Quantech QTC40160, Installation Operation & Maintenance, Page: 103 / 188

Section 7 - Operation
Quantech
103
Form QTC4-NM2
Issue date: 05/12/2023
7
Evaporator heater control
The evaporator heater and suction valve actuator are
both controlled by ambient air temperature when the
system is idle. If no systems are running and the ambi-
ent temperature drops below 4.4 0 C (40 0F), the heater is
turned ON and the suction valve is closed. If no sys-
tems are running and the temperature rises above 7.2 0C
(45 0F), the heater is turned OFF and the suction valve
opened. Whenever a system is running, the evapora-
tor heater is turned OFF and the suction valve is open.
Both evaporator heater outputs are always turned ON
and OFF together. An under voltage condition keeps
the heater OFF until full voltage is restored to the sys-
tem.
Compressor heater control
Each compressor has its own heater. The purpose of
the heater is to ensure refrigerant does not condense
in the compressor. There is no oil sump, but refriger-
ant could possibly condense in the rotors or the motor
housing. The heater will be OFF whenever the respec-
tive compressor is running. As soon as the compressor
shuts OFF, the heater will turn ON as long as all motor
temperature sensors in the compressor read less than
70°C (158°F). The heater will turn OFF, if any internal
compressor motor temperature sensor reads more than
71.1°C (160°F).
Alarms
Each system has its own alarm. The Alarm output is ON
(dry contact closed) when no fault condition is pres-
ent and OFF (dry contact open) to indicate an alarm
situation. The Alarm will be activated (contacts open),
if any of the following are true.
Chiller controller cannot detect the failure
of all the heaters used in compressor, oil
separator, evaporator shell and evaporator
water box, etc. with the chilled water pump
running, and having the evaporator heat-
ers well maintained are extremely crucial
especially in subfreezing regions. Chilled
water pump control contains the logic for
prevention of evaporator freezing.
• A System is faulted or inhibited from starting for
more than 5 s.
• The Unit is faulted or inhibited from starting for
more than 5 s.
• A System is locked out.
• The Unit is locked out.
• Power is removed from the chiller.
Chiller run contact
The Chiller Run dry contact is closed whenever any sys-
tem is running. It is open when all systems are shut OFF.
Flow switch control
A chilled liquid flow switch of suitable type MUST
be connected between Terminals 2 and 13 of 1TB to
provide protection against loss of liquid flow, which
will cause evaporator freeze-up if the chiller is
permitted to run.
Changing the switch point of the thermal
dispersion flow switch
To change the factory-set LED 7, complete the follow-
ing steps:
1. Press the ◄ or ► push button. The switch point
LED flashes.
2. Press the ◄ or ► push button as many times as
required in less than 2 s between each press. Each
press of the push button shifts the LED by one
position in the indicated direction.
3. Stop pressing the button when the switch posi-
tion LED changes to the required position. The
flow switch automatically returns to the operating
mode with the new setting in 2 s.
4. To prevent unintentional settings, press both push
buttons simultaneously for at least 10 s in oper-
ating mode to lock the switch electronically. To
unlock the flow switch, perform the same opera -
tion again. The setting remains the same in case
of power failure.
Run permissive
A Run permissive input is available for each system.