Installation Electrical
46
RTAF-SVX001K-EN
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 115/240 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 1 to 30 minutes (using Tracer™ TU). 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.
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 Symbio™ 800 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
Leaving Water Temperature Sensor Diagnostic)
or
•
Interrupt Failure diagnostic
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 relays 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 the table below.
Chiller events/Status description. The relay will be
energized when the event/state occurs.
NOTICE
Heater Damage!
Failure to follow instructions below could result in
damage to the heater.
If the chiller evaporator or evaporator water piping is
drained of water, the evaporator immersion heater
must be de-energized.
NOTICE
Evaporator 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 20. Pump relay operations
Chiller Mode
Relay Operation
Auto
Instant Close
Ice Building
Instant Close
Tracer Override
Timed Open
Stop
Timed Open
Ice Complete
Instant Open
Diagnostics Instant
Open
Table 21. Alarm and status relay
output configuration
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.