Electrical Pre-wire Advice


Senior Member
My brother is in the early stages of planning to build a new home and he is going to want me to offer some advice on planning the Electrical wiring. Does anybody have a checklist that they go by for planning AC wiring?

One thing I noticed in my house was that instead of single-gang boxes a lot of switches are actually in 4" square boxes with mud rings. It is a nice surprise whenever I go to change a switch in one of these because there is lots of room in the box and the wirenuts end up off to the side of the switch instead of stuffed behind. Would this be a good approach for new construction?

How about Romex vs. BX vs. EMT? Stranded wire vs. solid?
Arent the square boxes 2-gang? I think the space is great, but is one half have a metal plate covering the other half? (otherwise you could put a nail in the wall and strike one of those wire nuts or the wires themselves as you described it).

The other half has to be sealed, even if behind the sheetrock I would assume to be up to code (I'm not sure of the specifics, but I know for example you need to close off these boxes before you put sheetrock over them, so I am assuming a variation in this case). Even if it is covered, I've never heard of this (but I bet someone here will know more) and it might not be valid even if a plate is there.

Is it really a two gang box with a 1 gange switchplate (essentially)?
A 4" box is a little smaller than a double-gang box. If you put a single gang mud ring on it, it looks just like a single-gang box after the sheetrock is up. (The extra width of the box is inside the wall behind the sheetrock.)
Not an electrician, but . . .

Romex (plastic sheathed soild wire, for concealed in wall applications (inaccessable))

BX for exposed (flexible metal sheath, for wiring to circulator pumps for HVAC and the like)

EMT is conduit (no wires, you have to pull the wire after the conduit is in), not usually done in residential applications.

I've hardly ever seen stranded wire used in residential either . . .

A few neat ideas . . .

home runs for each outlet/switch/ceiling box, or at least individual lighting and power curcuits for each room . . . I see more and more of this lately

top outlet switched (on 15A lighting curcuit), bottom outlet un-switched (on 20A power curcuit)

. . .

don't foget . . .

sub panel for generator hookup

. . .

250A main is pretty much minumum nowadays . . . get a big breaker box, the fill up quick

that's all that pops into my head at the moment . . .

Pete C
Thanks for the feedback. I assume you agree that extra deep METAL J-boxes are the way to go (whether traditional or 4" square with adapter ring)? Also what do you terminate your home runs to? Right to the breaker box or some intermediate splice box?
Yikes! Homeruns for every termination? That's a lot of wiring! I can't see that as being practical; you'd think that joists and wall studs would start to look like swiss cheese what with all the holes you'd have to drill.... I definitely would advocate seperate circuits for each room however. On some rooms, seperate lighting/outlet circuits are nice too. Don't forget isolated ground in the office and a single dedicated circuit for any potential HA controller.

I've got those 4" square boxes with mud rings too and they sure are nice.
I know this is obvious - but neutrals in all boxes, especially multi-way boxes. Alot of multi-way switch boxes do not have a neutral and it sure would be nice for the newer automation switches.
You should probably check with your local building inspector, but some areas now require that all bedrooms be on independent circuits each with an ARC fault breaker. This was added to the building code recently to help cut down on lamp cord fires in bedrooms. Warning, these breakers take a full slot, so if you have a lot of bedrooms you'll chew up space in the breaker panel fast!

For the GFIs in your bathrooms you want to run 20A circuits and if possible indepent breakers there too. Imagine your son and daughter each flipping on their hair dryers at the same time. Breaker pops instantly...war breaks out soon after...

Also, keep any exterior outlets on the outside of the house isolated from the interior. I've seen electricians wire exterior GFIs to the the interior GFI loop and even though it isn't against code here it can be a very big pain in the neck if the landscaper is working outside and using the full capacity of the circuit and someone inside of the house wants to turn something on in a bathroom.

