Two Phase to Single Phase (split phase) Conversion

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TFelc

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I've come across an old property in West Philadelphia with a 2 Phase Service. Currently the shut off is controlled by an old Square D 4 pole fused disconnect. There is no longer any equipment or machinery in the building that utilize this service. Due to the funding the client has and the fact that L&I has failed them they need to update their service. supply to a commercial unit and three apartments.

Can I Break this into 2 single phase parallel split/phase disconnects? Again, no equipment left in the building is using 2 phase.
 
I would think it's possible. You mention a 4-pole disconnect. Is it a 4-wire system or 5-wire? You would need transformers to turn the 120 volts of each phase into two separate 120/240 V systems. A Scott-T transformer is possible, but more specialized and pricey.
 
Do I understand correctly that the existing service has two sets of ungrounded conductors that are 90 degrees (not 120 or 180 degrees) out of phase with each other? I have never actually come across such an animal.
 
IIRC 2-phase 5 wire is usually two 240/120 sets with the centers connected and grounded.

AFIAK, and I've tried to find others, real PoCo-distributed 2-phase only still exists in center-city Philadelphia and Hartford CT. How far "west" is this service (30th st or 65th st or ??)? It's also assuredly derived from the 3-phase distribution via a Scott-T transformer. Also IIRC, they only reason it still exists is that the PoCo would charge the building owner to change, so they don't.
 
TFelc said:
Can I Break this into 2 single phase parallel split/phase disconnects? Again, no equipment left in the building is using 2 phase.
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Yeah thats how most two phase is used these days, your service would be a service wireway and you tap single phase disconnects off each set of phases.
If you can keep the 4-pole service disconnect then create a wireway beneath then would have feeder taps to single phase disconnects.

You If I recall the color code was phase a is L1 black & L2 red and phase B is L3 blue and L4 yellow.
Your common neutral in the service wireway is 140% of your calculated load, after you split off a phase your neutral is normal size.
 
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CoolWill said:
You would need transformers to turn the 120 volts of each phase into two separate 120/240 V systems.
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A transformer is not necessary, parts of Philly has (or had) 5-wire, 4 hots and a large neutral as the secondary distribution, a single phase service drop or lateral is tapped off one set of phases. If a customer wanted poly phase both sets and a neutral are bought to the service.
CoolWill said:
A Scott-T transformer is possible, but more specialized and pricey.
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These were used in the 70's nad 80's to go from two phase 240 to 3-phase 208 but after VFD's became common people started powering 3 phase equipment like an elevator from a single phase 240V set instead of bothering with a transformer they over size the VFD.two_phase_5_wire.png
 
tortuga said:
A transformer is not necessary, parts of Philly has (or had) 5-wire, 4 hots and a large neutral as the secondary distribution, a single phase service drop or lateral is tapped off one set of phases. If a customer wanted poly phase both sets and a neutral are bought to the service.

These were used in the 70's nad 80's to go from two phase 240 to 3-phase 208 but after VFD's became common people started powering 3 phase equipment like an elevator from a single phase 240V set instead of bothering with a transformer they over size the VFD.View attachment 2578150
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Yes, with 5-wire it is simpler. But with 4-wire, if any exist, you would need transformers.
 
The two phase around here is or was a 600V two-phase at a old GE campus Pittsfield MA, it was 3-wire, a engineer explained it to me after I incorrectly called a 3-wire 120/208 'two phase'.
 
zbang said:
IIRC 2-phase 5 wire is usually two 240/120 sets with the centers connected and grounded.

AFIAK, and I've tried to find others, real PoCo-distributed 2-phase only still exists in center-city Philadelphia and Hartford CT. How far "west" is this service (30th st or 65th st or ??)? It's also assuredly derived from the 3-phase distribution via a Scott-T transformer. Also IIRC, they only reason it still exists is that the PoCo would charge the building owner to change, so they don't.
Click to expand...

