Carrier 30HX PRO Especificaciones descargar pdf (Pagina 31)

Master/slave operation requires the connection of a temperature

probe at the common manifold on each machine, if the heat

exchanger leaving water temperature is controlled.

The master/slave assembly can operate with constant or variable

flow. In the case of variable flow each machine must control its

own water pump and automatically shut down the pump, if the

cooling capacity is zero. For constant flow operation the pumps

for each unit are continuously operating, if the system is opera-

ting. The master unit can control a common pump that will be

activated, when the system is started. In this case the slave unit

pump is not used.

All control commands to the master/slave assembly (start/stop,

setpoint, heating/cooling operation, load shedding, etc.) are

handled by the unit which is configured as the master, and must

therefore only be applied to the master unit. They will be trans-

mitted automatically to the slave unit. The master unit can be

controlled locally, remotely or by CCN commands. Therefore

to start up the assembly, simply validate the Master operating

type (MASt) on the master unit. If the Master has been confi-

gured for remote control then use the remote volt-free contacts

for unit start/stop. The slave unit must stay in CCN operating

type continuously. To stop the master/slave assembly, select

Local Off (LOFF) on the master unit or use the remote volt-

free contacts if the unit has been configured for remote control.

One of the functions of the master unit (depending on its con-

figuration) may be the designation, whether the master or slave

is to be the lead machine or the follower. The roles of lead

machine and follower will be reversed when the difference in

running hours between the two units exceeds a configurable

value, ensuring that the running times of the two units are

automatically equalised. The changeover between lead machine

and follower may take place when the assembly is started up,

or even whilst running. The running time balancing function is

not active if it has not been configured: in this case the lead

machine is always the master unit.

The lead machine will always be started first. When the lead

machine is at its full available capacity, start-up delay (confi-

gurable) is initialised on the follower. When this delay has

expired, and if the error on the control point is greater than 1.7°C,

the follower unit is authorised to start and the pump is activated.

The follower will automatically use the master unit active set-

point. The lead machine will be held at its full available capa-

city for as long as the active capacity on the follower is not

zero. When the follower unit receives a command to stop, its

evaporator water pump is turned off with 20 seconds delay.

In the event of a communication fault between the two units,

each shall return to an autonomous operating mode until the

fault is cleared. If the master unit is halted due to an alarm, the

slave unit is authorised to start without prior conditions.

5.23 - Controlling Pro-Dialog Plus units with a System

Manager

Up to eight PRO-DIALOG Plus units (or System Manager

compatible units) can be controlled by one control module of

the FSM or CSM III type which can handle multi-tasking of

control functions such as starting units in sequence.

5.24 - Optional heat reclaim module

This option only applies to air-cooled units, equipped with a

water-cooled heat reclaim condenser. An additional 4 x DO

board must be installed. This board permits control of:

• two solenoid shutoff valves for the heat reclaim coil, one

per circuit.

• two drain solenoid valves, one per circuit. These permit

draining the refrigerant from the inactive coil, when the

unit changes over from the cooling mode to the heat

reclaim mode.

Selecting the heat reclaim mode can be done with either the

local interface or remotely with the (recl_sw) contact or by CCN.

The heat reclaim function is active when: the heat reclaim

entering water temperature is lower than the heat reclaim

setpoint, minus half of the heat reclaim dead band.

The heat reclaim function is not active when: the heat reclaim

entering water temperature is higher than the heat reclaim

setpoint, plus half of the heat reclaim dead band.

In the dead band the function remains in its active mode. The

default value of the dead band is 4.4°C. This value can be

modified by Carrier Service.

Change-over procedure from cooling mode to heat reclaim

mode:

• Start-up of the condenser pump

• Verification of the condenser flow switch control contact.

If this remains open after one minute of condenser pump

operation, the circuit remains in cooling mode and alarm

83 for circuit A (alarm 84 for circuit B) will be activated.

• As soon as the saturated condensing temperature reaches

30°C and the superheat reaches 8.3 K, the pumpdown

sequence is activated.

• Pumpdown: closing of the cooling mode coil shutoff

valve. Opening of the drain valve, closing of the EXV

valve.

• When the pumpdown pressure reaches the end of the

pump-down threshold, the pumpdown valve is closed and

the heat reclaim function is effective.

Item 17 and 18 of the INFORMATION menu permits consulting

different heat reclaim function sequences:

17 = sequence of circuit A

18 = sequence of circuit B

0 = cooling mode

1 = heat reclaim mode selection

2 = pumpdown sequence

3 = effective heat reclaim mode

4 = pumpdown fault*

5 = water flow switch fault*

* Alarm 83 for circuit A or 84 for circuit B is activated. Consulting the items 17

and 18 gives cause as (4) or (5). Resetting of the alarms re-initialises the

information.

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Carrier 30HX PRO Especificaciones Pagina 31

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