Software Release Notes
Secondary circuit controller
HSCVT4c1
CSCVT4c1
Changes this issue
Hardware
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.
General
The description is largely written for the Heating version
(HSCVT4c) of the product, there is also a version (CSCVT4c) 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.
Functional description
This controller provides control of a secondary circuit
which could be for radiators, air handlers, fan coils, water heating, chillers
etc. The secondary circuit can be controlled (by setting SPTY) as:-
- SPTY 0:a constant temperature set to the value of maximum
Flow MAXF
- SPTY 1:a setpoint which varies linearly between a maximum
and a minimum value based on the zone trim signal.
- SPTY 2:a setpoint which varies linearly between a maximum
and a minimum value based on the average zone trim signal.
- SPTY 3:a weather compensated temperature with zone trim
(only applicable to heating version)
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 two 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.
Demand Signaling
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.
The
Secondary Controllers will now decode received Constant Temperature demands
by converting them into a percentage demand and then prioritising this demand
along with any other demands which are being received. This has been included
so that the Controller still operates even if the sending controller has incorrectly
been setup to send a Constant Temperature setpoint. This practise should be
avoided wherever possible because the rescaling takes extra processing time
and will limit the demand fan in which the controller can handle. HTCT setting
in any controller should only be set if the target Controller is a Boiler and
the Heat is being taken off the Primary of the Boiler.
Occupation State
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.
Occupation Destination
The controller can 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. If the OCDS signal
is the only occupancy signal then the controller creates a 'simulated demand'
of 100% (50% if SPTY=3 weather compensated) see below.
| Target Module |
OCDS setting |
| HSC |
Heat Source number |
| CSC |
Cool Source number
+25 |
| AHU |
AHU number +50 |
| DHW |
Zone number( maximum
100) +100 |
External Source for Occupation
State
The
Secondary controller now supports input mode which allows an external
input to be used to provide an occupancy signal or an Alarm. The VFC is wired
into 'temp a' (centre pair of terminals) and the configuration parameter
INMD is set to between 1 and 5, see
configuration table.
Input Mode set to 5 enables a Pump
Fail Alarm
If an external source is the sole occupation source then
a 'simulated demand' is created, within the controller, which is then available
to be passed on to other controllers or sub modules. If the Secondary controller
is set to Weather Compensation (SPTY 3) the simulated demand is 50% since this
then provides the 'un-trimmed' weather compensation curve, it is recommended
that the compensation trim parameters TRNG and CRNG are set to zero since no
demand feedback is available), otherwise the 'simulated demand' is set to 100%.
Note it is not recomended that SPTY 2, control based on average demand is used
when the occupation source is 'external' since this parameter has no validity
if there are no real demand signals.
When input mode INMD 1 (AND function) is used the external
input can be used to 'enable' normal control, when the input is shorted the
controller responds to the heat demands received from other controllers, when
the input is open circuit the controller shuts down. This could be linked to
a flow fail signal or other similar interlock.
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.
Note the support of external source using
'sensor action=4' has been removed because the secondary controllers are now
always shipped using two input hardware, and changing to INMD brings this product
in line with the Fan Coil range and also provides more features.
Pump
ChangeOver Interlock
The operation of the secondary controller
can now be interlocked with the status of pumps controlled by registered PCO
controllers. The PCOs need to be issue 4c1 or later and be set to TYPE 4 (heating)
or TYPE 7 (cooling). The secondary controller needs to have Alarm Mode aet to
1 -4 for the pump interlocks to be active.
A
new switch Interlock Pump lLKP when set causes the secondary controller to ensure
that the flow has been establised by the PCO module before allowing any of its
outputs to energise. If both pumps fail then the secondary controller shuts
off its outputs, the secondary controller will generate a Pump Fail PMPF alarm.
The secondary controller will remain disabled with a red flashing error led
until either the end of occupation is detected or the override button
is pressed or the switch Interlock Pump ILKP is cleared.
A
further switch Establish Flow ESTF, when set causes the secondary controller
to wait until the pumps have run for their minimum on time before allowing any
outputs on.
These features were developed specifically
to support control of packaged chillers but also have general use with other
plant.
Pump
Alarm
If a single pump is being controlled
by the Controller then the state of this pump can be monitored with a readback
signal, by wiring a Flow switch or contactor auxilliary contact to 'input a'.
Set input mode INMD to 5 to select the Pump Alarm. An alarm will be generated
if the readback is not true within 30 seconds of the pump being started. The
sense of the readback signal can be changed with Alarm State ALST, if ALST is
0 then a short circuit should be applied when the pump is running. Remember
that Alarm Mode ALRM set to zero disables all alarms.
If switch Interlock Pump ILKP is
set then if a pump fail is detected the control outputs will be shut down and
will remain in this state until the next change of occupancy or until the override
button is pressed. The error led will flash red to indicate that a shut down
has occured.
Condensation
Sensor (cooling versions only)
One intelligent condensation sensor
can be registered to the Secondary controller. The state of the condensation
sensor can be monitored on input 4 and if the alarm mode is set an alarm will
be generated. (Further Condensation sensors ( recommended maximum 8) can be
registered and they will be allocated clone addresses, condensation will be
detected if any of the sensors detects condensation, note because these additional
sensors all have the same address they cannot be interregated over the network,
the only way to discover which sensor is in alarm would be to physically look
for the red led on the sensor.)
While the sensor detects condensation
the cooling demand output will be progressively reduced, reaching zero after
about 3.5 minutes. When all sensors are not registering condensation then the
controller will recover after about 5 minutes, the exact timing depends on how
many sensors are connected. When in Condensation shut down the Error Led will
flash red.
Status
Monitoring
The two inputs on the controller
can be utilised for Status monitoring if they are not being used for Temperature
Control or Occupancy control (see above). The State of the input can be read
on Configuration parameter C180 for input a and C181 for input b.
If using input b for
monitoring make sure that the control loops are disabled by setting Control
Mode CMDE to zero.
Registration
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.
Plots
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.
Driver
Settings
This controller uses the universal
hardware driver version 4d 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.
Hardware Test Mode
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.
See also Automatic
sensor calibration.
Configuration changes this issue
The configuration tables have been updated from the previous
issue, MNDV Minimum driver demand and INMD input mode have been added, and some
extra parameters are now available in the cooling version.
Alarm Mode ALRM has an extra state which alows the controller
to be shut down only on STOP alarms.
Frost Protect FRPT has an additional state to allow for
pump only frost operation
HSCVT4c1 config tables
CSCVT4c1 config tables
Engineering parameters