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Stormin Mormon May 27th 10 05:03 PM

440 volt three phase question
 
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..




RBM[_3_] May 27th 10 05:23 PM

440 volt three phase question
 

"Stormin Mormon" wrote in message
...
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.

No, it's 220 more or less, to ground




keith May 27th 10 06:05 PM

440 volt three phase question
 
On May 27, 10:03*am, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?


No.

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)




LSMFT May 27th 10 06:48 PM

440 volt three phase question
 
Stormin Mormon wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

There is normally a transformer in the panel to give you 120 volts if
120 volts is needed there. Don't you have a meter?




--
LSMFT

I haven't spoken to my wife in 18 months.
I don't like to interrupt her.

harry May 27th 10 06:51 PM

440 volt three phase question
 
On May 27, 4:03�pm, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

--
Christopher A. Young
Learn more about Jesus
�www.lds.org
.


With any three phase sytem (assuming it's symetrical) the line volts
= phase volts divided by root three
ie in your case 440/1.73 =254
This is because the phases are 120 degrees apart.
This is the voltage that would appear between phase and ground or
phase and neutral.
However it's not a good idea to run electrical equipment between
phase and ground as there is a good chance of electrocuting yourself
or someone else. The someone else could be some distance away too.

Evan[_3_] May 27th 10 10:03 PM

440 volt three phase question
 
On May 27, 11:03*am, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.



How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?

I asked the _age_ of the unit because there is supposed to be
a service outlet for 120 volt powered tools for maintaining the
roof top equipment installed somewhere near the unit...

And no, with a 3 phase 480 volt system it is typically 277 volts
on each leg...

~~ Evan

Stormin Mormon May 27th 10 11:21 PM

440 volt three phase question
 
Thank you. Saves me building a device, and not have it work.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


wrote in message
...


The nominal 480 wye to neutral is 277 volts. That is why you see 277v
lighting in big buildings



Stormin Mormon May 27th 10 11:22 PM

440 volt three phase question
 
Oh, thank you. I didn't know.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"keith" wrote in message
...
On May 27, 10:03 am, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?


No.



Stormin Mormon May 27th 10 11:22 PM

440 volt three phase question
 
Oh, thank you. I didn't know.



--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"RBM" wrote in message
...


No, it's 220 more or less, to ground





Stormin Mormon May 27th 10 11:23 PM

440 volt three phase question
 
Where I was working, there was a GFCI convenience outlet on the side
(120 VAC) but that got me to thinking. And, I'm learning.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"LSMFT" wrote in message
...

There is normally a transformer in the panel to give you 120 volts if
120 volts is needed there. Don't you have a meter?




--
LSMFT

I haven't spoken to my wife in 18 months.
I don't like to interrupt her.



Stormin Mormon May 27th 10 11:24 PM

440 volt three phase question
 
Thanks. That sounds reasonable. I do try not to use grounds as
neutrals, if at all possible.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"harry" wrote in message
...

With any three phase sytem (assuming it's symetrical) the line volts
= phase volts divided by root three
ie in your case 440/1.73 =254
This is because the phases are 120 degrees apart.
This is the voltage that would appear between phase and ground or
phase and neutral.
However it's not a good idea to run electrical equipment between
phase and ground as there is a good chance of electrocuting yourself
or someone else. The someone else could be some distance away too.



Stormin Mormon May 27th 10 11:25 PM

440 volt three phase question
 

How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?

CY: The unit looks maybe ten years old. It may well been 480, and I
typed it wong.

I asked the _age_ of the unit because there is supposed to be
a service outlet for 120 volt powered tools for maintaining the
roof top equipment installed somewhere near the unit...

CY: Actually, this one did have a convenience outlet. But,t hat gets
me thinking.

And no, with a 3 phase 480 volt system it is typically 277 volts
on each leg...

CY: Thanks.

