LAARS MC4EXT - Install and Operating Manual User Manual
Page 4
SECTION 2.
Operation
2.1 EXM Status Lights
Whenever the MCX is powered, the red LED
marked POWER, located in the upper left of the panel,
should be lit. If it is not, check the 120VAC power
source.
If the MCX is correctly connected to a powered
MC, the green LED marked COMM ERROR will blink
on and off, approximately once a second. If the light is
does not blink, check the connecting cables.
If the N.O. contacts of a Stage relay are
energized, the red LED immediately to the left of the
relay will be on. If the relay is not energized, the red
LED will be off.
2.2 Display Stage Status
The percent modulation and Mode of each stage
is displayed on the main screen of the MC control (see
Figure 9). Stages in the Automatic mode which are not
active show ---.
The default screen shows Stages A through D.
Simply rotate the ADJUST knob clockwise (without
pressing) to see the remaining Stages, E through L.
Rotate the ADJUST knob counterclockwise to go
back in the Stage order.
Stages A through D correspond to the Stages
marked A through D on the MC panel.
Stages E through L correspond to Stages of the
MCX.
2.3 Stage Settings
All Stage setting are made at the MC panel.
If the COMM ERROR LED is flashing, the MC
recognizes the MCX panel and all its Stages.
Carefully follow all the steps in the MC I/O
manual (Stage Settings) to set up Stages E through L.
WARNING
Each Stage, A through L MUST be setup properly.
Failure to do so will result in erratic set point control
and may cause system damage.
Increase
Mod
Decrease
Mod
Common
Stage E
Stage F
Stage G
Stage H
C2
C5
C8
C11
C3
C6
C9
C12
C1
C4
C7
C10
Stage I
Stage J
Stage K
Stage L
C14
C17
C20
C23
C15
C18
C21
C24
C13
C16
C19
C22
24V
Source (+)
Signal
Sink (GND)
C1
C4
C7
C10
C2
C5
C8
C11
C13
C16
C19
C22
C14
C17
C20
C23
GND
V+
C3
C6
C9
C12
C1
C4
C7
C10
C15
C18
C21
C24
C13
C16
C19
C22
135
W
Current
Voltage
Table 1.
Figure 8. Dry Contact Wiring.
Lockout
E
Lockout
F
Lockout
G
B1
B2
B3
B4
B5
B6
Dry Contact
Lockout
Signal
Figure 9. Main Screen Display and Operation.
PRESS TO SELECT
ADJUST
Rotate
Clockwise
PRESS TO SELECT
ADJUST
Rotate
Clockwise
140°F
<A>
B
C
D
100% 100% 100% 100%
140°F
E
F
G
H
100% 61% --- ---
140°F
I
J
K
L
Off Off Off Off
800.900.9276 • Fax 800.559.1583 (Customer Service, Service Advisors)
20 Industrial Way, Rochester, NH 03867
• 603.335.6300 • Fax 603.335.3355
1869 Sismet Road, Mississauga, Ontario, Canada L4W 1W8
• 905.238.0100 • Fax 905.366.0130
www.Laars.com
Litho in U.S.A. © Laars Heating Systems 080
6 Document 4206