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Dwyer 1911-20 Compact Differential Pressure Switch, Bare Switch (less Enclosure), 4.0-20.0 in WC, SPDT, 15A, UL/CSA/FM

Dwyer

MSRP: $94.80
$75.48
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SKU:
1911-20
Condition:
New
Availability:
Not in Stock | Lead Time: 4 weeks
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Range4.0-20.0 in WC
Deadband (Min SP)0.40 in WC
Deadband (Max SP)0.50 in WC
Switch TypeSPDT, 15 A @ 120-480 VAC
Repeatability+/- 3%
Process Connection1/8 in FNPT, front-mounted
VariantBare Switch
CertificationsUL, CSA, FM, CE

The Dwyer 1911-20 is the bare-switch version of the popular Series 1900, supplied without the standard conduit enclosure cover. The unit is intended for OEM panel integration or for factory installation in the optional weatherproof (-WP) or explosion-proof (-EXPL) housings. It covers a setpoint range of 4.0-20.0 in WC, switches 15 A at 120-480 VAC through an SPDT relay, and is built around Dwyer's force-motion amplifier mechanism for repeatable trip performance (+/-3%) at very low actuating pressures. Service is air and other non-combustible, compatible gases only.

Best for: very high static industrial fan supervision, baghouse and dust collector dP alarms, and large-AHU clogged-filter detection. The bare-switch format is intended for OEM integration into customer-supplied panels, or for factory installation in Dwyer's -WP weatherproof or -EXPL explosion-proof housings (sold separately under the 1911/1921 family).
2-YEAR
WARRANTY
Manufacturer-backed coverage. Dwyer Series 1900 switches carry a two-year limited warranty against defects in materials and workmanship. ZOT Supply is an authorized Dwyer distributor; product ships factory-new with full manufacturer warranty intact and access to Dwyer technical support.

Key Features

Force-Motion Amplifier Mechanism

Dwyer-engineered internal linkage amplifies diaphragm motion, giving the snap switch more travel per unit of pressure change. Result: +/-3% repeatability even at actuating pressures as low as 0.07 in WC.

15 A Switch Rating

SPDT snap switch is rated 15 A at 120-480 VAC, 60 Hz - significantly heavier duty than typical HVAC pilot relays. Drive small motors, contactors, or alarm circuits directly without an interposing relay. Derate to 10 A for high cycle rates.

Bare-Switch Format

Ships without the standard conduit enclosure cover for OEM integration into customer-supplied control panels or for factory installation in the optional -WP weatherproof or -EXPL explosion-proof housings. Lower BOM cost when the enclosure is provided by the assembly.

One-Side Installation

Pressure ports, electrical conduit, and setpoint adjustment are all located on the same side of the housing. The switch can be installed in corners or tight spaces where a conventional pressure switch with rear connections will not fit.

Wide Service Envelope

Operating temperature -30 to 180 F (32 F minimum for non-dry air), 80% RH non-condensing, up to 6,560 ft altitude. Continuous overpressure rated 45 in WC, 10 psig surge - tolerant of typical HVAC transients.

UL/CSA/FM/CE Listed

Series 1910 and 1920 carry multi-agency approvals: UL listed, CSA certified, FM approved, and CE marked. Installation category III (transient overvoltage); pollution degree 2. Ready for use in code-listed control panels.

Technical Specifications

SpecificationValue
Model1911-20
Operating Range4.0-20.0 in WC
Approx. Deadband at Min. Setpoint0.40 in WC
Approx. Deadband at Max. Setpoint0.50 in WC
ServiceAir and non-combustible, compatible gases (not for natural gas or other combustibles)
Wetted MaterialsConsult factory
Switch Type1 Form C relay, SPDT
Electrical Rating15 A @ 120-480 VAC, 60 Hz; resistive 1/8 HP @ 125 VAC, 1/4 HP @ 250 VAC, 60 Hz. Derate to 10 A for high cycle rates.
Repeatability+/- 3%
Electrical Connections3 screw-type terminals: common (COM), normally open (NO), normally closed (NC)
Installation CategoryIII (transient overvoltage)
Pollution Degree2
Process Connections1/8 in female NPT, front-mounted (high and low)
EnclosureLess conduit enclosure (bare switch); 7/8 in conduit connection on body. Use with -WP or -EXPL housing, or integrate into customer panel.
Temperature Limits, Operating-30 to 180 F (-34 to 82.2 C); 32 F minimum for non-dry air
Humidity Limit80% RH, non-condensing
Altitude Limit6,560 ft (2,000 m) max
Pressure Limit, Continuous45 in WC (11.2 kPa)
Pressure Limit, Surge10 psig (68.95 kPa)
Mounting OrientationDiaphragm in vertical plane
Setpoint AdjustmentSlotted screw inside conduit enclosure (tamper-resistant)
Weight1 lb 4.5 oz (581 g)
ComplianceCE, UL, CSA, FM
Manufacturer Part Number1911-20

