Another question about aluminum wire

[John Lanciani]

At the utility where I work 600 amps single phase is the max allowed and we frown on those. A request for 1200 amps would elicit a hearty laugh followed by a firm no.

Can you really get single phase 240 volt service at 1,200 amps? Anyone know what the amperage limit is on single phase service?

Seems that it would take some special transformer and wiring to get to that level of amperage. The transformers they use to service residential customers in my area supply a number of homes, each of which probably has 200 amp service. If they were to stick a 1,200 amp load on that it would probably blow the transformer.

So to supply that level of service they'd probably have to put a dedicated transformer just for that one customer.

Mike

[Doug Dawson]

At the utility where I work 600 amps single phase is the max allowed and we frown on those. A request for 1200 amps would elicit a hearty laugh followed by a firm no.

Take that frown and turn it upside down! Some of us have Christmas lights.

[Frank Pratt]

At the utility where I work 600 amps single phase is the max allowed and we frown on those. A request for 1200 amps would elicit a hearty laugh followed by a firm no.

That policy makes sense, but what if the customer is in an area not serviced by 3 phase power. It would be an unusual situation, and probably rural, but it must come up from time to time.

[Mike Henderson]

That policy makes sense, but what if the customer is in an area not serviced by 3 phase power. It would be an unusual situation, and probably rural, but it must come up from time to time.

I expect that unless you had a lot of political pull, they're tell you "Sorry, we can't provide that service for you."

Mike

[Frank Pratt]

I expect that unless you had a lot of political pull, they're tell you "Sorry, we can't provide that service for you."

Mike

In this area, they'll do give you pretty much whatever you want that their system supports, but you pay all the costs of bringing it in.

[Alan Lightstone]

Out of curiosity, is it possible to have them bring in two separate 600 amp services to one location?

And I thought my workshop was over the top with 200 amp service. Wow.

When they upgraded my house's transformer to be able to handle my 34kW solar array, they told me that my transformer could supply a small country.

[Jim Becker]

That policy makes sense, but what if the customer is in an area not serviced by 3 phase power. It would be an unusual situation, and probably rural, but it must come up from time to time.

Location is a big factor. The distribution plant along the road can only handle so much load and there are fewer connection points to the higher level distribution plant when you get into rural areas. I would imagine there is some small level of "oversubscription", just like is possible in our home breaker panels, because they know that most customers will never have continuous load even close to their drop's capacity (they laughed at me when I was concerned that the drop from the pole wasn't adequate for 400 amp service for our home and my shop...which I now understand never even comes close...) but I suspect there is some metric they follow to not overstep their "engineering comfort".

[Stan Coryell]

I believe in New Jersey, at least at one time, residential services were limited to 400 amp single phase by code. I'm not sure if that is still true. 400 amps is a lot of power. I think the concern is someone running a factory in their backyard.

There is an awful lot of "extra" engenerered into transmission and distribution. After transmission, two power transformers feed the same bus, that buss feeds say, 15 distribution circuits. Each one of those circuits feed a "ring ". Another station feeds the same rings the same way. This is redundancy.

The two power transformers, at the same station, are sized to be at less than 50% capacity about 80% of the time. The reason behind this, is so one transformer, buss, circuit breaker, ect. may be taken off for service or repair. This is also true in transmission.

The distribution circuits around here are 13.2kv or 4kv and 34.4kv.

13.2kv circuits are simple. 13.2kv at (max) 400 amps feeds into a ring (around a neighborhood). This ring is fed in multiple spots from different stations. The ring may be separated by reclosure devices (switches) in the event of high load or downed power lines. Depending on the projected load of an individual "circuit", the breaker may trip at anywhere from 10 amps to 400 amps. Most distribution circuits are strung for at least 400 amps. Remember, there isn't any insulation to catch on fire if the wire gets overloaded and hot.

4kv and 34kv are a little different. Same idea though.

As far as rural areas, say a dead end road. Those properties aren't fed with a ring. They are "dead ends" from the ring. No redundancy.

It's simple. If this part of the "ring" needs more power, just parallel another circuit onto it. It's more of a checkerboard than a ring.

Back to the OP. What loads are you running. There is a huge difference between 50 amps 240v single phase and 50 amps 240v three phase. What are your power requirements?

[Ole Anderson]

When we added air conditioning at church we ended up with a 400 amp single phase service. That much draw was overwhelming one leg of the neighborhood 3 phase service and the utility was getting complaints. When we added an elevator we were forced to install 3 phase service. Fortunately it was already at the closest pole.