Trane RTWD Installation Operation & Maintenance page 64

Installation – Electrical
Ice Building Option
CH530 provides auxiliary control for a customer
specifi ed/installed contact closure for ice building if so
confi gured and enabled. This output is known as the
Ice Building Status Relay. The normally open contact
will be closed when ice building is in progress and
open when ice building has been normally terminated
either through Ice Termination setpoint being reached
or removal of the Ice Building command. This output
is for use with the ice storage system equipment or
controls (provided by others) to signal the system
changes required as the chiller mode changes from
"ice building" to "ice complete". When contact 5K20 is
provided, the chiller will run normally when the contact
is open. CH530 will accept either an isolated contact
closure (External Ice Building command) or a Remote
Communicated input (Tracer) to initiate and command
the Ice Building mode. CH530 also provides a "Front
Panel Ice Termination Setpoint", settable through
TechView, and adjustable from -6.7 to -0.5°C in at least
1°C increments. When in the Ice Building mode, and the
evaporator entering water temperature drops below the
ice termination setpoint, the chiller terminates the Ice
Building mode and changes to the Ice Building Complete
Mode.
CAUTION
Evaporator Damage!
Freeze inhibitor must be adequate for the leaving water
temperature. Failure to do so may result in damage to
system components.
Techview must also be used to enable or disable Ice
Machine Control. This setting does not prevent the
Tracer from commanding Ice Building mode.
The following equations apply:
As generated from external source
As processed by CH530
64
Upon contact closure, the CH530 will initiate an ice
building mode, in which the unit runs fully loaded at all
times. Ice building shall be terminated either by opening
the contact or based on the entering evaporator water
temperature. CH530 will not permit the ice building
mode to be reentered until the unit has been switched
out of ice building mode (open 5K20 contacts) and
then switched back into ice building mode (close 5K20
contacts.)
In ice building, all limits (freeze avoidance, evaporator,
condenser, current) will be ignored. All safeties will be
enforced. If, while in ice building mode, the unit gets
down to the freeze stat setting (water or refrigerant), the
unit will shut down on a manually resettable diagnostic,
just as in normal operation. Connect leads from 5K20 to
the proper terminals of 1A10. Refer to the fi eld diagrams
which are shipped with the unit. Silver or gold-plated
contacts are recommended. These customer furnished
contacts must be compatible with 24 VDC, 12 mA
resistive load.
External Chilled Water Setpoint (ECWS) Option
The CH530 provides inputs that accept either 4-20 mA
or 2-10 VDC signals to set the external chilled water
setpoint (ECWS). This is not a reset function. The input
defi nes the setpoint. This input is primarily used with
generic BAS (building automation systems). The chilled
water setpoint set via the DynaView or through digital
communication with Tracer (Comm3). The arbitration of
the various chilled water setpoint sources is described in
the fl ow charts at the end of the section.
The chilled water setpoint may be changed from a
remote location by sending either a 2-10 VDC or 4-20 mA
signal to the 1A7, J2-1 and 2. The 2-10 VDC and 4-20 mA
each correspond to a -12 to 18°C external chilled water
setpoint.
Voltage signal
VDC = 0.1455* (ECWS)+0.5454
ECWS = 6.875*(VDC)-3.75
Current signal
mA = 0.2909 (ECWS)+1.0909
ECWS= 3.4375(mA)-3.75
RLC-SVX14H-GB