Honeywell TH9421C1004 Programmable Thermostat Installation Guide
- June 13, 2024
- Honeywell
Table of Contents
Honeywell TH9421C1004 Programmable Thermostat
For up to 4 Heat/2 Cool systems with Honeywell THM5421C or equivalent.
- Must be installed by a trained, experienced technician. Read these instructions carefully. Failure to follow these instructions can damage the product or cause a hazardous condition.
- CAUTION: ELECTRICAL HAZARD. Can cause electrical shock or equipment damage. Disconnect power before beginning installation.
- MERCURY NOTICE: If this product is replacing a control that contains mercury in a sealed tube, do not place the old control in the trash. Contact your local waste management authority for instructions regarding recycling and proper disposal.
This thermostat contains a Lithium battery which may contain Perchlorate material. Perchlorate Material—special handling may apply, See www.dtsc.ca.gov/hazardouswaste/perchlorate
Installation
- Thermostat can be mounted on 2″ x 4″ J box or on drywall or plaster using included wall anchors (drill 3/16″ holes for drywall; 7/32″ holes for plaster).
- Connect 1, 2, 3 terminals on thermostat to 1, 2, 3 terminals on EIM or Zone Panel; see EIM or Zone Panel Installation Guide for wiring diagrams.
Set date/time
Installer setup
- Press SYSTEM
- Press and hold for 5 seconds
- Change settings
Installer setup
Setup function /Settings & options (factory default in bold)
0110 Zone number| 0 Not zoned
1–9 Zone number
---|---
0120 Year
(first two digits)
| 20 ( 20 00- 20 99)
21 (21 00- 21 78)
0130 Year
(second two digits)
| 06 (20 06 ) [Other options: 00-99]
0140 Month| 6 ** [Other options: 1-12]
0150 Date| 15 [Other options: 1-31]
0160 Schedule format| 4 7-day programming**
0 Non-programmable
0165 Restore Energy
Star schedule
| 0 No
1 Yes
0172 System type| 1 Conventional
2 Heat pump
3 Heat only (no fan) E Auto Discover **
0174 Cooling compressor stages| 1 1 stage of cool [Other
options: 0 or 2 stages, or E]
0176 Heat or Heat Pump Aux stages| 1 1 stage of heat [Other
options: 0, 2 or 3 stages, or E]
0180 Fan control
(conventional heat)
| 0 Gas/Oil heat (equipment controls heating fan)
1 Electric furnace (thermostat controls heating fan)
2 Equipment controls stage 1, thermostat controls stage 2+ E Auto Discover **
0190 Changeover valve (O/B terminal)| 0 O/B terminal controls valve in cooling
1 O/B terminal controls valve in heating
0200 Backup heat
(Aux & EmHeat)
| E Auto Discover **
0 Electric backup heat
1 Fossil fuel backup heat
0210 External fossil fuel kit| 1 External fossil fuel kit controls backup heat
0 Thermostat controls backup heat (outdoor sensor required)
---|---
0220 Stage 1 compressor 1cycle rate| E Auto Discover **
[Other options: 1 to CPH]
0230 Stage 2 compressor cycle rate| E Auto Discover **
[Other options: 1 to 6 CPH]
0240 Stage 1 heat cycle rate (CPH= cycles per hour)| E Auto
Discover ** [Other options: 1 to 12 CPH]
0250 Stage 2 stage heat cycle rate (CPH)| E Auto Discover
** [Other options: 1 to 12 CPH]
0260 Stage 3 heat cycle rate (CPH)| E Auto Discover **
[Other options: 1 to 12 CPH]
0280 Backlight| 0 Backlight on for approx. 45 seconds after
keypress
1 Backlight always on low intensity, full bright after keypress
0300 Manual/Auto
changeover
| 0 Manual (User options: Heat/Cool/Off)
