RE. Abbreviations - electrical?

["Hart, Geoff" <Geoff-H -at- MTL -dot- FERIC -dot- CA>]

Stephen Parkes wondered about a few electrical abbreviations:

First, a preface. What's your audience? For a technical audience (which I'm
assuming), you'll want to use the correct unit abbreviation; for a general
audience, you may need to spell out all or part of the unit.

<<12 VAC or 12 volts AC (as in Alternating Current)>>

I've seen 12 VAC, but don't consider myself an authority on this unit. An
electrician I'm not.

<<12,000 watts  or 12,000 Watts  or 12kW>>

12 kW (Watt is the name of a Dead White Male, and named his unit before they
stopped recognizing proper nouns, and thus gets his eponymous unit
capitalized). One big exception: if all the other numbers you're presenting
are less than 1000 W, you should use W everywhere, not kW. Why? Because it's
easier to compare 
12 000 W with 12 W than it is to compare 12 kW with 12 W: the latter
comparison requires the reader to make an extra mental step or three
(spotting the k, recognizing what it means, adding three zeros to the
number, then comparing it with the 12). In general, avoid mixing units in
comparisons. (Just ask NASA if you don't believe me.)

<<40 amp or 40 Amp>>

Unfortunately, good ol' Andre Ampere wasn't a Dead White _English_ Male (nor
was his colleague Coulomb, whose own eponymous units go into making amperes
<g>), so evidently he (they) missed out on the capitalization of the unit
named after him. I've never seen cap-A Amp.

<<w/ ...... or  c/w.......  for parts to be included.>>

Haven't seen this one, so I'm afraid I can't help.

--Geoff Hart, FERIC, Pointe-Claire, Quebec
geoff-h -at- mtl -dot- feric -dot- ca

"Technical writing... requires understanding the audience, understanding
what activities the user wants to accomplish, and translating the often
idiosyncratic and unplanned design into something that appears to make
sense."--Donald Norman, The Invisible Computer