56
To find out the operating limits for each unit, based on the
brine type and the brine concentration, please refer to the
selection software.
Leaving water temperature, °C
Outside air temperature, °C
With propylene glycol at 40%
11.5.1 - Frost protection
The evaporator low pressure and frost protection depends
on the amount of antifreeze added to the water circuit
(evaporator approach as well as frost protection are based
on this amount).
It is therefore essential to control the amount of antifreeze
in the water loop at the first start-up (circulate for 30 minutes
to ensure good homogeneity of the mixture before taking
the sample). Refer to the manufacturer’s data to define the
frost protection, based on the concentration rate measured.
The frost protection value (temperature) must be used in
the unit software parameters (see Carrier Service Guide).
This value will allow the definition of the following limits:
1. Evaporator frost protection
2. Low pressure protection
It is recommended that the commissioning of a brine system
is done by Carrier.
For information: The protection values given by our supplier,
based on the antifreeze solutions used in the Carrier
Montluel laboratory, are as follows: (these values can change
for different suppliers).
10 -3.8 10 -2.6
15 -6.1 15 -4.3
20 -8.8 20 -6.6
25 -11.8 25 -9.6
30 -15.2 30 -13
35 -19.1 35 -16.7
40 -23.6 40 -20.7
45 -29 45 -25.3
Based on the table above, if the ethylene glycol concentration
by weight in the water loop is 35% the value of -19.1°C
must be used in the software.
It is essential to carry out an annual check (minimum) of the
amount of glycol, and adjust the frost protection value in
the software based on the rate measured. This procedure
must be systematic, if water or antifreeze solution is added.
Similarly, the four configuration examples shown above
also cover the application on the other 30RB units.
IMPORTANT: The unit duct connection must not create
any mechanical constraint on the fan support deck.
The fan housings 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 outlet of each duct provide an access hatch with a
minimum size of 700 x 700 mm to allow motor replacement
and disassembly of the fan wheel.
Fan motor electrical protection
In case of a locked rotor or an overload, the motors of
each circuit are electrically protected by the circuit drive.
Each drive follows a variable current characteristic, based
on the frequency from 10 to 60 Hz and the number of fans
controlled.
If a fan is not operating correctly, the drive automatically
detects the problem and sends an alert to the Pro-Dialog
display. Please refer to the Pro-Dialog control manual for
the list of specific alarms for this option.
This option allows production of brine down to -10°C. The
unit is equipped with reinforced evaporator insulation as
well as suction pipe insulation. The operating range is a
function of the suction pressure, which in turn is a function
of:
- the brine type,
- the brine concentration,
- the flow rate,
- the brine temperature,
- the condensing pressure (ambient temperature).
Example: For operation with propylene glycol at 40% and a
brine temperature of -10°C (entering temperature -5°C), the
maximum ambient operating temperature will be around 38°C.
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