1 Automatic (User options: Heat/Cool/Auto/Off) (System selects heat/cool based on indoor temp.)
0310 Auto changeover deadband| 3 Heat/cool settings 3°F apart
(1.5°C) [Other options: 2-9 (2°F to 9°F/1°C to 5°C)]
0320 Temperature display| 0 Fahrenheit
1 Celsius
0330 Daylight savings| 2 Auto-change to daylight savings time (2007 and beyond, for areas that use the new 2007 DST calendar)
1 Auto-change to daylight savings time (through 2006, and for areas that do not use the new 2007 DST calendar)
0 Daylight savings time is turned off
0340 Indoor temp. sensor| 0 Display temp. at thermostat location only
1 Display temp. at indoor sensor location(s)
2 Average between thermostat & sensor location(s)
0342 Outdoor temp. sensor| E Auto Discover **
0 None
1 Remote sensor
0345 Dual fuel heat
pump control
| 1 Balance point plus 2°F droop **
0 Balance point only **
2 Balance point/Aux Heat Lockout plus 2°F droop **
0346 Dual fuel heat
pump upstage to furnace timer
| 60 60 minutes **
0 Off
[Other options: 30, 45 or 75 minutes]
0350 Heat pump
compressor lockout
| 0 No compressor lockout ** [Other options: 5 to 60°F (-15°C to
15.5°C)]
0360 Heat pump
auxiliary lockout
| 0 No heat pump auxiliary lockout ** [Other options: 5 to 65°F
(-15°C to 18.5°C)]
0365 Discharge temp. sensor| E Auto Discover **
0 No
1 Yes
0370 Indoor humidity sensor| 1 Internal sensor in thermostat
0 Sensors disabled E Auto Discover **
0372 Indoor humidifica- tion control| E Auto Discover **
0 Off
1 Humidify (no frost protection)
3 Humidify (with frost protection)
---|---
0374 Humidifier fan action| 0 Humidify only while fan or heat
is on
1 Humidify forces fan on
2 Humidify only when heat is on
3 Humidifier operates independent of fan
0379 Dehumidification control| 0 No dehumidification control
1 Dehumidify with air conditioner
3 Whole house dehumidifier
0383 Over-cooling limit| 3 3°F (1.5°C) [Other options: 1, 2
(1°F or 2°F/0.5°C to 1.5°C)]
0384 Dehumidification fan action| 0 System fan turns on with
dehumidifier
1 Dehumidifier operates independent of fan
0390 Dehumidification away mode| 0 No
1 Yes
0391 Dehum. away mode fan setting| 0 Fan auto
1 Fan always on
2 Fan circulate
0392 Dehum. away mode low limit temp.| 76 Low limit temperature
76°F (24°C) [Other options: 70°F to 80°F (21°C to 27°C)]
0393 Dehum. away mode temp. setting| 85 Away temperature 85°F
(29°C) [Other options: 70°F to 99°F (21°C to 37°C)]
0394 Away dehumidifica- tion setting| 65 Away humidity level
65% [Other options: 55% to 70%]
0400 Ventilation control| 0 No ventilation
1 Ventilation always allowed
2 Ventilation not allowed during sleep period
0401 Number of
bedrooms
| 2 Two bedrooms [Other options: 1 to 6]
0402 Size of house| 10 1,000 square feet [Other options: 11 to
50 (1,100 to 5,000 square feet)]
0403 Ventilation level| 160 CFM (cubic feet per minute) [Other
options: (30 to 195 CFM)]
0404 Max. ventilation
% limit
| 50 50% ventilation limit [Other options: 30% to 60% or 100%]
P **** Meets ASHRAE 62.2 standard
F **** Does not meet ASHRAE 62.2 standard
0405 Ventilation fan action| 1 Ventilation on forces fan on
2 Ventilation does not force fan on
0406 Ventilation in high humidity| 1 On (heat mode only)
0 Off
0500 Furnace filter
change alert
| E Auto Discover ** **** 7 270-day run time
0 Off 8 365-day run time
1 10-day run time 9 30 calendar days
2 30-day run time 10 60 calendar days
3 60-day run time 11 90 calendar days
4 90-day run time 12 120 calendar days
5 120-day run time 13 180 calendar days
6 180-day run time 14 365 calendar days
0502 Furnace filter
alert options
| 0 Timer counts Heat & Cool run time
1 Timer counts Cool run time only
---|---
0510 Humidifier pad
change alert *****
| E Auto Discover **
0 Off
1 90 calendar days or 30 days run time
2 180 calendar days or 60 days run time
3 365 calendar days or 90 days run time
0520 UV lamp change alert| E Auto Discover **
0 Off
1 365 calendar days (1 year)
2 730 calendar days (2 years)
0530 Adaptive Intelligent Recovery™| 1 On **
