YORK INTERNATIONAL
54
Controls
CONTROL SEQUENCES COMMON TO ALL UNITS
GENERAL
The control system for the YORK eco² Packaged Roof-
top Unit is fully self-contained and based around an
OptiLogic
™
rooftop unit controller. To aid in unit setup,
maintenance, and operation, the OptiLogic
™
rooftop unit
controller is equipped with a user interface that is based
around a 4 line x 20 character backlit LCD display. The
LCD displays plain language text in a menu-driven for-
mat to facilitate use. In addition to the display, the
OptiLogic
™
user interface is also equipped with an LED
indicator light, which will warn of any abnormal opera-
tion of the equipment or communication failures.
For the maximum in system flexibility, the YORK eco²
Packaged Rooftop Unit can be operated by either a typi-
cal 7-wire thermostat (2 cool/2 heat), a space tempera-
ture 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 OptiLogic
™
rooftop unit controller can be connected to and oper-
ated by a Building Automation System (BAS). If required,
the OptiLogic™ rooftop unit controller can be equipped
with an optional BACNet IP communication card, which
allows communication, via Ethernet, to a BACNet IP
based BAS.
UNOCCUPIED / OCCUPIED SWITCHING
Depending on application, the unit can be indexed be-
tween 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 oc-
cupied modes of operation via a BAS command.
Note a unit operated from a space sensor can be
equipped to temporarily override an unoccupied mode
of operation. This Unoccupied Override feature is fully
configurable via the OptiLogic
™
user interface.
GAS HEATING OPERATION
Units supplied with gas heat can be equipped one, two,
or three independently operated burner modules. Each
module is fully self-contained furnace with all neces-
sary ignition controls, safeties, and gas valves. The
OptiLogic 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
OptiLogic 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 igni-
tion control will stop the furnace and allows the inducer
fan to operate for a 30-second post-purge. Each fur-
nace contains a direct spark ignition system and in-
cluded 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
OptiLogic controller if the Internal Scheduling is used.
If the Internal Scheduling is used, the Morning Warm-
Up start time is calculated through an adaptive algo-
rithm, which determines the optimum start time.
When Morning Warm-Up is required, the OptiLogic
controller starts the Supply Fan and qualifies the Re-
turn Air Temperature for 5 minutes. The internal heat
source (Gas, HW/Steam, or Electric) is controlled to
maintain the Return Air Temperature to the Morning
Warm-Up Setpoint, Morning Warm-Up ends when oc-
cupancy occurs (BAS, Internal Scheduling, or contact
closure), or when the Maximum Morning Warm-Up
Time has expired.
