Robertshaw 8425 NON-PROGRAMMABLE Thermostat
Application
The Robertshaw 8425 is a multi-stage thermostat designed to control 24 VAC heat pump systems.
Features
- Large backlit display
- Adjustable 1st stage temperature differential: 1.0°F to 3.0°F (0.5°C to 1.5°C)
- Adjustable 2nd stage temperature differential: 1.0°F to 6.0°F (0.5°C to 3.0°C)
- Adjustable 2nd stage delay (10-40 minutes)
- 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
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.
- DO NOT CONNECT TO 120 VAC. 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.
Recycling Thermostat
If this thermostat REPLACES a thermostat that contains mercury, DO NOT discard the old thermostat in the regular trash. Mercury is harmful to humans and the environment. For this reason, do not open, break, or crush the mercury cell. If mercury leaks from a damaged cell, DO NOT touch or handle mercury with bare hands. Use protective, non-absorbent gloves to place mercury into a sealable container. Fill the container with sand or another absorbent material and seal the container completely. Return the mercury or mercury products, in a sealed container, to Invensys Controls Americas or a local recycling center for proper disposal. If you have any questions, call Robertshaw technical support at 1-800-445-8299
- Invensys Controls Americas
- 28C Leigh Fisher Blvd.
- El Paso, TX 79906
- Attn: Mercury Recycling Center
Step 1: Replacing Existing Thermostat
| Old Terminal | New Label | Description |
| R, V-VR or VR-R | R | 24VAC, return |
| Y, Y1, M | Y1 | Compressor relay (Stage 1) |
| O or R | O | Reversing valve (cool active) |
| B | B | Reversing valve (heat active) |
| F or G | G | Fan control relay |
| Y2 | Y2 | 2nd stage cooling circuit |
| W2, W-U or E | W2/E | 2nd stage heating control or emergency heating for heat pumps |
| C, X or B | C | 24 VAC, transformer common side |
| L or X | L | System monitor |
| W or W1 | W1 | 1st stage heat – non heat pump |
- Turn off power to heating and cooling system.
- Remove cover from old thermostat to expose wires (Figure 1).
- Disconnect wires one at a time from existing terminals. Use enclosed labels to mark existing wires. Refer to cross-references in the Wiring Table if existing wiring does not directly match the labels.
- Remove existing thermostat base from wall
Step 2: Installing Model 8425 Thermostat
- Turn power off to the heating and cooling systems.
- Place EMER-HEAT-OFF-COOL in OFF position (Figure 2).
- Place
AUTO-ON switch into AUTO position (Figure 2).
- Remove the cover using a coin or screwdriver (Figure 3). Set aside
- Place thermostat against the wall at desired location. Make sure wires will feed through opening (Figure 4) on base of the thermostat.
- Mark placement of mounting holes (Figure 4). Set base aside.
- If mounting on drywall, tap plastic anchors into wall.
- NOTE: Enclosed plastic anchors do not require a drilled hole for drywall.
- If mounting on a surface other than drywall, drill the marked holes using a 3/16″ (5mm) drill bit.
- Align base with plastic anchors and feed wires through opening.
- Secure base to wall with supplied screws. NOTE: The thermostat will mount horizontally on a single gang junction box.
- Strip end of wires 5/16” (8mm) if needed.
- Terminal screws are already loose and ready for wire insertion.
- Insert wires into terminal strip (Figure 4) matching the label to the corresponding terminal (see Wiring Diagrams). Tighten screws.
- Make sure wire connections are secure.
- Push excess wire back through opening
Wiring Diagrams
TERMINAL LEGEND
| TERMINAL LEGEND – 8425 | |||
| TERM | EQUIPMENT TO CONNECT | REQ? | TERMINAL FUNCTION |
| R | 24 VAC hot connection | Yes | For input of 24VAC hot side of the transformer |
| C | 24 VAC common connection | Yes | For input of 24VAC common side of the transformer |
| L | System fault indicator connection | No | For connection of system fault indicator (if present) |
| W1 | First stage connection for non-heat-pump applications | No* | Energizes on a call for heat |
| 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 |
| W2/E | Second stage heat or Emergency heat connection | Yes* | Energizes on a call for second stage or emergency heat |
| B | Heat active reversing valve connection | Yes** | Energizes when in the HEAT or EM modes |
| O | Cool active reversing valve connection | Yes** | Energizes when in the COOL mode |
| G | Indoor fan connection | Yes | Energizes with E & Y1, Y2 and W2 terminals or with FAN option switched to the ON position |
- Set the Electric/Gas switch to either GAS for a gas/oil heating system or ELEC for an electric heating system (Figure 5).
- 6. Set the HP option switch to either the HP for heat pump or NON_HP for furnace applications (Figure 5).
- Replace thermostat cover by snapping into place.
Step 3: Testing the Thermostat
- Place the EMER-HEAT-OFF-COOL switch into the COOL position. The will be displayed.
- 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. - Put the EMER-HEAT-OFF-COOL switch into the OFF position. The air conditioning system should turn off.
- Put the EMER-HEAT-OFF-COOL switch into the HEAT position. The will be displayed.
- 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.
- Put the EMER-HEAT-OFF-COOL switch into the EMER position. The will be displayed.
- Press the
button until the temperature setting is at least 3 degrees above room temperature. The secondary heating system should turn on. - NOTE: The compressor will not turn when in emergency heat mode.
