Are you apprehensive when electric heat tracing is part of a project? There is no reason to be. Simply put, heat tracing involves placing a heating cable on a pipe, applying insulation over the cable and pipe, and controlling power to the cable. Keeping heat tracing projects simple is usually the best approach, which in turn keeps the design, documentation, installation and operation user-friendly and may even lower costs.
This article describes the basic requirements of a heat tracing project along with guidelines to help you simplify its design, control and cable selection while meeting the needs and expectations of the project’s end users. The electric heat tracing project discussed is a temperature-maintenance application that involves using heating cable to replace heat lost through pipe insulation for the purpose of maintaining fluids inside of a pipe within a specific temperature range.
The four basic requirements of any heat tracing project are:
- All electrical heat tracing must be ground fault protected per the National Electrical Code.
- The correct control device must be selected.
- The necessary power output of the heat tracing cable must be determined.
- The proper heat tracing cable type must be selected from the three industry-standard types.
These four requirements may at first seem daunting, but approaching an electric heat tracing project as a three-part process simplifies the job.
The basic parts of an electric heat tracing project are design, control and cable. Included under each basic part of the project below are some general rules-of-thumb to help with each step along the way.
Step 1: Design Your Industrial Heat Tracing System
- Identify the temperature requirements of each pipe along with pipe and insulation data.
- To keep costs down and maintain simplicity, select only the functions and features that are required for meeting the end-users’ needs. Avoid specifying all the functions or features of a manufacturer’s control or cable.
- Use the highest available voltage for the heat tracing cable. This is beneficial for using the maximum length of cable per circuit. This also provides the least amount of circuits for the system, which keeps it simple and generally lowers costs.
- Locate power connection points conveniently and for multiple cable use. This minimizes electrical components and labor.
- Label all cable connections, junction boxes and circuit designations on the installation drawings and in the field.
Note that heat tracing of fire suppression sprinkler lines is not covered in this article as it is a complex task and is beyond the scope. Additionally, if heat trace is being considered for raising the temperature of a pipe, it also is a more complex project and beyond the scope. However, some manufacturers offer assistance with temperature-raise designs.
Step 2: Determing How You Will Control the Electric Heat Tracing
- Consider using a circuit breaker panel board and a controller for control. This provides simplicity and allows the selection of breaker panels of the same type used in the facility. Combining circuit breakers, disconnects, contactors, controllers, etc., into one panel may add complexity, functions and cost unnecessary.
- Determine which functions are required. Temperature setpoint is the most common control function. Other common functions include low temperature alarm, high temperature alarm, low current alarm and ground fault alarm. If connection to a building automation system or other network is required, determine what information is necessary to be sent or received by the controller. Typically, dry alarm contacts are the only requirement, which simply can be read as an open or closed switch by most building systems.
- If time is an issue, select ready-made control products. Custom controllers can add time to equipment delivery.
- Always try to locate controls indoors in a secure, dry area.
- If you are heat tracing in a hazardous area, try to locate the controls in an ordinary location.
Step 3: Select Your Industrial Electric Heat Tracing Cable
Cable typically is selected based on cost, pipe temperature and environmental requirements. Three industry-standard cable types typically are used.
Self-Regulating Cable. This type of cable offers the lowest cost, low temperature use range and cut-and-terminate capability in the field. The amperage (current) and power output of self-regulating cable changes with temperature. This cable type has inrush current, which can result in shorter cable length per circuit.
Typically, this cable is used for freeze protection and heat tracing up to 150°F (65°C).
Constant-Watt Cable. This type of cable offers medium cost, a higher temperature range and cut-and-terminate capability in the field. The constant-watt cable has the advantage of current monitoring. Typically, this cable is used in industrial pipe-temperature maintenance. Depending on the cable jacket insulation, heat tracing maintain temperatures can be in the 400°F (204°C) range.
Mineral-Insulated Cable. This type of cable has a higher cost as well as a high temperature capability. Typically, the mineral-insulated cable is factory terminated to field measurements. Mineral-insulated cable can have HDPE jacket insulation for chemical resistance, a bare copper sheath, or a stainless steel sheath for high temperature and chemical resistance. Temperatures over 1000°F (538°C) are attainable with stainless steel sheath mineral-insulated cable.
Regardless of the type of cable selected, keep these guidelines in mind:
- If the cable may contact corrosive elements or other substances, send the chemical information to the manufacturers for cable selection.
- The manufacturers’ data sheets will have wattage, voltage, useable cable lengths per breaker ampacity, area designations, installation kits used, cable materials and other information you may need for cable selection.
- Check the maximum temperature of the pipe during all processes, including steam cleaning. Use these temperatures when selecting a cable type.
Fortunately, manufacturers are available to assist you with the entire process. Heat-loss calculations are provided by some manufacturers. You only need to provide pipe sizes, insulation types and thicknesses.
Many heat tracing manufacturers will help you select the cable, components and controls. Some manufacturers have 30 mA ground fault protection built into their control equipment. This avoids the use of expensive ground fault circuit breakers and their specific panel boards. Some manufacturers provide installation and shop drawings to make the project complete.
Following these guidelines and tips will reduce your apprehension of heat tracing projects and keep your heat tracing systems simple. Most importantly, you will be meeting your end-users’ needs and expectations.
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