0 Off
0540 Program periods| 4 4 program periods (Wake, Leave, Return, Sleep)
2 2 program periods (Wake, Sleep)
0580 Compressor off time (min.)| 5 5 minute compressor off
time ** [Other options: 0 to 4 minutes]
0600 Heat temperature range stop| 90 Max. heat temperature
setting is 90°F (32°C) [Other options: 40 to 90°F (4°C to 32°C)]
0610 Cool temperature range stop| 60 Min. cool temperature
setting is 60°F (15°C) [Other options: 60-99°F (15°C to 37°C)]
0640 Clock format| 12 12-hour time (i.e., “3:30 pm”)
24 24-hour time (i.e., “15:30”)
0650 Extended fan
timer (heat)
| 0 Off [Other options: Fan runs for 30, 60, 90 or 120 seconds after
call for heating ends]
0660 Extended fan
timer (cool)
| 0 Off [Other options: Fan runs for 30, 60, 90 or 120 seconds after
call for cooling ends]
0670 Keypad lock| 0 Keypad unlocked (fully functional)
1 Partially locked (access to temperature settings only)
2 Fully locked
0680 Heat temperature control| 2 Standard temperature control (recommended)
1 Choose if room is warmer than set temperature
3 Choose if room does not reach set temperature
0690 Cool temperature control| 2 Standard temperature control (recommended)
1 Choose if room is cooler than set temperature
3 Choose if room does not reach set temperature
0700 Temperature
display offset
| 0 Thermostat displays actual room temperature [Other options: -3°F
to +3°F offset (-1.5°C to 1.5°C)]
0701 Humidity
display offset
| 0 Thermostat displays actual room humidity [Other options: -5% to
+5% offset]
0710 RESET| 0 No reset
1 Reset installer options & program schedule to factory default (only date and time settings are retained)
- Humidifier Pad replacement will be displayed in the user interface as run time days if ISU 372 is set to 1 or 3 and calendar days if ISU 372 is set to 0.
Special function
- Auto Discover: Setup functions set to “E” (Auto Discover) will be configured automatically, based on information sent from connected equipment. When using Auto Discover, verify that the discovered value is correct. If it is not, the equipment is not communicating the information, and you must change settings manually.
- Adaptive Intelligent Recovery (Setup Function 0530): Allows the thermostat to “learn” how long the furnace and air conditioner take to reach programmed temperature settings, so the temperature is reached at the scheduled time.
- Compressor Protection (Setup Function 0580): Forces the compressor to wait a few minutes before restarting, to prevent damage. During this time, the message “Wait” flashes on the display.
- Southern Away Dehumidification Control (Setup Functions 0390-0394): This feature is useful for homes in southern climates. It allows humidity control when the the home is unoccupied for long periods during the hot/humid season. You can control temperature (Function 0393) and dehumidification (Function 0394) while away. You can control humidity with a dehumidifier or a cooling system (Function 0379). If a cooling system is used, humidity is controlled by cooling indoor air to the Low Limit Temperature (Function 0392). When the desired humidity is reached, the system will maintain the temperature you select in Function 0393.
- Heat Pump Control: Electric Backup (Setup Functions 0350-0360): If an outdoor temperature sensor is installed, select a compressor lockout temperature (Function 0350). Below this temperature, only electric heat operates. Also select an auxiliary lockout temperature (Function 0360). Above this temperature, only the compressor operates. Between these temperatures, both heat sources operate.
Heat Pump Control — Fossil Fuel Backup (Setup Function 0345):
- Option 0 (Balance point only): If outdoor temperature is above balance point (Function 0350), only the compressor operates. Below this temperature, only backup heat operates.
- Option 1 (Balance point + 2°F droop): As above, but backup heat is activated if room temperature drops by 2°F (compressor is deactivated).
