Drawing 12-018539 CAI Replace AHU2-5.pdf

SENSITIVE SECURITY INFORMATION WARNING: This record contains Sensitive Security Information that is controlled under 49 CFR parts 15 and 1520. No part of this record may be disclosed to persons without a

"need to know", as defined in 49 CFR parts 15 and 1520, except with written permission of the Secretary of

Transportation. Unauthorized release may result in civil penalty or other action. For U.S. government agencies, public disclosure is governed by 5 U.S.C. 552 and 49 CFR parts 15 and 1520.

is controlled under 49 CFR parts 15 and 1520. No part of this record may be disclosed to persons without a

"need to know", as defined in 49 CFR parts 15 and 1520, except with written permission of the Secretary of

Transportation. Unauthorized release may result in civil penalty or other action. For U.S. government agencies, is controlled under 49 CFR parts 15 and 1520. No part of this record may be disclosed to persons without a

"need to know", as defined in 49 CFR parts 15 and 1520, except with written permission of the Secretary of

Transportation. Unauthorized release may result in civil penalty or other action. For U.S. government agencies, is controlled under 49 CFR parts 15 and 1520. No part of this record may be disclosed to persons without a

"need to know", as defined in 49 CFR parts 15 and 1520, except with written permission of the Secretary of

Transportation. Unauthorized release may result in civil penalty or other action. For U.S. government agencies, public disclosure is governed by 5 U.S.C. 552 and 49 CFR parts 15 and 1520.

CONTROL SEQUENCE OF OPERATIONS

Facility Occupied, Unoccupied, and Ventilation-Delay Modes of Operation

Ventilation-delay-mode timing shall start prior to the occupied-mode timing. The DDC system shall prevent the outside air damper and the relief air damper from opening. At the time shown, the

DDC system shall place the system in the occupied mode. At the expiration of the ventilation-delay-mode timing period, the DDC system shall allow the outside air & relief air damper to open. At the time shown, the DDC system shall place the control system in the unoccupied mode of operation .If the night temperature sensor senses temperatures outside the limits (adjustable), the

DDC system shall initiate the ventilation-delay-mode.

Outside-Air, Return-Air, and Relief-Air Dampers

Facility Occupied Mode - The outside air, return air, and relief air dampers shall be under economizer control or minimum ventilation control.

Facility Unoccupied Mode - The dampers shall return to their normal positions (outside air -normally closed, return air - normally open & relief air - normally closed).

Ventilation-Delay Mode - The dampers shall return to their normal positions (outside air -normally closed, return air - normally open & relief air - normally closed), except when under economizer control.

Supply-Fan Control

Facility Occupied and Ventilation-Delay Modes - Supply fan shall start, and shall operate continuously.

Facility Unoccupied Mode - The supply fan shall stop and shall remain off. If the night temperature sensor senses temperatures outside the limits (adjustable) the supply fan shall be placed in the ventilation-delay mode until the temperature is within the limits. The DDC panel shall also send a night activate signal to the boiler and chiller DDC panel.

Variable Frequency Drive

The Variable Frequency Drive shall be set at a constant speed as needed to produce the airflow required.

Filters

A differential-pressure switch across each filter shall initiate a filter alarm when the pressure drop across that filter reaches 1 inch W.C.

Freeze Protection

All Modes - A freezestat, located just before the cooling coil, shall stop the supply fan, cause the outside air, return air and relief air dampers to return to their normal position (outside air - normally closed, return air - normally open & relief air - normally closed), and shall initiate a low-temperature alarm if the temperature drops below the freezestat's setpoint of 38 deg F. Return to normal mode of operation shall require manual reset at the freezestat. The DDC panel shall monitor the freezestat through auxiliary contacts and shall indicate an alarm condition when the freezestat trips.

Cooling Coil

Facility Occupied and Ventilation-Delay Modes - The control valve shall be modulated by the

DDC system from the signal of a thermostat located in the space to maintain the setpoint (adjustable).

Facility Unoccupied Mode - The DDC system shall close the cooling-coil valve.

Preheat Coil

Occupied and Ventilation-Delay Modes - The control valve shall be modulated by the DDC system from the signal of a thermostat located in the space to maintain the setpoint (adjustable).

Unoccupied Mode - The DDC system shall close the control valve. If OA temperature drops below 50

Deg F (adjustable), the control valve shall open to a preset position.

Minimum Ventilation

When the DDC system places the control system in the minimum ventilation mode, the outside air damper, return air damper & relief air damper shall open to the minimum ventilation setting.

Enthalpy Economizer Control

The economizer sequence will allow the primary source of cooling to come from the outside air. The economizer mode will be enabled when the return air enthalpy is greater than the outside air enthalpy but will also be subject to the following constraints.

OA Temperature Lockout: When the dry bulb temperature is above the outside air high limit of 65 Deg

F (adjustable) or below the low limit of 25 Deg F (adjustable), the economizer mode will be disabled.

The low limit is optional - it is provided for units where problematic mixing occurs during extreme cold conditions.

OA Humidity Lockout: When the OA humidity is greater than the humidity lockout setpoint of 85%

(adjustable), the economizer mode will be disabled.

When enabled, the outside air, return air & relief air dampers will modulate to maintain space temperature setpoint (adjustable).

When disabled, the system shall be in the Minimum Ventilation mode.

CONTROL SYSTEM NOTES

Provide a DDC control system that is bacnet compliant and compatible with the existing MMAC center-wide JCI Metasys CCMS.

Provide all control equipment, devices and wiring necessary to operate the unit per the Sequence of Operation listed above. Replace the existing space thermostat.

Install all control wiring in conduit.

Include proposed control drawings, equipment & device cut-sheets and sequence of operation in the mechanical equipment submittal prior to start of work.