2phase 4wire

Status
Not open for further replies.
S

Smash

Senior Member
Location
Philadelphia suburbs, PA USA
Old school city of Phila incoming power 2phase 4wire. I need to replace a 100amp 2ph 4wire fusible disconnect for a center city building. Water damage has completely rusted this disconnect away. This same water that’s seeps thru the 200 plus yr old wall is also threatening the main switchgear and original incoming power 2ph 4w This is a large box that provides main fuses for different floors and sub panels all split buss top one phase bottom other phase of this old system. 3ph 4w was brought in at another location for all mechanicals, HVAC and other motors when AC was added some 25yrs ago. The rest of the buildings 5 floors general lighting and receptacles are still on this old power. First things first I need to replace one disconnect 2ph 4w 100amp fusible. Obviously your not buying this off a shelf can I use two single phase disconnects and clearly label them as 2ph 4w This power has limited resources as far as code is concerned so I figured I’d start here.
 
Wow. I knew ABOUT this power, but this is the first I've seen of someone working on it. Good luck. My gut says you can do what you propose, so I'll be watching to see what happens.
 
Smash said:
... I use two single phase disconnects and clearly label them as 2ph 4w This power has limited resources as far as code is concerned so I figured I’d start here.
Click to expand...

4-pole fused disconnects are available
4-pole non-fused switches are available
(Square D digest)

Why wouldn't you use one of these?

(edit to add)
I've never seen a 2-phase system. So, there is likely lots I don't know.
 
Smash said:
Old school city of Phila incoming power 2phase 4wire. I need to replace a 100amp 2ph 4wire fusible disconnect for a center city building. Water damage has completely rusted this disconnect away. This same water that’s seeps thru the 200 plus yr old wall is also threatening the main switchgear and original incoming power 2ph 4w This is a large box that provides main fuses for different floors and sub panels all split buss top one phase bottom other phase of this old system. 3ph 4w was brought in at another location for all mechanicals, HVAC and other motors when AC was added some 25yrs ago. The rest of the buildings 5 floors general lighting and receptacles are still on this old power. First things first I need to replace one disconnect 2ph 4w 100amp fusible. Obviously your not buying this off a shelf can I use two single phase disconnects and clearly label them as 2ph 4w This power has limited resources as far as code is concerned so I figured I’d start here.
Click to expand...

"There remain few two-phase distribution systems, with examples in Philadelphia, Pennsylvania;
many buildings in Center City are permanently wired for two-phase"

-wikipedia

it appears that you are working on one of the few remaining unicorns.

the suggestion of using a 4W fused disconnect seems to be your best solution.
it would appear that you have two 120v single phase systems completely independent
of each other, rotated 90 degrees.

what would keep you from using a 120/208 3ph 4w system in direct replacement?
the branch circuits would all be 120v. 1 ph. even rarer was 2ph. 3w. systems, but
those seem to be long gone.
 
I say you need a single 4p disco, and not two 2p switches, to assure simultaneous operation.
 
How critical is simultaneous operation? Are there loads (or even the possibility of such) that use both phases?

I agree that if you need it, the 4-pole is the way to go, and it does seem like they are available. My question is one of mostly curiosity.
 
I see that Philadelphia PECO supplies 2-phase 5-wire 120/240V. So basically the distribution transformers use two center-tapped windings driven at 90 degrees from eachother, with a common neutral connection between the center taps. The schematic I saw of 2-phase 4-wire had two windings that were not connected and had no taps. So in this case I'm wondering if one side of the winding is grounded or if it's left ungrounded. Ungrounded might be OK for distribution but I wouldn't think so for a service.
 
Smash said:
Old school city of Phila incoming power 2phase 4wire. I need to replace a 100amp 2ph 4wire fusible disconnect for a center city building. Water damage has completely rusted this disconnect away. This same water that’s seeps thru the 200 plus yr old wall is also threatening the main switchgear and original incoming power 2ph 4w This is a large box that provides main fuses for different floors and sub panels all split buss top one phase bottom other phase of this old system. 3ph 4w was brought in at another location for all mechanicals, HVAC and other motors when AC was added some 25yrs ago. The rest of the buildings 5 floors general lighting and receptacles are still on this old power. First things first I need to replace one disconnect 2ph 4w 100amp fusible. Obviously your not buying this off a shelf can I use two single phase disconnects and clearly label them as 2ph 4w This power has limited resources as far as code is concerned so I figured I’d start here.
Click to expand...

Good ol' two phase, my home town favorite, Siemens used offer 5 wire two phase panelboards in there P1-5 Series.
Select 'Voltage and System type' = X when ordering P 10-15 of my old 2007 speedfax.
You will need to try a few times and talk to an old timer Siemens switchgear guy directly, then hand you order off to your supply house.
Go Phillys.
 