- Option 2: (Balance point/Aux Heat +2°F droop): Compressor works only above auxiliary lockout temperature, backup heat works only below balance point, 2°F droop between temperatures. If temperature is not reached in a reasonable time, set the upstage timer (Function 0346). After the designated time, the compressor will be deactivated and the system will switch to backup heat.
- Ventilation Control (Setup Functions 0400-0406): If the system includes a self-powered ventilation unit (Function 0400), the home can be ventilated on demand, or ventilated automatically if high humidity is detected while in heating mode (Function 0406).
Installer system test
System test /System status
1 Cooling system| 0 Off
1 Test cooling stage 1
2 Test cooling stages 1 & 2
---|---
2 Fan system| 0 Fan off
1 Fan on
3 Heating system| 0 Off
1 Test heating stage 1
2 Test heating stages 1, 2
3 Test heating stages 1, 2, 3
4 Test heating stages 1, 2, 3, 4
4 Emergency heating system| 0 Off
1 Test EmHeat stage 1
2 Test EmHeat stages 1, 2
5 Humidifier| 0 Off
1 On
6 Dehumidifier| 0 Off
1 On
7 Ventilator| 0 Off
1 On
Other messages
P **** Ventilation meets ASHRAE 62.2 standard (Function 0404)
F **** Ventilation does not meet ASHRAE
62.2 standard (Function 0404)
Err **** See error codes
CAUTION: EQUIPMENT DAMAGE HAZARD. Compressor protection is bypassed during testing. To prevent equipment damage, avoid cycling the compressor quickly.
How to Use the Installer System Test
The Installer Test is part of the Installer Setup Menu.
- Enter the Installer System Test by entering Installer Setup.
- The test appears at the end of the Installer Setup Numbers.
- See above for available Installer System Tests.
- If installed with a Discharge Air Temperature Sensor (ISU365=1), press MORE to view the discharge temperature, and press CANCEL to return to the Installer test screen.
Error codes
| 027 | Faulty thermostat (must be replaced) |
|---|---|
| 035 | Duplicate thermostat zone detected |
| 036 | Duplicate UV timer |
| 037 | Duplicate filter timer |
| 038 | Duplicate humidifier pad timer |
| 039 | Duplicate indoor humidity sensor |
| 040 | Compressor should be running but it is not |
| 050 | Duplicate outdoor temperature sensor |
| 052 | Faulty post-coil air discharge sensor |
| 053 | Faulty outdoor temperature sensor |
| 054 | Faulty indoor humidity sensor |
| 089 | Heating/cooling equipment is missing |
| 090 | Data interface is continuously busy |
| 091 | Thermostat is not receiving data from other equipment |
| 118 | Faulty discharge air temperature sensor |
| 119 | Faulty temperature sensor |
| 121 | Duplicate post-coil air discharge sensor |
Accessories
Please contact your distributor to order replacement parts
- Outdoor temperature sensor………………………..Part number C7089U1006
- Remote indoor temperature sensor………………Part number C7189U1005
- Discharge air temp. sensor………………………….Part number C7835A1009
- Energy recovery ventilator……………………………Part number ER200B2006
- Heat recovery ventilator………………………………Part number HR200B1005
- Fresh air damper…………………………………………Part number EARD6
- 2-Channel Telephone access module…………..Part number W8735D1009
- 4-Channel Telephone access module…………..Part number W8735D1017
- Bypass flow-through or steam humidifier……..Part number HE265A1007
- UV air purifier………………………………………………Part number UV100E1043
- Cover plate…………………………………………………Part number 32003796-001
- (Use to cover marks left by old thermostats.)
*Contact your dealer or Honeywell rep for a complete list of compatible products.
Contact
Need Help?
- For assistance with this product please visit http://yourhome.honeywell.com
- call Honeywell Customer Care toll-free at 1-800-468-1502
Automation and Control Solutions
- Honeywell International Inc.
- 1985 Douglas Drive North Golden Valley, MN 55422
- http://yourhome.honeywell.com
Honeywell Limited-Honeywell Limitée
- 35 Dynamic Drive
- Toronto, Ontario M1V 4Z9
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