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Dwyer Series M-51 Bi-Metal Air Temperaure Switch

Double Adjustable, Heavy Duty, Automatic Reset

Designed for use as a limit switch, fan control, or alarm switch, Model M-51 is used on all types of air conditioning ducts, furnaces, ovens, dryers, etc. Unit may also be used with damper control system to prevent spread of fire through ducts. Adjustments for both set and reset points. Visible dial shows duct temperature and switch set points. Dimensional Information

o U.L. listed
o Automatic or manual reset
o SPST mercury switch (SPDT switches available)
o Visible dial shows duct temperature
o Two adjustments: one sets high temperature set point, the other sets low temperature reset
Service: Compatible gases.
Temperature Limit: Process: range maximum, Ambient: 180°F (82°C).
Enclosure Rating: General purpose.
Switch Type: SPST mercury switch. Optional SPDT.
Electrical Rating: 10A @ 120 VAC/DC, 5A @ 240 VAC/DC. 3/4 HP @ 120/240 VAC single phase, 1/3 HP @ 120/240 VDC.
Electrical Connections: Screw terminal.
Conduit Connection: 7/8" (22.23 mm) hole for 1/2" (12.7 mm) conduit hub.
Process Connection: Mounting flange. Reversible for flat or curved surfaces.
Mounting Orientation: Horizontal and level.
Set Point Adjustment: Internal moveable pointers for set point and reset point.
Weight: 5 lb (2.27 kg).
Deadband: Adjustable from minimum in model chart to full range.
Set Point Scale: Indication in °F standard. °C optional.
Options: SPDT and DPST switches. Switch that closes on temperature increase.
Agency Approvals: UL and CSA. FM only on models M-51R-74 and MX-51R-75.
Model Switch Action on Temperature Range Minimum Dead Band Dimension A Switch
Number Temperature Rise °F (°C) °F (°C) Insertion Length Reset
 M-51-71 Opens 25 to 125 (-4 to 52) 12 (7) 5-3/8" (136) Automatic
 M-51R-71 Opens 25 to 125 (-4 to 52) 12 (7) 5-3/8" (136) Manual
 M-51-74 Opens 50 to 500 (10 to 260) 20 (11) 4-3/8" (111) Automatic
 M-51R-74 Opens 50 to 500 (10 to 260) 20 (11) 4-3/8" (111) Manual
 MX-51-75 Opens 50 to 650 (10 to 343) 20 (11) 4-3/8" (111) Automatic
 MX-51R-75 Opens 50 to 650 (10 to 343) 20 (11) 4-3/8" (111) Manual
*This model also FM approved
Temperature switch shall be direct acting bimetal type with fully adjustable set and reset points. Switch shall have visible dial and shall indicate duct temperature and switch settings. Dial shall be calibrated in degrees F. Switch shall be U.L. listed. Switch shall be Mercoid Model No. M-51_____.
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