Typical EHT isometrics include:
- Piping routing
- Piping components
- Location of the junction box and end seal kits
- Circuit Tagging
- Amount of cable per heat sink for valves, flanges, supports, etc.
- Pertinent electrical data: voltage, amperage, etc.
- Temperature data: Maintain temperature, max operating and exposure temperature, hazardous area classification and T-rating
Prior to installation, an insulation resistance test, also known as a megger test, should be conducted on the cable. nVent includes this in their instructions. The megger test pushes voltage at a very low amperage through the cable to check for any breaks in the cable’s jacketing. Breaks in the cabling could result in future system failure or even electrifying the pipe. The megger test is conducted at least five more times: before installation completion, before installing components, before installing the insulation, after installing the insulation, and prior to the startup of the circuit.
Ideally, the cable would be “paid out” (laying out the exact amount of cable needed) to the pipe by running the cable along the length of the pipe and taping it to every foot of heat trace cabling. Any extra cable must be allocated at the heat sinks (a body or material- usually a valve/flange/support- where heat is lost). The slack should be the equivalent length to the amount of cable required for the heat sink and then tied off at the other end. For example, if a valve requires three feet of cable, then the cable would be paid out and the valve would be wrapped with that amount of cable.
Once safety checks have been performed, cabling has been marked, cut, and set aside along with pipe straps, tape, and other accessories, the installation can finally begin.