Relief Valves; High Pressure Cutout - York YLAA Series Installation Operation & Maintenance

SECTION 4 – INSTALLATION
aluminum to copper. This transition should be done in
an external box separate to the power panel. Copper
conductors can then be run from the box to the chiller.
A 120-1-60, 15 amp source must be supplied for the
control panel through a fused disconnect when a con-
trol panel transformer (optional) is not provided (See
Figure 9 on page 39).
See unit wiring diagrams for field and power wiring
connections, chilled water pump starter contacts, alarm
contacts, compressor run status contacts, PWM input,
and load limit input. See SECTION 8 – UNIT OPERA-
TION for a detailed description of operation concern-
ing aforementioned contacts and inputs.

RELIEF VALVES

Relief valves are located on both the high and low
pressure side of the piping. High side relief valve pres-
sure setting is 650 PSIG. Low side relief valve pressure
setting is 450 PSIG.

HIGH PRESSURE CUTOUT

A high pressure cutout is installed in the discharge pip-
ing of each system. The cutout opens at 585 PSIG plus
or minus 10 PSIG and closes at 440 PSIG plus or mi-
nus 25 PSIG.
Evaporator Pump Start Contacts
Terminal block XTBC2 – Terminals 23 (115VAC) to
24, are nor mally- open contacts that can be used to
switch field supplied power to provide a start signal
to the evapo rator pump contactor. The contacts will be
closed when any of the following conditions occur:
1. Low Leaving Chilled Liquid Fault
2. Any compressor is running
3. Daily schedule is not programmed OFF and the
Unit Switch is ON
The pump will not run if the micro panel has been pow-
ered up for less than 30 seconds, or if the pump has run
in the last 30 seconds, to prevent pump motor over-
heating. See Figure 13 on page 42 and unit wiring
dia gram.
System Run Contacts
Contacts are available to monitor system status. Nor-
mally-open auxiliary contacts from each com pressor
contactor are wired in parallel with XTBC2 – Termi-
nals 25 to 26 for system 1, and XTBC2 – Terminals 27
to 28 for system 2. See Figure 4 on page 23, Figure
13 on page 42 and unit wiring diagram.
38
Alarm Status Contacts
Normally-open contacts are available for each re-
frigerant system. These normally-open contacts close
when the system is functioning normally. The respec-
tive contacts will open when the unit is shut down on
a unit fault, or locked out on a system fault. Field con-
nections are at XTBC2 - Terminals 29 to 30 (system 1),
and Terminals 31 to 32 (system 2).
Remote Start/Stop Contacts
To remotely start and stop the chiller, dry contacts can
be wired across terminals 13 and 51 on XTBC1. See
Figure 4 on page 23, Figure 10 on page 40 and
unit wiring diagram.
Remote Emergency Cutoff
Immediate shutdown of the chiller can be accom-
plished by opening a field-installed dry contact to
break the elec trical circuit between Terminals 5 to L on
terminal block XTBC2 . The unit is shipped with a fac-
tory jumper installed between Terminals 5 to L, which
must be removed if emergency shutdown contacts are
installed. See Figure 10 on page 40 and unit wiring
diagram.
Remote Temp Reset Input
The Remote Temp Reset input allows reset of the
chilled liquid set point by supplying a voltage or cur-
rent signal field wiring should be connected to XTBC1
– Terminals A+ to A-. A detailed explanation is pro-
vided in SECTION 7 – UNIT CONTROLS. See Figure
3 on page 22, Figure 4 on page 23 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%, 40%, 50%, 66% or 80%, depend-
ing on the number of compressors on unit. The field
connections are wired to XTBC1 – Terminals 13 to 21,
and work in conjunction with the PWM inputs. A de-
tailed explanation is provided in SECTION 7 – UNIT
CONTROLS. See Figure 4 on page 23, Figure 10 on
page 40 and unit wiring diagram.
When using the Load Limit feature, the
PWM feature will not function – SIMUL-
TANEOUS OPERATION OF LOAD
LIMITING AND TEM PERATURE
RESET (PWM INPUT) CANNOT BE
DONE.
FORM 150.72-ICOM6
ISSUE DATE: 12/29/2017
JOHNSON CONTROLS