AprilAire 8800/8819 — Communicating Thermostat System Installation Manual

System installation manual for the AprilAire Model 8800 Communicating Thermostat system — covers wiring and checkout for a networked RS-485 thermostat system using the Model 8819 Distribution Panel and Model 8811 Protocol Adapter.

Overview

This manual guides installers through installation, wiring, and checkout of an AprilAire Model 8800 Communicating Thermostat System. For a complete command set and programming suggestions, see the separate programming manual (Part No. 10009414) at www.aprilairepartners.com/docs/literature.

Warning: 120 volts may cause serious injury from electrical shock — disconnect electrical power to the HVAC system before starting installation (this is a low-voltage system). Installation must be performed by a qualified contractor per NEC standards and applicable local/state codes.

System Components

• Model 8800 Communicating Thermostat: RS-485 communicating thermostat configurable for single- and multi-stage heat/cool or heat pump systems, and as a whole-home humidifier/dehumidifier control.
• Model 8819 Distribution Panel: A switch-controlled communication bus wired to up to eight Model 8800 thermostats, allowing thermostat communication to be turned on/off at one convenient location for easier installation and troubleshooting.
• Model 8811 Protocol Adapter: Converts an RS-485 communication signal to RS-232 for reading by a host computer's serial port.
• Automation System Controller: RS-232 or RS-485 based controller, such as the AprilAire System Controller.
• Model 8081 / 8082 Support Modules (optional): Add temperature/humidity sensing capacity or sensor averaging for large areas. 8081 provides two temperature values (onboard + remote); 8082 provides one temperature and one humidity value. Warning: use only the correct support module per thermostat type — 8800s use 8081/8082 only; 8870s use 8061/8062 only (mixing causes damage).
• Model 8051 / 8052 / 8053 Remote Temperature Sensors (optional): Flush mount (8051), outdoor (8052), and wall mount (8053) sensors usable directly with the 8800 or with support modules.

Tools & Wire Needed

• Small flat-head screwdriver (1/8" wide tip) for terminal screws; medium flat/Phillips for component mounting
• Volt/ohm meter; wire strippers; small level
• Computer with RS-232 com port and a terminal emulator (e.g., HyperTerminal) for system checkout
• Multi-conductor thermostat cable (18–20 gauge) for control wiring
• Category 5 (4-pair twisted) communication wire for the thermostat network

Best Practices

• Use Category-5 cable for all communication wiring.
• Double-check terminal connections before powering up; use consistent wire colors as a guide.
• Use a Distribution Panel on any system with more than one zone to simplify wiring and troubleshooting.

Step 1 — Disconnect Power

Disconnect power at the zone control panel input terminals (if zoned) or at the HVAC equipment disconnect switch / breaker / fuse. Caution: Failure to disconnect power could damage HVAC equipment or thermostats — leave power off until all connections are made and verified.

Step 2 — Run Wires & Mount Components

Determine component locations, run and label wires (thermostat cable for HVAC control wiring, CAT-5 for the communication bus, straight-through serial cable for the protocol adapter), then mount each component per its own installation instructions.

Maximum Wiring Distances

A network interconnection worksheet is provided in the manual to record job title, location, date, contractor, and each thermostat's CAT-5 wire run and location address — fill it out and leave it with the system software package.

Step 3 — Connect Control Wires to HVAC/Zone System & Thermostats

A qualified HVAC technician should perform this step. Make sure HVAC power is off, then wire per the Thermostat Installation Instructions' diagrams for conventional heat/cool, heat pump, and humidistat configurations. Thermostat terminals include: B+ A+ B- A- C B O Y Y2 G RC RH W2 W R S2 S1 T1 T2 RSB RSA.

• Conventional heat/cool (single transformer): uses a jumper wire; thermostat powered from the 8819 or a 24VAC transformer.
• Heat pump (single transformer): uses a jumper wire; "O" is active in cooling, "B" is active in heating.
• Humidistat: supports both dry contact and powered contact humidifier/dehumidifier wiring configurations.

