Installation — Electrical; Typical Rtaa Chiller Interlock - Trane RTAA-70 Installation & Maintenance Manual

Figure 25

Typical RTAA Chiller Interlock

RTAA-SVX01A-EN
Installation — Electrical
minute. This will allow the compressor 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 on an immediate (non-friendly) shutdown and initiate an automatic
reset diagnostic.
Figure 25 shows a typical interlock of an RTAA chiller. There are three points
(six wires) on the chiller that are required to be connected.
1. External Auto/Stop (Terminals 1U1 TB3-3 and -4). This input would be
supplied by the field. A contact closure would start the chiller water pump
and chiller, via the UCM pump control contacts. Opening the contact
would put the operating compressors into the "RUN:UNLOAD" mode
and initiate a timing period (1 to 30 minutes, adjustable through the Clear
Language Display). This will delay termination of chilled water pump oper-
ation via the UCM pump control contacts. Examples of the input at termi-
nals 1U1 TB3-3 and -4 would be a time clock, ambient
thermostat, building automation system, etc.
2. UCM Pump Control Contacts (Terminals 1U1 TB4-8 and -9). This output is
a set of contacts that will close and start 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 pump contacts open.
3. Proof of Chilled Water Flow Interlock (Terminals 1U1 TB3-1 and -2). Con-
tact closure between the terminals indicates proof of chilled water flow.
Examples of this would be a pump starter auxiliary contact, flow switch,
differential pressure switch, or a contact from a building automation sys-
tem (see Chilled Water Flow Switch in the Water Piping section of this
manual). Opening of this contact would shutdown the chiller and initiate
an automatic reset diagnostic indicating loss of chilled water flow.
NOTE: Steps 2 and 3 are completed at the factory if unit is equipped with
optional pump package.
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