Electrical question

[Hedges]

I thought 3 windings on an E core was cheaper than 3 single phase transformers, a bit less steel. Don't remember for sure which they would have installed.
Either way, the price was almost all the labor of hanging a transformer on a utility pole and stringing wires, with insulators on a couple poles, to the 12kV (+/-) pole near by.

I don't know if any other company allowed to do such a hookup.

Of course I could have bought and installed transformers on my own property. But doubt it would be appropriate to bring 12kV to there.

The rules vary on what the neighborhood has. If there was already a low voltage transformer for 3-phase near by, might have been different.

I was trying to get power for future shop tools, 3-phase appliances like HVAC, and my Sunny TriPower.
But that GT PV inverter was rejected for not having the latest grid support and control features required as of 2020, so I backed off to using Sunny Boy. (will substitute Smart Energy which is replacing the discontinued model.)

I'll just use VFD for any tools.
Considered 3x Sunny Island to make 3-phase from single phase, but I haven't found a way to feed 120/240V to them, only 120V, cutting in half the pass-through current. I did get 3x SI to connect but had excessive current flow (using transformers to do vectors off 120/208Y phases to get 180 degrees phase.)

 

[timselectric]

When I saw 12kV 3-phase on the cross street two houses away, I was excited.
I requested 120/208V 150A service upgrade (to replace 120/240V 100A.)

Visiting the site, a PG&E guy said it might cost $15,000.
I said, "That's maybe twice what the transformer costs."

He later emailed and said I wasn't eligible to request 3-phase. Because my loads weren't 75 kVA.
That would have been for 120/208Y. Reading their rules, I pointed out that a 3 HP motor was sufficient for me to demand 120/240V high-leg, and they acquiesced.

However, the next person (in the list of people to wear me down), called and gave an estimate of $150,000.
Two trucks with crews, two days, at $25,000 per truck per day. Shut down the power line. Install one 3-phase transformer on a pole and string 200' of wire to it (then the drop to my house.)

No thanks, I said. I'll just install PV, a 3-phase inverter, and disconnect from PG&E.

(In reality, what I'll do is get 120/240V 200A upgrade. Since multiple customers will be served, even if they have to upgrade transformer it should be all their cost.)

Oh, and after I paid $150k (if I did), they would own the asset, probably claim on the books it was $150k worth of material and installation. Then they could collect 8% = $12,000 annually in income, declining as it was depreciated. Pretty good racket for a transformer and wire worth about $12k total, huh?

Wow
Just wow

 

[CoolWill]

208/120 you get 120 for phase to phase voltages not phase to neutral. Just like a leg of 240 to neural is 120v just with some phaser math involved.

No one is talking about 3 phase so it’s best to not muddy the waters.

I think you said that backwards.

 

[740GLE]

I think you said that backwards.

Ah shoot you’re right line to neutral is 120v, phase to phase is 208v

 

[740GLE]

I thought 3 windings on an E core was cheaper than 3 single phase transformers, a bit less steel. Don't remember for sure which they would have installed.
Either way, the price was almost all the labor of hanging a transformer on a utility pole and stringing wires, with insulators on a couple poles, to the 12kV (+/-) pole near by.

I don't know if any other company allowed to do such a hookup.

Of course I could have bought and installed transformers on my own property. But doubt it would be appropriate to bring 12kV to there.

The rules vary on what the neighborhood has. If there was already a low voltage transformer for 3-phase near by, might have been different.

I was trying to get power for future shop tools, 3-phase appliances like HVAC, and my Sunny TriPower.
But that GT PV inverter was rejected for not having the latest grid support and control features required as of 2020, so I backed off to using Sunny Boy. (will substitute Smart Energy which is replacing the discontinued model.)

I'll just use VFD for any tools.
Considered 3x Sunny Island to make 3-phase from single phase, but I haven't found a way to feed 120/240V to them, only 120V, cutting in half the pass-through current. I did get 3x SI to connect but had excessive current flow (using transformers to do vectors off 120/208Y phases to get 180 degrees phase.)

When you buy in bulk and factor in maintaining stock of replacement units individual cans comes our way ahead. By having 3 phase single tank, you almost double the stock codes and storage needs.

As for a third party electrical contractor completing work I might have been thinking of primary extension for a brand new service that you then transfer, not straight up modifying an existing service.

https://www.cmpco.com/documents/40117/46387301/Privately-Built%2BLine%2BExtension%2BChecklist%2B03.23.23.pdf/22cfa387-9e5b-08f2-8923-c5647d1c61e9?t=1680894282156

 

[timselectric]

Another benefit of 3 individual transformers is the ability to run on 2, if 1 fails. Giving time to replace the failed 1.

 

[Hedges]

Sure, if there was a long extension, even a high voltage transformer on it, private contractor might be the way to go.
This is a city lot, fronts on a road with overhead power above the sidewalk. 12kV 3-phase was about 150' from my house.
Presumably all that has to be done by PG&E.

https://diysolarforum.com/attachments/pole-supplying-house-img_3265-cropped-jpg.132665/

Another benefit of 3 individual transformers is the ability to run on 2, if 1 fails. Giving time to replace the failed 1.

For delta.

In this case I would have been getting 120/240V split phase from one transformer, possibly two other transformers for the high leg. Could have been one at 90 degrees? Nah, not available from 12kV Delta.

So I could run if either 240V side transformer went out, but not if the 120/240V split-phase one went out. Unless I had my own center-tapped transformer to establish neutral and ground.

Cost for utility transformer installation?

What has the utility company charged you for a transformer installation or upgrade on their side of the meter? How flexible/negotiable were they? I have a house in Oakland, CA. with 100A service. To support the PV install I want to do, and for more loads like electric heat (presently all gas)...

diysolarforum.com

 

[CoolWill]

A phase converter, even a big one, would come out way cheaper. The ROI for that PG&E outlay might as well be never.

 

[740GLE]

Another benefit of 3 individual transformers is the ability to run on 2, if 1 fails. Giving time to replace the failed 1.

Most 3 phase equipment doesn’t like losing a phase and should shut off to prevent over heating.

If the service is wired for open delta that’s a different story.

But yeah from a cost perspective of the utility replacing 1/3 the cost is way better than the entire thing.

 

[timselectric]

Most 3 phase equipment doesn’t like losing a phase and should shut off to prevent over heating.

If the service is wired for open delta that’s a different story.

Open Delta is what I was referring to.