Technical data

15
Room Temperature Set Point
The required room temperature is set from
the cascade controller and the actual room
temperature communicated to the cascade
controller from a remote room
temperature sensor.
Primary Circuit Pump Control
In all installations it is recommended that the
primary circuit pump start signal is provided
from the boilers. Each boiler has a shunt
pump output and these should all be wired
together in parallel to energise the pump
relay contactor. It is important that all boilers
are connected to the same supply phase, as
mixing phases could lead to higher voltages
present in the pump circuit than required. By
energising the primary pump via the boilers,
the boilers are prevented from firing without
circulation, in frost protection mode.
Should control of the primary pump be
required from an alternative source, such as
a BMS system, then the frost protection set
point for starting the primary pump should
be higher than 5°C water temperature.
This will ensure that the primary pump
will have started before the boilers can
operate under the influence of their integral
frost protection, which is set at 5°C water
temperature.
Interlocks
Remote interlocks, e.g. pressurisation unit,
flue fans etc can be connected directly to
each boiler module using the safety interlock
circuit input. Neither the RVA47 cascade
controller nor the RVA46 zone controller
have safety interlock circuit inputs.
Remote Start Stop
The RVA47 Cascade controller can
receive a remote start stop signal from an
external source. This signal must be via
a volt free contact. All time clock functions
including optimised start and stop must be
incorporated within the remote time clock
circuitry. The frost protection functionality
within the RVA47 Cascade controller
will always remain active.
Weather Compensation
When using an external air temperature sensor with remote enabled systems
(not 0 – 10 Volt) or integral time clock, the flow temperature can be
directly compensated. The heating curve corresponding to the required flow
temperature conditions is fully adjustable with curve settings from 2.5 to 40.
To further enhance comfort levels within the building, when used in conjunction
with a room temperature sensor, the cascade flow temperature set-point will be
adjusted, dependent on the actual room temperature. I.e. if the room temperature
is high then the control will further reduce the flow temperature automatically.
Further enhancements for comfort can be made using the offset adjustment for the
heating curve, programmable to reset the curve parallel to the original +- 4.5°C