Secondary Circuit Controller with Built-in pump Changeover facility for Constant Temperature Pump Sets CTU/DIN/PCO/3T/... (3 x Triac Outputs)
Main Features Controls a Secondary LPHW or Chilled Water Constant Temperature (CT) Pump Set Automatic Pump Changeover and Duty Rotation of Pump Set Collates Demand Signals from Multiple Zones Intelligent Demand Filtering Pump Exercising Routine

Summary Features

General

The SeaChange Secondary Circuit Controller with Pump Changeover is used specifically to control a CT circuit pump set (either LPHW or Chilled Water) where no temperature control is required. The circuit may feed Radiator zones, Air Handling Units, Fan Coil Units, DHW systems or other types of load; ideally all of the associated loads will be controlled by SeaChange 'Consumer' modules (for instance, Zone Controllers or AHU Controllers).

Configuration parameters can be set to allow operation to match the plant control requirements. A full table of configuration and monitoring parameters is detailed later in this data sheet.
A table of available product versions is shown on the last page.

Demand Control
The Secondary Circuit Controller is known as a Distributor Module ; it receives Heating or Cooling Demand signals from its Consumer Modules. It collates the demand signals and then passes a corresponding demand to a SeaChange Provider Module controlling the primary source of energy (eg Boilers or Chillers). In this way, the primary plant will run only when a demand for it’s services exists.

Intelligent Demand Filtering
The Secondary Circuit Controller has Intelligent Demand Filtering and can be set to produce a Demand for heating or cooling only when certain criteria are met, e.g. when at least 5 Fan Coils of the 50 on a circuit are demanding Cooling - this would prevent a large Chiller from running when only 1 Fan Coil was demanding cooling energy.

Operation
The Secondary Circuit Controller provides Duty Rotation and Auto Changeover of the pump set.

Duty Rotation of the pump set occurs automatically each time the pump set is started, or after a specific number of hours run.
The controller can use Contactor status signals or Flow Proving switches (single or dual) to monitor the status of the pump set. During operation Auto Changeover occurs when any of the monitored signals indicates a fault condition.

Different Failure Modes may be set if pumps fail to run (eg. both run, last to run remains on, both off). Reset after pump failure can be Manual or Automatic.

A Temperature Control variant of the Secondary Circuit Controller is available to control VT or CT circuits where the temperature in the secondary circuit is regulated by valves or other plant. This product is described in the separate datasheet M3.

Description of Features

Occupation State of the Secondary Circuit

The Secondary Circuit controller has no internal Occupation Time Schedules; instead it determines whether it is working in an Occupied Mode (pumps running) or Unoccupied Mode (pumps off) by 2 methods:

A) Occupancy determined by Zone energy demands
In this mode the Secondary Circuit controller determines whether it is working in an Occupied or Non-Occupied mode depending on the Heating or Cooling Demand Signals it receives from the Consumer Modules registered to it.

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. They are particularly useful when many Consumers are being fed from one large primary plant, and it is undesirable to allow this plant to run below a certain minimum load.

MIND minimum demand
The highest Demand signal from the Consumer Modules is compared with the Minimum Demand parameter MIND and if greater the Controller is put into occupied mode. Once occupied the Demand signal from the Consumers must drop below half the MIND setting to become non-occupied.

MNAV minimum average demand
The average Demand signal from the Consumer Modules is compared with this value and if greater the Controller is put into occupied mode. Once occupied the average Demand signal from the Consumers must drop below half the MNAV setting to become non-occupied. The average value is used to prevent a small demand from a single zone activating the controller.

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 become 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 Consumer Module 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 settings are: MIND = 50, MNAV = 20, MNOC = 5
The Controller will become occupied when the highest Consumer Demand is greater than 50% and the average Demand is greater than 20% and at least 5 consumers are occupied.

Example : Heating CT Circuit serving multiple Fan Coils. Occupancy state of the Secondary Circuit controller is derived from Heating demand signals from FCU controllers using MIND, MNAV, MNOC parameters.

CT setpoint for boilers is determined by MXCT parameter.

