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Power Supply Wiring; 115vac Control Supply Transformer; Control Wiring; Volts Free Contacts - Quantech QTC4 STYLE A Series Installation Operation & Maintenance

Air-cooled screw liquid chillers with variable speed drive, 150 - 500 tons, 525 - 1750 kw, 2 compressor, 60 hz.
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Copper power wiring only should be used for supply-
ing power to the chiller. This is recommended to avoid
safety and reliability issues resulting from connection
failure at the power connections to the chiller. Alumi-
num wiring is not recommended due to thermal char-
acteristics that may cause loose terminations result-
ing from the contraction and expansion of the wiring.
Aluminum oxide may also build up at the termination
causing hot spots and eventual failure. If aluminum
wiring is used to supply power to the chiller, AL-CU
compression fittings should be used to transition from
aluminum to copper. This transition should be done in
an external box separate to the power panel. Copper
conductors can then be run from the box to the chiller.
Caulk power and control wiring conduit
entering the power panel to assure moist
air from the building cannot enter the


Units require only one 3-phase supply, plus earth.
Connect the 3-phase supplies to the circuit breaker
located in the panel (See Table 4 on Page 47).
Connect a suitably sized earth wire to the PE terminal
in the panel.


A 3-wire high voltage to 115VAC supply transformer
is standard in the chiller. This transformer is mounted
in the cabinet and steps down the high voltage supply
to 115VAC to be used by the Controls, VSD, Feed and
Drain Valve Controller, Valves, Solenoids, Heaters, etc.
The high voltage for the transformer primary is
taken from the chiller input. Fusing is provided for the
Removing high voltage power to the
chiller will remove the 115VAC supply
voltage to the control panel circuitry
and the evaporator heater mat. In sub-
freezing weather, this could cause serious
damage to the chiller due to evaporator
freeze-up. Do not remove power unless
alternate means are taken to ensure op-
eration of the control panel, evaporator
heater mat, and waterbox heaters.


All control wiring utilizing contact closures to the con-
trol panel terminal block is nominal 115VAC and must
be run in shielded cable, with the shield grounded at
the panel end only, and run in water tight conduit. Run
shielded cable separately from mains cable to avoid
electrical noise pick-up. Use the control panel cable
entry to avoid the power cables.
Voltage free contacts connected to the panel must be
suitable for 115VAC10 ma (gold contacts recommend-
ed). If the voltage free contacts form part of a relay or
contactor, the coil of the device must be suppressed using
a standard R/C suppressor. The above precautions must
be taken to avoid electrical noise, which could cause a
malfunction or damage to the unit and its controls.


Chilled Liquid Pump Starter

Terminals 23 and 24 on 1TB close to start the chilled
liquid pump. This contact can be used as a master start/
stop for the pump in conjunction with the daily start/
stop schedule. Cycle the pumps from the unit panel if
the unit will be operational or shut-down during sub-
freezing conditions. Refer to the Evaporator Pump
Control on Page 96 for more information on testing
the pumps.

Run Contact

Terminals 21 and 22 on 1TB close to indicate that a
system is running.

Alarm Contacts

Each system has a single voltage-free contact, which
will operate to signal an alarm condition whenever any
system locks out, or there is a power failure. To obtain
system alarm signal, connect the alarm circuit to volt
free Terminals 25 & 26 (Sys 1), Terminals 27 and 28
(Sys 2) of 1TB.


Flow Switch

A chilled liquid flow switch of suitable type MUST be
connected between Terminals 2 and 13 of 1TB to pro-
vide protection against loss of liquid flow, which will
cause evaporator freeze-up if the chiller is permitted
to run. The flow switch circuitry is a 115VAC circuit.
Contacts must be rated for low current (5mA). Gold
contacts should be used.
ISSUE DATE: 4/2/2018


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