Trane Ascend ACR Series, Installation, Operation And Maintenance Manual

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42 AC-SVX001A-EN
LLIDs. Service power connection allows for a NEMA 5-
15 style extension cord to power on Class 2 devices (i.e.
UC800, LLIDs, EXVs, and TD7 display) with an external
power source, without the need of line voltage applied
to the unit. This connection is to be made at 1XJ50. The
extension cord power source is required to have
upstream current protection rated at no more than 10A.
The required voltage for the service power connection
is 115V at 60Hz and 110V at 50Hz.
Heater Power Supply
The evaporator shell is insulated from ambient air and
protected from freezing temperatures by
thermostatically-controlled immersion heaters. See
table below for evaporator heater summary. Whenever
the water temperature drops to approximately 37°F
(2.8°C), the thermostat energizes the heaters. The
heaters will provide protection from ambient
temperatures down to -20°F (-29°C).
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Table 13. Evaporator heater summary
Unit Size (tons)
Waterboxes
Supply
Return
2-pass Evaporator
150 to 165 400W 400W
180 to 200
400W (Qty 2)
400W
225 to 300 600W 600W
3-pass Evaporator
All sizes
400W (Qty 2)
400W
Chilled Water Pump Control
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An evaporator water pump output relay’s normally-
open contact closes to start the evaporator water pump
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. The relay’s contacts are
compatible with 115/240 VAC control circuits. See
Programmable Relays section for rating details.
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 relay is energized and
the normally-open contact is closed. When the chiller
exits the AUTO mode, the relay’s normally-open
contact is timed to open in an adjustable (using
Tracer
® TU service tool) 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 14. 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)
Chiller Shutdown
Diagnostics
(except freeze protection)
Instant Open
Freeze Protection related
chiller shutdown diagnostics
Initially: Remain Closed
Then: Delayed/Dependent Open
Chiller Off Cycle Freeze
Diagnostics
Instant Close – Dependent Open
(a) Operation can be instant open or instant close, depending on
diagnostic.
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
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