B) Occupancy determined by Occupancy Demand signals from another controller
In this mode the Secondary Circuit controller will enter the Occupied mode if any of the controllers Interconnected to it via Occupancy Demand enters Occupancy themselves.

Example : 2 CT heating circuits operated by occupancy only - no heating demand. Occupancy state of both Secondary Circuit controllers is determined by occupancy status of Zone controller. Zone heating demands are ignored. CT setpoint is calculated by MXCT parameter.

Demand Control

The Demand used by the Secondary Circuit Controller to enable its own pump set is also used as a Demand signal which needs to be sent to the module controlling the Primary energy feeding the Secondary Circuit. This is usually a Provider Module (e.g. Boiler or Chiller Controller) but could also be another Distributor Module (i.e. Secondary Circuit Controller) in which case the demand is sent as a % rather than a setpoint, and HTCT should be set to 0.

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.

Pump Control and Demand

The Default settings of MIND, MNAV and MNOC will cause the Secondary Circuit to shut down when all Loads are satisfied. This is best practise for energy efficiency; however, if space temperature sensors are badly sited or not representative of the entire zone temperature, it may be necessary to disable this feature. If it is desired for the Secondary Circuit pump to run at all times during any Consumer Module’s Occupancy period, then MIND, MNAV and MNOC should all be set to zero; energy losses due to unnecessary circulation of water or overheating/cooling of the space may result, however.

Inputs
One or two VFC inputs can be used for pump flow status; using flow switch, pressure switch, or contactor signals. If a common flow status signal is used, it can be connected to either input ‘status 1’ or ‘status 2’.

Note: the module requires pump running or flow confirmation signals. Do NOT use pump trip signals.

Number of Pumps
The Secondary Circuit Controller with Pump Changeover can control either a Twin Pump Set or a Single Pump, both offering features for flow detection, run on and hours run monitoring. Set NPMP =1 if only 1 pump is controlled, using ‘output 1’.

Duty Sharing
The Secondary Circuit Controller with Pump Changeover shares pump running times by automatically changing the duty pump allocation. This will occur each time the pump set is started, or after running the duty pump for the period set by parameter MXHR, whichever occurs first.

The duty pump allocation can be changed by pressing the override button briefly.

Pump Time Interlock Settings
The duty pump will run for the minimum run time set by parameter MNON. The pump minimum off time is fixed to 1 minute.

If parameter RNON is set, after a period of running the pumps under Demand, the duty pump will continue to run for the period set by MNON.

Pump Exercise
The Secondary Circuit Controller with Pump Changeover will automatically exercise the duty pump by running it for the minimum run period MNON if the pumps have been off for a long period. Parameter MXDY sets the number of days which the pumps can be off without being exercised. Setting MXDY = 0 disables the pump exercise feature.

Alarm Handling

The Secondary Circuit Controller with Pump Changeover may be set to ignore alarm conditions or report them to a SeaChange Doorway Supervisor (either locally connected to the system, or via an autodialling modem). The ALRM parameter is used to select the desired Alarm Mode.

The Secondary Circuit Controller with Pump Changeover generates an alarm if a pump is called to run and no flow is seen on either input after the grace Delay time. The sense of the flow inputs can be set by parameter ALST.

The Secondary Circuit Controller with Pump Changeover may be set to respond to the STOP System Stop Alarm which is generated by another Controller; this can be used to shut down the entire control system, or parts of it, if a particularly critical event occurs. See Boiler Controller datasheets B1 or B2 for more details about the System Stop Alarm.

Alarm codes as they appear at Doorway Supervisor and InSite tool:

See Failure Modes and Clearing Fault Conditions sections.

Local Indication of Alarms
Failure of the duty pump is indicated by the fault indicator flashing alternately red and green.
Failure of both duty and standby pumps is indicated by the fault indicator flashing red.

Failure Modes

Duty Pump Failure
When the duty pump starts, the Secondary Circuit Controller waits for a grace period set by DLAY. After the grace period has elapsed, if flow status is not seen on either input, the Controller will switch off the duty pump output, switch on the standy pump output, and switch on the Sounder output C.

