"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

On Oct 25, 12:58*pm, Karl Townsend
wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

I have seen this done by using a Delta transformer with a center tap
that is grounded. Each hot side of grounded winding is 120 VAC and
220 VAC between them. This can lead to all sorts of issues when
hooking up 3 phase with internal 110 taps. the 3 phase is no longer
ballanced around ground. Lets just say some circute breakers got a
work out untill I figured it out.

On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend
wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Unless you have equipment with conflicting requirements, I'd plan for
a 208 wye service in the shop in order to get get both three phase and
120 single phase. Regardless of what you do in the future, it sounds
like you have enough wire buried to feed the house from the shop.

--
Ned Simmons

On 2010-10-25, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

That would be "208 volts".

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

I would just have separate transformers if it was up to me.

i

On 2010-10-25, Ned Simmons wrote:
On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend
wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Unless you have equipment with conflicting requirements, I'd plan for
a 208 wye service in the shop in order to get get both three phase and
120 single phase. Regardless of what you do in the future, it sounds
like you have enough wire buried to feed the house from the shop.


And how is he going to have 220 in the house?

i

On Mon, 25 Oct 2010 15:39:24 -0500, Ignoramus3392
wrote:

On 2010-10-25, Ned Simmons wrote:
On Mon, 25 Oct 2010 14:58:56 -0500, Karl Townsend
wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Unless you have equipment with conflicting requirements, I'd plan for
a 208 wye service in the shop in order to get get both three phase and
120 single phase. Regardless of what you do in the future, it sounds
like you have enough wire buried to feed the house from the shop.


And how is he going to have 220 in the house?

i

He'll have 208/120, like most apartment buildings.

--
Ned Simmons

On Mon, 25 Oct 2010 15:39:00 -0500, Ignoramus3392
wrote:

On 2010-10-25, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

That would be "208 volts".

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

I would just have separate transformers if it was up to me.

i

Then you're paying for the xformer losses. With a 208/120 wye service
the power company keeps the transformers warm on their dime.

--
Ned Simmons

Karl Townsend wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Two legs and neutral of 120/208V Wye three phase service is generally
considered to be equivalent to 120/240V single phase service for most
uses. 120V only appliances will see no difference at all, 240V
appliances will be minimally affected and many have dual 208/240V
ratings anyway these days since apartments often have 120/208V service.

The key thing to watch out for with three phase service is the rates
such as the common peak metered commercial rates where you end up paying
for your highest use day, not your actual use. The four wires are
correct since either way, one end is the service end with ground and
neutral bonded and the other is a sub.

On Mon, 25 Oct 2010 16:03:09 -0500, "Pete C."
wrote:


Karl Townsend wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Two legs and neutral of 120/208V Wye three phase service is generally
considered to be equivalent to 120/240V single phase service for most
uses. 120V only appliances will see no difference at all, 240V
appliances will be minimally affected and many have dual 208/240V
ratings anyway these days since apartments often have 120/208V service.

The key thing to watch out for with three phase service is the rates
such as the common peak metered commercial rates where you end up paying
for your highest use day, not your actual use. The four wires are
correct since either way, one end is the service end with ground and
neutral bonded and the other is a sub.


Thanks Pete and Ned. This is a big enough job we don't want to do it
twice.

Karl

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

"Karl Townsend" wrote in message
...
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl


Suggest the "center tapped grounded delta" system...

SEE:

http://www.iatse611.org/education/Electrics.htm


--just don't forget....use phase "B" ONLY for 3 phase loads because it has a
208 volt potential to ground /neutral.

--

I"d leave the house as it is and pull out the long runs for use in
the shop once done.

I have single phase myself and added three phase rotary. I could have
the power line deliver me 3 phase - as I have 1500 feet 42KV 2 phase
and the house and shop tap off only one of the two legs. I'm a side
branch from the state highway - delivering power to my site - once a
sawmill. Mill is long gone, but the power allows all sort of possible
future expansions or changes.

Martin

On 10/25/2010 2:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

On Mon, 25 Oct 2010 23:28:06 -0400, John
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl

Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400,
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl



Karl,

Search for pole transformers. If its only the installation cost that is
different I would go for the extra buck and let the power company own
the transformer. If you happen to have one blow from lightning or some
other problem it will be a lot faster if they come and replace it rather
than you searching for a replacement. Also wait till you check on some
of the prices of those pole pigs. Unless you are going to draw a lot of
power you can run open delta with one 240 center tapped grounded and one
240 single phase unit. You only need two legs of the delta to get the
three phase but you get a little less regulation and can only pull the
wattage of the two transformers. Most smaller shops on three phase only
get two pigs on the pole.


