DRYWALL.
8. If mounting on a surface other than drywall, drill the marked holes
using a 3/16" drill bit.
9. Align base with plastic anchors and feed wires through opening.
10. Secure base to wall with supplied screws.
NOTE: THE THERMOSTAT WILL MOUNT HORIZONTALLY
ON A SINGLE GANG JUNCTION BOX.
11. Strip end of wires 5/16” if needed.
12. Terminal screws are already loose and ready for wire insertion.
Insert wires into terminal strip (Figure 5) matching the label to the
corresponding terminal (see Wiring Diagrams). Tighten screws.
13. Make sure wire connections are secure.
14. Push excess wire back through opening.
4
Mounting Holes
WIRING
OPENING
Figure 4
Y2
CLR
Y1
E
W2
G
O
B
Label
Y
Figure 5

5
T
yp
ical heat
p
um
p
with cool active reversin
g
valve and auxiliar
y
/emer
g
enc
y
heat.
T
yp
ical heat
p
um
p
with heat active reversin
g
valve and auxiliar
y
/emer
g
enc
y
heat.
T
yp
ical heat
p
um
p
with cool active reversin
g
valve and auxiliar
y
/emer
g
enc
y
heat.
Does not have se
p
arate wire for emer
g
enc
y
heat
(j
um
p
W2 & E
)
.
T
yp
ical heat
p
um
p
with cool active reversin
g
valve, auxiliar
y
/emer
g
enc
y
heat
and second sta
g
e of coolin
g
. S
y
stem fault indicator connected
(
L terminal
)
.
OB
9420 WIRING SAMPLE #1
Y1 E G W2CLRY2
9420 WIRING SAMPLE #2
CLRY2Y1EGW2OB
9420 WIRING SAMPLE #3
BY1 E G W2CL O
EG
RY2
Jumper
OB
9420 WIRING SAMPLE #4
CW2LRY2Y1
◆Wiring Diagrams

15. Replace thermostat cover by snapping into place.
16. Turn on power to system. Test thermostat as described in the
following section.
Step 3: Testing the Thermostat
WARNING: DO NOT SHORT (JUMPER) ACROSS TERMINALS
OF GAS VALVE OR SYSTEM CONTROL TO TEST
OPERATION. THIS WILL DAMAGE THE
THERMOSTAT AND VOID YOUR WARRANTY.
CAUTION: DO NOT SWITCH SYSTEM TO COOL IF THE TEMPERATURE
IS BELOW 50°F (10°C). THIS CAN DAMAGE THE AIR
CONDITIONING SYSTEM AND CAUSE PERSONAL INJURY.
1. Place the EMER-HEAT-OFF-COOL switch into
the COOL position. The display will read COOL.
2. Press the button until the temperature setting
is at least 3 degrees below the room temperature.
The air conditioning system should turn on within
a few seconds. The snowflake icon will be displayed
(1st stage cooling;  2nd stage cooling).
6
TERMINAL LEGEND - 9420
TERM EQUIPMENT TO CONNECT REQ? TERMINAL FUNCTION
C24VAC common connection Yes For input of 24VAC common
side of transformer
LSystem fault indicator connection No For connection of system
fault indicator (if present)
R24VAC hot connection Yes For input of 24VAC hot side
of transformer
Y2 Second stage cooling connection No Energizes on a call for
second stage cooling
Y1 First stage compressor connection Yes Energizes on a call for
first stage of heating and
cooling
EEmergency heat connection No* Energizes on a call for heat
in the EM mode only
GIndoor fan connection Yes Energizes with E, Y1, Y2 and
W2 terminals or with FAN
option switched to the ON
position
W2 Second stage heat connection No* Energizes on a call for
second stage of heat
(auxiliary heat)
OCool active reversing Yes** Energizes when in the in
valve connection COOL mode
BHeat active reversing Yes** Energizes when in the
valve connection HEAT or EM modes
*For systems using a backup heat source. If separate E terminal connection is not available,
jumper E and W2.
** Most heat pump systems will have a cool active or a heat active reversing valve. Use the
appropriate terminal.
!

