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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 1

st

stage temperature differential: 0.5°F to 3.0°F 

(0.5°C to 1.5°C)

• Adjustable 2

nd

stage temperature differential: 1°F to 6°F 

(0.5°C to 3.0°C)

• Adjustable 2

nd

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

Summary of Contents for 9420

Page 1: ...djustable 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...

Page 2: ...placing 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 Descrip...

Page 3: ...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 w...

Page 4: ...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 Wi...

Page 5: ...iary emergency heat Does not have separate wire for emergency heat jump W2 E Typical heat pump with cool active reversing valve auxiliary emergency heat and second stage of cooling System fault indicator connected L terminal O B 9420 WIRING SAMPLE 1 Y1 E G W2 C L R Y2 9420 WIRING SAMPLE 2 C L R Y2 Y1 E G W2 O B 9420 WIRING SAMPLE 3 B Y1 E G W2 C L O E G R Y2 Jumper O B 9420 WIRING SAMPLE 4 C W2 L ...

Page 6: ...nection Yes For input of 24VAC common side of transformer L System fault indicator connection No For connection of system fault indicator if present R 24VAC 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 coolin...

Page 7: ... 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 c...

Page 8: ...t 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 ...

Page 9: ...emperature 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 dif...

Page 10: ...ider 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 Technica...

Page 11: ...acement as provided under this warranty is the exclusive remedy of the consumer Climate Controls Americas shall not be liable for any incidental or consequential damages for breach of any express or implied warranty on this product or under any other theory of liability Except to the extent prohibited by applicable law any implied warranty of merchantability or fitness for a particular purpose on ...

Page 12: ...NOTES 12 ...

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