8.0 Controls Operation - Hamworthy MILBORNE381 Series Design Installation, Commissioning And Operating Instructions

8.0 CONTROLS OPERATION

8.1 Overview
The Milborne control system is a self contained , micro
-processor based package, controlling and monitoring
all safety and functional aspects of the boiler
performance and it's integration with external system
controls.
The controls are split into a Master and Slave
configuration, with the Master controlling up to 60
slaves. Every boiler module has a slave control and
either a 381 / 501 or 382 / 502 boiler must have the
Master control. All boiler performance information is
accessible and visible through the Master control
display.
The Master control will sequence modules with a lead
boiler rotation based on hours run. Each Master is
supplied with a mixed flow sensor for insertion into the
common flow pipework. The sensor must be fitted
closest to the heating system pipework, after the last
boiler in the cascade. The sequencing can be set in
Cascade mode, where
modulate to the maximum rate before switching on the
next boiler in the sequence. Alternatively, the
sequencing can be set in Unison mode, where
individual boilers operate at minimum rate, and
collectively modulate to satisfy the demand. Unison
mode can realise higher operating efficiencies due to
the superior part load performance at low firing rates.
The Master control will manage the operation of two
heating circuits plus a dhw circuit. The heating circuits
are designated as High temperature and Low
temperature, the latter incorporates control outputs for
both a pump and a mixing valve, whilst the former and
the dhw only have outputs for pump control. An
adjustable parameter is provided to enable pump
overrun for all three pumps - see section 4.6
All three circuits can be set to operate at different
temperatures. The low temperature and dhw circuits
having additional optional sensors for control of water
temperature. Any unused circuits can be disabled in
the parameter settings.
Should there be a malfunction of the Master control,
'Emergency Mode' can be activated which will allow
the system to operate at a default temperature—see
section 8.3.
The Master control will provide summer shutdown,
based on outside air temperature measured by the air
sensor supplied with each Master. An adjustable
parameter is available
temperature at which the heating circuits operate.
Two stage frost protection is provided by the Master
via the outside air temperature. Stage 1 will start the
primary pump and stage 2 will start the boilers based
on water temperature within the heating circuit.
Weather compensation is available for the heating
circuits based on outside air temperature and a
common curve. Each circuit can be offset from this
curve by setting the maximum and minimum water
temperatures in the parameters.
HAMWORTHY HEATING LTD
individual boilers firing
to select the desired
A comprehensive self diagnostic fault identification
system is incorporated within the Master control
allowing visibility of all boilers in the installation.
8.2 System Design
Hamworthy Heating strongly recommend the use of a
primary circuit configuration, with a suitably matched
pump (refer
Department for help or assistance if in doubt). This
ensures that the individual modules are flow rate
protected with the Master controlling the primary circuit
pump. Secondary circuits for high temperature
constant volume heating, domestic hot water and low
temperature variable flow heating, are also controlled
from the Master control - refer to figure 8.2.
8.2.1 Primary Circuit
Whenever there is a demand for heat from any or all of
the secondary circuits, the primary pump is initiated. A
start signal from the Master control connected to the
primary pump (P3), via a suitable contactor, will
maintain the primary flow until all heat demands are
satisfied and the overrun period is timed out. Where
twin head pumps are installed a changeover control
(not HHL supplied) external to the boiler is required.
The temperature set-point of the primary circuit is
equivalent to
requirement. The temperature sensor provided with
the Master boiler must be located between the Master
boiler and the low loss header - refer to figure 8.2.1
8.2.2 High Temperature Heating Circuit
Using constant volume flow, the high temperature
heating pump (P1) is initiated when there is a demand
from the associated room thermostat. The flow
temperature to the circuit can be fixed, or directly
compensated according to outside air temperature.
When there is a higher temperature demand for dhw,
the high temperature pump (P1), is disabled for the
duration of the dhw demand.
8.2.3 Low Temperature Heating Circuit
Using a mixing valve and optional flow temperature
sensor, the low temperature heating circuit can
operate at a lower temperature than the high
temperature heating and dhw circuits. The flow
temperature
compensated using the mixing valve according to the
outside air temperature. Regardless of demands on
the high temperature or dhw circuits, the low
temperature
uninterrupted. The low temperature pump (P4) must
be started via a double pole relay in conjunction with
the room thermostat for the low temperature zone -
refer to figure 4.6
8.2.4 Domestic Hot Water Circuit
Using a traditional calorifier, the dhw demand is
initiated by the cylinder thermostat (optional HHL
sensor is available), starting pump (P2) and adjusting
the primary circuit temperature to achieve the desired
dhw set-point.
26
MILBORNE
to Hamworthy Heating
the highest secondary
to the circuit can
heating circuit operation
Technical
circuit
be fixed, or
remains
500001130/J