Low-Pressure Switches | McMaster-Carr

	Maximum Setpoint Maximum Setpoint

	For Use With For Use With

	Minimum Setpoint Minimum Setpoint

	Pipe Size Pipe Size

1/8

1/4

1/2

	Operates On Operates On

Pressure

Differential Pressure

	Switch Starting Position Switch Starting Position

1 Off (Normally Open)

1 On (Normally Closed)

	Scale Scale

psi

in. of H2O

	Maximum Switching Current Maximum Switching Current

	Gender Gender

Male

Female

	Environment Environment

	Connection Material Connection Material

Brass

Aluminum

Stainless Steel

	Wire Connection Type Wire Connection Type


Screw Terminals	Wire Leads

	Width Width

	Height Height

	Maximum Process Temperature Maximum Process Temperature

	Environmental Rating Environmental Rating

	Gasket Material Gasket Material

Rubber

Stainless Steel

Brass

	Minimum Process Temperature Minimum Process Temperature

	Minimum Environment Temperature Minimum Environment Temperature

	Maximum Environment Temperature Maximum Environment Temperature

	Maximum Continuous Pressure Maximum Continuous Pressure

	RoHS (Restriction of Hazardous Substances) RoHS (Restriction of Hazardous Substances)

RoHS Compliant

RoHS Compliant with
Exemptions

	REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)

REACH Compliant

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About Pressure Switches

For Use With:
Style A: Air, Diesel Fuel, Hydraulic Fluid, Water
Style B: Air, Hydraulic Fluid (Petroleum Based)
Connection Material: See table
Connection: NPT Male
Maximum Switching Current:
Style A: 10A @ 125V AC, 10A @ 250V AC, 3A @ 480V AC
Style B: 15A @ 125V AC, 15A @ 250V AC, 15A @ 480V AC, 1A @ 30V DC, 30mA @ 125V DC

Sensitive to low pressures, these switches electrically activate automated controls or alarms when a set pressure is reached. They are often used in heating and ventilation systems. Switches are single pole, double throw (SPDT), so they switch one circuit on or off. They can be wired normally open (NO) or normally closed (NC). Switches are rated NEMA 1 for indoor use.

Switches with polycarbonate housing absorb vibration to avoid false switch activation caused by high-vibration applications.

						Temperature Range, °F		Conduit
	Setpoint, psi	Approximate Difference Between Setpoint and Reset Point, psi	Max. Short-Term Pressure, psi	Accuracy	Pipe Size	Environment	Process	For Trade Size	Connection Gender	Specifications Met		Each
Brass Connection
A	0.6-14.2	0.65	1,000	±2%	1/2	-20° to 165°	-20° to 165°	__	__	UL Recognized Component, CSA Certified	00000000	0000000
A	3 1/2-82	4	1,000	±2%	1/2	-20° to 165°	-20° to 165°	__	__	UL Recognized Component, CSA Certified	00000000	000000
Aluminum Connection—Polycarbonate Plastic Housing
B	3-30	0.85	230	±1%	1/4	0° to 160°	0° to 200°	7/8	Female	UL Listed, CE Marked	0000000	000000

Washdown Low-Pressure Switches

These switches are rated NEMA 4 or 4X for protection from dirt and washdowns. Sensitive to low pressures, they electrically activate automated controls or alarms when a set pressure is reached. Switches are single pole, double throw (SPDT), so they switch one circuit on or off. They can be wired normally open (NO) or normally closed (NC).

Style D has two setpoints, so it can control two independent circuits.

For Washdown Environments (NEMA 4)

For Use With: Air, Diesel Fuel, Hydraulic Fluid, Water
Connection Material:
Style A: Brass
Style B: 304 Stainless Steel
Connection:
Style A: 1/2 NPT Male
Style B: 1/4 NPT Female
Maximum Switching Current: 10A @ 125V AC, 10A @ 250V AC, 3A @ 480V AC

				Temp. Range, °F		Conduit
Setpoint, psi	Approximate Difference Between Setpoint and Reset Point, psi	Max. Short-Term Pressure, psi	Accuracy	Environment	Process	For Trade Size	Connection	Industry Designation	Environmental Rating	Specifications Met		Each
Style A
0.6-14.2	0.65	1,000	±2%	-20° to 165°	-20° to 165°	1/2	NPT Female	SPDT	IP65; NEMA 4	CSA Certified, UL Listed	00000000	0000000
3.5-82	4	1,000	±2%	-20° to 165°	-20° to 165°	1/2	NPT Female	SPDT	IP65; NEMA 4	CSA Certified, UL Listed	00000000	000000
Style B
0.068-1.6	0.04	3	±0.5%	-65° to 165°	-65° to 165°	1/2	NPT Female	SPDT	NEMA 4	__	0000000	000000
0.18-2.8	0.11	10	±0.5%	-65° to 165°	-65° to 165°	1/2	NPT Female	SPDT	NEMA 4	__	0000000	000000
0.66-17	0.19	60	±0.5%	-65° to 165°	-65° to 165°	1/2	NPT Female	SPDT	NEMA 4	__	0000000	000000

For Washdown and Corrosive Environments (NEMA 4X)

