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5 - PRO-DIALOG PLUS CONTROL OPERATION
5.1 - External thermostat control
In appropriate cases the unit may be controlled by an external
thermostat approved by Carrier. This function requires the use
of a thermostat with volt-free contacts (contacts without
potential), as well as a specific configuration of the Pro-Dialog
control. The function is only active when operating type
Thermostat (tStA) is selected.
In this operating type, the thermostat controls the following
functions:
•
stopping/starting the internal fan,
•
determining the room temperature control point,
•
selecting heating/cooling,
•
controlling compressor capacity, gas or electric,
•
controlling the economiser (fully open position or
minimum closed position only).
The PRO-DIALOG Plus system continues to control the
following functions:
•
defrosting related to the heat pumps,
•
head pressure control,
•
power exhaust control,
•
minimum stop/start times on the compressors,
•
unit diagnostics.
The following functions are disabled:
•
humidification,
•
controlling a proportional hot water system,
•
timer programming,
•
IAQ,
•
demand limit,
•
third stage electric heater (50AZ only).
The description of the thermostat outputs, based on the unit
type, is given in sections 3.6 and 4.3.9.
Cooling only unit
•
Contact G open: the internal fan is stopped and the econo-
miser is closed.
•
Contact G closed: the internal fan is activated and the
economiser is opened to its minimum position.
•
Contact Y1 closed and Y2 open: if the unit is fitted with an
economiser, it is opened to its maximum position if external
conditions permit (see section 5.16). Otherwise the econo-
miser is set to its minimum position and the first compressor
is started up. If the unit has no economiser, the first
compressor is started up.
•
Contacts Y1 and Y2 closed: the economiser is held fully
open if external conditions are still acceptable. A compres-
sor is started up. If external conditions no longer permit
the economiser to be used, it is set to its minimum position
and the second compressor is started up. If the outdoor
temperature is lower than 15
°
C, the compressors will not be
authorised to start up and only the economiser will be used.
If the unit has no economiser, the second compressor is
started up.
•
Contact W1 closed and W2 open: the first gas or electric
stage is started.
•
Contacts W1 and W2 closed: the second gas or electric
stage is started.
Single-circuit reversible unit
•
Contact G open: the internal fan is stopped and the econo-
miser is closed.
•
Contact G closed: the internal fan is activated and the
economiser is opened to its minimum position.
•
Contact O closed and Y closed: if the unit is fitted with an
economiser, it is opened to its maximum position if external
conditions permit (see section 5.16). Otherwise the
economiser is set to its minimum position and the
compressor is started up in cooling mode. If the unit has no
economiser, the compressor is started up in cooling mode.
•
Contacts O open and Y closed: if the unit is fitted with an
economiser, it is set to its minimum position and the first
compressor is started up in heating mode.
•
Contact W1 closed and W2 open: the first gas or electric
stage is started.
•
Contacts W1 and W2 closed: the second gas or electric
stage is started.
Twin-circuit reversible unit
•
Contact G open: the internal fan is stopped and the econo-
miser is closed.
•
Contact G closed: the internal fan is activated and the
economiser is opened to its minimum position.
•
Contact O closed, Y1 closed and Y2 open: if the unit is
fitted with an economiser, it is opened to its maximum
position if external conditions permit (see section 5.16).
Otherwise the economiser is set to its minimum position
and the first compressor is started up in cooling mode. If the
unit has no economiser, the first compressor is started up in
cooling mode.
•
Contacts O, Y1 and Y2 closed: the economiser is held
fully open if external conditions are still acceptable. A
compressor is started up in cooling mode. If external
conditions no longer permit the economiser to be used, it
is set to its minimum position and the second compressor
is started up in cooling mode. If the outdoor temperature is
lower than 15
°
C, the compressors will not be authorised to
start up and only the economiser will be used. If the unit
has no economiser, the second compressor is started up in
cooling mode.
•
Contact O open, Y1 closed and Y2 open: if the unit is fitted
with an economiser, it is set to its minimum position and the
first compressor is started up in heating mode. If the unit has
no economiser, the first compressor is started up in heating
mode.
•
Contact O open, Y1 and Y2 closed: the economiser is held
in its minimum position. The second compressor is started
up in heating mode.
•
Contact W1 closed: the first gas or electric stage is started.
NOTE: All compressor anti-short cycles remain activated
when the unit is under the control of an external thermostat.
