User manual

Page 30
Control Schemes
Note: No power supplies etc. shown All Boilers require a power supply etc. and local isolation.
The following drawings show control ideas for the SCB . Only 3 Boilers are shown, up to 12 boilers can be used on
the cascade system using a 2 wire bus connection to each Boiler NOTE the compulsory use of the cascade system is
required when using a common pressurized flue however separate flues provide the most efficient system. .
FTS
SCB
Boiler
SCB
Boiler
SCB
Boiler
Master Slave Slave
North
Wall
OS
On off control by others
All wiring & 2 core screened bus wiring by others
The Master Boiler controlling the Slave Boilers through a bus system using the Boiler bus cascade terminals 17 &
18. Weather dependant compensation is achieved using the 2 terminal outside temperature detector (OS) and 2 wire
flow temperature sensor (FTS) on the heating flow as shown. The Boilers will fully logic sequence using the in built
cascade system. On off control (using 13 & 14 terminals in the Master Boiler) is via a volt free contact by others, this
contact will switch all the boilers on & off through the bus connection. This contact should be used for safety
devices such as low & high water pressure. Up to 12 Boilers can be used on this system
FTS
SCB
Boiler
SCB
Boiler
SCB
Boiler
Master Slave Slave
All wiring & 2 core screened bus wiring by others
0 to 10 volt control by others
0 to 10 volt to the Master Boiler controlling the Slave Boilers through a bus system using the Boiler bus cas-
cade terminals 17 & 18. The 0 to 10 volt ( connected to Master Boiler terminals 15 & 16 ) will dictate the temper-
ature required. The in built cascade system will fully logic sequence the Boilers. 0 volts will stop the Boilers firing
and should be used for safety devices such as low & high water pressure. 10 volts gives maximum set temperature.
The Flow temperature sensor (FTS) will provide temperature information to the Master Boiler 12 Boilers maxi-
mum.