HD110301-1 Rev2
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STEP 3 – ELECTRICAL REQUIREMENTS
Design the heat tracing system using the most commonly expected start-up temperature.
Be practical. If you choose the most extreme (coldest possible) start-up temperature, for example
-40 degrees, you may unnecessarily shorten the circuit lengths, or require larger breaker sizes or
additional panels and power cable. However, keep in mind that if the heating system starts up at
a lower temperature than it was designed for, you may experience breaker tripping. Since fire
sprinkler systems are controlled to power on at 4°C/40°F, this temperature may be used for start-
up design.
To determine maximum circuit length and breaker size required, refer to tables found on the cable
data sheets available at
For voltages other than 120/240V refer to cable data sheets at
All heating cable systems require ground fault protection (27 or 30 mA trip level) as per the
National and Canadian Electrical Codes. This protection is provided in Drexan’s recommended
Controllers.
STEP 4 – SELECTING CABLE POWER OUTPUT
When determining the minimum ambient temperature for your location, always consider the
worst case or lowest temperature. Selecting a low ambient design temperature will provide an
increased safety factor.
From the following tables you can determine the amount of heat (watts/ft pipe) required to
maintain your pipe @ 40°F/4°C. MultiTrace is available in 4 nominal power outputs: 3W, 5W, 8W
and 10W per foot. If higher watt densities per foot are required, run multiple tracers on the line.
E.g. if 20W per foot is required, run 2 lengths of 10W cable.
For example: An ambient temperature of minus -20°F/-29°C and a 2” pipe with 1” of Glass Fiber
thermal insulation will require 3.8 Watts/foot of pipe.
Note: The charts used in this guide are based on Glass Fiber Thermal Insulation. These charts may
also be used with polyisocyanurate and Mineral Wool insulations of the same thickness.
Note: refer to the MultiTrace cable data sheet located on the Drexan HeatTracer Website:
