P/N 18271

Model 1200, Liquid Flow Switch, 1" FNPT, 0.75-6.0 GPM Increasing Flow, SPDT 20VA Pilot Duty, -14.7 to 400 PSI @ 100°F, -20°F to 300°F

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Product Information; Click to jump to Specifications

Description: This unit is an adjustable version of our model 1100, an Industrial Standard, if you need the same accuracy and ruggedness that the model 1100 offers but need a field adjustable set point, this is the model for you. The switch in this unit is silicone potted in a factory replaceable capsule to permit a very high vibration resistance as well as keeping it repairable in the event of failure. This model has a true globe-shaped one piece cast body that yields a lower pressure drop and minimizes turbulence while keeping the pressure capabilities very high.

Operation: Liquid flows through the housing, with flows below the "set point" the liquid flows around the shuttle, as the flow rate increases the magnet equipped shuttle starts to lift up compressing the spring until the flow rate reaches the set point in which case the magnet actuates a hermetically sealed reed switch inside the stem. Flows above the set point pass by the shuttle without issue holding the unit actuated until the flow rate begins to decrease where the spring begins to push the shuttle back down to resting position until the magnet extends far enough away from the switch causing it to de-actuate. Flow rates below the set point do not effect the unit and do not cause it to actuate. Adjusting the vane permits an amount of substance to bypass the piston entirely, this effectively raises the set point. The vane spins around 360° however it's operation is such, with the adjustment slot parallel to the inlet and outlet, the set point is highest. With the vane adjustment slot perpendicular to the inlet and outlet the flow set point is lowest.

Common Applications: Some common applications where this unit can be seen are coolant systems, HVAC equipment, and pump & bearing protection devices.

AdvantagesSpecialty Options
  1. True globe-shaped housings yield lower pressure drops and minimize turbulence
  2. Welding performed in low hydrogen environment
  3. Factory replaceable switch capsules
  4. Clean-In-Place; cleaning the unit can be done without having to remove the housing from line
  5. Shock and vibration approved
  6. NAV SEA Dept. of Navy APL Listed Mil-S-16032 Shipboard Alarm Systems
  7. Added retaining ring means shuttle cannot jam in place
  8. Complete bonnet assembly and components remain intact during removal
  9. Simple screwdriver adjustable set points
  1. Strain reliefs are standard. Optional silicone potting available
  2. Optional 100VA SPST reed switches are stocked
  3. Relays for higher loads, junction boxes, terminal strips, etc. are available. See accessories section for details
  4. Optional cables/ cordsets available
  5. Optional SST identification tags attached to unit
  6. Optional M/S connector MS3102E10S-3P, Hirschmann or other connectors available
  7. Optional port sizes and process connections such as BSP, SAE, silver braze, socket-weld etc. are available
  8. High temperature units up to 400°F available
  9. Calibration in other substances or flow conditions are available
  10. Monel trim
  11. Available housings in 316 SST instead of bronze
  12. All metal such as SST or Brass shuttles instead of Teflon available
  13. Buna O-Rings instead of Viton
Special Notes
  1. Standard flow calibration is in water at 70°. Calibrated on increasing flow
  2. Temperature effect on flow settings: water calibration; slight change, oil; varies with viscosity
  3. Other wetted materials: ceramic ring magnet
  4. For pipe sizes smaller than ¾”, install appropriate size bushings
  5. Calibration: Flow stands are calibrated to the National Bureau of Standards and Thomas Products Ltd. Recalibration schedule

Product Specifications

Flow Switch 2000

Manufacturer :
Thomas Products LTD.
Model Number :
Model 1200
Type :
Liquid Flow Switch
Special Features :
Mounting Type:
In-line/ Pipe Installation
Housing :
Process Connection :
UL Listed :
Flow Set Point :
0.75-6.0 GPM Increasing Flow
Set Point Accuracy :
Not specified, unit is adjustable
Set Point Differential :
10% Max
Repeatability :
1% Max Deviation
Dimensions :
'A' 3-1/4", 'B' 1-25/32", 'C' 3"
Mounting Attitude :
Suggested: Ports horizontal with lead wires up, set point may slightly change otherwise
Reed Switch :
SPDT 20VA Pilot Duty
Reed Switch Logic :
SPDT, Black-Common, Red-NC, Orange-NO
Leads :
24" 18 AWG Polymeric with 1/2" MNPT Conduit Connector
Wetted Materials :
Bronze, Brass, SST, Viton "A", PTFE, Ceramic Ferrite
Pressure Range :
-14.7 to 400 PSI @ 100°F
Proof Load :
800 PSI @ 100°F
Burst Strength :
1200 PSI @ 100°F
Temperature Range :
-20°F to 300°F
"O" Ring :
Viton "A"
Spring :
Shuttle :
Bonnet :
SST, and Brass
Check out these helpful videos for cleaning & general maintenance for some of our field serviceable products! https://www.youtube.com/playlist?list=PL_oLXohRDc29JLFLatP9Ainn_aF5FKeCL
Revision Level Changes Status
-NO Original release Current and active

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