Feature Notes
Pump Changeover Submodule with 3 x Triac Outputs
PCO / DIN / 3T / ...
Main Features Controls a Pair of Pumps or Fans providing Auto Changeover and Duty Rotation Can use Contactor status signals or Flow Proving Switches (single or dual) Hours Run logged for each Pump Pump Fail alarm output Pump Exercising Routine

Summary Features

General

The SeaChange PCO Changeover modules are Submodules, which can be used to extend the control capabilities of other SeaChange Modules. They can be used in conjunction with Boiler Controllers, for instance, to control primary or secondary twin pump sets and even twin flue dilution fans; or in conjunction with DHW and Secondary Circuit Controllers, to control associated twin pump sets.

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.

Operation

Changeover Submodules are driven by Control Demand signals from the module that they are registered to.

Different Driver Types may be selected to suit boiler, heating, or cooling applications.

Primary and VT pump variants allow twin pump sets to be controlled replacing the single pump outputs on a Boiler Controller.
Other variants allow twin pump sets to be controlled on the basis of Occupancy Times, Heating or Cooling Demand using Control Demand signals from other controllers.

Duty Rotation of the pump set occurs automatically each time the pump set is started, or after a specific number of hours run.
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 stays on, both off). Reset after pump failure can be Manual or Automatic.

Description of Features

Demand Control

The Changeover Submodule has no internal Occupation Time Schedules. Its operation is determined only by a Control Demand signal from the parent module it has been registered to.

The Control Demand interconnect signal from the parent module carries both the control loop demand output level and the parent module occupancy state.

Control based on Time only

Example : DHW Secondary Pumps
Twin Pump set controlled by Changeover Submodule registered to DHW Controller. Occupancy status information is encoded within the Control Demand interconnect. Choose a time based Heating variant e.g. PCO / DIN / 3T / 004

The Changeover Submodule will operate the pump set continuously during the Occupancy Times of the parent module, including Optimum Start and Stop.

Control based on Demand

Example : Heating Zone Pumps
Twin Pump set controlled by Changeover submodule registered to Zone Controller using Heating Control Demand output. Use variant PCO / DIN / 3T / 006.

The Changeover Submodule will operate the pump set only when there is a Heating Demand > 5% from the Zone Controller.

Example : Chilled Water CT Circuit Pumps
Twin Pump set controlled by Changeover Submodule registered to Secondary Circuit Controller using Cooling Control Demand output. Use variant PCO / DIN / 3T / 007.

The Changeover Submodule will operate the pump set only when there is a Cooling Demand > 5% from the Secondary Circuit Controller.

The Secondary Circuit Controller outputs can be interlocked with the pump set, so that they are held off until pump flow is proved. If pump set fails, the control outputs can be reset manually at the Secondary Circuit Controller. The pump set can automatically retry at next occupancy period. See Interlocks, Failure Modes and Clearing Fault Conditions sections.

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 Changeover Submodule 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 Changeover Submodule 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 Control Demand, the duty pump will continue to run for the period set by MNON.

Changeover Submodules controlling Primary or VT pump sets will have their pump run on time determined by the Boiler Controller they are registered to.

Pump Exercise

The Changeover Submodule 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.

Interlocks

Several SeaChange modules can be Interlocked to the Changeover Submodule in order to protect plant from running when there is no pump flow established. Examples are detailed in the Clearing Fault Conditions section.

Alarm Handling

The Changeover Submodule may be set to ignore alarm conditions, report them to a SeaChange Doorway Supervisor (either locally connected to the system, or via an autodialling modem), or to both report alarms and send STOP alarm to a Boiler Controller. The ALRM parameter is used to select the desired Alarm Mode.

The Changeover Submodule 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 Changeover Submodule 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:

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 submodule waits for a grace period set by DLAY. After the grace period has elapsed, if flow status is not seen on either input, the Changeover Submodule 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 Changeover Submodule 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.

Where the parent module does not have the facility to latch an alarm condition, the auto clear function in the Changeover Submodule can be disabled by setting ACLR = 0.

Examples of Clearing Dual Pump Failure Alarms:

Changeover Submodule (types 004 - 009 only) registered to Zone Controller:

Changeover Submodule (types 001, 002 only) registered to Boiler Controller:

Changeover Submodule (types 004,005,006 only) registered to DHW Controller:

Changeover Submodule (types 004,007 only) registered to Secondary Circuit or Chiller Controller:

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 Changeover Submodule 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 Changeover Submodule will receive Control Demand signals from other modules to determine when it operates. (see Demand Control section).

See our ‘Design Guide’ publication for details of how to create interconnects.

Options and Product Codes

Changeover Submodule

PCO / DIN / 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