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Dwyer 1900-5-MR Compact Manual-Reset Differential Pressure Switch, 1.4-5.5 in WC, SPDT, 15A, Latching Snap Switch

Dwyer

MSRP: $145.30
$115.70
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SKU:
1900-5-MR
Condition:
New
Availability:
Not in Stock | Lead Time: 4 weeks
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Range1.4-5.5 in WC
Deadband (Min SP)0.30 in WC
Deadband (Max SP)0.30 in WC
Switch TypeSPDT, 15 A @ 120-480 VAC
Repeatability+/- 3%
Process Connection1/8 in FNPT, front-mounted
VariantManual Reset
CertificationsNot agency listed

The Dwyer 1900-5-MR is the manual-reset (latching) version of the popular Dwyer Series 1900 compact differential pressure switch. The internal snap switch latches when pressure crosses the setpoint and stays latched until a technician physically resets it - the right choice for safety-critical applications where auto-reset is unsafe or prohibited by code. It covers a setpoint range of 1.4-5.5 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: blower and fan proof-of-flow, mid-pressure duct supervision, and refrigeration coil icing detection (defrost cycle initiation). The manual-reset feature is especially suited to single positive-pressure safety interlocks where an operator must physically acknowledge the trip before the system is allowed to restart - for example, high-limit duct pressure cutout on a fan, or filter-full alarm that should not silently auto-reset overnight.
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.
Important - not agency listed. The Series 1900-MR manual-reset option is not UL, CSA, or FM listed and is intended only for single positive-pressure applications. Differential-pressure or vacuum service is not supported on this variant. If your application requires UL/CSA/FM listing or differential measurement, select the standard 1910 or 1920 instead.

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.

Manual-Reset Latching

Internal snap switch latches in the tripped state and remains latched even after pressure falls below the setpoint. Operator must physically reset the switch - the right behavior for safety interlocks, high-limit cutouts, and any application where silent auto-reset would mask a fault.

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.

Force-Motion Amplifier (Same Core Mechanism)

The 1900-MR uses the same Dwyer force-motion amplifier and diaphragm assembly as the standard 1910, but pairs it with a different snap switch that latches on trip. Performance characteristics and dimensional envelope match the 1910 family.

Technical Specifications

SpecificationValue
Model1900-5-MR
Operating Range1.4-5.5 in WC
Approx. Deadband at Min. Setpoint0.30 in WC
Approx. Deadband at Max. Setpoint0.30 in WC
ServiceAir and non-combustible, compatible gases (not for natural gas or other combustibles)
Wetted MaterialsConsult factory
Switch Type1 Form C relay, SPDT (manual-reset latching)
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)
EnclosureStandard conduit enclosure with snap-on cover (7/8 in conduit connection)
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)
ComplianceNot agency listed (manual-reset variant)
Manufacturer Part Number1900-5-MR

Documentation

PDFCatalog DatasheetPDFInstallation and Operating Manual (Bulletin E-56)

Frequently Asked Questions

What pressure range does the 1900-5-MR cover?
This SKU is the -5 range, with an adjustable setpoint of 1.4-5.5 in WC. Approximate deadband is 0.30 in WC at the minimum setpoint and 0.30 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 1900-5-MR 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 1900-5-MR 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.
How does the manual-reset function on the 1900-5-MR work?
The internal snap switch is a latching type. When pressure rises above the setpoint, the contacts transfer (NO closes, NC opens) and stay in that state - even after pressure drops back below the setpoint. To return the switch to its rest state, a technician must remove the snap-on cover and physically press the reset button on the switch body. This behavior is intentional: it ensures a trip event cannot be silently masked by an auto-reset cycle, which is why the MR variant is used for safety interlocks and high-limit cutouts.
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 snap switch?
Remove the snap-on conduit enclosure cover by loosening its retaining screw and pulling firmly at the bottom. Three screw terminals are exposed: 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. The 7/8 in conduit connection accepts standard 1/2 in NPT conduit fittings with the supplied adapter. Always de-energize before wiring.
Brand:
Dwyer
Series:
1900
Sub-Family:
1900
Product Type:
Compact Manual-Reset Differential Pressure Switch
Operating Range:
1.4-5.5 in WC
Range Code:
-5
Deadband at Min Setpoint:
0.30 in WC
Deadband at Max Setpoint:
0.30 in WC
Service:
Air, Noncombustible Gases (not natural gas)
Switch Type:
SPDT, 1 Form C Relay (Latching)
Reset Type:
Manual Reset (Latching)
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:
Standard, with snap-on cover
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:
Not agency listed (manual-reset variant)
Weight:
1 lb 4.5 oz, 581 g
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