U.L. Recognized- File No. E31926
CSA Listed -File No. LR30200
FM Approved -File No. 1H3A2.AX
and 0A8A3AE
U.L. Approved File No. E183854
These two series of precision-calibrated switches provide reliable and consistent performance; repeatability is within 1%. CFS-925 and CFS-926 units are factory preset for actuation at specified flow rates.These switches provide accurate detection of excessive or insufficient flow rates in such applications as: protecting against loss of fluid flow in hydraulic systems, assuring proper coolant flow in semiconductor processing equipment, monitoring high pressure lubrication systems, and ensuring proper air flow in water/waste systems.
The CFS-925 series is a general purpose design for liquids or gases. The CFS-926 Series features a special low-flow piston. This additional piston allows the detection of fluid flow as low as 50 cc/min. These switches are ideal for applications such as gas sampling, liquid or gas leak detection, or chemical injection.
Click here for information on our other flow switches.
Wetted Materials:
Housing: Brass or 316 Stainless Steel
Piston In Brass Housing: Polysulfone for
water; Brass for oil or air
Piston in Stainless Steel Housing: 316
Stainless Steel
Low Flow Piston (CFS-926): Same as
Housing
Spring: 316 Stainless Steel
O-Ring: Viton®
Other Wetted Parts: Epoxy
Pressure Rating:
Max. Operating: 1000 PSIG
Proof: 2500 PSIG
Burst: 5000 PSIG
Operating Temperature:
With Brass or S.S. Piston: -20°F to +300°F
(-29°C to +148.9°C)
With Polysulfone Piston: -20°F to +225°F
(-29°C to +107.2°C)
Repeatability: 1% Maximum Deviation
Set Point Accuracy: ±10%
Set Point Differential: 15% Maximum
Switch: SPDT, 20 VA
| Switch Rating, Maximum Resistive Load | |||
| VA | Volts | Amps AC | Amps DC |
| 20 | 0-30 | 0.4 | 0.3 |
| 120 | 0.17 | 0.13 | |
| 240 | 0.08 | 0.06 | |
An additional lap-fitted piston is used in model CFS-926 to accurately detect low flow rates. Calibration is determined by one or more metering holes in the end of the low-flow piston which regulate bypass flow and therefore the actuation setting. When metered bypass flow is exceeded, the resultant pressure differential displaces the low-flow piston, moving the magnet carrier piston to actuate the reed switch. Two large bypass holes in the piston skirt are exposed after actuation to maintain low pressure drop.
Flow Setting, Air (Typical)
Dependent on operating line pressure. Examples of set point ranges at a given line pressure are shown below.
| Line Pressure | Actuation Point | |||
| CFS-925 | CFS-926 | |||
| Min. | Max. | Min. | Max. | |
| 5 PSIG (Minimum Line Pressure) | 0.5 SCFM | 10 SCFM | 2 SCFH | 15 SCFH |
| 100 PSIG | 1.5 SCFM | 25 SCFM | 7 SCFH | 50 SCFH |
Water flow units should not be used for air/gas applications: Gas flow units have a special dash-pot piston for reliable operation. Gas calibration is dependent upon line pressure, switch orientation, and the specific type of gas. The calibrated flow set point is subject to change with fluctuations in line pressure.
Specify Part Number based on desired housing material and flow setting.
Liquids other than water: Special calibration is available from Clark for media other than water. Please consult us with your requirements, including housing material (brass or stainless steel), flow media, operating pressure, flow set point and liquid viscosity (SSU). A lot charge will be applied for special calibrations.
Gas flow: Consult us for available calibrations. Specify: Housing material (brass or stainless steel), gas type, mounting orientation, operating pressure and actuation setting (SCFM or SCFH) and normal flow rate. A lot charge will be applied for special calibrations.
| FOR YOUR CONVENIENCE, THESE ITEMS ARE AVAILABLE ONLINE OR PLEASE CALL 1-800-253-2497 TO ORDER | |||
| Model | Part Numbers | Flow Setting GPM, ±10% | |
| Brass | 316 SS | ||
| CFS-925 | C26914 | C26926 | 0.10 |
| C26915 | C26927 | 0.25 | |
| C26916 | C26928 | 0.50 | |
| C26917 | C26929 | 0.75 | |
| C26918 | C26930 | 1.00 | |
| C26919 | C26931 | 1.50 | |
| FOR YOUR CONVENIENCE, THESE ITEMS ARE AVAILABLE ONLINE OR PLEASE CALL 1-800-253-2497 TO ORDER | ||||
| Model | Part Numbers | Flow Setting | ||
| Brass | 316 SS | cc/Min., ±10% | Equiv. GPM | |
| CFS-926 | C26938 | C26951 | 50 | 0.013 |
| C26939 | C26952 | 100 | 0.025 | |
| C26941 | C26953 | 150 | 0.045 | |
| C26942 | C26954 | 200 | 0.055 | |
| C26943 | C26955 | 250 | 0.065 | |
| C26944 | C26956 | 300 | 0.075 | |
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They are also available with FM-approved, explosion-proof junction box for Class I, Division 1, Group D hazardous locations. Units must be assembled completely at factory.
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