User manual

Page 29
Simple Relay control (using volt free contacts ) of the SCB.( NON ELECTRONIC CASCADE SYSTEM ) The
relay makes terminals 13 & 14 in each Boiler. All other control and safety devices control the relay. An unlimited
number of Boilers can be used on this control system providing each Boiler has its own clean relay contacts. No ex-
ternal temperature sensor fitted therefore no compensation. With this scheme 3 external sensors and 3 flow tempera-
ture sensors ( as there are 3 Boilers ) would be required to directly compensate each Boiler but with no sequencing
from the Boiler cascade controls.. See next page.
Control Schemes
Note: No power supplies etc. Shown. All Boilers require a power supply etc and local isolation.
The following drawing shows control ideas for the SCB . Compulsory use of the electronic cascade system is
required when using a pressurised common flue NOTE: separate flues provide the most efficient operation
on any multiple Boiler system.
SCB
Boiler
SCB
Boiler
SCB
Boiler
Relay by others
Relay with clean contacts