On Tuesday, May 1, 2018 at 5:18:55 PM UTC-5, Jimmy Wilkinson Knife wrote:
On Tue, 01 May 2018 22:01:15 +0100, Uncle Monster wrote:

On Tuesday, May 1, 2018 at 1:21:43 PM UTC-5, Ralph Mowery wrote:
In article , says...

It just seems odd not to have it 220 instead of 277 (not far different numbers). But I guess you have three phase completely seperate from your domestic stuff. Our 3 phase is also used for domestic supplies, we get one leg per house, so commercial stuff just takes all three phases, and still has the standard 220 to run
computers and lights.

Large consumers of electricity will have 480 v 3 phase. As stated, the
lights are usually mercury vapor (or similar) or flouresent. The
ballast are set for 277 as that is from the center of the Y winding to
one of the 480 legs. The lights are often split so some go to each leg
of the 480 and center of the Y. That way if something hapens to one
section of lights, the others stay on.

Lots of differences in large companies and small offices and homes in
the US.

Almost no standard homes will have 3 phase. They usually have a
transformer at the power pole that supplies 240 volts with the center
tap to give 120 volts for most of the recepticals and smaller loads and
240 for water heaters, AC or electric heat, stoves, and well pumps if
not on a water system.

In my experience, the large consumers of electricity are getting 4,160 or 13,800 service and own their own transformers. Of course, they are actually small consumers compared to some industrial users who have their own dang substation! There are some older homes in the old high-income neighborhood outside of Birmingham that have 3 phase power. The reason being that at the time the homes were built, they needed a large air conditioning system 5 tons and up and at the time the homes were built, there were no single phase AC units of 5-tons and up available so the large homes were supplied 3 phase power. I serviced some of those old 5-ton semi-hermetic AC units installed on a few of those classic grand old homes that were built in the 1950's and early 1960's. It was like working on commercial refrigeration and AC systems. At least no start relays and capacitors are needed for those 3-phase compressors. Those semi-hermetic compressors are also easily rebuildable and I did some
exchanges akin to installing a crate motor in a car or pickup truck. Those semi-hermetic compressors are quite heavy but I could always find a remanufactured unit. It was getting some help to carry the hunk of steel that was the biggest problem. I miss working. o_O

We had some Irish (never employ immigrunts) electricians doing an extension to a school I worked at.

Their first ****up was connecting two phases instead of a phase and neutral to a set of standard outlets, which destroyed 20 computers. I believe the problem was caused by new and old wiring colours, and the stupid little ****s got confused. We claimed off their insurance (then I er.... may have repaired the "broken" computers which had just blown a bulk capacitor each).

But then they managed to short a couple of incoming phases to the building and set fire to the switchroom - something wasn't tightened properly and came undone. The power company were not happy. Somebody had to pay for a huge diesel generator the size of a lorry/truck/whatever you call the big 50 tonne things over there, to supply the school for a week while they dug the ground up and re-laid the wires.
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I was never afraid of high voltage power, I treated it like a venomous snake and a woman who would betray me at any moment. There are standards and color codes that must be followed not so much for yourself but for anyone who comes behind you. I'd feel pretty bad if someone were to be hurt or killed because I didn't follow codes and wiring standards. I always had test equipment that I could trust. Test everything before energizing it and double check it after it's powered up. Electrical power can be very unforgiving especially at higher voltages. O_o

[8~{} Uncle Sparky Monster