Carrier AQUASNAP JUNIOR 30RA015 Скачать руководство пользователя страница 39

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Variable cooler flow rates

Variable rates may be applied to standard chiller. Unit will,
however, attempt to maintain a constant leaving chilled
fluid temperature. In such cases, minimum flow must be in
excess of minimum flow given in Minimum and Maximum
Cooler Flow Rates table on page 38 and Minimum Fluid
Volume in Circulation table below. Flow rate must also
change in steps of less than 10% per minute. Apply 6 gal.
per ton (6.5 L per kW) water loop volume minimum if flow
rate changes more rapidly.

Fluid loop volume

The minimum volume of fluid required to be in circulation
is a function of the number of compressors in the chiller as
well as the type of application. The minimum fluid in circu-
lation must equal or exceed the values in the following ta-
ble. Note that in process cooling applications, or for oper-
ation at ambient temperatures below 32 F (0° C) with low
loading conditions, there should be more volume than is re-
quired for normal air-conditioning applications.

MINIMUM FLUID VOLUME IN CIRCULATION

To achieve this fluid volume, it is often necessary to install
a tank in the loop. The tank should be baffled to ensure
there is no stratification and that water (or brine) entering
the tank is adequately mixed with liquid in the tank.

Tank volume

A properly baffled storage tank is available as an accessory.
These tanks are designed to physically fit beneath the
corresponding 30RA unit, taking up the same footprint.
Available volume is as follows:
30RA010-018

110 gallons (416 liters)

30RA022-030

152 gallons (575 liters)

30RA035-055

305 gallons (1155 liters)

NOTE: This tank requires a separate 230/1/60 power
source.

Strainers

A strainer with a minimum of 20 mesh must be installed in
the cooler fluid inlet line, just ahead of (and as close as pos-
sible) to the cooler.

Water system overview (closed loop systems
only)

The 30RA chillers are designed for use with closed sys-
tems, meaning that there is no more than one water-air
interface in the water loop. Cooling tower loops, for exam-
ple, have two water-air interfaces (sump and nozzles) and
would thus be classified as open, whereas a correctly
designed chilled water loop with the only water-air inter-
face being in the expansion tank is closed. Since closed
and open water systems behave very differently, the follow-
ing assumes that the chilled water loop is closed. A system
installed incorrectly such that air is not handled properly —
pipe leaks, vent leaks, air in pipes, etc. — may behave as
an open system and thus have unsatisfactory operation.
Pump seal wear can also cause leaks that cause poor sys-
tem operation.
Proper closed system design and installation procedures
should be followed closely. The system must be con-
structed with pressure tight components and thoroughly
tested for installation leaks. Factory-supplied hydronic sys-
tems are available with single or dual (for back-up) pumps.
The factory-installed system includes all of the components
within the dashed lines shown in the figure on page 29.
Installation of water systems should follow sound engi-
neering practice as well as applicable local and industry
standards. Improperly designed or installed systems may
cause unsatisfactory operation and/or system failure. Con-
sult a water treatment specialist or appropriate literature
for information regarding filtration, water treatment, and
control devices. A typical installation with components that
might be installed with the hydronic package of the 30RA
unit is shown on page 29. A typical dual pump package for
the 010-030 size models is shown on page 40.
It is recommended that isolation (shut-off) valves be placed
exterior to the unit to allow removal and service of the
entire pump assembly, if necessary. Also, if the unit is iso-
lated with valves, a properly sized pressure relief valve
should be installed in the piping between the unit and the
valves, following all applicable state and local codes.