INSTALLATION PLANNING
Minimum Pressure Tank and Supply Pipe Sizing
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Minimum Pressure Tank and Supply Pipe Sizing
A VFD system needs only a small pressure tank to maintain constant pressure, although a larger tank may
be used.
•
If adding a drive to a system with an existing large tank, refer to
“Tank Size and Bump Mode Adjust
•
The pressure tank pre-charge setting should be 70% of the targeted system pressure.
Refer to the following recommendations for best performance.
Submersible Pump Applications with Franklin Electric 2-Wire Motor
A minimum tank size of 20 gallons is recommended. This is to ensure water is available during the minimum
off time of the motor. If a smaller tank is used, the tank may empty if a large water demand immediately fol
-
lows a motor off cycle.
Submersible Pump Applications with PSC Motor
Surface Pump Applications
Minimum Supply Pipe Sizes
The minimum supply pipe diameter past the pressure sensor (transducer) should be selected not to exceed
a maximum velocity of 8 feet per second (2.4 m/s) based on the flow rate of the system.
IMPORTANT:
Water system piping should be performed by an experienced professional to ensure adequate
flow.
Pump Flow Rating
Minimum Tank Size
Less than 12 gpm (45.4 lpm)
2 gallons (7.6 liters)
12 gpm (45.4 lpm) and higher
4 gallons (15.1 liters)
Maximum Pump Flow
Minimum Tank Size
10 GPM
2 gallons (7.6 liters)
20 GPM
4 gallons (15.1 liters)
30 GPM
6
gallons (22.7 liters)
40 GPM
8 gallons (30.3 liters)
Maximum GPM (lpm)
Minimum Pipe Diameter
11.0 (41.6)
0.75”
19.6 (74.2)
1”
30.6 (115.8)
1.25”
44.1 (166.9)
1.5”
78.3 (296.4)
2”
122.4 (463)
2.5”
176.3 (667)
3”
240.0 (908)
3.5”
313.3 (1186)
4”
396.6 (1501)
4.5”
489.6 (1853)
5”
