Carrier AQUASNAP 30RBP Installation, Operation And Maintenance Instructions page 85

12 - OPTIONS
Rules for a correct duct network
■ Each duct must serve a maximum of 2 fans – DO NOT EXCEED
this limit.
■ In case of multiple fans in the same duct, they must belong to
the same refrigerant circuit and to the same V coil
system – DO NOT MIX refrigerant circuits or V coil systems in
the same duct.
IMPORTANT:
The duct connections on the units must not generate any
mechanical stress on the fan supporting structure.
The fan shrouds and the fan protection grilles must always
remain in their position inside the ducts.
Use bellows or flexible sleeves for the duct connection.
At the start of each duct, install an access hatch measuring
at least 700 x 700 mm to allow maintenance of fan components
(motor replacement, removal of impeller).
Fan motor electrical protection
In case of a locked rotor or an overload, the motors of each circuit
are electrically protected by the circuit variable speed drive.
Each drive follows a variable current characteristic, based on the
frequency from 10 to 60 Hz and the number of controlled fans.
If a fan stops working, the variable drive will automatically detect
the malfunction.
Refer to the control manual for the list of alarms specific to this
option.
12.2.8 - TOTAL/PARTIAL FREE COOLING (Option
305A; 305B)
Reducing operating costs and protecting the environment have
become the key concerns, both for air conditioning applications,
and for industrial processes and cooling data centres.
The Free Cooling option allows significant energy savings to be
made in all applications that require cooling throughout the year,
particularly when used in colder climates. In these regions, Free
Cooling can be used to fulfil a large proportion of the cooling
requirements both economically and in a way that respects the
environment.
Operating principle
When the outdoor air temperature is lower than the setpoint
temperature, the Free Cooling hydraulic system can be used to
cool the customer loop by allowing fluid to circulate in the micro-
channel coils, positioned in parallel with the MCHE condensers.
With this type of operation, it is possible to save energy when
outdoor temperatures are low.
Hydraulic Free Cooling is available as 2 options:
■ 305A: Total hydraulic Free Cooling: the FC coils are built into
each condenser on two refrigerating circuits (available in glycol-
based process circuit version or Glycol-Free process circuit
version supplied using pure water).
■ 305B: Partial hydraulic Free Cooling: the FC coils are built into
the condensers on a single refrigerating circuit.
Advantage of the Free Cooling Glycol-Free system
In applications or countries in which the use of glycol is strictly
regulated or banned, the Free Cooling Glycol-Free option is
equipped with a separation heat exchanger, and only the circuit
inside the unit contains glycol, while the user circuit contains pure
water.
This solution with an intermediate exchanger shifts the Free
Cooling mode activation thresholds by a few degrees, and the
heat exchangers selected by Carrier help to minimise this shift.
85