RTAD-SVX01F-E4 49
Installation - Electrical
Interconnecting Wiring
Chilled Water Flow (Pump) Interlock
The model RTAD chiller requires a
field-supplied control voltage contact
input through a flow proving switch
6S56 and an auxilary contact 6K51 of
the chilled water pump contactor.
IMPORTANT: Do not turn the chiller
on or off using the chilled-water
interlocks.
When making field connections,
refer to the appropriate field layout,
wiring schematics, and control
diagrams that ship with the unit.
Chilled-water pump control
CAUTION! The chilled-water pump
must operate for a minimum of one
minute after the UCM-CLD receives
a command, through the external
Auto/Stop input, to shut down the
chilled-water system.
On the RTAD units, the controller
will initiate the "Run:Unload" mode
to terminate a cycle from any of the
following:
• Stop key pressed
• Loss of load
• External Auto/Stop input opened
The "Run:Unload" operating mode
commands the compressor to
completely unload, which takes
about ½ minute. This will allow the
compressors to be totally unloaded
for the next start-up. If only the
proof-of-chilled-water-flow interlock
is used, the chiller will shut down
with an immediate (non-friendly)
shutdown and initiate an automatic
reset diagnostic.
1. External Auto/Stop (terminals
A1TB3-3 and -4). This input is
supplied by the field. A contact
closure will start the chiller water
pump and chiller, via the UCM-
CLD pump control contacts.
Opening the contact will put the
operating compressors into
"Run:Unload" mode and initiate a
timing period (1 to 30 minutes,
adjustable through the Clear
Language Display). This will delay
termination of the chilled-water
pump operation via the UCM
pump control contacts. Examples
of the input terminals 1UTB3-3
and -4 would be a time clock,
ambient thermostat, building
automation system, etc.
2. UCM-CLD Pump Control Contacts
(Terminals A1 TB4-8 and -9)
This output is a set of contacts that
will close, starting the chilled-water
pump when the external Auto/Stop
contacts are closed. When the
contacts are opened, 1 to 30 minutes
later (adjustable through the Clear
Language Display), the UCM-CLD
pump control contacts open.
3. Proof-of-Chilled-Water-Flow
Interlock (Terminals A1 TB3-1
and -2)
This terminal must be field-installed.
Contact closure between the
terminals indicates proof of chilled-
water flow. Examples of this are a
pump starter auxiliary contact, flow
switch, differential pressure switch,
or a contact from a building
automation system. Opening of this
contact will immediately shut down
the chiller and initiate an automatic
reset diagnostic, indicating loss of
chilled-water flow.
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