Carrier Pro-Dialog CONTROL 4 Manual de usuario descargar pdf (Pagina 16)



This contact checks the status of a loop (air ﬂow switch

and customer safety loop, see chapter 3.6). It prevents the

unit from starting if it is open when the delay at start-up has

expired. This open contact leads to an alarm shut-down, if

the unit is running.



The control point represents the air temperature that the

unit must control.

Control point = active setpoint + reset

5.3.1 - Active setpoint

Two setpoints can be selected. Usually, the second setpoint

is used for unoccupied periods.

Depending on the current operating type, the active setpoint

can be selected:

• by choosing the item in the GENUNIT menu,

• via the user’s volt-free contacts,

• via network commands

• via the setpoint timer program (schedule 2).

The following table summarises the possible selections

depending on the control types (local, remote or network)

and the following parameters:

• Setpoint select in local control: item LSP_SEL in the

GENUNIT menu permits selection of the active setpoint,

if the unit is in local operating type.

• Setpoint selection contacts: setpoint selection contact

status.

• Schedule 2 status: schedule for setpoint selection.

 











 



Local sp1 - - Occupied

Local sp2 - - Unoccupied

Local auto - Occupied Occupied

Local auto - Unoccupied Unoccupied

Remote - sp1 - Occupied

Remote - sp2 - Unoccupied

CCN sp1 - - Occupied

CCN sp2 - - Unoccupied

CCN auto - Occupied Occupied

CCN auto - Unoccupied Unoccupied

5.3.2 - Reset

Reset means that the active setpoint is modiﬁed so that less

machine capacity is required. This modiﬁcation is in

general a reaction to a drop in the load. For the Pro-Dialog

control system, the source of the reset can be conﬁgured in

the SETPOINT menu: it can be provided either by the

outdoor temperature (that gives a measure of the load

trends for the building) or imposed by the user.

In response to a drop in the outdoor temperature or to

user reset, the setpoint is reset to optimise unit performance

or enhance comfort.

If correction, based on the outdoor temperature is selected,

it is in accordance with the diagram below.



A SETPOINT/corhioat

B SETPOINT/corlooat

C SETPOINT/oat1_cor

D SETPOINT/oat2_cor

-3

-1

-20

OAT, °C

Setpoint correction = f(OAT)



The demand limit is used to restrict the unit power consump-

tion. The Pro-Dialog control system allows limitation of

the unit capacity, using user-controlled volt-free contacts.

The unit capacity can never exceed the limit setpoint acti-

vated by these contacts. The limit setpoints can be modiﬁed

in the SETPOINT menu.



The night period is deﬁned (see GENUNIT conﬁguration)

by a start time and an end time that are the same for each

day of the week. During the night period, the number of

fans operating can be reduced, and the unit capacity may

be limited.



This function adjusts the number of active compressors to

keep the air temperature at its setpoint. The precision with

which this is achieved depends on the air volume, the ﬂow

rate, the load, and the number of stages available on the unit.

The control system continuously takes account of the

temperature error with respect to the setpoint to determine

the optimal moment at which to add or withdraw a capacity

stage.

If the same compressor undergoes too many starts (per

hour) or runs below one minute each time it is started this

automatically brings about reduction of compressor starts,

which makes the controlled air temperature less precise.

The high and low pressure unloading functions can also affect

temperature control accuracy. Compressors are started and

stopped in a sequence designed to equalise the number of

start-ups (value weighted by their operating time).

1 2 ... 11 12 13 14 15 16 17 18 19 20

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Carrier Pro-Dialog CONTROL 4 Manual de usuario Pagina 16

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