Watts FS20 User Manual
For Commercial and Industrial Applications
GENERAL
SIGNALING
EQUIPMENT
11S1
ES-FS20
Job Name
Job Location
Engineer
Approval
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Series FS20
Nema 4X Flow Switch
Sizes: For pipes 1"- 6" (25 – 150mm)
Series FS20 provides accurate monitoring of liquid flow in
pipelines servicing water systems, heating systems, air conditioning, and processing installations for industrial and commercial applications. The FS20 series is recommended for use in
areas of high humidity for indoor or outdoor installations requiring Nema 4X watertight, dust-tight, and corrosion-resistant
enclosures. The switch is epoxy coated and corrosion resistant. The Nema 4X Flow Switch is designed to act as an automatic control or safety device for liquid flow. The single-pole,
double-throw switch can be wired to start or stop a motor
when a flow or no flow condition exists or activate an alarm
when flow is inadequate. The switch then turns off the alarm
when adequate flow is restored. Series FS20 flow switches
can be installed in a tee for horizontal or vertical piping.
Features
• Beryllium copper paddle
• Brass alloy bellows seals switch assembly from the line
• Two adjusting screws, fine and coarse, to adjust sensitivity
1
•
⁄2" (15mm) threaded conduit hub accepts standard
vapor-proof connectors
• Removable cover for easy access to switch terminals
• Corrosion-resistant
• Zinc die-cast enclosure
• Epoxy-coated finish
• 1" (25mm) NPT connection
• Switch assembly independent and removable from
mounting adapter
Contractor
Approval
Contractor’s P.O. No.
Representative
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Nema 4X Flow Switch
Paddles
3 in 1 Paddle – A segmented beryllium copper paddle is quickly adaptable for 1" through 3" pipe (25 through 80mm). The
extended beryllium copper paddle, also included, is for larger
pipe sizes up to 6" (150mm). Paddle length conforms to ASTM
tee standards.
Materials
Body: Cast brass ASTM
Bellows: Brass ASTM B-36
Cover: Epoxy coated die cast zinc
Enclosure: Epoxy coated die cast zinc
Paddle: Beryllium Copper ASTM B-194
Coupling: Brass ASTM B-36
O-rings: Buna N
Standards
Underwriter’s Laboratories Listed U.S.A. No. 11S1
Pressure-Temperature
Maximum Working Pressure: 150psi (10.3 bar) at 300ºF (148.9ºC)
Watts product specifications in U.S. customary units and metric are approximate and are provided for reference only. For precise measurements,
please contact Watts Technical Service. Watts reserves the right to change or modify product design, construction, specifications, or materials without prior notice and without incurring any obligation to make such changes and modifications on Watts products previously or subsequently sold.
Dimensions
31⁄4"
(82mm)
25⁄16" (59mm)
13⁄8" (35mm)
113⁄16" (284mm)
31⁄4" (82mm)
31⁄4"
(82mm)
7
⁄8" (22mm)
1
⁄2" (15mm)
Threaded
Conduit
Hut
17⁄8" (48mm)
HEX
1" (25mm)
Pipe Thread
Flow Rates
FLOW RATES Required to Actuate the FS20 Flow Switch in
Horizontal Pipe. Flow rates in U.S. gallons per minute (GPM).
Velocity in feet per second (FPS). *Equipped with extended
paddle trimmed to pipe size.
PIPE SIZE IN WHICH 25mm 32mm 40mm 50mm 65mm 80mm 100mm 125mm 150mm
FLOW SWITCH INSTALLED 1" 1
FACTORY OR
MINIMUM
FLOW SETTING
MAXIMUM
FLOW SETTING
ACTIVATION GPM 5.2 7.9 10.0 13.2 20.9 30.0 39.0 58.0 79.0
FLOW FPS 2.01 1.74 1.62 1.29 .92 1.30 1.0 .94 .88
DEACTIVATION GPM 2.0 3.2 5.3 8.1 9.9 12.0 19.0 29.0 39.6
NO FLOW FPS .77 .71 .86 .79 .44 .52 .50 .47 .44
ACTIVATION GPM 11.5 18.0 18.0 34.1 53.9 52.0 73.5 115.0 166.0
FLOW FPS 4.44 3.98 2.91 3.33 2.38 2.26 1.86 1.85 1.84
DEACTIVATION GPM 8.5 14.6 15.1 29.2 44.4 46.1 64.0 92.0 123.0
NO FLOW FPS 3.28 3.23 2.44 2.85 1.96 2.00 1.67 1.48 1.37
*Flow rates for these sizes are calculated.
A Watts Water Technologies Company
ES-FS20 0921 © 2009 Watts
1
⁄4"1
1
⁄2"2" 2
Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscanada.ca
1
⁄2" 3" *4" *5" *6"
USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.watts.com
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