Do not turn on HVAC system power yet — communication wiring comes next.

Step 4 — Connect Communication & Power Wires (Distribution Panel + Thermostat)

1. Make sure all switches on the Distribution Panel are OFF.
2. Connect communication wires from each thermostat to the Distribution Panel using consistent wire colors (orange/white, blue/white, green/white pairs typical for A+/A-/B+/B- runs).
3. Power each Distribution Panel with a Model 8029 24VAC transformer (or equivalent).

Step 5 — Connect Multiple Distribution Panels

If more than one Distribution Panel is used, daisy-chain the communication lines together using consistent wire colors, and power each panel with its own separate Model 8029 24VAC transformer (or equivalent 40VA 24VAC transformer). Ensure all panel switches are off before wiring.

Step 6 — Connect Protocol Adapter to Distribution Panel & Host Computer

1. Ensure all Distribution Panel switches are OFF.
2. Use CAT-5 wire to connect the Distribution Panel's main communication terminals to the Protocol Adapter's Breakout Adapter.
3. Connect the provided 3 ft. RS-232 cable from the Protocol Adapter to the computer/automation system (DB9 or DB25 connector as needed).
4. Power the Protocol Adapter with its plug-in transformer — the Power LED should light when powered.

RS-485/422 DB9 connector pinout: Pin 1 = A-, Pin 2 = A+, Pin 3 = B-, Pin 4 = B+, Pin 5 = GND, Pin 7 = +9V (Tx-/Tx+/Rx-/Rx+ signal roles vary by pin).

Step 7 — Check-Out HVAC System Operation

Use the thermostat's own checkout procedure (in its installation instructions) to confirm equipment control before verifying the communication network.

Set Thermostat Address & Node Count (required at EVERY thermostat)

1. Enter Installer Setup Menu: press MODE to set system OFF, press MENU, press and hold SETUP for 7 seconds until INSTALL SETUP appears, then press INSTALL SETUP.
2. Select System Setting 00 (Network Address): set sequentially starting at 1, up to 64 max — no two thermostats may share an address.
3. Select System Setting 01 (Number of Nodes): set to the total thermostat count on the network — must match on every thermostat.
4. Optionally set System Setting 02 (Baud Rate) — default 9600.
5. Press DONE to save, or CANCEL to exit without saving. Unattended for 60 seconds discards changes automatically.

To reset installer settings to default, press the RESET button inside the thermostat's battery cover.

Communication System Checkout (Legacy HyperTerminal Method)

The original manual documents using Windows HyperTerminal (Windows 95/98/2000/NT/XP) connected via the Protocol Adapter's RS-232 port to verify communication. Key serial settings: 9600 bps (or 19200 if thermostats are configured for that rate), 8 data bits, no parity, 1 stop bit, no flow control. Typing a character should flash the Protocol Adapter's RXD LED, confirming the link. This legacy PC utility is superseded on modern systems by the automation controller's own diagnostics — consult your automation system's documentation for current checkout procedures.

Appendix — Model 8870 Considerations

Special wiring applies when installing the Model 8800 alongside the 8870 Series Communicating Thermostat via a Model 8818 Distribution Panel, including dedicated RSR/RSC/RSB/RSA and T1–T4 terminal connections through an 8061/8062 support module. See the original PDF for the full interconnect diagram.

Appendix — Sensor Averaging

Four-sensor or nine-sensor temperature averaging is supported without support modules, using 2-wire thermostat cable (R=red, W=white) wired to the thermostat's S1/S2 (four-sensor) or S1–S9 (nine-sensor) terminals. Works with Model 8051 flush-mount or Model 8053 surface-mount sensors (same wiring for both).

Manufacturer

AprilAire (Research Products Corporation), P.O. Box 1467, Madison, WI 53701-1467. Phone: 800-334-6011. Fax: 608-257-4357. www.aprilairepartners.com.