For Use With: Air, Diesel Fuel, Gasoline, Hydraulic Fluid, Water
Connection Material: 316 Stainless Steel
Connection: 1/4 NPT Female
Maximum Switching Current: See table

					Temp. Range, °F		Conduit
Setpoint, in. of H2O	Approximate Difference Between Setpoint and Reset Point, in. of H2O	Max. Short-Term Pressure, psi	Accuracy	Maximum Switching Current	Environment	Process	For Trade Size	Connection	Industry Designation	Environmental Rating	Specifications Met		Each
Style C
4.5-30	2.5	20	±1%	15 A @ 125 V AC, 15 A @ 250 V AC, 15 A @ 480 V AC, 6 A @ 30 V DC, 500 mA @ 125 V DC, 250 mA @ 250 V DC	-20° to 150°	20° to 300°	3/4	NPT Female	SPDT	IP66; NEMA 4X	C-UL Listed, CE Marked, CSA Certified, CSA-US Certified, FM Approved, UL Listed	00000000	0000000
Style D
4.5-30	4.5	20	±1%	15 A @ 125 V AC, 15 A @ 250 V AC, 15 A @ 480 V AC, 500 mA @ 125 V DC, 250 mA @ 250 V DC	-20° to 150°	20° to 300°	3/4	NPT Female	SPDT	IP66; NEMA 4X	CE Marked, CSA Certified, CSA-US Certified, FM Approved, UL Listed	00000000	000000

Adjustable-Reset Pressure Switches

Choose when these switches reset to control the pressure range between when they activate and deactivate, commonly referred to as deadband and differential. You can adjust their reset point anywhere along the setpoint range. When they reach the set pressure, these switches power equipment, signal controls, or trigger alarms. They’re single pole, double throw (SPDT) and can either turn one device from off to on (normally open) or on to off (normally closed). An on/off indicator tells you the status of your equipment, letting you monitor your equipment even when it’s out of sight.

All are NEMA rated to protect their parts from dirt and stand up to some corrosion, but they shouldn’t be used outdoors. UL listed and CSA certified, they also meet American and Canadian safety standards.

Screw Terminals
Setpoint, psi	Approximate Difference Between Setpoint and Reset Point	Max. Continuous Pressure, psi	Max. Short-Term Pressure, psi	Accuracy	Max. Switching Current @ Voltage	Process Temperature Range, °F	Connection Material	For Use With	Environmental Rating		Each
1/4 NPT Male Pipe Connection
1/8-15	Adjustable	15	15	±1%	10 A @ 120 V AC 10 A @ 240 V AC	35° to 180°	Brass	Air, Diesel Fuel, Hydraulic Fluid, Water	NEMA 1	0000000	0000000
2-60	Adjustable	60	60	±1%	10 A @ 120 V AC 10 A @ 240 V AC	35° to 180°	Brass	Air, Diesel Fuel, Hydraulic Fluid, Water	NEMA 1	0000000	000000

Low Differential Pressure Switches

For Use With: Air
Connection Material: Aluminum
Connection: NPT Female
Switching Current: 15A
Switching Voltage: 120V AC/240V AC/480V AC

Often used with ovens, dryers, and HVAC systems, these switches detect small differences in pressure. When the differential pressure exceeds your setpoint, the switch is activated. Use them to automate controls or activate an alarm in your process. Switches are single pole, double throw (SPDT), so they switch one circuit on or off. They can be wired normally open (NO) or normally closed (NC).

					Temperature Range, °F		Conduit
Setpoint, in. of H2O	Approximate Difference Between Setpoint and Reset Point, in. of H2O	Max. Pressure, in. of H2O	Accuracy	Pipe Size	Environment	Process	For Trade Size	Connection Gender	Specifications Met		Each
Zinc-Plated Steel Housing
0.07-0.15	0.04	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	000000
0.15-0.55	0.1	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	00000
0.4-1.6	0.16	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	00000
1.4-5 1/2	0.3	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	00000
3-11 3/4	0.4	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	00000
4-20	0.5	45	±3%	1/8	-30° to 180°	-30° to 180°	7/8	Female	CE Marked, CSA Certified, FM Approved, UL Recognized Component	00000000	00000

Air-Pressure-Actuated HVAC Switches

Often used to detect clogged air filters and iced air conditioner coils, these switches sense small changes in pressure between two points in your duct.

Diaphragm Sensor
Setpoint, in. of H2O	Accuracy, in. of H2O	Temperature Range, °F	Current	Electrical Connection Type	Switch Type	Max. Pressure, psi	Low Pressure Side Connection	High Pressure Side Inside Connection	High Pressure Side Outside Connection		Each
0.05-5	0.025	-40° to 165°	2.9 A @ 240 V AC 5.8 A @ 120 V AC	Hardwire	SPDT	1	1/8 NPT Female	1/8 NPT Female	1/2 NPSM	000000	0000000
0.05-5	0.04	-40° to 165°	4.9 A @ 240 V AC 9.8 A @ 120 V AC	Hardwire	SPDT	1	1/8 NPT Female	1/8 NPT Female	1/2 NPSM	000000	000000