- 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.
- Put the AUTO-ON switch into the ON position.
- The blower fan should turn on. The display will show
- Put the AUTO-ON switch into the AUTO position.
- The blower fan should turn off
Step 4: Customizing the Thermostat
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. Use only when the primary stage of heat is not functioning or requires service.
- The display will show CHECK HP when the heat pump requires service.
Fan
- Auto: Equipment controls the fan.
- On: The fan operates continuously.
Temperature Differential
The temperature differential for 1st stage is factory set at 1.0°F (.5°C). This means that whenever the room temperature changes by one degree Fahrenheit from the temperature setting, the system will turn on. If the system turns on too often, increase the temperature differential. NOTE: The temperature differential for 2nd stage is factory set at 2.0°F (1.0°C)
The temperature differential for 1st stage is factory set at 1.0°F (.5°C). This means that whenever the room temperature changes by one degree Fahrenheit from the temperature setting, the system will turn on. If the system turns on too often, increase the temperature differential. NOTE: The temperature differential for 2nd stage is factory set at 2.0°F (1.0°C)
Changing Fahrenheit (°F) to Celsius (°C), the Temperature Differential, and the Filter Monitor
- The thermostat is preset to display the temperature in degrees Fahrenheit (U models) or degrees Celsius (Canadian models). The temperature display can be changed.
- Press and hold both the
buttons for three seconds. The display will flash either an F or C. Release buttons. Press or button to switch the display. - Wait five seconds or press and the display will switch to the differential setting for 1st stage heating and cooling.
- The display will read diFF. Press the button to adjust the differential up or down.
- Wait five seconds or press
and the display will switch to the differential setting for 2nd stage heating and cooling. - The display will read diF2. Press the button to adjust the differential up or down.
- Wait five seconds or press and the display will switch to the differential delay.
- The display will read dLY2. The differential delay is the length of time (in minutes) from when the 1st stage engages, until the 2nd stage engages to assist in heating or cooling.
- Press the or button to adjust the delay up or down
- Wait five seconds or press and the display will switch to the filter monitor setting.
- CHECK FILTER and the length of hours for the filter monitor will be displayed.
- Use the or to adjust the filter timer from 0 (OFF) to 9900 hours. NOTE: The filter timer is based on equipment run time. Select the length of time based on the recommended service interval for your filter.
- Press the to return to normal operation
Check Filter Reset
Once the filter timer has expired CHECK FILTER will turn on and stay on. To clear the message and reset the timer:
- Press the buttons and hold for 3 seconds. CLr will appear in the time display.
- Press any key to clear the message. The display will transition to the temperature scale display as described in the previous section.
- No further input is needed. Within a few seconds, the display will return to the normal operating mode.
Backlit Display
This thermostat is equipped with a backlight to make night time temperature adjustments quick and easy. Press the button to activate the backlight. The backlight will turn off after about 10 seconds of inactivity
This thermostat is equipped with a backlight to make night time temperature adjustments quick and easy. Press the button to activate the backlight. The backlight will turn off after about 10 seconds of inactivity
Reset
To reset the thermostat press the RESET button located above the upper left corner of the display
To reset the thermostat press the RESET button located above the upper left corner of the display
Troubleshooting
| Symptom | Remedy |
| The thermostat does not turn on the system. | Check to wire (see Installation
section). |
| Thermostat turns system on and off too frequently. | Increase temperature differential (see Changing the Temperature Differential section). |
| System fan does not operate properly. | Move Electric/Gas switch to either gas or electric, to match system (see Installation section). |
| Thermostat does not display proper room temperature. | Check F/C (Fahrenheit/Celsius) setting. See Changing Fahrenheit
(F) to Celsius (C). |
If problems with the thermostat cannot be resolved, call:
- Technical Support: (800) 445-8299
- Monday-Friday 7:30 AM – 5:30 PM CST
- For after hours service, a 24-hour automated help line is available
Warranty
Two-Year Limited Warranty
Invensys Controls Americas warrants to the original contractor installer, or to the original consumer user, each new Robertshaw thermostat to be free from defects in materials and workmanship under normal use and service for a period of two (2) years from date of purchase. This warranty and our liability does not apply to batteries or merchandise that has been damaged by misuse, neglect, mishandling, alterations, improper installation, or use in a way other than in accordance with Invensys Controls Americas recommendations and instructions. Invensys Controls Americas agrees to repair or replace at its option any thermostat under warranty provided it is returned within the warranty period, postage prepaid, with proof of the date of purchase. Cost of thermostat removal or reinstallation is not the responsibility of Invensys Controls Americas. Repair or replacement as provided under this warranty is the exclusive remedy of the consumer. Invensys 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 this product is limited to the duration of this warranty. Some states do not allow the exclusion or limitation of incidental or consequential damages, or allow limitations on how long an implied warranty lasts, so the above limitations or exclusions may not apply to you. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state
For warranty returns, send thermostat, shipping prepaid to:
- Invensys Controls Americas
- Warranty Claims Department
- 515 S. Promenade
- Corona, CA 92879-1736
Controls Americas
- 191 E. North Avenue
- Carol Stream, Illinois 60188
- United States of America
REFERENCE
DOWNLOAD MANUAL
Robertshaw 8425 NON-PROGRAMMABLE Thermostat User Manual
Leave a Reply