Specifications

72
When power is supplied to the device, a warm-up period is
initiated. The warm-up period may take up to 30 seconds.
When enough flow is detected, switch contacts will close. The
switch closure does not indicate minimum flow requirements
have been met for the machine. If nuisance trips of the sensor
are occurring, follow the steps below to correct:
1. Check to confirm that all strainers are clean, valves are
open and pumps are running. For the case of variable
frequency drive (VFD) controlled pumps, ensure the
minimum speed setting has not been changed.
2. Measure the pressure drop across the condenser. Use the
condenser pressure drop curves in Fig. 27-43 to calculate
the flow and compare this to system requirements.
3. If the contacts do not close with sufficient flow, then
check the wiring connection to the MBB. If the input sig-
nal is not closed, then the switch needs to be replaced.
Refrigerant Circuit
LEAK TESTING — Units are shipped with complete operat-
ing charge of refrigerant R-134a or nitrogen (see Physical Data
tables supplied in the 30XW installation instructions) and
should be under sufficient pressure to conduct a leak test. If
there is no pressure in the system, introduce enough nitrogen to
search for the leak. Repair the leak using good refrigeration
practices. After leaks are repaired, system must be evacuated
and dehydrated.
REFRIGERANT CHARGE — Refer to Physical Data tables
supplied in the 30XW installation instructions. Immediately
ahead of filter drier in each circuit is a factory-installed liquid
line service valve. Each valve has a
1
/
4
-in. access connection
for charging liquid refrigerant.
Charging with Unit Off and Evacuated
— Close liquid line
service valve before charging. Weigh in charge shown on unit
nameplate. Open liquid line service valve; start unit and allow
it to run several minutes fully loaded. Check for a clear sight
glass. Be sure clear condition is liquid and not vapor.
Charging with Unit Running
— If charge is to be added while
unit is operating, loop water temperatures should be near the
AHRI rating point (54/44 F evaporator; 85/95 F condenser). At
these conditions and with the circuit at full load, charge to a
clear sightglass and a liquid line temperature of 90 to 93 F (32.2
to 33.9 C).
Add 5 lb (2.3 kg) of liquid charge into the fitting located on
the tube entering the bottom of the cooler. This fitting is located
between the electronic expansion valve (EXV) and the cooler.
Allow the system to stabilize and then recheck the liquid
temperature. If needed, add additional liquid charge, 5 lb
(2.3 kg) at a time, allowing the system to stabilize between
each charge addition. Slowly add charge as the sight glass
begins to clear to avoid overcharging.
Safety Devices — The 30XW units contain many safety
devices and protection logic built into the electronic control.
Following is a description of the major safeties.
COMPRESSOR PROTECTION
Motor Overload
— The compressor protection modules
(CPM) protect each compressor against overcurrent. Do not
bypass the current transducers or make any changes to the
factory-installed and configured headers. The configuration of
these headers defines the must trip amps (MTA) at which the
CPM will turn the compressors off. Determine the cause for
trouble and correct the problem before resetting the CPM. See
Appendix D for MTA settings and configuration headers.
Each CPM board also reads the status of each compressor’s
high-pressure switch. All compressors have factory-installed
high-pressure switches. See Table 48.
Fig. 56 — Chilled Water and Condenser
Water Flow Switch
WIRING
a30-4708
OUT
OUT
IN
IN
LWT
EWT
CLWT
(OPTIONAL)
CWFS
CEWT
(OPTIONAL)
CDFS
(OPTIONAL)
Fig. 57 — Flow Switch (Typical)
LEGEND
CDFS — Condenser Water Flow Switch
CEWT — Condenser Entering Water Thermistor
CLWT — Condenser Leaving Water Thermistor
CWFS — Chilled Water Flow Switch
EWT — Entering Water Thermistor
LWT — Leaving Water Thermistor
A30-4846
IMPORTANT: When adjusting refrigerant charge, circu-
late fluid through cooler and condenser continuously to
prevent freezing and possible damage to both. Do not
overcharge, and never charge liquid into the low-pressure
side of system.