Set Water Flow Rate; Pump Modification/Trimming - Carrier 30RB060-390 Installation Instructions Manual

Head Pressure
(m) ft of fluid
LEGEND
NPSHr — Net Positive Suction Head (Pressure) Required
NOTE: Refer to the 30RB nomenclature, Fig. 1, for option identification. Refer to the Pump Impeller Sizes, Table 6, for more information.
Fig. 51 — Pump Curve VIIIB for Hydronic Package Dual Pump (Fresh Water)
Normally, a closed system needs to be filled only once. The
actual filling process is a fairly simple procedure. All air should
be purged or vented from the system. Thorough venting at high
points and circulation at room temperature for several hours is
highly recommended.
NOTE: Local codes concerning backflow devices and other
protection of the city water system should be consulted and
followed to prevent contamination of the public water supply.
This is critical when antifreeze is used in the system.
SET WATER FLOW RATE — Once the system is cleaned,
pressurized, and filled, the flow rate through the chiller and
heat reclaim needs to be established. Refer to the Job Sub-
mittal for flow rate requirements. See the Controls and
Troubleshooting literature for operating limits. On units
with the hydronic package, this can be accomplished by
using the balancing valve. Follow the manufacturer's rec-
ommendations for setting the balancing valve. Local codes
may prohibit restricting the amount of water using the bal-
ancing valve for a given motor horsepower. In this case, use
the method listed in the Pump Modification/Trimming sec-
tion. See Table 7 for the type of combination valve in 30RB
units with the optional hydronic package.
Table 7 — Combination Valve Details
30RB UNIT
060-130
150-190
NOTE: Carrier recommends a differential pressure gage when
measuring pressures across the pumps or balancing valves.
This provides for greater accuracy and reduces error build-up
(42.7) 140
(36.6) 120
(30.5) 100
(24.4) 80
(18.3) 60
(12.2) 40
N
P
S
(6.1) 20
NPSHr
H
r
(0.0) 0
0 200
(0.00) (12.62)
SINGLE/DUAL PUMP
FTV-4 in.
FTV-6 in.
400 600 800
(25.24) (37.85) (50.47)
Flow Rate
that often occurs when subtracting pressures made by different
gages.
A rough estimate of water flow can also be obtained from
the pressure gages across the 30RB heat exchangers.
Figures 52-56 show the relationship between gpm and heat
exchanger pressure drop. It should be noted that these curves
are for fresh water and "clean" heat exchangers; they do not
apply to heat exchangers with fouling. To read the chart,
subtract the readings of the two pressure gages on the hydronic
kit. This number is the pressure drop across the heat exchanger.
Adjust the factory-installed balancing valve or external balanc-
ing valve (in units without hydronic package) until the correct
pressure drop is obtained for the required gpm.
PUMP MODIFICATION/TRIMMING — Since the pumps
are constant speed, the only way to obtain greater flow with a
given pump/impeller is to decrease system head. This will
allow the pump to "ride" its curve to the right, resulting in
increased flow. If greater flow is necessary, consider opening
the combination valve. Also, verify that the strainer is clean,
and that no unnecessary system resistance is present, such as
partially closed isolation valves.
Once the combination valve is set, note the stem position. If
later service work requires the valve to be closed, it will be easier
to re-balance the system, if the original balance point is known.
Increasing system resistance by closing the balancing valve
will force the pump to "ride" its curve to the left, resulting in
less flow. Although this does reduce power consumption
slightly, it may not be the desirable method of reducing the
flow, especially if a large reduction is needed.
52
3450 RPM
1000 (gpm)
us
a30-5471
(63.09) (l/s)