John

john wrote:

Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400,
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl


Karl,

Search for pole transformers. If its only the installation cost that is
different I would go for the extra buck and let the power company own
the transformer. If you happen to have one blow from lightning or some
other problem it will be a lot faster if they come and replace it rather
than you searching for a replacement. Also wait till you check on some
of the prices of those pole pigs. Unless you are going to draw a lot of
power you can run open delta with one 240 center tapped grounded and one
240 single phase unit. You only need two legs of the delta to get the
three phase but you get a little less regulation and can only pull the
wattage of the two transformers. Most smaller shops on three phase only
get two pigs on the pole.

John

He's probably looking for a pad mount transformer, not a pole pig.

Pete C. wrote:

john wrote:

Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400,
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl


Karl,

Search for pole transformers. If its only the installation cost that is
different I would go for the extra buck and let the power company own
the transformer. If you happen to have one blow from lightning or some
other problem it will be a lot faster if they come and replace it rather
than you searching for a replacement. Also wait till you check on some
of the prices of those pole pigs. Unless you are going to draw a lot of
power you can run open delta with one 240 center tapped grounded and one
240 single phase unit. You only need two legs of the delta to get the
three phase but you get a little less regulation and can only pull the
wattage of the two transformers. Most smaller shops on three phase only
get two pigs on the pole.

John

He's probably looking for a pad mount transformer, not a pole pig.


Pad mount are more involved than hanging one on the pole. Security and
limiting the access involve a secure fencing system or vault or some
other secure enclosure. Someone will try to steal the copper and run up
the electric demand.

John

On Tue, 26 Oct 2010 12:13:09 -0400, john
wrote:

Pete C. wrote:

john wrote:

Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400,
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl


Karl,

Search for pole transformers. If its only the installation cost that is
different I would go for the extra buck and let the power company own
the transformer. If you happen to have one blow from lightning or some
other problem it will be a lot faster if they come and replace it rather
than you searching for a replacement. Also wait till you check on some
of the prices of those pole pigs. Unless you are going to draw a lot of
power you can run open delta with one 240 center tapped grounded and one
240 single phase unit. You only need two legs of the delta to get the
three phase but you get a little less regulation and can only pull the
wattage of the two transformers. Most smaller shops on three phase only
get two pigs on the pole.

John

He's probably looking for a pad mount transformer, not a pole pig.


Pad mount are more involved than hanging one on the pole. Security and
limiting the access involve a secure fencing system or vault or some
other secure enclosure. Someone will try to steal the copper and run up
the electric demand.

John

We're talking on down the road here, but I'm pretty sure its got to be
pad mount. They said $5-7.5K just for the transformer, so buying his
own looks like a real option. I told him to buy two, one on site
spare. Bet they go for a song IF you can find the right one.

I'm giving the kid a Mazak M4 lathe and a Matsuura MC-1000V twin
spindle bedmill when he's ready. These machines both need serious
three phase.

P.S. I'm testing the D.C. power supply for the mill this afternoon.
Been debugging this panel the last day or so.

Karl

john wrote:

Pad mount are more involved than hanging one on the pole. Security and
limiting the access involve a secure fencing system or vault or some
other secure enclosure. Someone will try to steal the copper and run up
the electric demand.


Um no..

These things are everywhere with no additional
security.

http://www.alfatransformer.com/photos/padphoto.jpg

John wrote:

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.

Do you mean 2 high voltage wires or 2 transformers?

Three phase is possible with 2 transformers, but not
with 2 high voltage lines.

On Oct 25, 12:58*pm, Karl Townsend
wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

One consideration that is not electrically oriented is if there is a
house fire and there is no meter for the firefighters to pull for
their safety, they will just stand by and watch the house burn.

Paul

On Oct 26, 12:27*pm, Jim Stewart wrote:
John wrote:
With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.

Do you mean 2 high voltage wires or 2 transformers?

Three phase is possible with 2 transformers, but not
with 2 high voltage lines.

Open Delta. Only two transformers, and ONLY two high voltage lines to
feed the TWO transformers. Pretty common all over.

Jim Stewart wrote:
John wrote:

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.

Do you mean 2 high voltage wires or 2 transformers?

