When to use 15A vs. 20A circuits (and #14 vs #12 wire)?

[Matt Whiting]

Why not put in 20A breakers? 15A and 20A cost the same. Making the home owner buy another breaker to fully utilize the capacity of the wire is just dumb.

Matt

[dave]

Building more capacity than is required is a waste of resources. Same mentality as driving a vehicle with bad mileage for no compelling reason. There is so little conservation in most houses. With fluoresant lighting, 10 amp breakers would be overkill. When people start paying 25 cents and up a KWH maybe there will be some forced common sense.

[Matt Whiting]

Not at all. It is all a matter of your time horizon. Most houses will last at least 100 years if properly maintained. The electrical wiring will likely last at least 50 years before needing replacement. You have no way to know what the load requirements will be in 10 years, let alone

50 years. Kitchens built 50 years ago had plenty of ampacity for the needs then, but their wiring is now woefully inadequate for a modern suite of appliances. It is almost certain that electrical needs will increase rather than decrease, even with more efficient appliances and lighting. Providing more than just the bare minimum capacity for today's needs is not at all wasteful as it costs a lot more resources to retrofit later. And, as another poster already pointed out, the lower IsquaredR loss in the heavier wire actually saves energy and money over the long haul.

Matt

[Greg]

I think the technology is going toward lower current, not higher The HVAC system will probably be drawing half of what it did in 1980 for the same house right now. People are warming up to flourecents, TVs are a big lamp now..

"Data" is the 21st century "power". If I was building for 50 years from now I would be running a lot of "smurf" and keeping my options open.

[Trent©]

Most new homes come with a panel full of 15A breakers...plus a bunch of 20A...and some 30s, 50's, etc.

Most new homes sell.

Have a nice one...

Trent

Budweiser: Helping ugly people have sex since 1876!

[Trent©]

Even motors are using less energy than in the past.

Have a nice one...

Trent

Budweiser: Helping ugly people have sex since 1876!

[Trent©]

Go with 15A. The wire is much easier to work with...especially if yer chaining from one recpt to the next. And you can back wire them with standard recepts...which you can do with #12 wire. Its easier to get all that wire in a duplex box if its 14 wire.

You might consider getting Arc breakers...which might already be code in your area.

No. If you need to upgrade, it'll simply be because yer tripping a breaker...which will logically usually require an additional circuit instead of a larger breaker.

Breakers are usually the same price...wire is a little more for 12. Working with the larger wire is the real pain.

Make sure you check yer code to see what size is needed for specific circuits.

Good luck.

Have a nice one...

Trent

Budweiser: Helping ugly people have sex since 1876!

[Greg]

Exactly. The real loads are in the kitchen, laundry and bathroom. NFPA has dealt with that by adding 12 ga circuits. The rest of the house is basically running light bulbs and transistors. If a person builds a shop, it is really up to them to come up with a plan for the extra power. You can't expect a builder to anticipate that need in advance unless it was spec'ed in the house.

[default]

If you were really clever, you'd be putting in easily accessible raceways, and not worrying so much about what goes in them.

[bill shipley]

[Matt Whiting]

The same thing as will happen with a 15A breaker. An 18 gauge cord with a short will carry 20A more than long enough to trip the breaker before it gets hot enough to cause a fire.

Matt

[Greg]

The question was never whether a bolted fault on a small conductor would trip the O/C device. What happens if this is an arcing fault or an overload?

[AndrewJ]

Yes, everytime you use an outlet you are heating your home with electric heat. The heaver the wiring the less heat. Codes do not factor in effeciency in any way so you should. The heaver guage pays for its self very quickly. In 18 years my company has never run a 15A line to anything.

[John Smith]

We use #12 wire everywhere for both 15A and 20A circuits.

For those loads which truly require a 20A circuit, they get a 20A breaker and most of the time these wiring runs are reasonably short.

For all other non-specialized wiring we install #20 / 15A combo as a safety precaution.

All bedrooms get 15A arc-fault type breakers.

[dave]

So at say 15 cents per killowatt hour you might save 50, 60, or maybe 80 cents this year. Sorry but this does not even make sense for a solar powered house. Don't even want to go there with the heating part. Ya can get it all here