Documentation

PDFCatalog DatasheetPDFInstallation and Operating Manual (Bulletin E-56)

Frequently Asked Questions

What pressure range does the 1911-20 cover?
This SKU is the -20 range, with an adjustable setpoint of 4.0-20.0 in WC. Approximate deadband is 0.40 in WC at the minimum setpoint and 0.50 in WC at the maximum setpoint. Maximum continuous overpressure is 45 in WC (11.2 kPa); maximum surge pressure is 10 psig (68.95 kPa).
Can the 1911-20 be used outdoors or in cold environments?
The published operating range is -30 to 180 F. However, the -30 F lower limit applies only to dry air. For humid HVAC air or any service where moisture is present, the practical minimum operating temperature is 32 F - below freezing, moisture inside the switch can freeze and prevent the diaphragm from operating reliably. For wet, oily, or outdoor service, specify the -WP (weatherproof, NEMA 4) housing option from the 1911/1921 family.
Is the 1911-20 rated for natural gas or other combustible gases?
No. The Series 1900 family is rated only for air and other non-combustible, non-aggressive gases. Use with combustible media can cause operating faults or unsafe conditions. For natural gas service or installation in Class I Div 1 hazardous areas, see the explosion-proof Dwyer Series 1950G family instead.
What's the difference between the 1911-20 and the 1910-20?
The switch mechanism inside is identical. The difference is that the 1911-20 ships without the standard conduit enclosure cover - it's a bare-switch SKU, intended either for integration into a customer-supplied control panel or for factory installation in Dwyer's optional -WP weatherproof housing (NEMA 4) or -EXPL explosion-proof housing (Class I Group D, Class II Groups E/F/G, NEMA 7/9/3). If you need the standard enclosed switch as a complete unit, order the 1910-20 instead.
What is the Dwyer force-motion amplifier and why does it matter?
The force-motion amplifier is a Dwyer-engineered internal mechanical linkage that multiplies the small motion of the pressure diaphragm into a larger motion at the snap switch lever. The practical benefit is that the switch can resolve very small pressure changes (as low as 0.07 in WC trip points) while maintaining +/-3% repeatability across many thousands of cycles. This is what lets the compact 1900 family compete on accuracy with much larger, more expensive industrial pressure switches.
How do I wire the bare switch?
Three screw terminals on the snap switch body are labeled COM (common), NO (normally open), and NC (normally closed). On rising pressure past the setpoint, COM transfers from NC to NO. Wire COM to your input/load common, and use NO for fail-safe-open logic or NC for fail-safe-closed logic. Because this SKU ships without the standard cover, the terminals must be protected by a customer-supplied enclosure or by the Dwyer -WP or -EXPL housing the switch is factory-installed in. Always de-energize before wiring.
Brand:
Dwyer
Series:
1900
Sub-Family:
1911
Product Type:
Compact Differential Pressure Switch (Bare, less Conduit Enclosure)
Operating Range:
4.0-20.0 in WC
Range Code:
-20
Deadband at Min Setpoint:
0.40 in WC
Deadband at Max Setpoint:
0.50 in WC
Service:
Air, Noncombustible Gases (not natural gas)
Switch Type:
SPDT, 1 Form C Relay
Reset Type:
Automatic
Electrical Rating:
15 A at 120-480 VAC, 60 Hz
Repeatability:
+/- 3%
Process Connection:
1/8 in FNPT, Front
Conduit Connection:
7/8 in (1/2 in NPT compatible)
Conduit Enclosure:
Less enclosure (bare switch)
Pressure Limit (Continuous):
45 in WC, 11.2 kPa
Pressure Limit (Surge):
10 psig, 68.95 kPa
Temperature Range:
-30 to 180 F, -34 to 82.2 C (32 F min for non-dry air)
Humidity Limit:
80% RH non-condensing
Altitude Limit:
6,560 ft, 2,000 m
Installation Category:
III
Pollution Degree:
2
Mounting Orientation:
Diaphragm Vertical
Setpoint Adjustment:
Slotted screw inside enclosure (tamper-resistant)
Certifications:
CE, UL, CSA, FM
Weight:
1 lb 4.5 oz, 581 g
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