30 July 1996

Functional Description: Pump Changeover Module PCO-DIN

This module provides control for pairs of pumps where automatic changeover on failure of a pump is required. The module has a relay output for each pump and two flow detection inputs. The flow condition must be indicated by shorting the input pins with a volt free contact.

The PCO node can be registered to a Boiler Controller, VT controller, CT controller, DHW Controller or a Zone controller.

On receipt of a command to run the pump, the pump which has been off longest will be started, if after the flow proving 'delay' (set by config variable DLAY, default 10seconds) neither of the two inputs have been made then the first pump will be stopped and the other pump started. This condition is indicated by the top LED alternating red and green. If again no proof of flow is received then both pumps will be run this is indicated by the top LED flashing red.

The error condition is reset by the flow proving signal being reinstated or by the command signal being removed, i.e. it will start with no error at commencement of the next occupied period.


During normal operation the top LED will be steady green, the lower status LED will show green if the controlling device 'is occupied'.

Registration

The PCO module has a TYPE configuration variable, this must be set up , probably at the factory, to determine the type of pump set to be controlled and the type of module to which the PCO will be registered. The first three type values are used when the PCO is to be registered with a Boiler controller and it will then take over the pump control for Primary, VT or DHW pumps as defined by the TYPE value.

The remaining types register the PCO module as an 'actuator' to any module which allows the registration of actuators. The types select the method of pump control, OSS, OCC or when the demand is greater than 5%, thus allowing the pumps to be stopped when there is no demand. This is summarised in the following table.

TYPE

BLR VT

BLR DHW

DHW

ZONE

1

Primary

Primary

2

VT

Heating

3

DHW

4

OSS

Heating OSS

5

OCC

Heating OCC

6

>5% demand

Heating >5%

7

Cooling OSS

8

Cooling OCC

9

Cooling >5%

If the PCO is registered to another node but it's type value is inconsistent, e.g. type value 2 but registered to a DHW controller, the top LED will flash amber to warm the type is set incorrectly.

When registering a PCO module to a boiler controller, the boiler controller must be version 2q or later and the boiler controller must be put into config mode. This is because the PCO is the first module which can be registered to either a zone type module or a boiler type module so it is essential that the appropriate module is identified by selecting config mode. A maximum of three PCOs can be registered to a Boiler controller.

For registration with Zone, VTC, CTC, DHW controllers a PCO is treated like any other actuator and must be counted as one of the allowable eight actuators per controller.

The code will run on ACT-DIN-RLY  or ACT-PTR-RLY hardware.