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The PA404 is a series 40 (2-wire, SPST) pressuretrol controller for use in 24, 120, 240 or 277 volt control circuits or in self powered (millivoltage) applications.


  • The PA404A is a pressure actuated high limit, safety control for steam heating boilers. It breaks an electrical circuit to shut down the burner if steam pressure rises above a safe level.
  • The PA404B is used with suspension-type unit heaters to make the fan circuit when a pressure rise indicates the presence of steam.
  • Each model contains an SPST MICRO SWITCH snap-acting switch.
  • Sensitive pressure-actuated diaphragm expands or contracts with pressure variations, moving a lever mechanism which operates the snap switch.
  • A screw on top of the case allows set point adjustment without removing the cover.
  • Differential is adjusted by means of a dial located inside the case..

Product Specifications

Safety control for steam heating boilers
Dimensions (in.)
4 15/32 in. high x 3 3/8 in. wide x 2 1/4 in. deep
Dimensions (mm)
114 mm high x 86 mm wide x 58 mm deep
Maximum Safe Operating Pressure (psi)
20 psi
Maximum Safe Operating Pressure (kPa)
137 kPa
Case: Gray enamel finish
Recommended minimum set point is differential setting plus 1 1/2 psi.
Item Type
Electrical Ratings
0.25 A @ 0.25 to 12 Vdc; 120 Vac, Resistive: 8.3A; 240 Vac, Resistive: 8.3A; 277 Vac, Resistive 7.2A
Approvals, Underwriters Laboratories Inc.
UL Listed: File no. MP466, Guide no. MBPR.
Approvals, Canadian Standards Association
CSA Listed: File no. LR1620.
Operating Humidity Range (% RH)
95% RH, non-condensing
Temperature Ratings (C)
66 C - Maximum Ambient
Temperature Ratings (F)
150 F - Maximum Ambient
Sensor Element
Stainless Steel diaphragm
Operating Range (psi)
3 psi to 15 psi Adjustable
Operating Range (kPa)
21 kPa to 103 kPa Adjustable
Differential Pressure Range (psi)
1 to 5 psi Adj.
Differential Pressure Range (kPa)
7 to 35 kPa Adj.
Differential Type
Additive or Subtractive
Switching Action
Makes at set point minus differential on pressure fall; Breaks at set point on pressure rise
Pressure Surge (max. psi)
50 psi
Pressure Surge (max. kPa)
345 kPa
Adjustable Scale Range (psi)
0.5 psi to 9 psi
Adjustable Scale Range (kPa)
3 kPa to 62 kPa
Pilot Duty Ratings
150 VA @ 277 Vac
Switch Type
SPST snap-acting switch
Pipe Connection
1/4 in. female pipe threads
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