Wiring Guidelines

The table lists minimum recommended cable specifications for indoor installations. Part numbers are examples only; equivalent cables meeting the stated requirements are acceptable.
 

RS-485 Wiring Requirements

Trunk configuration and length

• Wire RS-485 communications in a point-to-point daisy-chain topology. T-taps, stubs, spurs, and star configurations are not permitted.
• Keep total trunk length to 200 feet or less.
• Keep the maximum distance between any two adjacent devices on a trunk to 50 feet or less.
• Connect no more than 32 devices to a single RS-485 trunk.
• Repeaters are not permitted.

Termination resistors

• Install a 120-ohm termination resistor at each end of the RS-485 trunk, connected across the positive (+) and negative (-) receiver terminals.
• Do not connect termination resistors to the third (ground/common) conductor or to the cable shield/drain wire.
• Note: ClimaVision devices are equipped with onboard end-of-line (EOL) resistor jumpers or dip switches. An external termination resistor is not required when ClimaVision devices are installed at both trunk ends. Ensure EOL jumper/dip switches are in the proper position.

Polarity

• RS-485 is polarity sensitive. Terminate positive (+) and negative (-) conductors to their correct respective terminals at all devices.

Shield and Drain Wire Termination

• Ground the cable shield/drain wire at one end of the trunk only, at the controller end. Leave the drain wire ungrounded at all other locations.
• At each intermediate device location, butt-splice the shield/drain wire and continue through to maintain shield continuity.
• At the ungrounded end of the trunk, wrap the drain wire a minimum of four (4) rotations around the outer cable jacket and secure with a minimum of two (2) wraps of electrical tape. Do not cut the drain wire short inside the cable jacket.

Common/Ground Conductor

• At each intermediate device location where a common terminal is not available, butt-splice and tape the common reference/ground conductor to maintain continuity.
• At the terminal end of a trunk, wrap and tape unused common reference conductors in the same manner specified for ungrounded drain wires. Do not cut short inside the cable jacket.

Cable Separation and Routing

• Do not run RS-485 communication cables in a conduit or cable bundle with conductors carrying 120 v or greater.
• Do not run RS-485 communication cables in a conduit or cable bundle with power-carrying conductors of any voltage.
• Do not share or connect the RS-485 common/ground conductor with ground conductors from power-carrying cables.

Control Wiring Guidelines

Cable Routing and Continuity

• Use a dedicated cable for each input or output. Do not share cables for multiple sensors or output signals.
• Run all cabling as home runs directly from the controller to the field device. Splices are not permitted.
• Install cable clear of all sharp objects and free of sagging.
• Install tie wraps in a manner that prevents pinching or deformation of the cable jacket.
• Label each cable clearly within 1/4 inch of the wire termination at both ends, using the tag name designated in the project documentation.

Conductor Color Code - Control Wiring

Conductor Color Code - Thermostat Wiring 8-Conductor

General requirements applicable to all cable:

• Use stranded bare copper or stranded tinned copper conductors only. Copper-clad aluminum (CCA) conductors are not permitted.
• All shielded cables must include a drain wire. Terminate the drain wire per section 3.4.
• Cable ratings must comply with applicable nec articles for the installation environment. Use plenum-rated (CMP) cable where required by code.
• These specifications apply to indoor installations only. Outdoor or direct-burial applications require cables rated for the applicable environmental conditions.