Carrier AQUASNAP MPW015-045 - Manual (Page 21)

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2. Insert and secure the red (+) wire to terminal 5 of the
space temperature sensor terminal block.
3. Insert and secure the white (ground) wire to terminal 4 of
the space temperature sensor.
4. Insert and secure the black (–) wire to terminal 2 of the
space temperature sensor.
5. Connect the other end of the communication bus cable to
the remainder of the CCN communication bus.
Energy Management Module (Fig. 10) — This
factory-installed option (FIOP) or field-installed accessory is
used for the following types of temperature reset, demand
limit, and/or ice features:
• 4 to 20 mA leaving fluid temperature reset (requires
field-supplied 4 to 20 mA generator)
• 4 to 20 mA cooling set point reset (requires field-
supplied 4 to 20 mA generator)
• Discrete inputs for 2-step demand limit (requires field-
supplied dry contacts capable of handling a 24 vac,
50 mA load)
• 4 to 20 mA demand limit (requires field-supplied 4 to
20 mA generator)
• Discrete input for Ice Done switch (requires field-
supplied dry contacts capable of handling a 24 vac,
50 mA load)
See Demand Limit and Temperature Reset sections on
pages 27 and 31 for further details.
Loss-of-Cooler Flow Protection — A proof-of-
cooler flow device is factory installed in all chillers.
Condenser Flow Protection — A proof-of-condens-
er flow protection accessory can be field installed in the con-
denser water piping of all chillers. The unit must be configured
for the input to be enabled.
Thermostatic Expansion Valves (TXV) — All
units are equipped from the factory with conventional TXVs.
The 30MPA units and 30MPW units with medium temperature
brine also have factory-installed liquid line solenoids. The liq-
uid line solenoid valves are not intended to be a mechanical
shut-off. For 30MPW units, when service is required, reclaim
the refrigerant from the system.
For 30MPA units when service is required, the compressor
and evaporator can be serviced by closing the factory-installed
liquid line service valve and field-installed discharge line ser-
vice valve. After the valves are closed, reclaim the refrigerant
from the system.
The TXV is set at the factory to maintain approximately 8 to
12° F (4.4 to 6.7° C) suction superheat leaving the cooler by
monitoring the proper amount of refrigerant into the cooler. All
TXVs are adjustable, but should not be adjusted unless abso-
lutely necessary.
Capacity Control — The control system cycles com-
pressors, digital scroll modulting solenoid (if equipped), and
minimum load valve solenoids (if equipped) to maintain the
user-configured leaving chilled fluid temperature set point. En-
tering fluid temperature is used by the main base board (MBB)
to determine the temperature drop across the cooler and is used
in determining the optimum time to add or subtract capacity
stages. The chilled fluid temperature set point can be automati-
cally reset by the return fluid temperature, space, or outdoor-air
temperature reset features. It can also be reset from an external
4 to 20-mA signal (requires energy management module FIOP
or accessory).
The capacity control algorithm runs every 30 seconds. The
algorithm attempts to maintain the Control Point at the desired
set point. Each time it runs, the control reads the entering and
leaving fluid temperatures. The control determines the rate at
which conditions are changing and calculates 2 variables based
on these conditions. Next, a capacity ratio is calculated using
the 2 variables to determine whether or not to make any
changes to the current stages of capacity. This ratio value
ranges from –100 to +100%. If the next stage of capacity is a
compressor, the control starts (stops) a compressor when the
ratio reaches +100% (–100%). If installed, the minimum load
valve solenoid will be energized with the first stage of capacity.
Minimum load valve value is a fixed 30% in the total capacity
calculation. The control will also use the minimum load valve
solenoid as the last stage of capacity before turning off the last
compressor. A delay of 90 seconds occurs after each capacity
step change. Refer to Table 19.
MINUTES LEFT FOR START — This value is displayed
only in the network display tables (using Service Tool,
ComfortVIEW™ or ComfortWORKS ® software) and
represents the amount of time to elapse before the unit will start
its initialization routine. This value can be zero without the
machine running in many situations. This can include being
unoccupied, ENABLE/OFF/REMOTE CONTACT switch in
the OFF position, CCN not allowing unit to start, Demand
Limit in effect, no call for cooling due to no load, and alarm or
alert conditions present. If the machine should be running and
none of the above are true, a minimum off time (DELY, see
below) may be in effect. The machine should start normally
once the time limit has expired.
MINUTES OFF TIME (Configuration
 OPT2 
DELY) — This user-configurable time period is used by the
control to determine how long unit operation is delayed after
power is applied/restored to the unit. Typically, this time period
is configured when multiple machines are located on a single
site. For example, this gives the user the ability to prevent all
the units from restarting at once after a power failure. A value
of zero for this variable does not mean that the unit should be
running.
LEAD/LAG DETERMINATION — This is a configurable
choice and is factory set to be automatic for all units unless the
unit is equipped with minimum load, then circuit A is lead
(Configuration  OPT2  LLCS). The value can be changed
to Circuit A or Circuit B leading as desired. Set at automatic,
the control will sum the current number of logged circuit starts
and one-quarter of the current operating hours for each circuit.
The circuit with the lowest sum is started first. Changes to
which circuit is the lead circuit and which is the lag are also
made when total machine capacity is at 100% or when there is
a change in the direction of capacity (increase or decrease) and
each circuit’s capacity is equal.
CAPACITY CONTROL OVERRIDES — The following over-
rides will modify the normal operation of the routine.
Deadband Multiplier — The user configurable Deadband
Multiplier (Configuration  SLCT  Z.GN) has a default
value of 1.0. The range is from 1.0 to 4.0. When set to other
than 1.0, this factor is applied to the capacity Load/Unload
Factor. The larger this value is set, the longer the control will
delay between adding or removing stages of capacity. Figure
11 shows how compressor starts can be reduced over time if
the leaving water temperature is allowed to drift a larger
amount above and below the set point. This value should be set
in the range of 3.0 to 4.0 for systems with small loop volumes.
Figure 12 shows the operating envelope for the compressor.
CAUTION
Care should be taken when interfacing with other manufac-
turer’s control systems due to possible power supply
differences, full wave bridge versus half wave rectification.
The two different power supplies cannot be mixed.
ComfortLink™ controls use half wave rectification. A
signal isolation device should be utilized if a full wave
bridge signal generating device is used.