26
7.3 - flow detection
Evaporator flow switch and chilled water pump interlock
IMPORTANT: It is mandatory that the water flow switch
must be energised while the machine is in operation.
Failure to follow this instruction will void the Carrier
guarantee.
The water flow switch is installed on the evaporator water
inlet and adjusted by the controls, based on unit size and
application. If adjustment is necessary, it must be carried
out by qualified personnel trained by Carrier Service.
Terminals 34 and 35 are provided for field installation of
the chilled water pump interlock (auxiliary contact for pump
operation to be wired on site).
7.4 - Evaporator water box bolt tightening
The evaporator is of the shell and tube type with
removable water boxes to facilitate cleaning. Re-tightening
or tightening must be done in accordance with the
illustration below.
Water box tightening sequence
legend:
Sequence 1 : 1 2 3 4
Tightening torque
Sequence 2 : 5 6 7 8
Bolt size
Sequence 3 : 9 10 11 12
M16 - 171 - 210 Nm
Sequence 4 : 13 14 15 16
NOTE: Before this operation we recommend draining the
circuit and disconnecting the pipes to be sure that the bolts
are correctly and uniformly tightened.
7.5 - freeze protection
The evaporator, the pipes and the hydronic module pump
might be damage by freeze. The components of the unit
(evaporator and hydronic module) will be protected by
following the recommendations below. Protection of the
remainder of the system is the responsability of the
installer. Damage due to freezing is not covered by the
warranty.
7.5.1 - standard machine
If the chiller or the water piping is in an area where the
ambient temperature can fall below 0 °C it is
recommended to add an antifreeze solution (45%
maximum, 40% in case of unit with hydronic module) to
protect the unit and the water piping to a temperature of
10 K below the lowest temperature likely to be reached at
the installation site. Use only antifreeze solutions,
approved for heat exchanger duty. If the system is not
protected by an antifreeze solution and will not be used
during freezing weather conditions, draining of the cooler
and outdoor piping is mandatory. Damage due to freezing
is not covered by the warranty.
7.5.2 - optional evaporator freeze protection (30XaV-Ze)
In cases where it is not possible to apply the recommenda-
tions in paragraph 7.5.1, the units can be equipped with
heaters to protect the evaporator against freeze (option
41A or 41B with hydronic kit). The antifreeze solution and
heaters can be combined.
Freeze protection of units with hydronic modules requires
that water circulates in the hydraulic circuit. The unit
mounted pump will start, automatically, periodically.
To verify that the heater circuit is 'live'. See Chapter -
“Standard maintenance”.
IMPORTANT: Depending on the climatic conditions in
your area you must:
•
Add ethylene glycol with an adequate concentration
to protect the installation up to a temperature of 10
K below the lowest temperature likely to occur at the
installation site.
•
If the unit is not used for an extended period, it is
recommended to drain it, and as a safety precaution
add ethylene glycol to the heat exchanger, using the
drain point located near the water inlet connection
(a purge connec-tion is available somewhere on the
heat exchanger water box in case the machine is not
perfectly level).
•
At the start of the next season, refill the unit with water
and add an inhibitor.
•
For the installation of auxiliary equipment, the instal-
ler must comply with basic regulations, especially for
minimum and maximum flow rates, which must be
between the values listed in the operating limit table
(application data).
7.6 - Protection against cavitation (with option 116)
To ensure the durability of pumps fitted with hydronic
modules, the control algorithm of 30XAV-ZE units
includes protection against cavitation. A pressure below 80
kPa will prevent the unit from starting, or will cause a
shutdown.
To obtain an adequate pressure, it is recommended:
•
to pressurise the hydronic circuit between 100 kPa
(1 bar) and 400 kPa (4 bars) maximum at the pump
inlet
•
to clean the hydronic circuit during water filling or
during its modification
•
to regularly clean the screen filter.