Three phase is possible with 2 transformers, but not
with 2 high voltage lines.



Three phase can be had off of two hi voltage primary wires.
It is just that you have no choice but to go open delta on the lv.


John

john wrote:
Jim Stewart wrote:
John wrote:

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.

Do you mean 2 high voltage wires or 2 transformers?

Three phase is possible with 2 transformers, but not
with 2 high voltage lines.



Three phase can be had off of two hi voltage primary wires.
It is just that you have no choice but to go open delta on the lv.

Yuck. You're right. But you do have to have
a neutral referenced to the hv wires.

http://blog.allshookup.org/wp-conten...-schematic.png

What an ugly kludge. I'm surprised anyone
would use such a thing.

Slab type transformers aren't particularly difficult to locate outdoors or
indoors.

An armor channel covers the HV side conductors downward along the side of
the utility pole, as underground service is typical with pad xfmrs.

Various sizes of outdoor-duty types can be seen around commercial sites, and
also mobile home parks and campgrounds.

In a wire mill environment where I worked years ago, the KV lines were run
underground into the facility, and the switchgear, xfmrs and various
cabinets were mounted on a reinforced overhead slab standing on beams.
The 3-phase 460VAC circuits were branched out with buss systems.

--
WB
..........


"john" wrote in message
...

Pad mount are more involved than hanging one on the pole. Security and
limiting the access involve a secure fencing system or vault or some other
secure enclosure. Someone will try to steal the copper and run up the
electric demand.

John

"Wild_Bill" wrote in message
...
Slab type transformers aren't particularly difficult to locate outdoors or
indoors.

An armor channel covers the HV side conductors downward along the side of
the utility pole, as underground service is typical with pad xfmrs.

Various sizes of outdoor-duty types can be seen around commercial sites,
and also mobile home parks and campgrounds.

In a wire mill environment where I worked years ago, the KV lines were run
underground into the facility, and the switchgear, xfmrs and various
cabinets were mounted on a reinforced overhead slab standing on beams.
The 3-phase 460VAC circuits were branched out with buss systems.

--
WB
.........
Yes, but typically the utility will only provide a pad mount if the user is
not close enough for secondary service from a pole or existing pad mount.



"john" wrote in message
...

Pad mount are more involved than hanging one on the pole. Security and
limiting the access involve a secure fencing system or vault or some
other secure enclosure. Someone will try to steal the copper and run up
the electric demand.

John

Wild_Bill wrote:
Slab type transformers aren't particularly difficult to locate outdoors
or indoors.

An armor channel covers the HV side conductors downward along the side
of the utility pole, as underground service is typical with pad xfmrs.

Various sizes of outdoor-duty types can be seen around commercial sites,
and also mobile home parks and campgrounds.

In a wire mill environment where I worked years ago, the KV lines were
run underground into the facility, and the switchgear, xfmrs and various
cabinets were mounted on a reinforced overhead slab standing on beams.
The 3-phase 460VAC circuits were branched out with buss systems.


All the plants that I do maintenance in are old.... transformers all sit
behind a chain link fence.

Now that I think about it most residential developments around here
are fed underground with a nice neat little pad and transformer a couple
of feet high and about 4 foot square. A commercial installation would
be just a little bit bigger.

I'm surprised that the electric co. doesn't supply you the transformer
for free if you use a minimum amount of power.


John

Personal would be on the ground seems to me.

Small company ? - larger one ?

Building contractors put them in neighborhoods - have overages ?
Cosmetic ?

Martin

On 10/26/2010 8:12 AM, Pete C. wrote:

john wrote:

Karl Townsend wrote:
On Mon, 25 Oct 2010 23:28:06 -0400,
wrote:

Pete C. wrote:

Jon Elson wrote:

On 10/25/2010 02:58 PM, Karl Townsend wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.
There are essentially 4 ways to wire a 3-phase 2xx Volt service.
There is 240 V delta, and 208 V Wye service. 240 V delta is not what
you want here. 208 Wye service will work, but if you hook the house
to 2 of the 3-phase hots, you get 208 V on the appliances that expect
240. Check the air conditioners, etc. carefully for their ability to
run off 208.

Then, there are two variants of the above systems, you may not be able
to get these installed by your local electric company. One is
corner-grounded delta, that gives you 2 240 V hots, good for running machine
tool motors, the advantage is you can use normal 2-pole electrical
panels and 2-pule breakers. No 120 V in that service, so not suitable
for the house.

