Sequential Board (Sq2.0) - McQuay MWM Service Manual

MCQUAY Service Guide Book

5.3 Sequential Board (SQ2.0)

Dip switch setting of sequential controller are as
the following:
Main Board SQ2.0
1. Models Selection
Model
a. No heater
b. 1 heater
c. 2 heater
Where n = no. of compressor(s)
Postfix no. = no. of heater(s)
2. Stage Differential Temperature
Differential temperature
difference between turning on or off a compressor
to another compressor in thermostat cycle.
The stage differential
selected from the range shown below:
Dip Dip
switch 1 switch 2
Off Off
On Off
On/Off On
is the temperature
temperature can
a. Default
b. 0.5°C
c. 1.0°C
d. 1.5°C
Note: 1.5°C only valid for 2 and 3 compressors
model. For 4 compressors model, maximum
allowed is 1.0°C.
The default differential temperature is base on
number of compressor model, the setting is as
below:
Model
1 compressor
2 compressors
3 compressors
4 compressors
3. Operating Modes
The system has 4 operating modes to select with
respect to each model selection:
Model Auto Cool Heat Fan
SQCn
SQHnh
SQHnh
Where x denotes modes available
n = no. of compressor(s)
h = no. of heater(s)
4. Hot Keep Option
a. Fan off
b. Fan on
5. Last Memory Functions
The power up settings for either with or without
the last memory Backup is based on the J_LST
be setting.
a. Last memory Backup
b. W/o last memory Backup
*For SQ1.0, the jumper is JH1.
28
Controller Configuration
Dip switch 3
Off
On
Off
On
Diff. Temperature
Not. Applicable
1.5°C
1.0°C
0.5°C
- X -
- X X
X X X
Dip switch 6
Off
On
Dip switch 4
Off
Off
On
On
Dip
switch
5
X Off
X Off
X On
J_LST Setting
J_LST Plugged
J_LST Removed