McQuay M4AC040A, Installation And Maintenance Manual

Page: 5 / 59

Antifreeze Protection
The antifreeze heater is activated if the water leaving temperature falls below 2
q
C (without glycol) in order to
prevent heat exchanger from freezing up.
Standard Factory Setting
Entering Water Temp.
q
C
Min Entering Max. Entering
Cooling Mode 12 3 15
Heating Mode 40 35 50
Antifreeze 3 - 4 3
Electronic Controller Setting
The temperature setting in the unit is preset in factory. It is recommended to observe and adjust the setting
before commissioning the unit.
The following steps are to adjust the setting temperature :
a) For cooling mode, press the SW1 button switch once in the PCB (see table below).
b) The green LED will blink for few seconds.
c) Adjusting the small variable resistor VR3 to the required water entering temperature by using a suitable
tool.
d) If glycol added for low temperature operation, the entering water temperature (3
q
C to 9
q
C) can be set by
adjusting the DIP switch (SW2).
e) For heating mode, press SW1 button switch twice and then the red LED will blink for a few seconds.
f) Adjust the variable resistor (VR1) to set the required water entering temperature for heating mode.
g) Press the SW1 three time to monitor the antifreeze temperature.
h) Variable resistor VR2 is adjusted to set the antifreeze temperature in order to prevent the water freezing
in the system.
SW2 Settings (For Cool Mode)
SW2 SET TEMP. °C
SW2-3 SW2-2 SW2-1
Set by VR3 (fixed) off off off
3 off off on
4 off on off
5 off on on
6 on off off
7 on off on
8 on on off
9 on on on
If DIP switch is set to (off, off, off), the set temperature is determine by VR3 setting, otherwise setting above
will override the VR3 setting.
Note : (Factory standard setting is recommended. If glycol added, the entering water temperature can be
set by adjusting DIP switch SW2)
4