Combus Operation And Wiring - DSC Maxsys PC4020 Installation Manual

PGM1 (50/170mA max.*)
PGM2 (50/170mA max.*)
Combus (500mA max.)**
Total (must not exceed 500mA)
*PGM1/PGM2 (Standard Output) = 50mA max.
NOTE: PGM1/PGM2 (Addressable Loop) = 170mA max.
NOTE: To calculate Addressable Loop current, see 2.9
'AML Device Wiring'.
**See 'Combus Current Calculation Chart' below.
NOTE: For UL Listed applications, the total standby and
alarm current cannot exceed 900mA.
Module Ratings
The current draw of compatible modules is listed below:
Device .................................................Current Draw (mA)
Keypad (LCD45XX)......................................................... 50
PC4108A Zone Expander ............................................... 30
PC4116 Zone Expander................................................... 30
PC4164 Wireless Receiver............................................. 110
PC4701 Fire Module ........................................................ 35
PC4702BP Dual Bell Output Module............................ 75
PC4204 Relay Output Module ....................................... 30
PC4204CX Combus Repeater......................................... 30
PC4216 Low Current Output Module .......................... 15
ESCORT4580 Audio Assistant ..................................... 150
PC4401 Interface Module ............................................... 35
PC4820 Access Control Module .................................... 35
PC4936 Audio Interface Module ................................... 65
PC4850 Module .............................................................. 135
Calculating Total Current Requirement
Once you have determined which modules will draw
power from the main panel, use the following chart to cal-
culate the Combus current.
Combus Current Selection Chart
Item Current (mA)
Keypad 50
PC4108A* 30
Current required for connected devices =
PC4116* 30
Current required for connected devices =
PC4164 110
PC4701 35
PC4702BP 75
PC4204/PC4204CX 30
PC4216* 15
Current required for connected devices =
ESCORT4580 150
PC4401 35
PC4820 35
Total Combus Current =
x Quantity Total (mA)
x
x
x
x
x
x
x
x
x
I n s t a l l a t i o n
Combus Current Selection Chart
Item Current (mA)
PC4850 135
PC4936* 65
T-Link 150
Skyroute 30
Total Combus Current =
NOTE: *These units draw current from the Combus to
power devices external to the module. This current must
be added to the total Combus current. See manufac-
turer's specifications for the current draw of each
device. Each LED assembly draws up to 20mA of current.

2.5 Combus Operation and Wiring

The Combus is used by the control panel and the modules
to communicate with each other. The four Combus termi-
nals of the main panel must be connected to the four Com-
bus terminals or wires of all modules.
Modules can be home run, connected in a daisy chain or
T-tapped anywhere on the Combus.
The following rules MUST be followed when wiring the
Combus:
1. The Combus must be run in minimum 22-gauge wire.
2. No module can be more than 1000' (305m)
length from the main control panel.
3. Shielded wire should only be used in areas that
present excessive RF noise or electromagnetic interfer-
ence. If shielded wire is used, the maximum distance a
module can be located from the main panel is signifi-
cantly reduced. Check the capacitance limit of the wire
to calculate the maximum distance (see 'Capacitance
Limits' below).
4. The total capacitance of the Combus wiring must not
exceed 80nF (see 'Capacitance Limits' below).
5. Do not run Combus wire runs in parallel with AML
wire runs. Maintain minimum 2" separation between
the cables.
Line Loss
When current is drawn through a piece of wire, voltage
will be lost due to the wire's resistance. This voltage loss
must be considered for all installations.
To ensure proper operation, at least 12.5V
applied to all modules on the system (when AC is applied
and the battery is fully charged). If less than 12.5V
applied, system operation will be adversely affected.
To correct the problem, try any or all of the following:
1. Connect a PC4204/PC4204CX power supply near the
module to provide power to the Combus.
2. Reduce the length of the Combus run to the module.
3. Increase the gauge of wire.
a n d W i r i n g
x Quantity Total (mA)
x
1000' (305m) in cable 1000' (305m) 1000' (305m)
must be
DC
is
DC
3