York YLUA0248 Series, Installation Operation & Maintenance

Page: 36 / 158

JOHNSON CONTROLS
36
FORM 150.73-NM2
ISSUE DATE: 09/07/2020
SECTION 4 – INSTALLATION
See Air Proving Switch/Remote Start-
Stop Contacts.
Air Proving Switch/Remote Start-Stop
Contacts
The Air Flow Switch MUST NOT be used
to start and stop the chiller (i.e. starting
and stopping the chilled water pump). It
is intended only as a safety switch.
The air proving switch is field wired to XTBC1 termi-
nals 13 to 50 (SYS 1) and 13 to 51 (SYS 2) to prevent
operation of the refrigerant circuit when the supply air
blower is not operating.
If separate evaporator blowers are used with respect
to each refrigerant system in the condensing unit, then
two air proving must be wired in series across XTBC1
terminals 13 - 50 and 13 - 51 (one for each evaporator
blower). See Figure 10 on page 43 and unit wiring
diagram.
When using Zone Thermostats in Suction Pressure con-
trol mode, the air proving switch(s) should be wired in
series with the respective Zone Thermostats.
Remote Start/Stop Contacts
To remotely start and stop the condensing unit, dry
contacts can be wired in series with the air proving
switch and XTBC1 - terminals 13 to 50 (SYS 1) and
13 to 51 (SYS 2). See
Figure 10 on page 43 and unit
wiring diagram.
Remote Emergency Cutoff
Immediate shutdown of the condensing unit can be
accomplished by opening a field installed dry contact
to break the electrical circuit between terminals 5 to L
on terminal block XTBC2. XTBC2 is located in the
power panel. The unit is shipped with a factory jumper
installed between terminals 5 to L, which must be re-
moved if emergency shutdown contacts are installed.
See Figure 10 on page 43 and unit wiring diagram.
Evaporator Blower Start Contacts
For constant fan operation: Terminal block XTBC2 -
terminals 23 to 24, are normally open contacts that can
be used to switch field supplied power to provide a start
signal to the evaporator blower contactor. Contacts will
close whenever the daily schedule is programmed for
cooling. See Figure 10 on page 43 and unit wiring
diagram.
Compressor Run Contacts
Contacts are available to monitor “Compressor Run”
status. Normally-open auxiliary contacts from each
compressor contactor are wired in parallel with XTBC2
- terminals 25 to 26 for system 1, and XTBC2 - termi-
nals 27 to 28 for system 2. See Figure 10 on page 43
and Unit Wiring Diagram.
Alarm Status Contacts
Normally-open contacts are available for each refriger-
ant system. These normally-open contacts close when
the system is functioning normally. The respective
contacts will open when the unit is shut down on a unit
fault, or locked out on a system fault. Field connections
are at XTBC2 terminals 29 to 30 (SYS 1), and termi-
nals 31 to 32 (SYS 2). See
Figure 10 on page 43 and
unit wiring diagram.
Remote Reset of Setpoint
Remote reset of setpoint can only be enabled in Dis-
charge Air Temperature mode. The 4-20mA or 0-10V
input allows reset of the discharge air temperature
setpoint (when unit is programmed for Discharge Air
Temperature Control mode) by supplying a “timed”
contact closure. Field wiring should be connected to
XTBC1 - terminals 13 to 20. A detailed explanation
is provided in the Unit Control section. See Figure 2
on page 20, Figure 3 on page 21, and unit wiring
diagram.
Load Limit Input
Load limiting is a feature that prevents the unit from
loading beyond a desired value. The unit can be “load
limited” either 33% or 66% on 3 or 6 compressor units,
50% on 2 or 4 compressor units, 40% or 80% on 5
compressor units, depending on the number of com-
pressors on the unit. The field connections are wired
to XTBC1- terminals 13 to 21, and work in conjunc-
tion with the PWM inputs. A detailed explanation is
provided in the Unit Control section. See Figure 10 on
page 43 and unit wiring diagram.