Temperature Sensor Configuration for Fan Cycling by Temperature
International Mechanical Code (IMC) requires that all Type-1 Commercial Cooking operations have fans which activate automatically when the cooking process begins.
To achieve compliance with code, numerous manufacturers install temperature sensors within the kitchen hood to activate the fans when the temperature increases from the cooking process.
This article describes how to "tune" the settings of these sensors to match the heat loading of the cooking equipment under the hood to avoid fan cycling.
Common causes for fan cycling are listed below:
- Standing gas pilots on cooking equipment produce sufficient heat to activate the sensors and fans.
- Incorrect mounting location of the room temperature sensor.
- The Temperature Sensor Offsets need to be adjusted.
- The Preset Room Temperature needs to be adjusted.
- The Hysteresis Timer needs to be adjusted.
For information on HMI Menu Access and Navigation, please see the article HMI Menu Access and Navigation elsewhere in this section.
Fan cycling can often be alleviated by adjusting the temperature sensor offset(s), temp hysteresis, and/or hysteresis timer.
However, many times fan cycling is corrected by only adjusting the temperature sensor offset(s).
The offset is configurable for each temperature sensor probe that is connected to the ECPM03 Board.
When adjusting the offset(s), it is recommended to increase the setting by 5°F increments.
Once the setting is adjusted and the changes are saved, it is best to monitor operation for a day or two to find out if the setting change has corrected the issue.
Temp Sensor Config – This allows the user to set various configurations for the temperature sensors.
If the temp hysteresis and/or hysteresis timer are adjusted, it is recommended to also monitor operation for a day or two after changing the setting.
The temp hysteresis and the hysteresis timer are not typically adjusted; however, they are configurable settings that may resolve the issue.
Explanations for the temp hysteresis and the hysteresis timer are below.
Temp Hysteresis – 2.0°F (default). The hysteresis is used to prevent the fans from
cycling on and off when the temperature in the tempering space is near the activation
value. The fans will turn on when the duct temperature exceeds the activation value,
but they will only turn off when the duct temperature goes below the activation
temperature minus the temperature hysteresis. For example, if the Activation
Temperature is at 85°F and Temperature Hysteresis is set to 2°F, the fans will turn on at
85°F and will turn off at 83°F.
Hysteresis Timer – 00:30:00 (30 minutes default). The hysteresis is used to prevent
the fans from cycling on and off too often due to small appliances generating just
enough heat to turn on the fans but not enough to keep them on for a long time. The
hysteresis timer will maintain the fans on after they have been activated by temperature
for a minimum time set by this timer, even if the temperature in the duct cools back
down.
Room Temperature Sensor
The Room Temperature Sensor is a 10K ohm type-2 thermistor. The sensor
provides room temperature reading to the control board. The sensor should be installed on a
wall within the space but not directly under the hood or close to an appliance. Sensor
readings may be affected by heat.
Typically, a system will have one room temperature sensor. However, systems configured
with 2 fan zones have the option to be ordered with 2 room temperature sensors, one for
each zone. They should be mounted in the space accordingly.
Do not install the sensor on the ceiling or at a location that will not be an accurate
representation of the ambient room temperature.
If the room sensor is not installed in an adequate location, it can be assigned as a preset room temp.
This will allow the controls to monitor a constant temperature in place of a fluctuating temperature.
Preset Room Temp – 75.0°F (default). Allows the user to adjust Preset Room Temperature.