Harold and Susan Vordos wrote:
"William" wrote in message
...
snip-----


I have a 480 volt service to my shop and house. The main down side
like mentioned above is the transformer to supply the lower voltage
power. The problem with the transformer is it's cost of operation!!
They suck lots of power just sitting there running! Having said
that though, I would still run the same system for my shop if I was
going to reinstall it today.

William...



I've given the idling transformer some thought, but I'm in the
opposite position. I have only one machine that will run on 480
volts (can't be run lower), so my 3 phase delta 240 volt system is
perfect for my application. The 480 volt transformer for the one
machine will be kept turned off unless the machine is in service.
That way I'm not heating the shop unnecessarily.



The idle current form a small transformer that you run one machine off will
not be that bad . My problem is that I needed/wanted to have 200 amps of
power on the lower voltage (120/208) in my case derived from my single 600
amp 480/277 feed. since it's on my side of the meter it's covered by the
NEC and that requires a 75kva transformer for the 200 amps even though I
will NEVER pull 200 amps through it! In fact the Utility co feeds the whole
600 amp service with 3, 25kva cans on the pole ( at my request they will
replace them with larger ones if I want/need them but they charge a min fee
based on the size of the cans so the smaller ones work for me!)


I avoided the lost spaces in my 3 phase panel by installing a single
phase and a three phase panel. the shop is large, so it justified
both panels. Only the 3 phase is on a demand meter, so I minimize my
chances of paying high prices for power. On the other hand, I do
have two power bills, but that was inevitable if I wanted three phase
service. Policy at our Public Utility District is that 3 phase
service is considered industrial------not residential-----so you have
to have different metering. 3 phase is always on a demand meter here.


My system is all demand metered ( and only one bill that way) BUT, at the
magic "75kva average over a 15 min interval " they kick in the demand charge
( if during the 3 summer / 3 winter peak months) You can BET I will never
let that happen as it's CHA CHING!! if it does. At almost $15.00 per KVA +
the KW charge for the whole month. The 75 kva is a lot of power though and
I don't think I will exceed that.


No way was I going to install a wye system.

I wanted the wye and the 277 volts for the HID lighting is great. The cost
of Cu wire is out of sight and I can run most of my machines off 12 gauge
wire if I want. I only have 2 machines that didn't like the 480 volts, and
one runs fine on the 208 and the other (the blade welder for the band saw)
would have probably worked ok but I picked up a single phase 480volt to 240
volt transformer for cheep for the times I have to use that unit.

William....