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Remote bulb thermostats regulate temperature of air or liquids in ducts, pipes, tanks and boilers.


  • Suitable for applications requiring temperature control of air or liquids where controller must be placed outside the sensing area.
  • Typical uses include control of dampers and valves in heating, cooling and heating-cooling systems.
  • Fast response models (available for use in return air duct) operate approximately four times faster than standard models.
  • Controller can be mounted in any position. Ambient temperature compensation provides good temperature control.
  • Refer to T775 Electronic Remote Temperature Controller where more exact control is required and/or remote controller location is preferred.
  • T678 models have a maximum connected load of 2000 VA.

Product Specifications

Control of dampers and valves in heating, cooling or heating-cooling systems
Dimensions (in.)
5 5/8 in. high x 2 in. wide x 2 5/8 in. deep
Dimensions (mm)
143 mm high x 51 mm wide x 67 mm deep
maximum connected load = 2000VA
Item Type
50 Hz; 60 Hz
Approvals, Underwriters Laboratories Inc.
UL Listed: E4436, Vol. 4, Sec. 11, Guide XAPX
Approvals, Canadian Standards Association
Certified: File No. LR95329-1
Contact Ratings
120 Vac-- 8.0 AFL, 48.0 ALR; 240 Vac-- 5.1 AFL, 30.6 ALR; 277 Vac--4.2 AFL, 25.2 ALR
120 Vac or 240/277 Vac
Setpoint Temperature Range (F)
55 F to 175 F
Operating Temperature Range (F)
200 F Maximum
Operating Temperature Range (C)
93 C Maximum
Relay Outputs
2 SPDT switch contacts
Sensor Inputs
Sensor Element
Copper bulb
Capillary Length (ft)
5 ft
Capillary Length (m)
1.5 m
Bulb Size (in.)
1/2 in. x 3 9/16 in.
Bulb Size (mm)
13 mm dia. x 106 mm long
Differential Temperature (F)
3.6 F
Differential Temperature (C)
2.0 C
Interstage Differential Temperature (C)
2.0 C to 6.7 C
Interstage Differential Temperature (F)
3.6 F to 12 F
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