7
NOTE: ONCE THE THERMOSTAT TURNS OFF, A BUILT IN 5-MINUTE
DELAY PREVENTS THE SYSTEM FROM TURNING ON AGAIN.
THIS PROTECTS THE COMPRESSOR. NO ADDITIONAL TIME
DELAY RELAY IS REQUIRED. TO OVERRIDE THE 5-MINUTE DELAY
FOR INSTALLATION, PRESS THE RESET BUTTON.
3. Put the EMER-HEAT-OFF-COOL switch into
the OFF position. The air conditioning system
should turn off. The display will read SYSTEM OFF.
4. Put the EMER-HEAT-OFF-COOL switch into
the HEAT position. The display will read HEAT.
5. Press the button until the temperature
setting is at least 3 degrees above room
temperature. The heating system should
turn on. The fan may not turn on immediately,
depending on the fan delay built into the furnace.
The flame icon will be displayed
(1st stage heating;  2nd stage heating).
6. Put the EMER-HEAT-OFF-COOL switch into
the OFF position. The heating system should
turn off. The fan may continue to run for a
short period of time. The display will read
SYSTEM OFF.
7. Put the -ON-AUTO switch into the ON
position. The blower fan should turn on.
The display will show a and ON.
8. Put the -ON-AUTO switch into the AUTO
position. The blower fan should turn off.

Step 4: Customizing the Thermostat
◆Settings
System
Cool: The thermostat controls the cooling.
Off: The heating and cooling systems are off.
Heat: The thermostat controls the heat.
Emer: The thermostat controls the second stage emergency heat.
Used only when the primary stage of heat is not functioning or
requires service. The display shows EMER when emergency heat is
activated.
Fan
Auto: Equipment controls the fan.
On: The fan operates continuously.
Temperature
Heating: The default temperature for heating is 70°F (21°C). To
change the default setpoint, put the system switch in HEAT and
press the or button to adjust the temperature setting up or
down. The display will show SET. The display will return to the
current room temperature three seconds after the last input and
the new setpoint will be saved.
Cooling: The default temperature for cooling is 78°F (25°C). To
change the default setpoint, put the system switch in COOL and
press the or button to adjust the temperature setting up or
down. The display will show SET. The display will return to the
current room temperature three seconds after the last input and
the new setpoint will be saved.
8
Figure 7

9
◆Temperature Differential 2nd Stage Delay
The temperature differential is factory set at 1.0°F (.5°C) for the 1st stage
differential and 2°F (1°C) for the 2nd stage. This means that whenever the
room temperature changes by one degree Fahrenheit from the tempera-
ture setting, the system will turn on. If the system turns on too often,
increase the temperature differential.
This thermostat is equipped with an adjustable 2nd stage time delay. The
delay is factory set at 20 minutes. The time delay setting prevents the 2nd
stage system from activating until the delay time has expired. If the 2nd
stage is turning on too often, increase the time delay.
The 2nd stage will turn on when the room temperature changes from
the desired temperature by the sum of the 1st and 2nd stage differential
settings. The 2nd stage also will turn on if the temperature has not
increased (or decreased in the event of cooling) for a period of
20 minutes.
◆Changing Fahrenheit (°F) to Celsius (°C),
Temperature Differential, and
2nd Stage Delay
1. The thermostat is preset to display the temperature in degrees
Fahrenheit (US models) or degrees Celsius (Canadian models). The
temperature display can be changed. Press and hold both the
and button for three seconds. The display will read F or C.
Release buttons. Press the or button to switch the display.
2. After three seconds the display will switch to the 1st stage
differential settings. The display will read DIFFERENTIAL 1st. The
temperature differential is factory set at 1.0°F (0.5°C). Press the or
button to adjust the differential up or down.
3. After three seconds the display will switch to the 2nd stage differ-
ential setting. The display will read DIFFERENTIAL 2nd. The temper-
ature differential is factory set at 2°F (1°C). Press the or button
to adjust the differential up or down.
4. After 3 seconds, the display will switch to the 2nd stage delay
setting. The second stage delay is factory set at 20 minutes. Press
the or button to adjust the time delay in 5 minute increments.
5. Wait three seconds or press and the display will return to the
original room temperature.
◆Backlit Display
This thermostat is equipped with a backlight to make nighttime temper-
ature adjustments quick and easy. Press the button to activate the
backlight. The backlight will turn off after about 5 seconds of inactivity.

10
WIRING
OPENING
Reset Switch
◆Reset
To reset the thermostat press the RESET button located just below the
lower left corner of the display.
Step 5: Troubleshooting
Symptom Remedy
Display shows CHECK Monitors system status. Call your
local HVAC service provider.
Check F/C (Fahrenheit/Celsius)
setting. See Changing Fahrenheit
(F) to Celsius (C).
Thermostat does not display
proper room temperature.
Thermostat turns system on and
off too frequently.
Thermostat does not turn on system. Check wiring (see Installation
section).
Increase temperature differential
(see Changing the Temperature
Differential section).
If problems with thermostat cannot be resolved, call:
Technical Support: [phone]
Monday-Friday 7:30 AM - 5:30 PM CST