~~ Evan



David Nebenzahl May 27th 10 11:29 PM

440 volt three phase question
 
On 5/27/2010 1:03 PM Evan spake thus:

On May 27, 11:03 am, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)


How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?


Right; we should all tighten up our terminology, nominal voltage-wise.

It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those
weird older numbers that were used, like 117 volts: WTF did that come
from???)


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

The Daring Dufas[_6_] May 28th 10 07:02 AM

440 volt three phase question
 
Evan wrote:
On May 27, 11:03 am, "Stormin Mormon"
wrote:
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.



How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?

I asked the _age_ of the unit because there is supposed to be
a service outlet for 120 volt powered tools for maintaining the
roof top equipment installed somewhere near the unit...

And no, with a 3 phase 480 volt system it is typically 277 volts
on each leg...

~~ Evan


Usually, equipment is rated for a range of voltages. A lot of HVAC
equipment has different taps on the 24 volt control transformer to
pick a different primary voltage. I've seen some air handlers that
had a tap on the control transformer for 110 volts and another for
120 volts. Of course on larger package units there will be taps on
the primary of the control transformer to choose between 208 or 240.
I've seen a lot of blower motors that show a rating of 100-125 VAC
60 Hz on the nameplate.

TDD

John Grabowski May 28th 10 02:36 PM

440 volt three phase question
 

" I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)


How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?


Right; we should all tighten up our terminology, nominal voltage-wise.

It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those
weird older numbers that were used, like 117 volts: WTF did that come
from???)



*I have found that the actual voltage varies by power company. One company
in NJ supplies 460/265 volts while another supplies 480/277. It is quite
possible that Stormin is dealing with 440 volts.

When I worked for my father decades ago he did a lot of industrial work and
we quite often had to add buck and boost transformers to equipment because
the juice from the power company did not match the nameplate requirements
for a machine.


dpb May 28th 10 02:55 PM

440 volt three phase question
 
John Grabowski wrote:
....

*I have found that the actual voltage varies by power company. One
company in NJ supplies 460/265 volts while another supplies 480/277. ...


More than likely it's owing to variations in distribution or even local
voltage drops rather than a difference in system generation setpoints
between utilities.

--

John Grabowski May 28th 10 03:31 PM

440 volt three phase question
 

*I have found that the actual voltage varies by power company. One
company in NJ supplies 460/265 volts while another supplies 480/277. ...


More than likely it's owing to variations in distribution or even local
voltage drops rather than a difference in system generation setpoints
between utilities.



*Many years ago I had an issue with the voltage at a hospital that I was
working at. It seemed that there was low voltage everywhere. I had the
power company come in and monitor the building for a week, but they assured
me that they only supply 460/265 and that is what we were getting. The
ballasts for the fluorescent lighting were rated for 277 volts. I had to go
to every transformer in the building and change the taps so that we could
get 120 volts out of an outlet instead of the 102-105. I also had to
install a few buck and boost transformers on some A/C equipment.

Of course variation in distribution, voltage drop and distance from
transformers does have an effect.


Tom Horne[_4_] May 28th 10 07:31 PM

440 volt three phase question
 
On May 27, 5:22*pm, "Stormin Mormon"
wrote:
Oh, thank you. I didn't know.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"RBM" wrote in message

...

*No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

David Nebenzahl May 28th 10 08:56 PM

440 volt three phase question
 
On 5/28/2010 5:36 AM John Grabowski spake thus:

" I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?


Right; we should all tighten up our terminology, nominal voltage-wise.

It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those
weird older numbers that were used, like 117 volts: WTF did that come
from???)


*I have found that the actual voltage varies by power company. One company
in NJ supplies 460/265 volts while another supplies 480/277. It is quite
possible that Stormin is dealing with 440 volts.


Don't doubt you at all; however, the *nominal* voltages are still
120/240/480. What you're describing are basically under-voltage situations.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

harry May 28th 10 09:44 PM

440 volt three phase question
 
On May 28, 6:31�pm, Tom Horne wrote:
On May 27, 5:22�pm, "Stormin Mormon"

wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
�www.lds.org
.


