L91 Proportioning Pressuretrol
Modulating Pressure Controllers that provide direct control of
modulating motors or valves used on automatic burners or
steam heating systems.
Controllers are Series 90
• Models available for pressure systems up to 300 psi
• May be used with steam, air, noncombustible gases, or
other fluids noncorrosive to brass or phos-bronze (300
psi model) bellows.
• When used with steam boilers, a steam trap (siphon
loop) is recommended.
• Wiper on controller potentiometer moves in response
to pressure changes.
• L91D has two potentiometers for unison control of two
• L91B,D models have adjustable proportioning
(throttling) range to allow selection of desired
pressure control range.
• Adjustments made with screws on case top.
• Large, easily-read scaleplates in both U.S. customary
(oz/sq. in., psi, or in. Hg) and metric (kPa, MPa, or mm
• Steel case with clear plastic cover to observe pressure
settings and potentiometer action.
• Fitting with 1/4 -18 NPT threads allows rapid
• Surface mount with screws through knockout holes in
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