Interconnecting Wiring; Chilled Water Pump Control; Programmable Relays - Trane Tracer TD7 User Manual

Interconnecting Wiring

Chilled Water Pump Control

NOTICE:
Equipment Damage!
If the microprocessor calls for a pump to start and
water does not fl ow, the evaporator may be damaged
catastrophically. It is the responsibility of the installing
contractor and/or the customer to ensure that a pump
will always be running when called upon by the chiller
controls.
An evaporator water pump output relay closes when
the chiller is given a signal to go into the Auto mode
of operation from any source. The contact is opened to
turn off the pump in the event of most machine level
diagnostics to prevent the build up of pump heat.
The relay output is required to operate the Evaporator
Water Pump (EWP) contactor. Contacts should be
compatible with 115/240 VAC control circuit. Normally,
the EWP relay follows the AUTO mode of the chiller.
Whenever the chiller has no diagnostics and is in the
AUTO mode, regardless of where the auto command
is coming from, the normally open relay is energized.
When the chiller exits the AUTO mode, the relay is timed
to open in an adjustable (using TU) 0 to 30 minutes.
The non-AUTO modes in which the pump is stopped,
include Reset, Stop, External Stop, Remote Display Stop,
Stopped by Tracer, Start Inhibited by Low Ambient Temp,
and Ice Building complete.
Table 5. Pump Relay Operation
Chiller Mode Relay Operation
Auto Instant close
Ice Building Instant close
Tracer Override Close
Stop Timed Open
Ice Complete Instant Open
Diagnostics Instant Open
When going from Stop to Auto, the EWP relay is
energized immediately. If evaporator water fl ow is not
established in 20 minutes (for normal transition) or 4
minutes, 15 seconds (for pump commanded ON due to
an override safety), the UC800 de-energizes the EWP
relay and generates a non-latching diagnostic. If fl ow
returns (e.g. someone else is controlling the pump),
the diagnostic is cleared, the EWP is re-energized, and
normal control resumed.
RLC-SVU006A-E4
Installation Electrical
If evaporator water fl ow is lost once it had been
established, the EWP relay remains energized and a
non-latching diagnostic is generated. If fl ow returns, the
diagnostic is cleared and the chiller returns to normal
operation.
In general, when there is either a non-latching or latching
diagnostic, the EWP relay is turned off as though there
was a zero time delay. Exceptions whereby the relay
continues to be energized occur with:
• Low Chilled Water Temp. diagnostic (non-latching)
(unless also accompanied by an Evap Leaving Water
Temperature Sensor Diagnostic)
or
• Loss of Evaporator Water Flow diagnostic (non-
latching) and the unit is in the AUTO mode, after
initially having proven evaporator water fl ow.

Programmable Relays

A programmable relay concept provides for enunciation
of certain events or states of the chiller, selected from a
list of likely needs, while only using four physical output
relays, as shown in the fi eld wiring diagram. The four
relays are provided (generally with a Quad Relay Output
LLID) as part of the Programmable Relay Option. The
relay's contacts are isolated Form C (SPDT), suitable
for use with 120 VAC circuits drawing up to 2.8 amps
inductive, 7.2 amps resistive, or 1/3 HP and for 240 VAC
circuits drawing up to 0.5 amp resistive.
The list of events/states that can be assigned to the
programmable relays can be found in Table 6. The relay
will be energized when the event/state occurs.
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