Is Metal or Nylon Preferred For Wire Support?
Nylon tie-wraps become brittle when subjected to the heat of engine spaces. Chafe-protected metal clamps are the way to go.
August 30, 2014
Question: My dockmates and I have a bit of a debate going about wire support. The issue is whether or not the metal P-clamps you can see holding the wiring harnesses in place in my engine room are overkill.
The metal, chafe-resistant P-clamps shown above are the ones to trust. Wiring that drops onto a hot engine or into a drive belt will ruin your day.
The harness uses multiple nylon tie-wraps in addition to the rubber insulated P-clamps. My friends think all that’s required are the nylon tie-wraps, only with screw tabs on them, at least every 18 inches. I’ve had trouble with the nylon wraps getting brittle after a few years and actually breaking. Is there an industry standard that addresses this issue?
Answer: You win the debate. In fact the ABYC E-11 standard does address this issue and requires chafe-protected metal clamps just like the ones in your photo, to be used to support wiring harnesses routed above moving machinery and engines. The maximum spacing on the clamps is 18 inches regardless of where the cable runs are routed. The reason for this is what you've already experienced: the nylon tie-wraps will heat-harden and become brittle after a few years of exposure to engine room temperatures. The last thing you want is a large wiring harness like the one you show in your photo suddenly falling onto hot exhaust manifolds, spinning pulleys, or drive shafts. Hence the requirement for chafe-protected metal clamps.
