Controls - York ECO R-407C User Manual

Controls

GENERAL
The control system for the YORK eco
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 dis-
play. The LCD displays plain language text in a menu-
driven format 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
operation of the equipment or communication failures.
For the maximum in system flexibility, the YORK ECO
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 OptiLogic™
rooftop unit controller can be connected to and oper-
ated by a Building Automation System (BAS). If re-
quired, 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.
26
CONTROL SEQUENCES FOR ALL UNITS
2 Packaged Roof-
ECONOMIZER OPERATION
The unit can be equipped with one of three types of
optional economizers, dry bulb, single enthalpy, or com-
parative enthalpy. When the unit controller determines
that Outside Air is suitable for economizing, the unit
controller will control the outside air damper(s) open to
provide economizer cooling. If economizer cooling alone
is insufficient for the cooling load, the unit controller
shall stage up compressors, one at a time, to meet
demand.
The control logic for the three types of economizers is
as follows:
2
Dry Bulb Economizer
The dry bulb economizer is the default economizer con-
trol scheme. With the dry bulb economizer, the unit con-
troller monitors the Outside Air temperature only and
compares it to a reference temperature setting. Outside
Air is deemed suitable for economizing when the Out-
side Air temperature is determined to be less than the
reference temperature setting. This method of econo-
mizing is effective, but is prone to some changeover in-
efficiencies due to the fact that this method is based on
sensible temperatures only and does not take Outside
Air moisture content into consideration.
Single Enthalpy Economizer
With the optional single enthalpy economizer, the unit
controller monitors the Outside Air enthalpy in addition
to the Outside Air temperature and compares it to a
reference enthalpy setting and a reference tempera-
ture setting. Outside Air is deemed suitable for econo-
mizing when the Outside Air enthalpy is determined to
be less than the reference enthalpy setting and the Out-
side Air temperature is less than the reference tem-
perature setting. This method of economizing allows
the reference temperature setting to be set higher than
the DB Economizer and is consequently a more effi-
cient packaged rooftop economizer.
Comparative Enthalpy Economizer
With the optional comparative enthalpy economizer, the
unit controller monitors and compares the Outside Air
and Return Air enthalpies in addition to comparing the
Outside Air temperature to the reference temperature
setting. Outside Air is deemed suitable for economiz-
ing when the Outside Air enthalpy is determined to be
YORK INTERNATIONAL