This firmware can be used on ACT-DIN-RLY hardware issue G, universal inputs, 512k prom.
The description is largely written for the Heating version (HSCVT3a) of the product, there is also a version (CSCVT3a) which controls a cooling Secondary circuit or enables chillers and associated pumps. The cooling version is essentially the same as the heating version except the weather compensation mode is not supported.
This controller provides control of a secondary circuit which could be for radiators, air handlers, fan coils, water heating etc. The secondary circuit can be controlled (by setting SPTY) as:-
Providing a valid temperature sensor is fitted, the controller provides
closed loop control of a water circuit with local temperature measurement. All the output
driver types available on Actuator controllers are supported so although the expected use
is to control a modulating three way valve and a circulating pump (type 7) other options
are available.
If no valid sensor is fitted then the highest demand (or average demand
if SPTY=2) from the zones is used to drive the outputs directly (driver mode).
The controller receives zone trim demands from zone controllers which
are utilising it's heat output and these demands are used to modify the setpoint for the
secondary circuit. The controller passes on it's demand to the Boiler Controller in the
form of a CT setpoint. This setpoint is 10 degrees above the setpoint for the secondary
circuit but this offset may be varied with the LOSS config variable.
When there is insufficient demand from the zone controllers the controller operates with a frost or non occupied setpoint (10C). See later section Occupation State.
The controller can be used to control an independent source of heat, for
example a separate boiler or district heating supply valve. In this case the HTSC config
variable should be set to 0. This will prevent the controller requesting heat from the
main Boiler Controller.
A maximum of three Pump Changeover modules or Actuator
Controllers can be registered with the VT controller. This allows additional pumps or
valves to be controlled on the secondary circuit.
It is possible to disable the temperature control loops and use the temperature inputs to monitor the Flow and Return temperatures on the circuit. The configuration variable CMDE if set to 0, will disable the control and cause the demand signal gathered by the secondary controller to be passed directly to the driver.
The occupied or non-occupied state of the controller is
determined by the settings of minimum demand MIND, minimum average demand MNAV and minimum
number occupied MNOC. These parameters can be used singly or together.
MIND minimum demand
The highest trim signal from the zones is compared with this value and if greater the Controller is put into occupied mode. Once occupied the trim signal from the zone must drop below half the MIND setting to select non-occupied
MNAV minimum average demand
The average trim signal from the zones is compared with this value and if greater the Controller is put into occupied mode. Once occupied the average trim signal from the zone must drop below half the MNAV setting to select non-occupied. The average value is used to prevent a small demand from a single zone activating the controller this is of particular concern when it is being used as a constant temperature circuit.
MNOC minimum number of occupied zones
The number of zones occupied is compared with this value and if greater
the Controller is put into occupied mode. Once occupied the number of
occupied zones needs to fall below half the MNOC setting to select non-occupied.
To disable a particular test set the parameter to zero. If all three
parameters are zero the Controller will become occupied if any zone is occupied.
If more than one test is in action (not zero) then the occupancy state
is determined by ANDing the result of each test.
For example if the setting are
MIND 50
MNAV 20
MNOC 5
The Controller will become occupied when the highest Zone trim is greater than 50% and the average trim is greater than 20% and at least 5 zones are occupied. It is anticipated that this level of sophistication might be needed when the controller is being used to enable high capacity chiller plant.
Note if no temperature sensor is fitted then the controller operates in
driver mode, passing on the highest or average demand (depending on the setting of SPTY)
to the output stages but only whilst Occupied.
Support has been added to allow the Occupation state of a Secondary
Controller to be determined by an external input. To activate this state set sensor action
SACT to 4 and wire the external signal (volt free contact only) to the sensor terminals
'temp b'. A closed contact will force occupation. This has been implemented as an OR
function with the above occupation logic so this feature could be used as an additional
demand source. If the external source is to be the only occupation signal then ensure that
no other devices are pointing to the Secondary Controller's Heat or Cool source.
If a temperature sensor is also required, use the two temperature input version of the hardware and wire the temperature sensor to terminals 'temp a'.
The Controller must be registered with a Boiler Controller, the first
controller so registered is designated Heat Source 2 , (the boiler itself being heat
source 1). To effect this registration the Boiler must be put into Config Mode.
Zone Controllers (or AHUs and FCUs) are registered to the Secondary
Circuit Controller(VT) by putting the Secondary Controller into Config mode and pressing
the registration button on all zones which use heat (or cool for CSC versions) from this
circuit. The VT controller will change the HTSC variable in the zone controllers to match
it's heat source number. Note leave at least 10 seconds between the registration of
each zone.
If the heat source number for the circuit is known and the zone
controller has already been registered with the boiler, the same effect can be achieved by
simply changing the HTSC config variable on the Zone controller to the appropriate heat
source number.
Registration of the cooling CSC version is the same except the CLSC
parameter is updated, the first controller registered is designated number 2, because when
using a Floor Controller as the System Master it takes the designation of Heat source 1
and cool source 1.
There are two plots setup as normal on the first two 'sensors'.
Plot 1 Measured Temperature
Plot 2 Control output
This controller uses Configurable
Plots like most of the other SeaChange controllers.
The plots are now automatically re-scaled within the controller to
achieve the best resolution for the data recorded. This happens at the end of every 96
readings when new maximum and minimum settings are calculated and also if a new value is
outside the current range settings.
The configuration tables have been updated quite substantially from the previous issue, CMDE control mode has been added, (replaces DRVO introduced in version 3a4) and some redundant parameters have been removed from the Cooling version.
HSCVT3a5 config tables
CSCVT3a5 config tables