"RBM" wrote in message


...


�No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

John Grabowski May 28th 10 10:26 PM

440 volt three phase question
 

" I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)

How old is this roof top unit... Seriously 440 volts ? Are you sure
that it isn't 480 volts ?

Right; we should all tighten up our terminology, nominal voltage-wise.

It's 120, 240 and 480. *Not* 110, 220 and 440. (Not to mention all those
weird older numbers that were used, like 117 volts: WTF did that come
from???)


*I have found that the actual voltage varies by power company. One
company in NJ supplies 460/265 volts while another supplies 480/277. It
is quite possible that Stormin is dealing with 440 volts.


Don't doubt you at all; however, the *nominal* voltages are still
120/240/480. What you're describing are basically under-voltage
situations.



*LOL What about 208?


George May 28th 10 11:55 PM

440 volt three phase question
 
On 5/28/2010 3:44 PM, harry wrote:
On May 28, 6:31�pm, Tom wrote:
On May 27, 5:22�pm, "Stormin Mormon"

wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
�www.lds.org
.


wrote in message


...


�No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.

Stormin Mormon May 29th 10 01:00 AM

440 volt three phase question
 
More likely, I forgot the number, and typed it wong. I don't deal with
480/3 very often.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"John Grabowski" wrote in message
...


*I have found that the actual voltage varies by power company. One
company
in NJ supplies 460/265 volts while another supplies 480/277. It is
quite
possible that Stormin is dealing with 440 volts.




Existential Angst May 29th 10 06:03 AM

440 volt three phase question
 
"Stormin Mormon" wrote in message
...
I've had the moment to work on 440 volt roof top heating and AC.

Once in a while, need some power to run a 120 volt device. Is it 120
volts from one leg to ground?

(Yeah, I could just check it. But I was on the roof yesterday, and not
sure how long until I get to another roof.)


No offense, Stormin, but the fact that you even have to ask such a Q means
you have no effing clue about electricity, and thus you proly should not be
fooling around with stuff that runs on electricity.

Proly missionary work is more your aptitude....

--
EA




--
Christopher A. Young
Learn more about Jesus
www.lds.org
.






harry May 29th 10 09:14 AM

440 volt three phase question
 
On May 28, 10:55�pm, George wrote:
On 5/28/2010 3:44 PM, harry wrote:





On May 28, 6:31 pm, Tom �wrote:
On May 27, 5:22 pm, "Stormin Mormon"


�wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


�wrote in message


...


No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected �visually. �Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -


That is completely wrong.

Stormin Mormon May 29th 10 12:48 PM

440 volt three phase question
 
So, tell us what's right.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"harry" wrote in message
...

You can make a very reliable determination with just a meter and
knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -


That is completely wrong.



George May 29th 10 01:32 PM

440 volt three phase question
 
On 5/29/2010 3:14 AM, harry wrote:
On May 28, 10:55�pm, wrote:
On 5/28/2010 3:44 PM, harry wrote:





On May 28, 6:31 pm, Tom �wrote:
On May 27, 5:22 pm, "Stormin Mormon"


�wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


�wrote in message


...


No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected �visually. �Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -


That is completely wrong.


Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?

harry May 29th 10 05:08 PM

440 volt three phase question
 
On May 29, 12:32�pm, George wrote:
On 5/29/2010 3:14 AM, harry wrote:





On May 28, 10:55 pm, �wrote:
On 5/28/2010 3:44 PM, harry wrote:


On May 28, 6:31 pm, Tom � wrote:
On May 27, 5:22 pm, "Stormin Mormon"


� wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


� wrote in message


...


No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -


- Show quoted text -


That is completely wrong.


Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide quoted text -

- Show quoted text -


If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.

