Chinese (Simplified)EnglishFrenchGermanHindiItalianJapaneseKoreanPortugueseRussianSpanish

Preferred Instruments

Preferred Instruments manufactures microprocessor based controllers, instruments, and electric actuators for combustion and process applications. Preferred Instruments also manufactures oil tank gauging and leak detection equipment. A major component of the Instrument group sales is from control systems integration and personal computer based Supervisory Control and Data Acquisition systems. Preferred Utilities' industrial factory is located in Danbury, CT

Draft Damper Assembly

The Model E-Link Draft Damper Assembly is part of a full scope control package that assures safe and efficient control with undivided system responsibility.


  • Complete Draft Damper Assembly saves installation time and cost by supplying a factory mounting Actuator, Draft Transmitter, and a Low Draft Switch
  • The Model E-Link Draft Damper Assembly and JC-22D Draft Controller form a complete draft control package


The Model E-Link Draft Damper Assembly pre-mounts a Model SM-15 servo actuator and JC-22XMTR Draft Range Transmitter Assembly. Only a stack draft connection is required. The Model E-Link Draft Damper Assembly is part of a full scope control package that assures safe and efficient control with undivided system responsibility.


Provide a factory assembled furnace outlet draft damper assembly for each boiler. Factory mount the draft damper actuator, draft transmitter and time delayed high pressure cut out. The draft damper shall be a dual opposed blade design, have 24″ inside diameter (select from 12″, 16″, 20″ or 24″ diameter to match boiler or furnace outlet, consult factory for larger sizes), constructed of 10 gauge rolled steel. Non-opposed blade damper designs are not acceptable. The draft range transmitter and time delayed, high pressure (low draft) cut-out assembly shall be totally enclosed in a single dust-tight, splash-proof enclosure. A single draft connection shall be internally piped to a -1″ W.C. to +1″ W.C. 4-20 mADC transmitter and an independent low draft switch. The low draft switch setpoint shall be field adjustable from +0.15″ W.C. to +4.0″ W.C.  The low draft switch shall be mounted and wired to a pilot light so as to illuminate when the low draft switch activates and to a 5 second time delay relay so as to provide an isolated “Low Draft Cut-Out,” 10 A contact for use in the Flame Safeguard Limit Circuit. The time delay feature helps avoid nuisance burner shutdowns due to momentary draft fluctuations. The actuator shall have adequate power to automatically position the damper and shall be suitable for control by the Draft Controller. The actuator shall be totally enclosed in a dust-tight housing, have integral, snap-action, travel limit and open proving switches, electrically isolated feedback potentiometer. A output shaft shall have an integral brake for precise positioning without backlash, rotate 90º in 30 seconds and be capable of being stopped, started, or instantly reversed without loss of power or overloading.  The damper actuator and damper assembly shall be stroked at the factory to ensure proper alignment.  “Shipped Loose” components will not be accepted. The draft damper assembly shall be a Preferred Instruments, Danbury CT, Model E-link Draft Damper Assembly.