Running 3 phase power to residential home

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lgmagone

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I have two options for running power to a house I would like to build:

a) Extend single-phase power line 1,600 feet to house underground.

b) Extend three-phase power 2,300 feet underground.

Wondering if anyone can describe in relative terms the cost difference between the two? I would very much enjoy having three phase power at my house.
 
Presumably you have done a load calculation per Article 220.

What is the load at the house and how does that equate to the feeder size that you would run at 120/240V single phase or 120/208V 3 phase considering any voltage drop you want to mitigate?

Then it is a cost estimating exercise based on lots of unknowns in the 1600' or 2300' regarding rocks and other obstructions. Would it be all before the meter or after, meaning is it following NEC rules or utility rules for sizing and installation?
 
zbang said:
Some PoCos won't sell 3-phase to individual residential customers unless it's a really large building, better check the offerings, that might decide it for you.
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Another thing to check on is if your utility will add Power Factor penalties and Demand meters to a 3 phase service. That is often the case and is a rude awakening for people used to residential single phase service.
 
Keep in mind that the heating power of a 240v appliance (water heater, clothes dryer, etc.) will be only 75% on 208v.
 
lgmagone said:
I have two options for running power to a house I would like to build:

a) Extend single-phase power line 1,600 feet to house underground.

b) Extend three-phase power 2,300 feet underground.

Wondering if anyone can describe in relative terms the cost difference between the two? I would very much enjoy having three phase power at my house.
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As others have said, we need more details. I assume this would be primary. Does poco let you run primary or do you have to pay them to do it? If it's an mgn system, then you only need one concentric neutral cable and its about $2.15 per foot. Probably will want to protect it with 2" PVC, .70 cents per foot. If it's a Delta distribution system, you need two cables for single phase. If it's three phase you need 3. Poco may have charges also, which could be substantially more for three phase.
 
190607-1950 EDT

lgmagone:

You list yourself as an engineer. Are you electrical or something else?

Why would you like 3 phase at your home? I would like it at my home, and it would be available? Do I badly need it? No. No justification for the cost. If I need it for experiments I go the the shop. Back when I had some machinery in my garage I used a rotary converter. Satisfactory for some machines.

If I want three phase I want it from a 3 phase open delta. This provides a wild leg added to a conventional 240 V center tapped winding.

If you want a smooth running motor, and no starter mechanism, then you want a 3 phase motor. You can get this result from a VFD from single phase input. Or a capacitor run single phase motor will have less torque ripple than a straight single phase motor.

I have never experimented with a synchronous motor as a phase inverter, but it should be a better inverter than an induction motor. Also could use a single phase motor with inertia load to drive a 3 phase alternator (a 3 phase motor).

If you only have 1 phase power provided have the power company transformer at your home to reduce problems from long line voltage drop.

Why underground wire vs overhead?

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190608-1018 EDT

What is on the pole is at least what determines whether you can get 3 phase at any reasonable cost.

In my neighborhood we have 3 phase delta on the pole, no neutral, probably wye at the substation, and a number of 3 phase users.

At the shop I believe the primary is 3 phase wye on the pole, and that our 2 transformers are fed from neutral and 2 hot lines. Our output is 3 phase open delta. The single phase transformer is the larger of the two.

At my daughter's home, about a mile or two from either the shop or my home, she only has single phase available fed from a wye source.

In our city and many areas around we have 3 phase delta on the pole in residential neighborhoods. How does one tell? There are three wires, similarly insulated, and no obvious neutral. The transformers, of necessity, will have two insulated primary inputs.

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I can't imagine a utility primary without a neutral. If there are secondary conductors strung between poles, their neutral can also be the primary neutral.

For example, the lower left wires in this pic:

170px-Utility_pole_transformers.jpg
 
LarryFine said:
I can't imagine a utility primary without a neutral. If there are secondary conductors strung between poles, their neutral can also be the primary neutral.

For example, the lower left wires in this pic:

View attachment 23068
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Some people find this strange, but there are extensive distribution systems in certain parts of the country that are ungrounded Delta. Upstate NY has lots of it. IIRC Michigan does too.

Also worth noting is the number of bushings doesn't necessarily determine whether it's a grounded system or not. My poco uses the same transformer for their ungrounded 4800 as their 13.2/7.62 mgn system ( it has a selector switch). So that is two bushing even though they don't need the second for the mgn system. It is also possible that they upgraded a Delta system to a wye to increase capacity, and the existing transformers were reused but now connected line to neutral.
 
LarryFine said:
I can't imagine a utility primary without a neutral. If there are secondary conductors strung between poles, their neutral can also be the primary neutral.

For example, the lower left wires in this pic:

View attachment 23068
Click to expand...
Primary has no neutral if the upstream source is delta.

A majority of what is out there for local distribution is from a wye secondary and they do utilize the neutral, plus it is the grounded conductor of the system.
 
190608-1209 EDT

The primary distribution system in my neighborhood is definitely a delta for the primary from my perspective, three wires only and no neutral. I have no idea what is at the substation for the source. I have no primary neutral on the pole, or under ground. I am isolated from any neighbor that is not on my transformer secondary. I have only one neighbor, and two street lights, on my 50 kVA transformer.

The only electrical connection with other neighbors is via water, and gas lines, and earth.

.
 
lgmagone said:
I have two options for running power to a house I would like to build:

a) Extend single-phase power line 1,600 feet to house underground.

b) Extend three-phase power 2,300 feet underground.

Wondering if anyone can describe in relative terms the cost difference between the two? I would very much enjoy having three phase power at my house.
Click to expand...

someone is gonna have to change a pole pig, or run an open delta, which is most likely.
without a compelling connected revenue load, this isn't gonna happen anywhere.

just a swag, but somewhere in the $12k~$16k range is probably realistic.

i have a brand new in the box 3 hp M/G rotophase you can have for $300 plus shipping.
they were somewhere just shy of $2k, ten years ago.
 
It's interesting that other POCOs charge more for 3-phase service. Here in Tampa, TECO charges the same for single phase or three phase. Looking at upgrading service to three phase to handle some woodworking equipment and future pool pump and on demand water heaters (multiple) to balance loads.
 
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