I believe the code forbids running cables so that they
Are in contract with each other. If you pass through
A beam, I believe they allow 24 inches of contact.
How many cables can go through each hole and
How big must a hole be?
What is the allowable method of running several
Cables perpendicular to a run of joists? Must they
Each be in a separate hole and each hole 3 diameters
Away and in a horizontal,not vertical, plan?
Second part of the question is what about house
Insulation and cables running in it? In a partion, this
Is less likely but on outer walls, such as in kitchen,
The cables are going to be subject to heating , no?

Cables not allowed to contact each other is not true. The 24 inch you refer to means if a group of two or more cables are bundled over a 24 in length, the ampacity of each cable must be derated. Derating is too complex to explain here. Kepp the cables that are bundled together to no more than two and there will not be a problem.

First off, drilling holes for cables must be done in the proper location. Holes in any wood frame member must not be closer to the edge than 1-1/4 inch. This is to revent nalis or screws being driven into the wood from being driven into the cable. If you cannot keep the cable away from the edge 1-1/4", you must use a steel plate min 1/16" thick to protect the cable.

Holes in Horizontal joists and rafters must not be done in the center third of the member. For eaxmple, in the basement, you see a joist running from the front to the center of the building, supported by a main beam, this joist is 9 feet. The center 3 feet cannot have holes, the 3 feet to the right and to the left can have holes, spaced evenly across the joist, and not closer to the top or bottom edge 1-1/4in.

This does not mean you can fill these areas with holes. Discretion must be used to not weaken the framing member, this is why holes in the center third must not be drilled at all.

Since there are probably many cables, drilling say a 3/4" n hole and running two cables through. Keeping each hole spaced three diamters is a good rule of thumb.Two cables in one hole next to other cables, two by two, will not need to be derated.

For more detail the size and quantity of holes may need to be consulted with the local building inspector. I can tell you, do not drill a 3 inch hole and run 10 cables through it. The large hole will weaken each joist, and the amount of cables next to each other will cause you to derate each cable.

Where cables are run through wood framing that will be insulated, drill one hole for no more than two cables. Over heating will not be an issue. If you have the room one hole per cable will be preferred.

Any hole should be just large enough to allow the cable to pass through with out any restriction or friction when pulling, but not too large that removes more wood then necessary.

There are many rules by the electric code and building codes that dictate installing cables in wood frame, once you see how it is done, you can see common sense is a good rule.

Review this and see if I was able to make any sense. Get back if you have any other questions. I may suggest finding some how to books with phots, or even finding a builidng that has been wired recently to look at and get some idea how to do install the wiring.

First, please be assured that Im not doubting your
Knowledge compared to mine! But look here on
The bundling question: http://www.iaei.org/foc/cmp6.htm
Looks to me that the "two cables under one staple"
Rule of thumb is going to be a thing of the past.
Somewhere I saw that , I think, 3M makes a
Rated bit that maintains cable separation. Perhaps
Like the little fellows that space spark plug wires
On autos.
If 3 12/2 cables go through one 3/4 hole in a
6" thick beam but are mechanically separated
(staple) approaching and exiting, would that
be ok under the 24" rule, no derating required?
Also, Im pretty sure that on joists and beams
You must be 2" in from the ends and edges, min.
Holes must be vertical stack on studs. Would
They be required to be vertical or horizontal on
Joists and beams?
I have looked at several books, including
Rex Cauldwell's book, as well as the code
Itself.
Your help is appreciated, believe me!

The 3M device you mention is called the " Stacker", and is used to comply with running multiple cables vertically on a stud to comply with the 1-1/4" requirement. It keeps the cable in the center of a stud.

The dimension is not 2", and is 1-1/4" from the edge of any framing member, both through and stapled on the side.

See NEC 2002 Sec 300.4 (A)(1) for cables through holes in wood members
See NEC 2002 Sec 300.4 (D) for cables near edges of wood members.

If you run the three cables through a hole, then spread them between each beam, you are not bundling together longer than 24 inches, and will not need to derate.

But even if you ran 3- 12-2 cables through holes and bundled together without separating, you will need to derate the cable's ampacity 80 %, having 6 current carrying conductors, #12 NM cable , 90 deg C is rated 30 Amps, which allows for a max amps of 24 amps. A 20 amp breaker will still be allowed.