Technical data

12
Options for Multiple Boilers only
Boiler sequencing cascade controller (RVA47)
LPB bus communications Clip-in module (OCI420)
Programmable room sensor (QAA70)
Outside air sensor (QAC31)
Room sensor non-adjustable (QAA10)
Room sensor offset adjustable (QAA50)
Zone controller (RVA46)
DHW Cylinder Sensor Kit (QAZ21)
LPB Bus Communications Clip-in Module
1 clip-in module is required for every boiler in a multiple boiler arrangement.
Two clip-in modules are supplied as part of the Boiler Sequencing Cascade Controller
kit, so for three boilers or more, additional clip-in modules must be ordered.
Boiler Sequencing Cascade Controller
Multiple Purewell VariHeat boilers can be sequenced using this cascade
control kit. The kit includes:
n RVA47 controller
n Insertion type water temperature sensor with pocket
n Two clip-in LPB bus communication modules*
* Note: When controlling more than two boilers, then additional
clip-in LPB bus communication modules must be ordered separately.
(I.e. A four boiler installation with a cascade control kit requires
two additional LPB bus communication clip-in modules)
Features:
n Provides cascade control from either external enable signals, 0-10v
analogue heat demand signal or built-in time clock setting
n Up to 12 boilers may be sequenced
n Lead boiler rotation
n 7 day time clock with automatic summer/winter clock adjustment
n 3 programmable periods per day
n Constant or variable temperature flow
n Compensated flow temperature based on external and room air temperatures
n Optimised start and stop based on external and room air temperatures
n Frost protection based on boiler water temperature
n Building frost protection based on room air temperature
n Summer shutdown based on outside air temperature
n Holiday period. Frost protection remains active
n Reduced temperature/night set back for non occupancy hours
n Pump kick for pumps controlled from boiler
n RVA47 controller is designed for mounting in a remote panel (not HHL supply)
To achieve full functionality an outside air sensor must be fitted.
The boiler cascade will operate according to the integral seven day time
clock with automatic summer/winter hour change. Three time periods are
programmable for each day. When there is no time demand, the boiler will
revert to the reduced temperature / night set back set-point, provided a room
temperature sensor is fitted. Otherwise the cascade will not operate unless
the frost protection function of the boiler and/or cascade is activated.
On Purewell VariHeat boilers, the control
options for multiple boilers are different
to those for single boilers.
Please refer to page 11 for controls
on a single boiler.
The Purewell VariHeat boiler in a multiple
boiler installation may be controlled by a
boiler sequencing cascade controller. This
provides cascade control from either external
enable signals or from internal time clock
settings. Up to 12 boiler modules may be
controlled and communication between the
cascade controller and boilers is via an LPB bus.
The boiler sequencing cascade controller is
a sophisticated controller which, when used
with a room temperature sensor and outside
air sensor, will provide enhanced comfort
control for the heating zone it is connected to.
Additionally a domestic hot water cylinder
circuit may also be controlled from the boiler
cascade controller.
Where the building has more than one
heating zone, additional zone controllers
can be added to provide a comprehensive
building heating control.
Programmable Room Sensor
The programmable room sensor
communicates room temperature to the
RVA47 Cascade Controller and allows the
user full adjustment of the room temperature,
time clock, holiday periods and frost
protection settings. The unit also displays fault
codes from the boiler plant. Alternatively, non
adjustable and offset adjustable room sensors
are also available, for installations requiring
users to have less access to system settings.
Features:
n 3 programmable periods per day
n Reduced temperature/night set back for
non occupancy hours
n Holiday period. Frost protection remains
active
n Programme lock to prevent tampering
n Indication of operating parameters and
boiler fault condition
n 7 day time clock with automatic summer/
winter clock adjustment
Control Details
Purewell VariHeat Multiple Boiler Installations