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6- STANDARD CONTROL OPERATIONS AND OPTIONS
6.1 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 SmartVu control. The function is only
active when operating type Thermostat (TSTAT) is selected
in the GENCONF menu.
In this operating type, the thermostat controls the
following functions:
•
Stopping/starting the internal fan
•
Determining the space temperature control point,
•
Selecting heating/cooling
•
Controlling compressor capacity, gas or electric
•
Controlling the economizer (fully open position or
minimum closed position only).
The SmartVu 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 hot-water system
•
Timer programming
•
Purge.
The description of the thermostat outputs, based on the
unit type, is given in the chapter 3.6 -
“Connections at the
user terminal block”.
6.2 Cooling only unit
•
Contact G open: The internal fan is stopped and the
economizer is closed.
•
Contact G closed: The internal fan is activated and the
•
economizer is opened to its minimum position.
•
Contact Y1 closed and Y2 open: If the unit is fitted with
an economizer, it is opened to its maximum position, if
•
external conditions permit (see chapter 5.16 -
“Economizer”).
•
Otherwise the economizer is set to its minimumposition
and the first compressor is started up. If the unit has no
economizer, the first compressor is started up.
Contacts Y1 and Y2 closed: The economizer is held fully
open if external conditions are still acceptable. A compressor
is started up. If external conditions nolonger permit the
economizer to be used, it is set to itsminimum position and
the second compressor is started up. If the outdoor
temperature is lower than 15°C, thecompressors will not be
authorised to start up and onlythe economizer will be used. If
the unit has no economizer, 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.
6.3 Single-circuit heat pump unit
•
Contact G open: The internal fan is stopped and the
economizer is closed.
•
Contact G closed: The internal fan is activated and the
economizer is opened to its minimum position.
•
Contact O closed and Y closed: If the unit is fitted with
an economizer, it is modulated to maintain the minimum
supply air temperature setpoint at +2.8°C, if external
conditions permit (see chapter 5.16 -
“Economizer”).
Otherwise the economizer is set to its minimum position
and the compressor is started up in cooling mode. If
the unit has no economizer, the compressor is started
up in cooling mode.
•
Contacts O open and Y closed: If the unit is fitted with an
economizer, 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.
6.4 Dual-circuit/dual-compressor heat pump unit
•
Contact G open: The internal fan is stopped and the
economizer is closed.
•
Contact G closed: The internal fan is activated and the
economizer is opened to its minimum position.
•
Contact O closed, Y1 closed and Y2 open: If the unit is
fitted with an economizer, it is opened to its maximum
position, if external conditions permit (see chapter 5.16 -
“Economizer”). Otherwise the economizer is set to its
minimum position and the first compressor is started up
in cooling mode. If the unit has no economizer, the first
compressor is started up in cooling mode.
•
Contacts O, Y1 and Y2 closed: The economizer 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 economizer 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 economizer will be
used. If the unit has no economizer, the second
compressor is started up in cooling mode.
•
Contact O open, Y1 closed and Y2 open: If the unit is
fitted with an economizer, it is set to its minimum
position and the first compressor is started up in heating
mode. If the unit has no economizer, the first
compressor is started up in heating mode.
•
Contact O open, Y1 and Y2 closed: The economizer 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
