Installation and Maintenance Manual

Installation Electrical
RTAE-SVX001B-EN 35
Interconnecting Wiring
Chilled Water Pump Control
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 115/240VAC 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 (usingTechView) 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 AmbientTemp, and Ice
Building complete.
When going from Stop to Auto, the EWP relay is energized
immediately. If evaporator water flow 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 flow returns (e.g.
someone else is controlling the pump), the diagnostic is
cleared, the EWP is re-energized, and normal control
resumed.
If evaporator water flow is lost once it had been
established, the EWP relay remains energized and a non-
latching diagnostic is generated. If flow 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 Temperature diagnostic
(non-latching unless also accompanied by an Evap
L
eaving WaterTemperature Sensor Diagnostic)
or
• Interrupt
Failure —AFDxA diagnostic (where x is
either 1 or 2 to indicate which drive is affected), in
which a compressor continues to draw current even
after commanded to have shutdown.
or
• Loss of Evaporator Water Flow diagnostic (non-
latching) and the unit is in the AUTO mode, after
initially having proven evaporator water flow.
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 field 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 19.The relay
will be energized when the event/state occurs.
NOTICE:
Equipment Damage!
If the microprocessor calls for a pump to start and
water does not flow, 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.
Table 18. 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 Operation
(a)
(a)Operation can be instant open or instant close, depending on diagnostic.
Chiller Shutdown
Diagnostics
(except freeze protection)
Instant Open
Freeze Protection related
chiller shutdown diagnostics
Delayed/Dependent Open
Chiller Off Cycle Freeze
Diagnostics
Instant Close – Dependent Open
Table 19. Alarm and status relay output configuration
table
Description
Alarm - Latching
This output is true whenever there is any
active latching shutdown diagnostic that
targets the Unit, Circuit, or any of the
Compressors on a circuit.
Alarm - NonLatching
This output is true whenever there is any
active non-latching shutdown diagnostic that
targets the Unit, Circuit, or any of the
Compressors on a circuit.
Alarm
This output is true whenever there is any
active latching or non-latching shutdown
diagnostic that targets the Unit, Circuit, or
any of the Compressors on a circuit.