Residential Circuit Layout

Question

I own a home that was built in the 1960s in Hawaii. The home is of Traditional Japanese construction (all wood framing, flooring, w/plaster) from Japan. The wiring throughout is a black clad two conductor wiring (no ground) that I want to get rid of.

In addition to the age and composition of the wire, is the fact that the circuits are laid out in one of the most haphazard fashions that I have seen, and makes no real sense to me. Each wire from the breaker panel goes to a junction box, from which as many as 10 other wires sprout going to individual sockets, switches and lighting circuits, causing a large bundle of wire to be routed through a beam and into the wall cavity (see photo album).

I want to tear all of this wiring (and sockets, and breaker box) out and replace with newer material that is properly grounded. As a first step, I wanted to ask about circuit layout. Are residential circuits typically laid out in a by-room basis? For example a circuit for Living Room, a circuit for Master Bedroom, etc, or are they further divided by use? For example Kitchen Lighting, Kitchen Plugs, Living Room Lighting, Living Room Plugs?

I am doing this somewhat on the cheap, and I intend to have it permitted and inspected, but in an attempt to get something started on it, I wanted to at least conceptualize the circuit layout and scope of work.

Answer 1

Lights are typically put on a separate circuit from the receptacles, especially in places where GFCIs are required (kitchens, baths, and garages). This gives the benefit that when a breaker trips, you are not left in the dark. In many cases, #14 wire is used for lighting circuits whereas #12 wire is used for receptacle circuits. Keeping them on separate circuits allows you to use different size wires for each.

In addition, circuits are generally laid out by room, but it's not always the case that each circuit is one room. Adjacent rooms, or similar rooms, may be combined on one circuit, depending on the sizes of the rooms and how many receptacles each will contain. If your living room and dining room are adjacent, for instance, receptacles from both rooms may be on the same circuit, and lights from both rooms may be on the same circuit. Two adjacent bedrooms may share the same (AFCI-protected) circuit (this cuts down on the number of AFCI breakers needed, saving some expense). A great room that's very large may have it's own circuit for receptacles, but share a circuit for lights.

You may want to run additional dedicated circuits for unique equipment you plan to run, like computers in a home office (especially high-end machines), woodworking equipment, etc. There is nothing wrong with having a single receptacle be on a separate circuit in a room, or have half the room be on one circuit and half on another. Since you're doing the work now, when you've already lived there, you know better how you use the space, so set it up so it works best for you (while maintaining code).

Keep in mind any special-use circuits (oven, dryer, water heater, etc) will be their own circuit by definition, as these are usually 240V. Also keep in mind that the kitchen requires 2 separate small-appliance circuits, and the portion of those circuits in the kitchen need to be GFCI protected.

When you do get everything laid out and run, make sure to clearly label the panel. Perhaps even a separate diagram or spreadsheet showing which breaker every single receptacle, light, and switch is connected to. I might even go so far as to diagram where each wire is run through walls and ceilings. Digital files are cheap, and you never know when that info might come in handy. Along the same lines, consider installing conduit and/or low-voltage cable (networking / TV) at the same time; the best time to run new cable is when the walls are already open.

Answer 2

When you're new to electrical, don't get too mad at how the last guy did it. I have a rule: the last guy may not be any good, but if he did something I don't understand, he always has a reason. I will later uncover the reason.

In America (unlike some places) we physically wire things with a tree topology. It is often a vine, a single string going panel-A-B-C-D, but the kind of star pattern in your photo is allowed, for one circuit.

Unfortunately from your photos it looks like he's feeding most of the house from a heavy feeder, with no overload protection at all on the individual cables. That's not allowed. The entire circuit would need to be on a breaker fit for the smallest wire in the circuit - probably would not work!

Don't be cheap on breaker spaces

There's one place most of us really want you to splurge: the service panel. I want you to not only get the biggest panel you can possibly stand to get, but also get a large subpanel if your house's topology puts a lot of loads far from the panel. Seriously, a 42 space main, and a 42 space subpanel, is not even excessive. You have the panel spaces right when you only use 40% of them.

Because then, you can do neat things like serve 6, 8 or even 20 kitchen receptacle circuits, like one circuit per receptacle (or even two, if money was no object, but those GFCI breakers will break your back). Put a 30A on-demand water heater at each point of use. Give every bedroom 2 circuits. Stick a 240V circuit (2 breaker spaces each) under some windows window for A/C, tanning bed, whatever. You are free, you have the space, unlike hundreds of frustrated posters on here.

Spread circuits around

Speaking of that. The only reason they go one circuit per bedroom is to be cheap. Depending on what performance you want, it may make sense to have 2 circuits per bedroom, or even 2-3 circuits per 2-3 bedrooms (e.g one circuit per shared wall, powering both sides of wall). That way if the daughter has basically no big loads, but son has a gaming PC, laser printer and window A/C, he can spread that across 2-3 circuits without running extension cords through doors.

2 circuits per bathroom, or even 3-4, is not excessive, if someone of a certain gender has a room heater, hair curler and hair dryer all running at once - each of those loads takes typically 1500W so even a 20A (2400W) circuit can't support two. Of course this is unlikely to happen in both bathrooms at once, so two bathrooms could share those circuits.

Answer 3

Wow! I have never seen wiring like that. Out of curiosity, what size breaker/fuse protect those feed wires?

I concur that the house is overdue for rewiring and upgrading. Please do it soon.

There is no requirement for a circuit per room. I have lived in places that did that and it is a pain when a room blows and then there is no light and no ability to bring in a light and plug it in within that room.

In addition to what mmathis said, electrical code is now that all bathrooms must have 20 amp (minimum) circuits, even for lighting and the exhaust fan according to my inspector. (I never did bother to check him on that one.)

There are some non-intuitive requirements: one that upset my wife after living in the house for 5+ years, is that there must be an outlet within 3 (5?) feet of a doorway. We knew perfectly well we did not need those and only put outlets where we would want them, which was within 8 inches of each window, two on long walls, and at least one on every wall where it made sense. As a result of forcing this requirement into our ideal plan, we have one place where there are outlets 4.5 feet apart.

I generally plan wiring to minimize(-ish) the use of wire since the circuit panel tends to be at one end of the house and the majority of plain outlets and lights are at the other end. So most designs have only a few lengthy circuits which include one or two (but not all) outlets in the living room on the way to the bedrooms (for example).

Within one wall which has rooms on both sides, put all those outlets on the same circuit. That saves wire and also makes it easier for both rooms to have at least two circuits in them, solving the darkness problem when a circuit trips.

The one area I did not scrimp on was the kitchen. Originally, this 1950s kitchen had only a single 120 volt circuit which was shared in the bathroom and one of the bedrooms. It tripped all the time because it ran the refrigerator, garbage disposal (which we added), magnificently inefficient lights, and one awkwardly placed outlet for mixers/blenders/microwave/waffle iron/etc. The new kitchen has six 20 amp circuits plus a 240 volt range circuit. Four 120 volt circuits feed four power strips under each cabinet; the microwave is on one of those; the 3 light circuits are on the other 3 outlet circuit. (Yeah, there are now 22 individual outlets in the kitchen.) Another circuit feeds the dishwasher/disposal and the last feeds the natural gas range plus exhaust hood.