Building Automation System Control Panels

Control panels used for Building Automation System (BAS) controllers shall meet the following requirements:

Any control panel with a BAS controller in it shall not have line voltage (>50VAC/DC) located in the same enclosure. Place line voltage controls in a separate panel from the BAS controller enclosure. Line voltage may enter the control panel, but must be contained within conduit or other suitable enclosures when inside the control panel. (i.e. a fully enclosed control transformer may be mounted inside the control enclosure if all line voltage power wiring is in conduit)

Power for the BAS controller shall be provided by the HVAC unit it controls or from a dedicated power source specific to the BAS control system. When power is supplied by a source other than the controlled HVAC equipment a local disconnect switch shall be provided. This may be in the form of a lighting type toggle switch with a locking hasp or a transformer mounted rocker switch. Dedicated 120VAC power sources for BAS control systems shall not have any other foreign loads attached to the circuit and shall be clearly labeled “BAS Controls” at the breaker panel.

A single 120VAC outlet for connection to a laptop shall be provided at the main BAS control panel (typically the BACnet router control panel) and may be fed from the dedicated BAS control system power circuit. This outlet shall be labeled as a power-limited outlet specifying the available VA.

Low voltage power breakers (typically 24VAC) shall be resettable without exposing line voltage power sources.

Low voltage power sources for control panels shall be equipped with manually resettable breakers. Fuses and fusible winding transformers shall not be used.

Exception: Low voltage power sources for terminal units (VAV boxes, fan coils, unit heater) may be protected by fuses or fusible winding transformers.

Terminal blocks in BAS control cabinets for connection to field devices are recommended, but not required with the following exceptions:

i. Where a fire alarm shutdown input is connected to a BAS control panel a terminal block with red terminals shall be provided. These terminals shall be labeled “FA” or “FA-#” where # is a unique identification number.

ii. Where a freeze-stat input is connected to a BAS control panel a terminal block with blue terminals shall be provided. These terminals shall be labeled “FZ” or “FZ-#” where # is a unique identification number. Guidance: The use of specific terminals for fire alarm connections provided a common demarcation point for connection the fire system that is typically done by an alternate contractor. These unique terminals also allow simplified troubleshooting for field technicians working on the system.

iii. Terminals, when used, for general input and output points shall be gray in color and uniquely identified.

iv. Terminals, when used, for low voltage power source main connections shall be orange or yellow in color and uniquely identified

Hinged door cabinets shall be used for all low voltage BAS control cabinets. Cabinets with hinged doors used for BAS controls shall come equipped with a key locking device, a padlock hasp or be able to be field modified to accept a manufacture provided locking kit specific to the enclosure.

BAS control cabinets shall be located in mechanical spaces, mounted to the outside of rooftop units, or in ceiling spaces next to or on equipment served. Under no circumstance shall BAS controllers be mounted in line voltage compartments of HVAC equipment, locations near unprotected rotating equipment, locations near hot surfaces (like near steam lines), or locations that require special permits to access.

When HVAC equipment provides built-in control space specifically designed for low voltage controls and there is no line voltage hazard exposed when the compartment is opened, these areas may be used for BAS controllers. The compartment must clearly be labeled “24VAC BAS Controls” on the outside of the access door. Guidance: The general concept of this section is to assure BAS controls can be accessed easily and safely. The separation of line and low voltage is typically easy to achieve for these types of systems if proper design considerations are made.

BAS control cabinets larger than 12”x12” shall be equipped with removable back panels.

A scaled back panel drawing shall be provided showing all mounted components and wire management devices.

Back panels shall be laid out to provide manufacture required space around components or adequate space to connect and disconnect wires from devices without removing the device, whichever is greater.

Wire management devices, like wire duct, shall be used to route wires. These devices and sizes shall be shown on the back panel layout.

Main BAS control panel locations shall be shown on floor plans.

Power requirements shall be shown on design plans, including power distribution panel, breaker identification, and load information. This information must be mirrored in electrical panel and distribution design documents.

For control panels requiring network connections, the requirements shall be shown on design plans.

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