George May 29th 10 08:52 PM

440 volt three phase question
 
On 5/29/2010 11:08 AM, harry wrote:
On May 29, 12:32�pm, wrote:
On 5/29/2010 3:14 AM, harry wrote:





On May 28, 10:55 pm, �wrote:
On 5/28/2010 3:44 PM, harry wrote:


On May 28, 6:31 pm, Tom � wrote:
On May 27, 5:22 pm, "Stormin Mormon"


� wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


� wrote in message


...


No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -


- Show quoted text -


That is completely wrong.


Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide quoted text -

- Show quoted text -


If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.


I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.

Don Klipstein May 29th 10 09:41 PM

440 volt three phase question
 
In article , George wrote:
On 5/29/2010 11:08 AM, harry wrote:
On May 29, 12:32�pm, wrote:
On 5/29/2010 3:14 AM, harry wrote:

On May 28, 10:55 pm, �wrote:
On 5/28/2010 3:44 PM, harry wrote:

On May 28, 6:31 pm, Tom � wrote:
On May 27, 5:22 pm, "Stormin Mormon"

� wrote:
Oh, thank you. I didn't know.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.

� wrote in message

...

No, it's 220 more or less, to ground

It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -

That is completely wrong.

Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide quoted text -

- Show quoted text -


If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.


I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.


It sounds easy enough for a 440V delta circuit to have all 3 legs
measure 277 volts from ground. One way for that to happen is if there is
significant and equal stray capacitance from each leg to ground. Another
is if someone connects a "Y" load to the circuit, and connects the load's
center point to ground.

--
- Don Klipstein )

metspitzer May 29th 10 10:04 PM

440 volt three phase question
 
On Sat, 29 May 2010 14:52:54 -0400, George
wrote:

On 5/29/2010 11:08 AM, harry wrote:
On May 29, 12:32?pm, wrote:
On 5/29/2010 3:14 AM, harry wrote:





On May 28, 10:55 pm, ?wrote:
On 5/28/2010 3:44 PM, harry wrote:

On May 28, 6:31 pm, Tom ? wrote:
On May 27, 5:22 pm, "Stormin Mormon"

? wrote:
Oh, thank you. I didn't know.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.

? wrote in message

...

No, it's 220 more or less, to ground

It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -

That is completely wrong.

Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide quoted text -

- Show quoted text -


If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.


I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.


If I was unsure of the voltage, what I would do is call maintenance
and ask.

John Grabowski May 29th 10 11:01 PM

440 volt three phase question
 
No, it's 220 more or less, to ground

It is entirely possible that the 440 volts is from a delta
configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

You can make a very reliable determination with just a meter and
knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -

That is completely wrong.

Really? So if we take the original question where the OP could have
used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide
quoted text -

- Show quoted text -

If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.


I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.


If I was unsure of the voltage, what I would do is call maintenance
and ask.



*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral. The
NEC allows it though.


George May 29th 10 11:17 PM

440 volt three phase question
 
On 5/29/2010 5:01 PM, John Grabowski wrote:
No, it's 220 more or less, to ground

It is entirely possible that the 440 volts is from a delta
configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

You can make a very reliable determination with just a meter and
knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -

That is completely wrong.

Really? So if we take the original question where the OP could have
used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?-
Hide quoted text -

- Show quoted text -

If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.

I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.


If I was unsure of the voltage, what I would do is call maintenance
and ask.



*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


That is because of the way the power company arranges that type of
service. One of the transformers used in the delta connection has a
center tap. They did that it situations where most of the load would be
3 phase but the same service could still supply 120 general purpose
loads without the need for an on premise transformer.

John Grabowski May 29th 10 11:52 PM

440 volt three phase question
 
No, it's 220 more or less, to ground

It is entirely possible that the 440 volts is from a delta
configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne

It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.

You can make a very reliable determination with just a meter and
knowing
how 3 phase AC works.- Hide quoted text -

- Show quoted text -

That is completely wrong.

