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JC-15D Flue Gas Temperature Monitor

Application | Overview | Features

The JC-15D Flue Gas Temperature Monitor is a microprocessor based indicating instrument with an optional heavy duty Thermocouple Assembly.

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JC-15D Flue Gas Temperature Monitor
JC-15D Flue Gas Temperature Monitor

  • Application

The JC-15D is used to monitor boiler efficiency (higher stack temperature translates into lower efficiency) and as a high stack temperature switch. According to the Hartford Steam Boiler Inspection and Insurance Co., “Three out of every four (boiler) accidents are caused by overheating, and 80% of the overheating losses resulted from continued firing with low water levels; despite the fact that boilers, …are equipped with up-to-date controls.”

When a boiler runs out of water, the stack temperature gets very high very fast. A high stack temperature switch can alert the flame safeguard system and shut down the burner before the boiler is damaged, and potentially prevent a boiler explosion. 


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  • Overview

The JC-15D Flue Gas Temperature Monitor is a microprocessor based indicating instrument with a heavy duty Thermocouple Assembly. Flue gas temperature is continuously displayed using a highly visible backlit LCD display. An intuitive bar graph display and alarm messages provide clear stack temperature status. Bar graph Scaling, Alarm Setpoints, and Time Delays are all field selectable. All adjustments can be made directly from the faceplate of the instruments by scrolling through user friendly, English language menus. The type J Thermocouple Assembly is constructed of a seal welded inconel sheath for corrosion protection, and can be directly installed in the boiler's flue gas outlet. The unit includes a ½" male NPT process connection, cast iron head with thermal block, and ½" female NPT electrical connection 

Alarm Sequence: Bar graph and numeric displays continuously indicate the flue gas temperature (FGT). If the FGT exceeds the warning setpoint for more than 30 seconds (adjustable), the bar graph blinks, the WARNING message appears, and the alarm relay energizes. If the FGT continues to increase and exceeds the shutdown setpoint for more than 30 seconds (adjustable), the bar graph blinks, the SHUTDOWN message appears; the shutdown relay de-energizes and latches into “Manual Reset” mode. The burner shuts down if the JC-15D shutdown relay is wired into the burner interlocks. The shutdown Relay remains de-energized and the SHUTDOWN message remains on the display until the operator presses the RESET pushbutton.  The alarm relay can be used to activate an external bell or horn. The alarm relay de-energizes when the warning and shutdown alarms are both inactive. Alternately, pressing the JC-15D Alarm Silence pushbutton, or energizing the 120 Vac Alarm Silence input, or a Modbus command can de-energize the alarm relay in order to silence an audible alarm.

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  • Features
  • RS485 Modbus Communication

  • 4-20mADC Retransmission

  • 4 Digit Display

  • 200 Segment Bar Graph

  • Large LCD Graphic Display

  • Field Adjustable Using English Language Menus

  • Low Boiler Efficiency Alarm Message and Contact

  • Burner Shutdown Contact and Message


Power Supply: 120 VAC, +/- 15%, 50/60 Hz, 15 VA

Case Size: 8"H x 3.5"W x 7.5"D

Enclosure Type: NEMA 4 Faceplate

Ambient Temperature: +32° to 122° F

Displays: High Contrast LCD Display, 4" high, 0.5% Resolution Bar Graph

Bar Graph Range: 0°-2000° F field adjustable

Alarm Setpoints: Two (2) Adjustable With Adjustable Time Delays 


Input Types: Type J or Type K Thermocouple, Field Selectable

Accuracy: 0.005% Resolution, 0.07% Accuracy

Break Protection: Upscale   


Relay: Two SPDT Relays 10 A Resistive, 8 FLA, ½ HP, 120 VAC

Retransmit: 4-20 mADC, 650 Ohm Load Maximum

Network: 1200 - 38400 Baud; RS485 Modbus, ASCII or RTU 


Assembly: Type J Ungrounded

Probe Material: Inconel

Insertion Length: 20"

Connection: ½" MNPT 

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