Gems Sensors S-925 Series Instruction Bulletin

Important Points!
Product must be maintained and installed in strict ac-
cordance with the National Electrical Code and Gems
product catalog and instruction bulletin. Failure to ob-
serve this warning could result in serious injuries or
damages.
An appropriate explosion-proof enclosure or intrinsically
safe interface device must be used for hazardous area
applications involving such things as (but not limited to)
ignitable mixtures, combustible dust and flammable mate-
rials.
*** Warning: To prevent ignition of flammable or combus-
tible atmospheres, disconnect power before servicing.
Pressure and temperature limitations shown on individual
catalog pages and drawings for the specified flow switches
must not be exceeded. These pressures and tempera-
tures take into consideration possible system surge pres-
sures/temperatures and their frequencies.
Selection of materials for compatibility with the media is
critical to the life and operation of GEMS flow switches.
Take care in the proper selection of materials of construc-
tion; particularly wetted materials.
P/N 72949
Rev. P
Life expectancy of switch contacts varies with appli-
cations. Contact GEMS if life cycle testing is required.
Ambient temperature changes do affect switch set
points, since the specific gravity of a liquid can vary with
temperature.
Flow switches have been designed to resist shock and
vibration; however, shock and vibration should be mini-
mized.
Liquid media containing particulate and/or debris
should be filtered to ensure proper operation of GEMS
products.
Electrical entries and mounting points may require liq-
uid/vapor sealing if located in an enclosed tank.
Flow switches must not be field repaired.
Physical damage sustained by the product may ren-
der it unserviceable.
Installation . . .
Unless otherwise specified at time of purchase, units are calibrated in a vertical position, with lead wires up.
Install unit in piping system, using standard pipe fitting procedures. Hold inlet fitting with wrench at installation
to prevent fitting torque accumulation. Be sure to keep thread sealing compound out of unit. Make sure that
flow is in proper direction - marked "IN" and "OUT" on housing. See wiring diagrams for electrical connections.
CAUTION: See "Switch Ratings" before connecting power.
CAUTION: Flow settings for FS-920 series switches are normally calibrated using water** @ +70°F on
increasing flow. If unit will be used to monitor liquids other than water, gas or air, Factory should have been
consulted at time of purchase for special calibration. All air/gas units are factory-calibrated using a special
piston. Water-calibrated units are not recommended for air/gas applications.
**Note: Flow settings for FS-930 Viscosity Compensating type switches are calibrated in a vertical position
(lead wires up) with 300 SSU oil. Set points will be maintained within 20% of settings in a liquid viscosity
range of 40 to 2,000 SSU.
Specifications . . .
FS-925/FS-926
Wetted Materials
Housing Brass or 316 SS
Piston
Brass Housing Polysulfone/Water - Brass/Oil or Air
Stainless Steel Housing 316 SS
Spring
O-Ring
Other Wetted Parts
Pressure Rating
Operating
Proof
Burst
Operating Temperature
Brass or SS Piston -20°F to +300°F
Polysulfone Piston -20°F to +225°F
Repeatability
Set Point Accuracy
15% Max.(FS-925) - 20% (FS-926)
Set Point Differential
Switch*
Inlet/Outlet Ports
Electrical Termination No. 18 AWG, 24" L., Polymeric Lead Wires
Piston-Type Flow Switches
Series FS-925/926 & FS-927/930
Instruction Bulletin No. 72949
FS-930 FS-927
Brass Brass
Brass Brass
N/A
N/A
316 SS
Viton ® N/A
Epoxy SS
1000 PSIG 1000 PSIG,Max.
2500 PSIG
5000 PSIG
-20°F to +300°F -20°F to +200°F
N/A
1% Maximum Deviation 15%, Max. N/A
±10% ±15%
20% Max.
SPDT, 20 VA SPST, 20 VA
1/4" NPT
1/4" NPT
No. 18 AWG, 24" L.,
PVC Lead Wires