Chromalox CWM Constant-Wattage Heat Trace Cable

Constant-wattage heat trace cable for process temperatures up to 350 °F

The Chromalox CWM is a parallel constant-wattage heat trace cable for process temperature maintenance and freeze protection where a given watt density is needed at all times. A nickel-chromium heating wire wound over a pairing jacket gives uniform output over the whole length, from a few feet to 780 ft (238 m) from a single power point, with no in-rush current at start-up. The cable can be cut to length and spliced in the field, and its fluoropolymer jacketing suits chemically hostile environments.

Because output is constant it suits higher-temperature applications that need higher watt densities, and the sheet notes that it is not suited for overlapping. Cable jacket colours identify each wattage and voltage code, and an extensive range of wattages and voltages is available.

Technical specifications

Models, output and circuit length

Alternate-voltage output is also published: for example the CWM 12-2 delivers 9.0 W/ft at 208 V and 16.0 W/ft at 277 V, and the CWM 12-4 delivers 2.3 W/ft at 208 V. Always take the output at the actual supply voltage from the sheet before designing a circuit.

Design, accessories and ordering checks

Chromalox points designers to its ChromaTrace project design software, the Heat Trace Design Guide (PJ130), the Pipe Heat Tracing Design Worksheet (PJ305) and the Industrial Heating Cable Installation Instructions (PJ438). Power connection, splice and tee, end seal, ambient-sensing and line-sensing thermostat accessories are available in the U Series, DL Series and EL Series, and Chromalox advises using only its own accessories to keep performance, warranty and approvals valid. A thermostat or controller such as the controllers listed on this site is needed to hold the pipe temperature.

Before ordering confirm the pipe material and size, insulation, the maintenance temperature and the maximum exposure temperature, supply voltage, circuit length against the table, the area classification and the ground fault protection arrangement. The cable is a heating product and the design must be calculated for each pipe run.

How the Chromalox CWM works

Two copper bus wires run along the cable. A nickel-chromium heating wire is wound over the pairing jacket and touches the bus wires at set points. Current flows through each short section and gives heat. The output stays constant along the length.

Where the CWM is used

• Process temperature maintenance
• Freeze protection
• Pipes needing higher watt density
• Chemically hostile areas
• Metal pipes and vessels

Selection checklist for the CWM

• Maintenance temperature
• Watt density
• Supply voltage
• Circuit length
• Pipe material
• Insulation thickness
• Ground fault protection
• Cut-to-length need

Installation, commissioning and maintenance notes for the CWM

Do not overlap the cable. Fix it to the pipe with tape along its length. Make the power connection and end seal with the right kit. Fit ground fault protection. Test the insulation resistance before and after the thermal insulation is fitted.

Requesting a quotation for the Chromalox CWM

Please send the pipe size, the temperature to hold and the voltage. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

CWM cable type

It is a parallel constant-wattage heat trace cable.

CWM length

A single power point can feed up to 780 ft or 238 m.

CWM start-up

There is no in-rush current at start-up.

CWM field work

The cable can be cut to length and spliced in the field.

CWM jacket

The fluoropolymer jacket suits chemically hostile areas.

CWM overlap

The cable is not suited for overlapping.

CWM jacket colours

The jacket colour shows the wattage and voltage code.

CWM bus wires

It has two 12 AWG copper bus wires.

CWM insulation

The insulation is FEP with a tinned copper braid.

CWM supply voltage

The supply is 120 V, 208 to 277 V or 480 V by model.

CWM maintenance temperature

The maximum maintenance temperature is 350 degrees F.

CWM exposure temperature

The maximum exposure with power off is 392 degrees F.

CWM installation temperature

The minimum installation temperature is minus 40 degrees F.

CWM cable size

The cable is 9.0 x 6.2 mm.

CWM bend radius

The maximum bend radius is 28.5 mm.

CWM ground fault

Ground fault protection with a 30 mA trip level is recommended.

CWM models

Models include CWM 4-1CT, 8-1CT and 12-1CT at 120 V.

Cable records for the CWM

Record the circuit length, the insulation resistance and the date.

Choosing the right CWM output

Choose the output from the pipe size and the temperature to hold.

Documents and quotation

The Chromalox CWM data sheet (EHT-DS-CWM) is attached. Seven Star LLC, an independent supplier in Muscat, quotes by model code, voltage and length; stock and lead time are confirmed at quotation.