Just out of curiosity, what is 2phase 4wire?
How is it configured?
 
Smash said:
Old-school city of Philadelphia incoming power 2phase 4wire. ...
Click to expand...
I didn't know 2P4W was still in use. I would enjoy knowing more. For example, how is the incoming service configured? 2 x 120/240 volts? What voltage(s) are supplied to large industrial buildings? How many transformers on a pole? How is power generated, transmitted & distributed? How are substations configured? Can you send pictures?
 
drcampbell said:
I didn't know 2P4W was still in use. I would enjoy knowing more. For example, how is the incoming service configured? 2 x 120/240 volts? What voltage(s) are supplied to large industrial buildings? How many transformers on a pole? How is power generated, transmitted & distributed? How are substations configured? Can you send pictures?
Click to expand...
Can you even have 120/240 with two phase 4 wire? I can see it with 5 wire system.

There is no place to solidly ground a 4 wire system either. Can ground one lead of one phase but that still leaves the other phase with no ground reference. If you ground one lead of each winding don't you essentially create two phase three wire system?
 
kwired said:
There is no place to solidly ground a 4 wire system either. Can ground one lead of one phase but that still leaves the other phase with no ground reference. If you ground one lead of each winding don't you essentially create two phase three wire system?
Click to expand...
If you ground one line of each secondary, you create what is basically an L, which resembles two lines and the neutral of a 3ph Y system except for timing; 90 deg vs 120 deg.
 
drcampbell said:
I didn't know 2P4W was still in use. I would enjoy knowing more. For example, how is the incoming service configured? 2 x 120/240 volts? What voltage(s) are supplied to large industrial buildings? How many transformers on a pole? How is power generated, transmitted & distributed? How are substations configured? Can you send pictures?
Click to expand...

Generation Plants in south eastern PA were all put in during the brief heyday of two phase, once the heavy infrastructure was installed there is little point in changing it, as the only dis-advantage of two phase is you use more wire and gear.
Unlike the disadvantages to NYC's 120/240V DC grid which was a mess.

Two phase motors have great starting torque and are awesome for car lifts, elevators and compressors.

The 5th wire is your neutral and it needs to be 140% of the hots.

It packs more punch than 208Y120 as you get real 240.

Color coding is often red - red / blue - blue, I believe its ~170V between any red and blue.

I have been meaning to setup a scott-T transformer for educational purposes.

Attached pics of some 'modern' two phase stuff.

I dont know the history of ITE but they made all the gear for a long time.


kwired said:
Can you even have 120/240 with two phase 4 wire? I can see it with 5 wire system.

There is no place to solidly ground a 4 wire system either. Can ground one lead of one phase but that still leaves the other phase with no ground reference. If you ground one lead of each winding don't you essentially create two phase three wire system?
Click to expand...
 

Attachments

  • PECO_2PH.jpg
    PECO_2PH.jpg
    138.3 KB · Views: 3
  • twophase_sw.jpg
    twophase_sw.jpg
    116.2 KB · Views: 2
You can have a two-phase/4-wire distribution system fed from a two-phase/5-wire source with the neutral point solidly grounded but not routed to the load. It would be safely grounded and support 240 and also 120(sqrt2) via line to line connections. It is true that without the neutral in the service wire set there is no code compliant way to get 120V.

Sent from my XT1585 using Tapatalk
 
tortuga said:
Generation Plants in south eastern PA were all put in during the brief heyday of two phase, once the heavy infrastructure was installed there is little point in changing it, as the only dis-advantage of two phase is you use more wire and gear.
Unlike the disadvantages to NYC's 120/240V DC grid which was a mess.

Two phase motors have great starting torque and are awesome for car lifts, elevators and compressors.

The 5th wire is your neutral and it needs to be 140% of the hots.

It packs more punch than 208Y120 as you get real 240.

Color coding is often red - red / blue - blue, I believe its ~170V between any red and blue.

I have been meaning to setup a scott-T transformer for educational purposes.

Attached pics of some 'modern' two phase stuff.

I dont know the history of ITE but they made all the gear for a long time.
Click to expand...

The I-T-E Imperial Corp. was headquartered in Spring House, PA.
 
I’m heading back down there today and will take some pictures. For some reason this disconnect is on its own feeding a second floor split bus (one phase for each) sub panel. All other floors feed large transformers first than to other panels. I will check out theses transformers as well or are they phase changers will see.
 
LarryFine said:
If you ground one line of each secondary, you create what is basically an L, which resembles two lines and the neutral of a 3ph Y system except for timing; 90 deg vs 120 deg.
Click to expand...
Effectively makes it two phase three wire system the way I see it.
 
Status
Not open for further replies.
Top