Practicality of adding 3-phase power to residence?

Question

How practical is it to add 3-phase power to a residence (assuming that the street has 3-phase on the poles)?

In my case I would be using it only for occasional use, such as for some heavy duty machine tools in a basement, and maybe a motor for a large gate or door.

Will it be prohibitively expensive, or on the same order as the costs for normal 240V 2-phase power? Will power companies typically unite the bills, or can I expect to have to pay two different bills, one for the 240V and one for the 3-phase?

Answer 1

A quick search indicates that acquiring 3 phase power from a local utility may be prohibitively expensive. The article I read suggests that such a resource will carry an installation expense in areas not rated for commercial service and may also carry a minimum charge on the utility bill.

If your objective is occasional use of heavy equipment such as a machine tool, it may be more practical to use a device called a rotary converter. You would want to ensure your selected device has the necessary capacity for your expected load maximum, with a bit of reserve tossed in for good measure.

If only a single machine is going to be using 3-phase power, another device known as a VFD would be of value. A VFD will provide variable speed to an otherwise single speed motor as well as other features one can determine by searching for that term.

There are plans online to build your own rotary converter. A friend without internet access, many years ago, connected two motors together via belts, powering one with line current and used the gizmo to run a monster Czech lathe in his shed. He had to "kick-start" it periodically by kicking one of the pulleys, but it worked. I'm sure a commercially produced version would not require such manual intervention.

The above assessment was performed based on a US installation. Other countries may have different circumstances.

Answer 2

It's always an interesting question. I have seen it at some large farms etc. The main problem is distribution from your utility provider. Residentially zoned areas are not normally run in a true 3 phase system. So in order to provide a three phase they will do a split phase using two transformers and provide you with a delta, or the three phase with 120V to ground on two phases and 240V to ground on the other. Now this is not the old split phase panels they used to have in the 30's and 40's. That's actually a simulated three phase.

If you have just a few three phase peices of equipment you can use VFD's as discussed above or you can use a motor generator either static (solid state) or rotary (mechanical). You can Google motor generator and it will provide you with all the information you need. You could also purchase a three phase generator.

Expect to see a big spike in your electrical use. Good Luck

Answer 3

You are absolutely going to get a different billing. You will have to pay a considerable amount of money to get the service set up in the first place. Since all three-phase installations are for businesses, they are all professionally installed and they will expect yours to be too.

If you are lucky the three-phase up pn the pole will be 480. (Many 240V machines can be jumpered to run on 480.) If not you will also have to pay some upfront costs for them to fit transformers.

If you're worried about the monthly cost of a second metering, I hope I am painting the picture that this is going to be costly.

Generally I hear this after someone has acquired themselves a fine deal on a machine tool on Craigslist. This is why it was a deal. As such, money is usually a serious factor, and spending even a mere $1000 provisioning service is out of the question for them. If that made you go "well maybe", you may want to look at a phase converter capable of converting 240V single-phase to 3-phase.

You don't want to mess with 208 3-phase. That is a compromise voltage used when a single service must provide all loads in a facility, and most of the loads are 120V, i.e. Residential or light commercial. It adds a neutral, giving a "wye" configuration, with 208V between any two legs. 208 is a compromise voltage and does not work nearly as well as 240V. it may be possible to boost it to 240.

If you must drive the entire building off one service, another, better, way to do at same thing is provision 240V "wild leg" delta. This is what you get when you add a phase converter to household power.

Answer 4

Where I live, residential customers pay for amount of electricity used only, but commercial and industrial customers pay a "demand charge" too. Therefore, it makes sense to make a one-time investment of three phase power, especially if using larger equipment, etc.