3 phase residential with one leg 'out' - Page 2

 
Thank you much for the response Norman -
I looked at the power pole - and there are 2 transformers - One big
Flash Gordon looking one that has 3 lines each going to three wires
traversing to other poles. 2 of 3 wires to my house attach to 2 of
those (as other houses also do). The third wire from my house goes to
a main terminal of another smaller ('pole pig' sort) transformer
mounted next to big one. Appears to be only 2 lines out of smaller
transformer - one line to my house and the other line goes straight to
the big transfomer  -  but can't quite see where connected to large
transformer without doing climbing into neighbors yards/fences. I am
little confused how I get three phase out this - still researching how
that might work
I remember years ago - squirrel short caused power out and utility man
came to my house and asked if I knew I had a "dedicated
tranformer"...I didn't know what he was talking about - and said
"no"....so I am now beginning to understand some of those mysteries
from the past...like finding in attic a huge (but only 1HP)  3-phase
motor connected by belt drive to giant defunct wood squirrel cage
ceiling fan  (from the days before AC). ..besides that huge fan in
cieling...I see no indications why this house would be 3-phase -
unless in the late 40's they just did it that way..this house would be
in 'farm country' back then..now near heart of city..
Thanks again for you response

  wrote:


 You have 208, not 220 volts.

 
clare@snyder.on.ca wrote:

No, he has 220 volts, he also has 110 volts and 208V. 208 volts commonly
comes with 120/208 volt three phase Wye service, but he has open delta
service, and if he has 110 loads off of it he has a "wild leg" to watch
out for as well.

The transformer that was offline was clearly the one with the non center
tapped output, so previously he didn't have that "wild leg" to watch out
for and he didn't have three phase service.

His "house" 110/220 panel is fed from the center tapped output of one of
the transformers, giving him a neutral and two hot legs for the 110/220
house loads. The other three phase panel for the "ranch" loads has the
same two hot legs as the "house" panel and has the additional third hot
leg provided from the other transformer. This ranch panel if it does not
have the neutral fed into it will be a straight 220 volt three phase
delta service. If the neutral leg is present there, he can put 110 volt
loads on as well, but has to be careful because the third leg is the
"wild leg" and is 208V relative to that neutral, not 110V like the other
two hot legs.

Diagrams help a lot with this, but I don't think I'm up to trying to
draw transformers in ASCII art. There should be some sites with diagrams
if you search for "open delta" and "wild leg". Certainly the OP should
not go messing around much with his new found three phase service before
finding such diagrams and understanding them.

 
Thanks again Pete - I think you are spot on. And apologies for an
error in original post - I have 4 wires coming to house (not 3 as
stated)- didn't realize until closer examination that the support/
anchor cable was also the 'neutral' 4th wire.
At end of this webpage: http://www.eng-tips.com/viewthread.cfm?qid=157326
 is a diagram that must be exacly what my setup is . Across my 3 fuses
at 'a', 'b', and 'c' in that diagram (inout to house) I measure 240,
238, and 235 volts. My 'ranch' panel DOES have "110" V circuits. One
thing bothering me a little is (from same diagram), I have 240 volts
across 'a' and 'b'...but only 108 and 105 volts  measuring from 'a'
and 'b' to neutral (measured at bus bar and incoming bare cable) - I
expected 120 V. (Sorry - wish I knew how to attach diagram). Thank you
Pete and Norman for your input - I learned much...

 Pete C. wrote:

Well, the 'wild leg' as you call it isn't exactly 208V.  If the
center-tapped side is truly 110/220 and the smaller transformer is also 220,
then from the third phase to neutral is only 190V.

But still, it's different enough that if you mistakenly use it instead of
one of the 'hot' legs from the larger, center-tapped transformer, it will
blow whatever 110V load you hook up to it.

daestrom