13
Local and Remote relays
Local relays
are located on the main input PCB and are designated to specific
conditions which exist within the Combi system and can be programmed to be normally
energised.
Remote relays
are located on one of two 32 channel relay boards and can be
programmed to be operated according to detected events which occur such as alarms
and faults. The first 16 relays can be programmed to be normally energised.
The local relays are as follows (all contacts are rated at 5A 250Vac)
Common Over range alarm
will energise if any gas is over range. S.P.C.O
Common High alarm
will energise if any gas is in high alarm.
D.P.C.O
Common Low alarm
will energise if any gas is in low alarm.
D.P.C.O
Fault
will de-energise if any fault exists in the system.
S.P.C.O
Option 5
will energise if voting 5 conditions are met.
S.P.C.O
Option 6
will energise if voting 6 conditions are met.
S.P.C.O
Option 7
will energise if voting 7 conditions are met.
S.P.C.O
Option 8
will energise if voting 8 conditions are met.
S.P.C.O
Sounder Relay
will energise if a new alarm occurs, and is de-energised
when mute,
UP (1)
, is pressed
A small relay on the front panel energises if a sensor is inhibited.
This includes “power up inhibit” periods
The 64 additional remote relays which are S.P.C.O types can be programmed to operate
on an event as an individual relay 1 to 64. Alternatively the first 16 relays can be
programmed to use patterns. See
ENGINEER’S
menu 23 Event to Relay.
Modbus set up and indicators
Modbus is a means of obtaining data from the gas detection system via a MODBUS
master controller. The Combi system is a SLAVE to the commands received from the
master via two RS485 twisted pair communication cables. When a command is received
on one of these cables, the reply is sent on the same cable thus giving rise to half duplex
communication. For maintenance purposes, two LED’s situated on the main processor
PCB close to the connectors show when a reply is being sent on that particular cable.
In a MODBUS system that makes use of both these cable, both these LED’s flash
periodically to indicate successful communication. Once the communication has started,
the Combi system will monitor how long since the last command was received and if this
is greater than 50 seconds a communications failure (COMMS FAIL) alarm will occur.
Each Combi system has an internal address, which is used both for Modbus address and
CAN bus address (see repeaters). This address and other parameters can be set and will
be remembered at power up using
ENGINEER’S
menu 27 Setup Network. The speed of
communication (baud rate expressed in bits per second) is set using menu 34.
All communicating devices in a Modbus system should be set to the same baud rate and
the Combi system is capable of supporting 19200, 9600 and 4800 baud. 9600 is set by
default.
