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Since the expansion tank acts as a reference point for the
pump, there cannot be two reference points (two expansion
tanks) in a system (unless manifolded together). If system
volume or other design considerations warrant the placement
of another expansion tank somewhere in the system, the expan-
sion tank in the 30RA hydronic package MUST be disconnect-
ed from its hose and the end of the hose securely plugged.
This is also true for applications where two or more 30RA
chillers are placed in parallel. There should not be more than
one expansion tank in the system (unless manifolded together
as seen in Fig. 12). The expansion tanks must be disconnected
from the 30RA hydronic package. It is permissible to install the
expansion tank(s) in a portion of the return water line that is
common to all pumps, providing that the tank is properly sized
for combined system volume.
If the application involves two or more chillers in a primary-
secondary system, a common place for mounting the
expansion tank is in the chilled water return line, just before the
decoupler. See Fig. 12 for placement of expansion tank in
primary-secondary systems.
The expansion tank included in the 30RA hydronic package
is a diaphragm tank, meaning that a flexible diaphragm physi-
cally separates the water/air interface. With this type of expan-
sion tank, it is undesirable to have any air in the water loop. See
the section on air separation on page 13 for instructions on
providing air separation equipment.
FILLING THE SYSTEM — The initial fill of the chilled
water system must accomplish three purposes:
1. The entire piping system must be filled with water.
2. The pressure at the top of the system must be high enough
to vent air from the system (usually 4 psig is adequate for
most vents).
3. The pressure at all points in the system must be high
enough to prevent flashing in the piping or cavitation in
the pump.
The pressure created by an operating pump affects system
pressure at all points except one — the connection of the
compression tank to the system. This is the only location in the
system where pump operation will not give erroneous pressure
indications during the fill. Therefore, the best location to install
the fill connection is close to the expansion tank. An air vent
should be installed close by to help eliminate air that enters
during the fill procedure.
Ensure the following when filling the system:
1. Remove temporary bypass piping and cleaning/flushing
equipment.
2. Check to make sure all drain plugs are installed.
Table 4 — Head (Ft Water) as Read on Balancing Valve for 30RA010-030
SETTING
0
5
10
0
0
0
0.1
10
0
0.1
0.3
20
0
0.2
0.7
30
0
0.5
2
40
0
1.6
6.2
50
0
4.1
16.2
Table 5 — Head (Ft Water) as Read on Balancing Valve for 30RA032-055
SETTING
40
50
0
0.9
1.4
10
1.6
2.5
20
3.4
5.3
30
8.5
13.3
40
23.7
37
50
54.6
85.3
15
20
25
30
35
0.3
0.6
0.9
1.3
1.8
0.7
1.2
1.8
2.7
3.6
1.6
2.9
4.6
6.6
8.9
4.6
8.1
12.7
18.3
14
60
70
80
85
2
2.7
3.5
4
3.6
5
6.5
7.3
7.6
10.4
13.6
15.3
19.2
26.2
34.2
38.6
53.2
72.4
94.6
106.8
119.8
122.8
167.2
218.3
246.5
276.3
3. Open the blow-down valve to flush the strainer.
Normally, a closed system needs to be filled only once. The
actual filling process is generally a fairly simple procedure. All
air should be purged or vented from the system. Thorough
venting at the high points and circulation at room temperature
for several hours is 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 especially important when anti-freeze is used
in the system.
Set Water Flow Rate — Once the system is cleaned, pressur-
ized, and filled, the flow rate through the chiller needs to be
established. On units with the hydronic package, this can best
be done using the balancing valve.
In order to adjust the balancing valve, put a differential
pressure gage across the pressure taps on the valve. Make sure
that all system isolation and control valves are open. Use
Tables 4 and 5 or a Bell & Gossett balancing valve calculator to
determine GPM. To read Tables 4 and 5:
1. Measure the pressure drop across the balancing valve. If
the pressure reading is in psi, multiply psi x 2.31 to con-
vert to feet of water before using Tables 4 and 5.
2. Go to the row in the chart corresponding to the setting on
the valve, interpolating if necessary.
3. The GPM corresponding to the pressure drop measured is
the flow through the balancing valve.
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
that often occurs when subtracting pressures made by different
gages.
On primary/secondary systems, it is advisable to set the
30RA balancing valve to maintain design flow plus 10%
through the chiller.
A rough estimate of water flow can also be obtained from
the pressure gages across the 30RA heat exchanger.
Figures 15A-16B show the relationship between GPM and
heat exchanger pressure drop. It should be noted that these
curves are for "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 balancing
valve (units without hydronic package) until the correct pres-
sure drop is obtained for the required GPM.
GPM
40
45
50
55
60
2.3
2.9
3.6
4.4
5.2
4.7
6
7.4
8.9
10.6
11.7
14.8
18.2
GPM
90
95
100
105
110
4.4
4.9
5.5
6
8.2
9.1
10.1
11.2
12.3
17.2
19.1
21.2
23.4
25.7
43.2
48.2
53.4
58.9
64.6
133.4
147.8
163
178.9
307.9
341.1
376.1
412.8
15
65
70
75
80
85
6.1
7.1
8.1
9.2
10.4
12.4
14.4
16.6
18.9
115
120
125
130
6.6
7.2
7.9
8.5
9.2
13.4
14.6
15.8
17.1
28.1
30.5
33.1
35.8
70.6
76.9
83.4
90.2
195.5
212.9
231
249.8
451.1
491.2
533
576.5
90
95
100
11.7
13
14.4
135
140
10
10.7
18.5
19.9
38.7
41.6
97.3
104.7
269.4
289.8
621.7
668.6
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