Installation Electrical
70 RTHD-SVX02H-EN
Module Connections for Intercon-
necting Wiring
All connectors can be unplugged or the wires can be
removed from the screw assembly. If an entire plug is
removed, make sure the plug and the associated jack are
marked for proper location identification during reinstal-
lation.
D
CAUTION
Equipment Damage!
Plugs and jacks must be clearly marked before discon-
necting, because specic plugs will t into other jacks.
Possible damage to equipment may occur if the plugs
are reversed with the jacks.
Interconnecting Wiring (Field Wiring Re-
quired)
Important:
Do not turn chiller on or off using the chilled
water pump interlocks.
When making field connections, refer to the appropriate
field layout, wiring, schematics and controls diagrams
that ship with the unit. The diagrams in this manual are
typical only and may not match the unit.
Whenever a contact closure (binary output) is refer-
enced, the electrical rating is:
At 120 VAC 7.2 amp resistive
2.88 amp pilot duty
1/3 hp, 7.2 FLA, 43.2 LRA
At 240 VAC 5.0 amp resistive
2.0 amp pilot duty
1/3 hp, 3.6 FLA, 21.6 LRA
Whenever a dry contact input (binary input) is refer-
enced, the electrical rating is 24VDC, 12 mA.
Whenever a control voltage contact input (binary input)
is referenced, the electrical rating is 120 VAC, 5mA.
Note: Asterisked connections require the user to pro-
vide an external source of power. The 115V con-
trol power transformer is not sized for additional
load.
Chilled Water Pump Control
UC800 has a evaporator water pump output relay that
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 ma-
chine level diagnostics to prevent the build up of pump
heat. To protect against the build-up of pump heat for
those diagnostics that do not stop and/or start the pump
and to protect against the condition of a bad flow switch,
the pump shall always be stopped when the evaporator
pressure is seen to be close to the Low Side Evaporator
Pressure relief valve setting.
Chilled Water Flow Interlock
UC800 has an input that will accept a contact closure
from a proof-of-flow device such as a flow switch. The
flow switch is to be wired in series with the chilled water
pump starter’s auxiliary contacts. When this input does
not prove flow within 20 minutes relative to transition
from Stop to Auto modes of the chiller, or if the flow is
lost while the chiller is in the Auto mode of operation,
the chiller will be inhibited from running by a non-latch-
ing diagnostic. The flow switch input shall be filtered
to allow for momentary openings and closings of the
switch due to turbulent water flow. This is accomplished
with a 6 seconds filtering time. The sensing voltage for
the condenser water flow switch is 115/240 VAC.
IMPORTANT!
DO NOT cycle the chiller through starting
and stopping the chilled water pump. This could cause
the compressor to shut down fully loaded. Use the exter-
nal stop/start input to cycle the chiller.
Condenser Water Pump Control
UC800 provides a contact closure output to start and
stop the condenser water pump. If condenser pumps are
arranged in a bank with a common header, the output
can be used to control an isolation valve and/or signal
another device that an additional pump is required.
Condenser Water Pump Prestart time has been added to
help with cold condenser water problems. In very cold
outdoor ambients, the cooling towers sump cold water
would reach the chiller some time after the low system
differential pressure protection had run through its
ignore time, and result in an immediate shutdown and
latching diagnostic. By simply starting the pump earlier,
and allowing mixing of the warmer indoor loop with the
cooling tower’s sump, this problem can be avoided.
Condenser Water Flow Interlock
The UC800 shall accept an isolated contact closure input
from a customer installed proof-of-flow device such as a
flow switch and customer provided pump starter auxil-
iary contact for interlocking with condenser water flow.
The input shall be filtered to allow momentary openings
and closings of the switch due to turbulent water flow,
etc. This shall be accomplished with a 6 seconds filtering
time. The sensing voltage for the condenser water flow
switch is 115/240 VAC.
On a call for cooling after the restart inhibit timer has
timed out, the UC800 shall energize the condenser water
pump relay and then check the condenser water flow
switch and pump starter interlock input for flow confir-
mation. Startup of the compressor will not be allowed
until flow has proven.
If flow is not initially established within 1200 seconds
(20 minutes) of the condenser pump relay energizing,
an automatically resetting diagnostic “Condenser Water
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