GENERAL
The control system for the YORK Eco² Packaged Rooftop Unit is fully self-contained and based around a Rooftop Unit controller. To aid in unit setup, unit con- troller is equipped with a user visual LCD interface that consists of a 2 character above a 4-character display on the front of the Simplicity Elite control board. The two digit indicates the parameter of point number, and the 4-digit displays the current value or setting such as time delay, cooling set point temperature, etc. This interface provides verification of the systems operating status, enables field installed options, and aids in troubleshoot- ing system faults.
Four program buttons, located around the LCDs, allow the user to view and/or change 89 default parameter settings, acknowledge 42 alarm codes, and perform a unit run test. Up to five (5) alarm Codes are displayed on the 4-character LCD.
Greater access to programming can be gained through a Palm Pilot or Personal Computer (PC). Additionally, up to 64 of the Simplicity family of controllers can be networked together using a 3-conductor shielded cable to communicate with your PC via the available YORK recommended FREE net Serial Adapter and free YORK downloaded software.
An LED located on the lower center of the board provides a flash rate of 1 second (heart beat) when no alarms are present. A flash rate of 250 ms indicated that a current alarm is present. The LED lights up constantly if the board has failed and needs replaced, and will not light when the board power is lost.
See the YPAL unit Installation/Operations Manual (IOM) For 100.50-NOM6 (1107) for further Simplicity Elite technical information about the normal Sequence of Operation and user selectable options for our custom- ized applications.
Some common selections include Occupied/Unoc- cupied/recovery scheduling, equalized runtime for compressors, Morning warm-up, Economizer operation, Comfort, and Demand ventilation.
For the maximum in system flexibility, the YORK Eco² Packaged Rooftop Unit can be operated by either a typical 7-wire thermostat (2 cool/2 heat), a space tem- perature sensor, or stand-alone (VAV only). Note, a field wiring terminal block is provided to facilitate unit setup and installation.
In lieu of the hard-wired control options, the rooftop unit controller can be connected to and operated by a Building Automation System (BAS). The Rooftop Unit controller is equipped with a Modbus (RTU) communica-
tion. Optional BACnet (MSTP) is available with a Modlinc translator, which allows communication to a BACNet (MSTP) based BAS.
UNOCCUPIED / OCCUPIED SWITCHING
Depending on application, the unit can be indexed between unoccupied and occupied modes of operation by one of three methods: hard-wired input, internal time clock, or BAS. A contact-closure input is provided for hard-wiring to an external indexing device such as a central time clock, thermostat with built-in scheduling, or a manual switch. The unit controller is also equipped with a built-in 7-day time clock which can be used, in lieu of the contact closure input, to switch the unit be- tween Unoccupied and Occupied modes of operation. The internal time clock is fully configurable via the user interface and includes Holiday scheduling. In addition to the hard-wired input or the internal time clock, the unit can also be indexed between unoccupied and occupied modes of operation via BAS command.
GAS HEATING OPERATION
Units supplied with gas heat can be equipped with one, two, or three independently operated burner modules. Each module is a fully self-contained furnace with all necessary ignition controls, safeties, and gas valves. The rooftop Unit Controller determines how the furnaces are started and stopped and prevents furnace operation if the Supply Fan airflow is not sufficient or if the Supply Air Temperature is excessively high.
If a furnace module receives a signal to start from the Unit Controller, the ignition control engages the furnace inducer (draft) fan for a 30-second pre-purge cycle. At the end of the 30-second pre-purge, the ignition control will stop the furnace and allows the inducer fan to oper- ate for a 30-second post-purge. Each furnace contains a direct-spark-ignition system and includes safeties for flame and inducer fan verification, high temperature and flame roll-out.
MORNING WARM-UP
Morning Warm-Up can be initialized by BAS or by the Unit Controller if the Intelli-Start is used. If the Intelli-Start is used, the Morning Warm-Up start time is calculated through an adaptive algorithm.
When Morning Warm-Up is required, the Unit Controller energizes the VAV heat relay, starts the Supply Fan and qualifies the Return Air Temperature for 5 minutes.
The internal heat source (Gas, HW/Steam, or Electric) is controlled to maintain the Return Air Temperature to
