FlexFit Linkageless Controller

The FlexFit solution is a less costly, less time-consuming retrofit from jackshaft (linkage) to modern parallel positioning (linkageless) controls in your boiler room. 

Up-to-date technology with automatic adjustment and remote monitoring options make energy waste, emergency service and costly fixes a thing of the past. 

  • Simple to install, directly mounts in Honeywell 7800 and Fireye E-110 flame safeguard wiring bases
  • Easy to operate user interface and quick commissioning set up
  • Increased burner efficiency and decreased electrical cost

See 3 Reasons to "Go Linkagless" today!

  • Overview and Features
  • Application
  • Documents
Overview and Features

The FlexFit controller brings linkageless control to your burner with an integrated flame safeguard system. This quick and easy retrofit solution increases savings, efficiency, and improves control in the boiler room. The FlexFit flame safeguard plugs directly into Fireye E110 and Honeywell RM7800L wiring bases, eliminating extensive re-wiring.

Retrofitting a burner with a FlexFit provides advanced features such as: oxygen trim for fuel savings and Safety, FD Fan variable speed drive (VSD) for electrical savings, automatic gas valve proving for Safety, high flue temperature lockout prevents boiler damage, and draft control for stable combustion. Linkageless control also provides wider burner turndown which reduces startstop cycling, purge heat losses, and burner corrosion.

  • Installation, electrical, and fuel savings
  • Greater efficiency
  • Firing Rate control
  • FD fan VFD control
  • O2 trim control
  • Draft control
  • FlexFit-110, FlexFit-85, and FlexFit-78 are all UL approved for U.S. and Canada.
  • BMU-SM-xx Servo Actuators (3, 15, and 37 ft-lb) are all UL Approved for US and Canada.
  • QD1 servo Quick Disconnect cabling is IT-ER Exposed Run UL Approved for US and Canada.
  • Flame Scanners BMU-UV, BMU-UVSC (self-check), and BMU-IR are all UL Approved for US and Canada.


FlexFit reduces operating costs with Oxygen Trim, FD Fan VSD speed control, Draft control, and wider burner turndown. FlexFit enhances Safety with Low Oxygen trip, High Flue Gas Temperature trip, Gas Valve Proving, and Servo Self-Checking.


FlexFit-78 plugs directly into a Honeywell RM7800L flame safeguard wiring base. FlexFit-110 plugs directly into a Fireye E110 flame safeguard wiring base. This cuts down installation time and cost.


The FlexFit is designed to control single burner firetube boilers. Leveraging the industry leading BMU platform, the FlexFit can be used in new installations OR be easily retrofitted into existing jackshaft control panels that use supported common flame safe guards.

Fuel savings is accomplished with parallel positioning combustion control with optional oxygen trim. Electricity savings is provided by the ability to control a Variable Speed Drive for the FD Fan.

In addition to flame safeguard and combustion control, the FlexFit also includes optional draft control.

The FlexFit communicates to Building Automation Systems by Modbus or optional Ethernet.

Because it is microprocessor-based and pre-engineered, the FlexFit is an economical alternative to more expensive PLC-based boiler controllers. The parts are in stock for immediate delivery and require no programming.


FlexFit Controller Specification

FlexFit Sell Sheet

FlexFit Manual

FlexFit_Edit Software