MIL and NEMA standards for rugged wiring

[reconvolution]

Colleagues,

I'm looking for standards for rugged wiring. My gut feeling is that there are MIL and NEMA standard that cover that. If anyone knows part numbers for these standards, could you please post them?

Any suggestion, insight or reference is really appreciated!

Cheers,
- Nick

 

[VEBill]

Old joke: "The nice thing about standards is that there are so many from which to choose."

The applicable standards vary with application, and also with the particular aspect of the harness design, build and installation it is that you're concerned with.

Here's an index:

http://www.dscc.dla.mil/Programs/MilSpec/

What's your application?

 

[reconvolution]

The device I'm doing wiring for is a 20kW generator. It will be working semi-outdoors in a shed. It will have an internal combustion engine that will generate some vibration and heat.

 

[VEBill]

For the AC output, you follow your local and national electrical code. If it's being switched in as a backup for commercial power (as is common), then you need to pay attention to how the switching is required to be done - details such as grounding and neutral switching can be confusing.

Best advice would be to hire a licensed electrician (assuming that you're not one yourself).

I don't think that you need to refer to any military specifications. Unless the shed is a military installation; in which case your generator installation services contract documents would run to 12,000 pages. ;-)

 

[reconvolution]

Yes, local codes will cover the mains AC wiring. I’m more concerned about the rest of the wiring.

Imagine that one needs to build a solid wire harness for an existing car engine from scratch. What's given is the working engine with ad-hoc rat's nest wiring.

What are the best practices? Clad wires? Build conduits? Are there types of insulation that make wires more vibration resistant? What temperatures to expect on wires? What hardware to use for securing the wires?

Of course, it would help to get a wire harness from a car, dissect it to see _how_ it was built. I’ll do that. Standards, however, can help understand _why_ is was designed that way.

As you probably know, MIL were precursors of many non-military standards. Many medical device, automotive standards are based on 70s and 80s MIL standards. IPC standards have borrowed heavily from MIL standards, and later replaced them. The beauty of those old MIL standards is that they are good, often concise, often freely available.

Cheers,
- Nick

 

[VEBill]

I think that your question is now clear enough to answer.


You need a wire type that has good vibration resistance, good heat resistance, and good resistance to oils and fuels.

E.g. MIL-W-22759 (for example). Typically PTFE insulation. MIL-W-* will bring up assorted mil wire specs. Once upon a time Kapton was popular, but it was later proven to have issues with carbon tracking and arc-flame propagation.


If you need to have a "mil" connector, and don't mind paying several hundred dollars each (not to mention the required crimp tools), then "38999" is the required keyword (see also PEI-Genesis). Obviously your existing generator isn't going to have such a connector already installed, but perhaps you're going to rewire.


Dressing wires such that they don't destroy themselves is more-or-less common sense. There are standards for various platforms (planes, subs, etc.), but they wouldn't add much value to a generator in a shed. Leave service loops.


E3 (EMI/EMC) is another potential issue. Shielded wires and correct grounding schemes if required (probably not).

 

[R1V2E3]

Start with Mil-W-5088 (old doc with plenty of information)