DIYbanter - View Single Post - Liability & responsibility of electrician?

Doug Miller

In article , wrote:
On Mon, 6 Jul 2009 04:44:03 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

Doug Miller wrote:
Yes, I'm afraid you are missing the point. Different locations, even though
attached to the same local grid, may have different supply voltages because
they are receiving those supplies through different transformers.

I got that. What is wrong is that the person who wrote that originally (was
it you?) used that to explain why a regular house outlet could be 220 volts
on one side of town, and 240 volts on another, both connected to the same
"grid".

There's going to be some variation, but not that much.

Sorry, but that's not correct. Suppose you have two nominally identical
transformers, each specified to produce a secondary voltage of 230VAC when
4KVAC is applied to the primary. If the tolerance is +/- 5%, one could have a
secondary voltage as low as 218.5, and the other as high as 241.5, without
there being anything wrong with either of them.

Moreover, it's entirely possible to have connected to the same local
distribution grid 30-year-old transformers that are designed and speced to
produce a secondary voltage of 220VAC, and brand-new transformers that are
designed and speced to produce 240VAC. Throw in a small tolerance, and you
might see service entrance voltages ranging from 215 to 250 at different
services on the same local grid.

There simply is no support for your notion that service voltages must be the
same at different locations attached to the same local distribution grid. The
power company distributes the same voltage everywhere, true -- but the service
entrance voltage is determined by the individual transformer at each
individual point of service. There is _no reason_ to suppose that will be the
same everywhere.