JOHNSON CONTROLS
35
SECTION 4: INSTALLATION
FORM 150.73-NM1
ISSUE DATE: 07/03/2024
4
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 41 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 4 on page 22,
Figure 10 on page 41, 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 41 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 A+ to A-.
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 41 and unit wiring diagram.
When using the Load Limit feature, the
PWM feature will not function. SIMUL-
TANEOUS OPERATION OF LOAD
LIMITING AND TEMPERATURE
RESET (PWM INPUT) CANNOT BE
DONE.
Compressor heaters
Compressor heaters are standard on all models. If pow-
er is OFF more than two hours, the crankcase heaters
must be energized for 18 h to 24 h prior to restarting a
compressor. This ensures that liquid slugging and oil
dilution does not damage the compressors on start.
Refrigerant piping
General
When the unit has been located in its final position, the
unit piping may be connected. Normal installation pre-
cautions should be observed in order to receive maxi-
mum operating efficiencies. System piping should
conform to the Johnson Controls DX piping guide
Form 050.40-ES2 or ASHRAE refrigeration handbook
guidelines. All piping design and installation is the re-
sponsibility of the user.
Johnson controls assumes no warranty
responsibility for system operation or
failures due to improper piping, piping
design, control problems, or lack of oil
return.
All expansion valves, liquid line solenoid valves, filter
driers, sight glasses, refrigerant, and refrigerant piping
are supplied and installed by others. TXV sizing should
be equal in size or slightly smaller than the capacity of
the circuit. If multiple coil sections are utilized, a TXV
for each section, sized accordingly, must be installed.
Refrigerant piping reference
Copper line sizing
When selecting pipe diameter and material for remote
condenser piping systems, it is recommended that
ASTM B280 material, type L or K is used. According
to ASME Standard B31.5-2006 (table 502.3.1), ASTM
B280 copper does not require a derate when brazed. By
comparison, ASTM B88 material does take an anneal-
ing penalty when brazing, which, in some applications,
could reduce the calculated yield strength to a level be-
low the system design.
For more details, refer to ASHRAE Refrigeration
Handbook, Chapter 2 and YORK DX Piping Guide
Form 050.40-ES2.
Table 5 on page 37 lists refrigerant line connections
sizes per unit model number.
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