Really? So if we take the original question where the OP could have
used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?-
Hide quoted text -

- Show quoted text -

If you read my post, If there are just three line connections brought
out, no, you can't tell whether its "star" or "delta" connected.

I did. You didn't describe that limitation but you could still be a
long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one
of
the meter probes on ground.

If I was unsure of the voltage, what I would do is call maintenance
and ask.



*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


That is because of the way the power company arranges that type of
service. One of the transformers used in the delta connection has a center
tap. They did that it situations where most of the load would be 3 phase
but the same service could still supply 120 general purpose loads without
the need for an on premise transformer.




*So a volt meter will tell you if the service is a delta or a Y.


Don Klipstein May 30th 10 12:29 AM

440 volt three phase question
 
In article , John Grabowski wrote:

*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


What you are describing sounds to me like a 240V "star" system with high
leg, a variant of Y. Two of the phases are 240V center tap with the center
tap connected to neutral. That provides four 120V legs. The third is 240V
with one end rather than the center tap of that transformer's winding
connected to neutral to provide the "high leg". It is possible to use the
center tap of that to provide a fifth 120V leg.

--
- Don Klipstein )

John Grabowski May 30th 10 12:40 AM

440 volt three phase question
 

*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


What you are describing sounds to me like a 240V "star" system with high
leg, a variant of Y. Two of the phases are 240V center tap with the
center
tap connected to neutral. That provides four 120V legs. The third is
240V
with one end rather than the center tap of that transformer's winding
connected to neutral to provide the "high leg". It is possible to use the
center tap of that to provide a fifth 120V leg.



*It's been a while since I have worked on three phase, but I seem to recall
on a three phase 240 volt delta system, the high (Orange) leg is around 180
volts to ground. I only remember one phase as being center tapped. Next
time I meet with someone from the power company I will ask them to refresh
my memory.


John Grabowski May 30th 10 03:39 AM

440 volt three phase question
 
*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


What you are describing sounds to me like a 240V "star" system with high
leg, a variant of Y. Two of the phases are 240V center tap with the
center
tap connected to neutral. That provides four 120V legs. The third is
240V
with one end rather than the center tap of that transformer's winding
connected to neutral to provide the "high leg". It is possible to use
the
center tap of that to provide a fifth 120V leg.



*It's been a while since I have worked on three phase, but I seem to
recall on a three phase 240 volt delta system, the high (Orange) leg is
around 180 volts to ground. I only remember one phase as being center
tapped. Next time I meet with someone from the power company I will ask
them to refresh my memory.



*I was just looking in my PSE&G handbook and found a drawing for three phase
services. They supply 3 phase 4 wire 120/240 volt delta, 3 phase 4 wire
120/208 volt wye, 3 phase 4 wire 277/480 volt wye services and they also
list 3 phase 4 wire 265/460 volt wye but in parentheses they have
"Obsolete". I guess the 460 is being or has been phased out (No pun
intended). For the delta service they want the orange leg on the right
terminal in the meter and of course after that it must go on the center
terminal as per the NEC. As I mentioned before PSE&G wants the neutral in a
separate panel from the high leg, therefore two panels must be installed;
one single phase with neutral and one three phase without neutral. I think
JCP&L will accept the neutral and high leg together, but I would have to
double check.


harry May 30th 10 09:25 AM

440 volt three phase question
 
On May 29, 7:52�pm, George wrote:
On 5/29/2010 11:08 AM, harry wrote:





On May 29, 12:32 pm, �wrote:
On 5/29/2010 3:14 AM, harry wrote:


On May 28, 10:55 pm, � wrote:
On 5/28/2010 3:44 PM, harry wrote:


On May 28, 6:31 pm, Tom � wrote:
On May 27, 5:22 pm, "Stormin Mormon"


� wrote:
Oh, thank you. I didn't know.


--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


� wrote in message


...