The last form is center-grounded delta. It gives you both a 3-phase
service, as well as one phase that is grounded at the center-tap. So,
those two hots and neutral look exactly like single-phase home service.
There is a third leg to provide the 3rd phase.

IF!! you can get your electric utility to provide this service, it
probably is the best choice, as you get real 240 V single phase
service PLUS 3-phase with only 5 wires (3 phases, neutral and ground).

Jon

That last one is also known as "wild leg" delta service since the third
phase is not at 120V relative to the ground/neutral, and that third
phase is normally color coded orange to identify it. It wouldn't be a
problem for the house, since that wild leg wouldn't be fed to the house,
but it has been known to cause confusion and blown up 120V stuff in many
installations. Another issue with this type of service is that some
three phase machines may want 120/208V Wye service with it's neutral to
phase voltage at 120V for all phases.

Generally, if you ask the utility for three phase service, you will be
getting 120/208V Wye service unless you specifically ask for something
different. Expect a lot of questions if you ask for three phase service
and a lot more if you ask for anything but the common commercial
120/208V Wye service.

As noted, most appliances these days are 208/240V rated since 120/208V
service is very common in apartment buildings. Check everything to be
sure, but you're not likely to find much that isn't ok with 208V.


The 240 volt systems were designed to save the power company from
installing an extra pole transformer for 240 volt single phase service.

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.


John

Guys, thanks for the discussion on types of three phase. Bit more to
this than I thought. he's talked with the power company and will get
FAR lower install cost if he provides and maintains the transformer.
We're, of course, looking for a used one. With all the different
primary voltages out there and now all the flavors of three phase,
this looks like a tuff task.

Karl


Karl,

Search for pole transformers. If its only the installation cost that is
different I would go for the extra buck and let the power company own
the transformer. If you happen to have one blow from lightning or some
other problem it will be a lot faster if they come and replace it rather
than you searching for a replacement. Also wait till you check on some
of the prices of those pole pigs. Unless you are going to draw a lot of
power you can run open delta with one 240 center tapped grounded and one
240 single phase unit. You only need two legs of the delta to get the
three phase but you get a little less regulation and can only pull the
wattage of the two transformers. Most smaller shops on three phase only
get two pigs on the pole.

John

He's probably looking for a pad mount transformer, not a pole pig.

Ugly ? - add another transformer and you have true 100% power 3 phase.

With two - and that two gave you three phase and split 220 as well.

So it used the center tap on the right side If split 22O came from
the house on the underground - and the three phase from the pad
transformer, then only three secondary wires are used.

The Military and police/fire all use Three Phase. Delta-Delta.

The idea - overrate the transformer by at least 1/3 but normally 1/2.
Then if or when worse comes to worse, and an input leg is lost, or
a winding is lost (bullet...) the secondary can continue at ~66% e.g.
100% of wanted (due to overrate.) They could take a hit on the primary
and secondary and still stay alive.

Martin

On 10/26/2010 3:42 PM, Jim Stewart wrote:
john wrote:
Jim Stewart wrote:
John wrote:

With 208 single phase two pole transformers were needed, and if three
phase were required you needed to install three transformers to obtain
the star or wye configuration. By using the center-tapped transformer
neutral transformer it eliminated a second transformer. If three phase
was required it was necessary to add only one more transformer rather
than two, except when higher power rating were required and a third
transformer is used. That was the difference between open leg delta and
a full delta secondary. A lot of people are confused by seeing only two
high voltage primary wires and getting fed with three phase into their
building but that is very common.

Do you mean 2 high voltage wires or 2 transformers?

Three phase is possible with 2 transformers, but not
with 2 high voltage lines.



Three phase can be had off of two hi voltage primary wires.
It is just that you have no choice but to go open delta on the lv.

Yuck. You're right. But you do have to have
a neutral referenced to the hv wires.

http://blog.allshookup.org/wp-conten...-schematic.png


What an ugly kludge. I'm surprised anyone
would use such a thing.

Meter on the pole or in the pad transformer - normally on the end
and the sides hinge open. Nothing is hardwired by professionals.

Our big pad units had meters on then.

Martin

On 10/26/2010 1:16 PM, KD7HB wrote:
On Oct 25, 12:58 pm, Karl
wrote:
"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

One consideration that is not electrically oriented is if there is a
house fire and there is no meter for the firefighters to pull for
their safety, they will just stand by and watch the house burn.

Paul