ECN Forum Forums General Topics of the Trade General Discussion Area 2-wire / 3-wire service

I was watching an old Cary Grant movie this evening ("Mr. Blandings Builds His Dream House"), and at one point they just happen to mention running a 220-volt cable for an electric stove.

That was back in 1948 and it got me to thinking. When did it become common for residential service in the U.S. to be 3-wire instead of just 2-wire 110-120 volts?

Paul,

I don't know the answer to the question but I wisk I had a nickel for everytime someone thought to tell me that they "had 220" in the house, ... or for the times I've said "Everyone's got 220"

Bill

Many people here know that their household voltage is 240, but that's often about as far as their knowledge goes!

By the way, I am right i thinking that the nominal official voltage is actually 117/234 volts? Do the utilities have a specified allowable tolerance? Ours is 6%. (To be more precise, it WAS 6%, but there's some changes going on at the moment. Explanations later, if wanted!)

Paul,

The Power Company in Western Pennsylvania has a user tolerance of: +/- 5% for 120/240V,1Ph. and +/- 10% for >=230V, 3Ph

I have only had the opportunity to change out a few very old 120V services , mostly on neglected buildings. The meter bases & main disco's were usually small, fed K&T, and became 'desktop trinkets' for those who admired their oddity.

It really depends on the region. I believe the 1940s began the increase in services. However, somewhere around 1988, I replaced a 120 Volt 30 amp service.

My first ever rewire was from a 30A 120V to a 200A 120/240V...

That was about '85... (working with Hixson)

Haven't run across another though...

Concerning 2W 120V services there are still quite a few here in Houston. Mostly in the oldest areas of the city. We even have some that are K&T and the tubes stick out of the wall with small #10AWG. There is no W/H just the tubes. These generally have "A base" type meters. Probably dates back to the 40's. Although these are still in existence, the cust is required to upgrade to current standards if any work to the meterloop is performed.

Thanks for all the info.

The lowest rated service I still see fairly reglarly is 40A (at 240V only, remember). Most of the older 30A services seem to hve gone now,certainly in this area. New sevices are generally 80 to 100A, but there are still a lot of 60A about.