No, it's 220 more or less, to ground


It is entirely possible that the 440 volts is from a delta configured
transformer that is not ground referenced or is corner grounded.
Point is that one shouldn't assume that the transformer that is
supplying the current is Y configured.
--
Tom Horne


It's only possible to determine how a three phase transformer is
connected visually. Ie by checking the connections.


You can make a very reliable determination with just a meter and knowing
how 3 phase AC works.- Hide quoted text -


- Show quoted text -


That is completely wrong.


Really? So if we take the original question where the OP could have used
their meter and as an example observed 480 VAC between each phase leg
and 277 from each phase leg to neutral we couldn't declare with
confidence that the source transformers were connected in "Y" ?- Hide quoted text -


- Show quoted text -


If you read my post, If there are just three line �connections brought
out, no, you can't tell whether its "star" or "delta" connected.


I did. You didn't describe that limitation but you could still be a long
way from completely wrong with only a meter if you only had access to
the phase legs. Since a "Y" connection neutral is always bonded to
ground I could still get the same readings I described by placing one of
the meter probes on ground.- Hide quoted text -

- Show quoted text -


But you still wouldn't know whether it was star or delta connected.

harry May 30th 10 09:35 AM

440 volt three phase question
 
On May 29, 11:29�pm, (Don Klipstein) wrote:
In article , John Grabowski wrote:
*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. �On a Y connection the reading to
ground will be the same. �In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral. �
The NEC allows it though.


� What you are describing sounds to me like a 240V "star" system with high
leg, a variant of Y. �Two of the phases are 240V center tap with the center
tap connected to neutral. �That provides four 120V legs. �The third is 240V
with one end rather than the center tap of that transformer's winding
connected to neutral to provide the "high leg". �It is possible to use the
center tap of that to provide a fifth 120V leg.

--
�- Don Klipstein )


What you are describing is called a zig zag connected transformer,
common in the US but rarely used in the UK except for producing a
phase shift for rectification purposes. (DC output more ripple free )
http://www.langlois-france.com/pdf/ZIG-GB.pdf

Don Klipstein May 30th 10 09:36 AM

440 volt three phase question
 
In article , John Grabowski wrote:

*As I recall on a delta connection one of the phases will have a higher
reading to ground than the other two. On a Y connection the reading to
ground will be the same. In NJ, Public Service Electric and Gas will not
permit that high leg to be installed in the same panel as the neutral.
The NEC allows it though.


What you are describing sounds to me like a 240V "star" system with high
leg, a variant of Y. Two of the phases are 240V center tap with the
center
tap connected to neutral. That provides four 120V legs. The third is
240V
with one end rather than the center tap of that transformer's winding
connected to neutral to provide the "high leg". It is possible to use the
center tap of that to provide a fifth 120V leg.



*It's been a while since I have worked on three phase, but I seem to recall
on a three phase 240 volt delta system, the high (Orange) leg is around 180
volts to ground. I only remember one phase as being center tapped. Next
time I meet with someone from the power company I will ask them to refresh
my memory.


A 240V phase-to-phase delta with grounded of center tap of one of the
three transformer windings feeding it would have its "high leg" at 208V
from "neutral", same as 120V "leg-to-ground" "Y" or "star" having any
"leg" of this being 208V from a leg one phase apart.

Furthermore, a "delta" source can power a "Y" load unless the source to
the load has neutral disagreeing with a delta's neutral being connected to
center tap of one of the 3 feeding transformer windings. And a "Y" source
can power a "delta" load.

These compatibilities are qualified by compatibility in voltage
leg-to-leg, or "phase-to-phase", which I consider to be more of a notation
for "delta" and less for "Wye".

Furthermore, I have seen some preference for 3-phase power to be
delivered from a source in form of delta without neutral connected to any
point of the 3 feeding transformers' windings when there is lack of need
for anything else. The reasoning is that failing-open of one of the 3
same-level-upstream transformer windings only reduces how much power can
be delivered, with little to no compromise otherwise in ability to use
all 3 phases.

--
- Don Klipstein )


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