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JOHNSON CONTROLS
28
FORM 100.50-EG5 (108)
Controls
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 verifi cation of the systems operating status,
enables fi eld 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 fi ve (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 fl ash rate of 1 second (heart beat) when no alarms are
present. A fl ash 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 fl exibility, 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 fi eld
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 confi gurable 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 airfl ow is not suffi cient 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
fl ame and inducer fan verifi cation, high temperature and
fl ame 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
qualifi es 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
CONTROL SEQUENCES FOR SIMPLICITY ELITE CONTROLLED UNITS