York R-407C manual Guide Specifications continued, Controls, Accessories And Options, Economizers

Guide Specifications (continued)

CONTROLS

Afactory-mounted unit controller with a 4x20 character alphanumeric display and user keypad shall be included as standard. The controller and keypad shall be housed inside the low-voltage compartment of the control/power panel. On units with supply or exhaust VFDs, the VFD keypads shall be located inside the same panel as the unit controller and interface keypad. Control operating data, setpoints, unit setup, configuration, service and history shall all be accessible via a single key. A sys- tem alarm LED shall indicate failures to the operator with more detail provide in the menu screens. The user interface shall function with a simple menu-driven dis- play for easy access to unit data with integral time clock for weekly and holiday scheduling. The unit keypad shall include password protection to prevent unautho- rized access and tampering with unit setpoints and con- figuration.

A single terminal strip shall be provided for all thermo- stat and customer hard-wired field connections.

Unit controls shall be completely factory packaged and compatible with a room thermostat. Constant volume units shall operate with a two (2) cool/two (2) heat ther- mostat. Staging decisions shall be based upon the de- viation of space temperature from set point and the rate of change of the space temperature.

VAV units shall operate with a sensor in the supply air stream for cooling operation. Staging decisions shall be based upon the deviation of supply air temperature from set point and the rate of change of the supply air temperature.

Controllers shall have the following safeties (both VAV and CV):

•High and low pressure cut-outs (one each refriger- ant circuit)

•Minimum on time for compressors

•Delay between compressor stages

•Anti-short cycle delays (minimum off time) for com- pressors and supply fan

•Cooling lockout at 40° F; 0° F if equipped for low ambient operation

•Air flow proving switch requiring proper air flow for cooling operation

ACCESSORIES AND OPTIONS

Full perimeter and partial perimeter roof curbs - 14” high roof curb with wood nailer. Roof curb covers the entire perimeter of the unit (full curb) or that portion of the unit that has airflow (partial curb).

Supply Fan VFD Manual Bypass – provides full air- flow in the event of a VFD failure.

Power Supply Connections – single-point power with manual disconnect, and dual-point power wiring options are available for various applications.

Supply air setpoint reset by outside air or space air temperature - Allows VAV supply air setpoint to float upward (saving energy) if the outdoor air temperature or the space temperature is sufficiently low.

Supply Fan Isolation – the entire supply fan assem- bly shall be isolated from the unit base with 2" deflec- tion springs.

Supply and Exhaust Fan Motors – high efficiency ODP, and standard and high efficiency TEFC motors are available all meeting the Energy Policy Act of 1992 (EPACT).

Low Ambient Operation – a low ambient kit is avail- able to control compressor head pressure via VFD con- denser fan speed control. Head pressure control is accomplished by monitoring head pressure with suc- tion and discharge line pressure transducers rather than less accurate temperature control.

ECONOMIZERS

Manual Damper Economizer – economizer is avail- able with a manual damper adjustable between 0-25 percent.

Two-Position Damper Economizer – economizer is available with a two-position damper with the open po- sition adjustable between 0-25 percent. The operation of the two-position economizer shall be based on oc- cupancy; occupied is open, unoccupied is closed.

40 YORK INTERNATIONAL