Failure of the duty pump is indicated by the fault indicator flashing alternately red and green.

Duty and Standby Pump Failure
If following a duty pump failure, the standby pump also fails to generate flow status, then the Controller will take action according to the Failure Mode set by FMD.

Failure of both duty and standby pumps is indicated by the fault indicator flashing red.

Clearing Fault Conditions
A fault condition can be cleared manually by pressing the Override pushbutton, and will occur automatically at the end of Occupancy if ACLR = 1 (default).

In some applications it may be desirable to latch the alarm in a Failure Mode condition, so that manual intervention is required before plant is brought on again.

The auto clear function can be disabled by setting ACLR = 0.

Submodules

The Secondary Circuit controller can have up to 2 actuator submodules registered to it, and also up to 8 condensation sensors sharing a common address.

Condensation Sensor
Intelligent condensation sensors can be registered to cooling versions of the Secondary Circuit controller. The state of the condensation sensors can be monitored on input I4 and if the alarm mode is set, can be used to generate alarms. Up to 8 sensors can be registered, sharing the same cloned address.

When the sensor detects that condensation is present, the cooling demand is progressively reduced to zero. Cooling control recovers a few minutes after condensation is no longer present.

Frost Protection

If the Boiler Controller (which is responsible for global Frost Protection in a SeaChange system) enters Frost Protect mode, the Secondary Circuit Controller will run its pump set if FRPT = 1.

Sensors and Plots
The run hours for each pump are available as sensor1 and sensor 2 and these are plotted for the last 96 days using the normal Doorway plots. The stored hours run for each pump can be reset using Switches 3 & 4. The maximum hours counted before roll over is 9999 hours.

The plot configuration parameters have been added so that InSite can determine that the plots exist, these parameters are not changeable since the hours run plot is a special case of the plotting routine and is not configurable. The plot provides the daily hours run for the last 96 days, this is best plotted as a bar graph.

Commissioning

Manual Override

Allows the outputs to be exercised during commissioning and maintenance activities. Holding the override button pressed until the Status Lamp flashes green will cause the controller to be switched from automatic control to Override Mode. Subsequent pressings of the manual override button will cycle through the available Override modes.

1. Hold down Override until Status lamp flashes
   Controller changes to Override Mode and runs pump set.
2. Press Override again
   Controller cancels Manual Override and reverts to automatic control.
   

As this feature does not time out, care should be exercised to ensure the module is returned to the automatic mode on completion of the commissioning or maintenance activities.

Occupancy Override can also be achieved via Doorway and InSite; using AUTO and OVRD monitoring parameters. The status lamp indication shows a different sequence.

Override from Off to ON : Status lamp flashes long ON, short Off
Override from ON to Off : Status lamp flashes long Off, short ON
See our ‘Design Guide’ publication for details of the Override features.

Registration

Registration is the simple process by which logical connections are made between Controllers in a SeaChange system; it is done during commissioning and involves pressing buttons on the Controllers in a specific sequence.

For further details of the registration process, see our ‘Design Guide’ publication.

Address Allocation and System Housekeeping

Like all SeaChange Controllers, the Secondary Circuit Controller must be registered with other modules in order to create a working system. During the Registration procedure, the address of each Controller is allocated by the module that contains System Housekeeping. Check that you have an appropriate System Housekeeping Module; see our ‘Design Guide’ publication.

Interconnects

The Secondary Circuit controller may receive signals from a Zone Controller or other Consumer module, either by Zone Energy Demand or Zone Occupancy Demand signals (see Occupation State section). It may also send signals to other modules (e.g. an Actuator submodule).

These Interconnects are put in place by Registration; again, see our ‘Design Guide’ publication.

Options and Product Codes
Secondary Circuit Controller with Pump Changeover

CTU / DIN / PCO / 3T / [driver option]

Driver options

SC Controls Ltd

PO Box313
Wadhurst
East Sussex
TN5 6JL

phone 08707 606040
fax 08707 606041
e-mail seachange@sccontrols.co.uk
http:// www.seachange.co.uk