I thought I read more recently that PECO was starting to give up on 2 phase and wanting people to swap it out anyway.
 
TFelc said:
I've come across an old property in West Philadelphia with a 2 Phase Service. Currently the shut off is controlled by an old Square D 4 pole fused disconnect. There is no longer any equipment or machinery in the building that utilize this service. Due to the funding the client has and the fact that L&I has failed them they need to update their service. supply to a commercial unit and three apartments.

Can I Break this into 2 single phase parallel split/phase disconnects? Again, no equipment left in the building is using 2 phase.
Click to expand...

If 2 of the hots and the neutral can give 120-0-120 standard 240 volt service, do you have enough amps to run the whole thing off of one phase only, and ignore the other phase?
 
Birken Vogt said:
If 2 of the hots and the neutral can give 120-0-120 standard 240 volt service,
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Both phases have that , its pretty handy I'd keep it.
From what recall a 75kVA single phase load would be a about 320A 120/240 split phase, 225A Two phase and about 200A 3 phase delta.
I have seen many services back in my Philly days that were upgraded to a simple wireway with a 5-wire two phase service entrance conductors, then two single phase loadcenters side by side one off phase A (lines a-aa) the other off phase B (lines b-bb) as shown in my diagram above.
 
Was there ever anything in PECO other than 5 wire like you drew above?

I have heard of 4 wire but don't know how they would have done it (no neutral?)

And 3 wire? Similar to open jaw delta?
 
Birken Vogt said:
Was there ever anything in PECO other than 5 wire like you drew above?

I have heard of 4 wire but don't know how they would have done it (no neutral?)

And 3 wire? Similar to open jaw delta?
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4-wire was just two separate ungrounded 120 volt phases. 3-wire was that, but with one side of each phase joined together into a neutral. Due to the phase relationship, the neutral had to be 140% larger than the phase conductors.
 
zbang said:
IIRC 2-phase 5 wire is usually two 240/120 sets with the centers connected and grounded.

AFIAK, and I've tried to find others, real PoCo-distributed 2-phase only still exists in center-city Philadelphia and Hartford CT. How far "west" is this service (30th st or 65th st or ??)? It's also assuredly derived from the 3-phase distribution via a Scott-T transformer. Also IIRC, they only reason it still exists is that the PoCo would charge the building owner to change, so they don't.
Click to expand...
Also seems somewhat likely they may charge higher base fee or even higher rate to supply this system and you may be better off in the end to change over to typical single or three phase service depending on the capacity needs.
 
Birken Vogt said:
Was there ever anything in PECO other than 5 wire like you drew above?

I have heard of 4 wire but don't know how they would have done it (no neutral?)

And 3 wire? Similar to open jaw delta?
Click to expand...

Three wire would be two phase coils 90 degrees from each other but connected at one end.

Open delta is similar in that they connect at one end but are at 120 degree angle instead of 90. You could run a two phase motor from said delta, if proper voltage, it would produce some torque but not quite as it was designed to.
 
kwired said:
Also seems somewhat likely they may charge higher base fee or even higher rate to supply this system and you may be better off in the end to change over to typical single or three phase service depending on the capacity needs.
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Another reason for my post above about only using 3 of the wires/one of the phases, if enough amps right now, for the entire building, so the POCO can later convert their stuff to single phase and not affect your customer at all.
 
Birken Vogt said:
Another reason for my post above about only using 3 of the wires/one of the phases, if enough amps right now, for the entire building, so the POCO can later convert their stuff to single phase and not affect your customer at all.
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Just make sure there is enough source capacity. You likely only have half the VA rating as you do if you utilize both phases
 
I wonder if the rates are higher for 2- than3-phase- it has to be a long-tarriff'd service type with no new installations in years, so all the fixed costs are long paid for. I do recall from previous threads about the topic, the folks in Phila were installing new scott-t transformers just inside the service and wiring the buildings with 3-phase because it was cheaper than paying to change the service.
 
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