Carrier 30WG 080 - 10 - NOMINAL WATER FLOW CONTROL WITH FIXED-SPEED PUMP; 10.1 General; 10.2 - Water flow control procedure

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9.3 - Frost protection
The units are designed to be installed under cover at outside
temperatures between +5 °C and +40 °C. Therefore they do
not include anti-freeze protection, as standard.
If the water piping is in an area where the ambient temperature
can fall below 0 °C it is recommended to install a trace heater
on the piping and to add an antifreeze solution 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 the freezing weather conditions,
draining of the cooler and outdoor piping is mandatory.
Damage due to freezing is not covered by the warranty.
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
heat exchanger water entering purge valve connection.
• • At the start of the next season, rell the unit with
water and add an inhibitor.
• • For the installation of auxiliary equipment, the installer
must comply with basic regulations, especially for
minimum and maximum ow rates, which must be
between the values listed in the operating limit table
(chapter 5 - “Application data”).
• • To avoid corrosion by differential aeration, the
complete heat exchange circuit must be charged with
nitrogen, if it is drained for longer than one month. If
the heat exchange uid does not comply with Carrier
recommendations, the circuit must immediately be lled
with nitrogen.
9.4 - Flow switch (units without hydronic module)
IMPORTANT: On 61WG/30WG/30WGA units, the unit
water ow switch must be energised, and the chilled water
pump interlock must be connected. Failure to follow this
instruction will void the Carrier guarantee.
The ow switch is supplied, installed on the evaporator
leaving water pipe and preset at the factory to cut out when
there is insufcient water ow.
Terminals 34 and 35 are provided for eld installation of the
chilled water pump interlock (auxiliary contact for pump
operation to be wired on site).
10 - NOMINAL WATER FLOW CONTROL WITH FIXED-
SPEED PUMP
10.1 - General
The water circulation pumps of the 61WG/30WG units have
been sized to allow the hydronic modules to cover all possible
congurations based on the specic installation conditions,
i.e. for various temperature differences between the entering
and the leaving water (∆T) at full load, which can vary
between 2.5 and 7 K for evaporators and 3 and 18 K for
condensers.
This required difference between the entering and leaving
water temperature determines the nominal system ow rate.
It is above all absolutely necessary to know the nominal
system ow rate to allow its control via a manual valve.
Manual control valves for the unit are not supplied and must
be installed upstream and downstream of the evaporator and
condenser water loops to ensure correct ow control.
With the pressure loss generated by the control valve in the
hydronic system, the valve is able to impose the system
pressure/ow curve on the pump pressure/ow curve, to
obtain the desired operating point (see example).
The pressure drop reading in the plate heat exchanger is used
to control and adjust the nominal system ow rate. The
pressure drop is measured with the pressure sensors
connected to the heat exchanger water inlet and outlet.
Use this specication for the unit selection to know the
system operating conditions and to deduce the nominal air
ow as well as the plate heat exchanger pressure drop at the
specied conditions. If this information is not available at the
system start-up, contact the technical service department
responsible for the installation to get it.
These characteristics can be obtained from the technical
literature using the unit performance tables or the Electronic
Catalogue selection program for all conditions.
10.2 - Water fow control procedure
As the total system pressure drop is not known exactly at the
start-up, the water ow rate must be adjusted with the control
valve to obtain the specic ow rate for this application.
Proceed as follows:
Open the valve fully.
Start-up the pump using the forced start command (refer to
the controls manual) and let the pump run for two consecutive
hours to clean the hydronic circuit of the system (presence
of solid contaminants).
Read the hydronic module pressure drop by taking the
difference of the readings at the machine connected to the
hydronic module inlet and outlet. Compare this value after
two hours of operation.