This firmware can be used on ACT-DIN-RLY hardware issue J, universal inputs, 512k prom. or equivalent Triac boards. Code for AOP versions could be povided if required.
The description is largely written for the Heating version (HSCVT4b) of the product, there is also a version (CSCVT4b) 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 action may be modified
by the setting of HTCT). 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.
An extra configuration parameter has been introduced which selects whether the demand signaling is via % demand or Constant temperature setpoints. This is in line with similar changes made in Zone and DHW controllers. Since the CT temperature range already has setup parameters the parameter in the Secondary controller is only 0 or 1. HTCT (CTCT in cooling version) set to 1 will force the controller to send the demand as a CT setpoint.
Note the current controller range only supports CT setpoint demands on Boiler Controllers, it is expected that other controllers may support CT setpoints in the future.
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. The number of Zone Occupied is filtered and will
only change at a maximum rate of one zone per minute.
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.
The controller can now send it's Occupancy state to any other module which supports receiving OCDS, at present that is AHU, DHW, and other HSC or CSC controllers. This enables the demand fan-in, with filtering if appropriate to be done on a secondary controller which then sets say a Fresh Air AHU to run. To avoid the inevitable confusion regarding whether a demand link or an OCDS link is being made this feature is restricted to manual setting of OCDS in the sending controller, the table sets out the rules for OCDS numbering. Secondary Controllers will OR the Occupancy signal which arrives via OCDS with the normal Occupancy calculation.
| Target Module | OCDS setting |
| HSC | Heat Source number |
| CSC | Cool Source number +25 |
| AHU | AHU number +50 |
| DHW | Zone number( maximum 100) +100 |
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.
This controller uses the universal hardware driver version 4a which allows many combinations of output to be achieved.
Secondary Controllers can be used in many applications and sometimes it is needed to have say a Cooling controller which reacts to cooling demands but controls a heating function. This controller now calculates both a heating and a cooling control loop to the same setpoint and measured value, the heating and cooling outputs are then passed to the hardware driver the setings of which will determine how the hardware reacts. So in this example the cooling secondary controller would have it's heating driver set and it's cooling driver disabled.
This has been included to allow hardware to be re-tested at the final booking out station and also to be easily checked at any time in the field.
The controller is put into test mode by setting config 120 to 1 or by holding the service pin down as the unit is powered up. If the later method is used then the unit will need to be re-registered after the test since this action also clears any slaving which might have been setup.
Test mode is cleared by power cycling or by setting C120 back to 0.
Test mode cycles the outputs, and flashes the leds see full test specification. The values for the analogue inputs and the potentiometer can be monitored on configs 170 onwards.
The configuration tables have been updated from the previous issue, MNDV Minimum driver demand has been added, and some extra parameters are now available in the cooling version.
HSCVT4b1 config tables
CSCVT4b1 config tables