Lastly, being on Cocoontech you probably already know this, but run a dedicated 20A circuit (or two) with 12GA ROMEX to your future media center location for that future Plasma TV and whole house audio system. Clean power to the stereo components is worth it when it costs only a few extra dollars for romex. Btw, plan for a whole house surge protector at the breaker panel too (<$200). These usually go in a small enclosure next to the break panel and will need to connect to it with a dual-phase i.e. 220V 20A circuit (as short as possible)!
If you are planning using any of the newer technolory (UPB, Zwave) you might want to consider Plastic J boxes as opposed to metal. I'm sure someone has done research on this.
upstatemike said:
A 4" box is a little smaller than a double-gang box. If you put a single gang mud ring on it, it looks just like a single-gang box after the sheetrock is up. (The extra width of the box is inside the wall behind the sheetrock.)
Ahh thanks. I was at work (picture fingers spread to about four inches...). Makes sense now. That must be nice to work with I've had problems with lack of space myself.

On the sub panel recommendation, I almost did this when I had my house electrical system upgraded and cleaned up, but then cut it when the extent of clean up went much further than I expected. I also saw that most of the standby generators included a panel with the price (and I wanted a standby generator versus a portable). (and yes I have way too many projects, this is one is now very far down the list however).

If you are not using one of the portable ones, is it indeed good advice to skip the sub panel until you buy the standby generator? I hadn't come back to this since (although the recent hurricanes down south made me think about it), anyone using one of these or have other recommendations?
Oh a few things that came up that my wife wants that if you are prewiring may make sense:

1. Outlet for christmas tree or the like (may or may not be an issue depending on placement)
2. Outlet near the stairs to put lights on the banister if you want to.
3. Outlet near the front door for a wreath, or similar lighted options
4. Similar outlet for christmas lights on the outside of the house

If you are not planning on central air, separate circuits for AC units where appropriate.

Attic outlets and/or lighting so when you go up there you can flip a switch and see (I saw this once and thought it was a great idea).

Future LCD/Plasma locations (may be hard to plan this) in the bedrooms. If you know where they would go, you could run the electric and mount the receptacles (or seal them properly if not, depending on what makes code or not).

Also some people like to put lights under the eaves of the roof which is another consideration.

And one last one: Place out back, away from the house for a bug zapper.
If you are a Christmas light fiend, put switched outlets under the eaves and in a few places around the outside of the house. I have three switched circuits under the eaves (front, rear, garage) controlled by Leviton relay switches, all on the same x10 address. 20 minutes before sunset HS turns everything on. I forgot to spec the ground level circuit(s) when I built, so I'm stuck with plug-in modules there. I need to run a new circuit to supply power to the fish pond, so I might run a switched lighting circuit at the same time.

Depending on how much you plan on installing automation, you can wire the house with NO 3-way (or 4-way, etc) switches, and install the loads in out of the way locations. Then install multi-button switches, (ie a KeypadLink) at the locations wher you normally would have switches. When you do this, it eliminates the "switch banks" that normally crop up around the doorways, especially exterior doors. Very versitile, and it removes a lot of visual clutter.

Look around for places that you MIGHT want electricity in the future, either for electrical appliances, or lighting. Some suggestions are near the fireplace mantle (so you don't have to string an extension cord 8 ft for xmas light on the mantle), lighting for picture frames or artwork, in cabinet lighting, etc. In one house, a structural requirement left a ledge on the wall of a mid-level stairway landing. The homeowner was going to drywall the top portion so it would be a normal flat wall. I suggested that she leave the ledge, and add receptacles on both sides. Now she has pottery on the ledge and a lighted picture above it. It always draws comments from guests, and the homeowner thinks I walk on water.

As for current code, as dublin00 mentions, an Arc-Fault interrupter is required on all bedroom receptacles. I'm not sure if an individual circuit is required for each bedroom (I always do it that way), but I believe it is. You need a individual 20 amp circuit to each bathroom (with a GFI protecting all receptacles), as well as the dining room. TWO 20 amp circuits are required in the kitchen.

As always, CHECK WITH THE LOCAL INSPECTOR! The NEC might be "national", but the implimentation and interpretation varies widely by jurisdiction. This is NOT a case were it's easier to ask for forgiveness after the fact rather than permission beforehand.
jlehnert said:
As always, CHECK WITH THE LOCAL INSPECTOR! The NEC might be "national", but the implimentation and interpretation varies widely by jurisdiction. This is NOT a case were it's easier to ask for forgiveness after the fact rather than permission beforehand.
I'm having the local inspector over for dinner next week. (he is also the fire chief and the mayor). I'm sure we can work something out.