Tom&Shelly wrote: How big of a percentage of failure is acceptable? For trailer manufacturers, from what I've heard, it's incredibly high.
I would be willing to bet you a jelly doughnut that the failures are from terrible installations rather than solid wire. The general build quality for commercial RVs is terrible, isn't that why we're all building our own trailers?
Tom&Shelly wrote:Right to the equipment? That surprises me as the shops I've been in had stranded wire from the walls to the equipment. Probably industry standard, though I never asked. Probably solid wires down the walls to the termination, but again, I never paid that close attention.
I can't remember ever seeing stranded wire in the field that was smaller than a #8. Strain relief was always by flexible conduit to the device if it was high vibration.
bdosborn wrote: P.S. in all my years as a consultant I never had a solid vs stranded discussion with clients, code officials or contractors. It wasn't ever an issue I encountered in the critical facilities I worked on.
Tom&Shelly wrote:Well, it is specified in the code, isn't it? NEC or industrial "equivalent"? (eg NFPA 79)
Certainly the wiring for spacecraft was spelled out in the n'th degree, and it was always stranded.
I checked the NEC 550 RV code and the only place where stranded is required is from the generator to the first point of connection.
E) Supply Conductors. The supply conductors from the engine generator to the first termination on the vehicle shall
be of the stranded type and be installed in listed flexible conduit or listed liquidtight flexible conduit. The point of first
termination shall be in one of the following:
(1) Panelboard
(2) Junction box with a blank cover
(3) Junction box with a receptacle
(4) Enclosed transfer switch
(5) Receptacle assembly listed in conjunction with the generator
However, after checking 552 Park trailers I found the following:
(B) Low-Voltage Wiring.
(1) Material. Copper conductors shall be used for low-voltage circuits.
Exception: A metal chassis or frame shall be permitted as the return path to the source of supply
Conductor Types. Conductors shall conform to the requirements for Type GXL, HDT, SGT, SGR, or Type SXL or
shall have insulation in accordance with Table 310.104(A) or the equivalent. Conductor sizes 6 AWG through 18 AWG or
SAE shall be listed. Single-wire, low-voltage conductors shall be of the stranded type.
So there you have it, per the NEC, LV wiring is required to be stranded in a Teardrop but solid is allowed for 120V.
Bruce