The NFPA is the ‘National Fire Protection Association’ which is a nonprofit organization that is dedicated to ‘eliminating death, injury, property and economic loss due to fire, electrical and related hazards’. They have more than 300 consensus codes and standards and they offer training, research and education to its members.
NFPA 79 specifically ‘provides safeguards for industrial machinery to protect operators, equipment, facilities and work-in progress from fire and electrical hazards’.
The ‘NFPA 79 Electrical Standard for Industrial Machinery’ is updated every 3 years and is currently undergoing one. There is a key change for VFD cable that is used on machinery in an NFPA 79 environment.
Paragraph 126.96.36.199 in the NFPA 79 2018 Edition states:
“Electrical conductors and equipment supplied by power conversion equipment as part of adjustable speed drive systems and servo drive systems shall be listed flexible motor supply cable marked RHH, RHW, RHW-2, XHH, XHHW or XHHW-2.”
As we know, there are a number of options when it comes to VFD cable.The risk in not choosing the best option is that if your VFD cable goes bad it can become a safety hazard, cause your drive to malfunction or end in complete system failure.
A common choice is thermoplastic insulation (PVC/nylon). The problem with PVC is that it is not ideal in moist environments or, in longer cable runs, thermoplastic PVC can melt and be deformed by heat from a short circuit… do you know what your cabling is made of?!?
To comply with these new recommendations you can easily check your cable print legend or spec sheet. If the cable is UL Listed you want to find out about the insulation used.
What you want to see is:
- RHH: Rubber high heat resistant
- RHW: Rubber heat and water resistant
- RHW-2: Rubber heat and water resistant 90°C dry and 90°C wet locations
- XLPE: Cross linked polyethylene is a thermoset insulation material
- XHH: Crosslinked high heat resistant
- XHHW: Crosslinked high heat and water resistant
- XHHW-2: Crosslinked high heat and water resistant 90°C dry and 90°C wet locations
- THHN: Thermoplastic high heat resistant, nylon coated
- T…: If it starts with a ‘T’ it most likely thermoplastic and should not be used
- Unknown: if material will not be disclosed or they are only rated AWM (appliance wiring material), beware!
Equipment, including drives, can be a costly investment. You do not want to skimp on the VFD cable and risk the drive, or worse, the system. Use Lutze DRIVEFLEX® VFD cables and you will have peace of mind. Every cable in this series is made with XLPE insulation and is available in two types – XHHW-2 or RHW-2.
XLPE insulation has very low capacitance, high impedance and high voltage breakthrough resistance. Cable with XLPE insulation is also ideal for drive applications with pulse width modulation (PWM) because it can cope with high voltage spikes and power distortions from the drive output.
One other bonus of using Lutze DRIVEFLEX® VFD cable is that you will be compliant with paragraph 188.8.131.52 NFPA 79 2018!
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