DSC PC4020 - V3.3 Installation Manual download pdf (Page 8)

Capacitance Limits

An increase in capacitance on the Combus will affect data

transmission and will cause the system to slow down.

Capacitance will increase for every foot of wire added to

the Combus. The capacitance rating of the wire used will

determine the maximum length of the Combus.

For example, 22-gauge, non-shielded, 4-conductor wire

has a typical capacitance rating of 20 picofarads per foot

(which is 20nF/1000’). For every 1000' of wire added –

regardless of where it is run – the capacitance of the Com-

bus will increase by 20nF.

The following chart indicates the total Combus wire

allowed depending on the capacitance rating of the wire

used:

Wires run in parallel also increase Combus capacitance.

For example, when using 20nF wire, the following would

be some of the combinations allowed:

• Four wire runs at 1000'/305m each

• Six wire runs at 666'/203m each

• Eight wire runs at 500'/152m each

• 10 wire runs at 400'/122m each etc…

NOTE: Contact the wire manufacturer for the capaci-

tance ratings of the wire being used.

PC4204/PC4204CX Power Supply

PC4204/PC4204CX power supply modules are required

to power additional modules and devices when the total

current from the main panel is insufficient. A PC4204/

PC4204CX should also be used if excessive line loss is

encountered.

PC4204/PC4204CX Current Requirement

AUX

AUX AUX

AUX - 1.0A available for devices connected to the AUX

terminal, including devices connected to relay outputs

and modules connected for Combus repower (see 2.5

‘Combus Operation and Wiring‘).

Combus Repower

Only Relay 1 on the PC4204/PC4204CX can be used for

Combus repower. The Combus must be wired to the

PC4204/PC4204CX according to the following diagram

for Combus repower:

PC4204

PC4204CX

IMPORTANT NOTE: Do not use any power supply other

than the PC4204/PC4204CX to repower the Combus. In

the event of a power surge or transient, a module may

lock up and cease to communicate with the control

panel. If the panel loses communication with the mod-

ule, it will initiate a module reset and will power down

the Combus for five seconds in an attempt to reset the

problem module. After five seconds, the panel will reap-

ply power to the Combus and the problem module

should begin to operate as intended.

NOTE: If a power supply other than the PC4204/

PC4204CX is used, the Combus repower function will

not operate as intended.

NOTE: New versions of the PC4204/PC4204CX power

supply module have a jumper marked ‘J1’. Ensure that

this jumper is configured for ’Combus Relay’. Other-

wise, the power reset function will not operate. For

more information regarding the PC4204/PC4204CX,

please refer to the PC4204/PC4204CX Installation

Instructions.

2.6 Zone Wiring

Zones on the system are wired according to the diagrams

below. Once you have selected which type of zone super-

vision you require, you must program the ’Zone Supervi-

sion’ section. See 5.1 ‘Zone Supervision‘ for instructions.

NOTE: Fire, LINKS Supervisory, LINKS Answer, AC Delay

or Forced Answer zones always use single EOL supervi-

sion, regardless of the programmed zone supervision.

No End of Line (No EOL)

All No EOL zones are normally closed loops. The zone

will be violated when it is open.

Single End of Line (EOL)

All Single EOL zones have a 5600Ω resis-

tor across them. If the zone is shorted or

open, it will be violated. Resistors

should always be placed at the device

end of the wire run.

If programmed as a fire or waterflow

zone, the open zone will generate a trou-

ble condition and the short will generate an alarm.

Double End of Line (DEOL)

All Double EOL zones have two 5600Ω resistors across

them. DEOL loops will allow the panel to detect zone

faults, zone tampers, violated zones and restored zones.

Wire Capacitance per

1000'(300m)

TOTAL Combus Wire

Length

15nF 5300'/1616m

20nF 4000'/1220m

25nF 3200'/976m

30nF 2666'/810m

35nF 2280'/693m

40nF 2000'/608m

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 59 60

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DSC PC4020 - V3.3 Installation Manual Page 8

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