newbie for 1000A 120/240V 1PH residential service build

[aes92000]

Afternoon All,
i visit and read many helpful items but my first time posting.
I apologize if this may be in wrong forum secton.
if it is, please redirect me of the correct section so i dont waste anyones time.

i am a master electrician in houston, texas and have done many 400-600A services.
this 1000A is getting me a little stressed since the CPE standard book is just giving me what is needed but not a diagram
it calls for a bussed ct can for feeders and i have not done anything like this. (other than tap boxes for multi tentant)
i have googled, yahooed and forum several times with some very helpful reads and pictures but i am afraid to go off of anything on the web simply because it is not my service or how i thought it would be built.
that may be my fault for thinking i know how it should be built.
i reached out to the utility engineer with the response of "it is in the standards".

estimated calculated load @ 889A (all aluminum feeders for service build)
i plan on 3 sets of 600MCM XHHW with 3" pvc underground to pad xfrmr for feeders into ct can about 250 feet
1000A fused disco into service gutter for several 4/0 AL load taps (200A MB discos and 4/0 Al ser cables out to load centers)
250CMC GEC and 2 - 3/4x10 rods


if anyone can give some guidance, i would so very much appreciate it or where i may be able to get more information to help me.
i just want the grey hair to stop growing. LOL

 

[hmspe]

There should not be much difference in the basic design of a 1000 amp service or a 600 amp service other than having the equipment rated for the higher amperage and fault current. Milbank and Erickson make CT cabinets for 1000 amps. If you contact a vendor they should have CPE's requirements and they should be able to help you select equipment.

 

[Carultch]

Afternoon All,
i visit and read many helpful items but my first time posting.
I apologize if this may be in wrong forum secton.
if it is, please redirect me of the correct section so i dont waste anyones time.

i am a master electrician in houston, texas and have done many 400-600A services.
this 1000A is getting me a little stressed since the CPE standard book is just giving me what is needed but not a diagram
it calls for a bussed ct can for feeders and i have not done anything like this. (other than tap boxes for multi tentant)
i have googled, yahooed and forum several times with some very helpful reads and pictures but i am afraid to go off of anything on the web simply because it is not my service or how i thought it would be built.
that may be my fault for thinking i know how it should be built.
i reached out to the utility engineer with the response of "it is in the standards".

estimated calculated load @ 889A (all aluminum feeders for service build)
i plan on 3 sets of 600MCM XHHW with 3" pvc underground to pad xfrmr for feeders into ct can about 250 feet
1000A fused disco into service gutter for several 4/0 AL load taps (200A MB discos and 4/0 Al ser cables out to load centers)
250CMC GEC and 2 - 3/4x10 rods


if anyone can give some guidance, i would so very much appreciate it or where i may be able to get more information to help me.
i just want the grey hair to stop growing. LOL

The essential difference to consider, is that once your circuit exceeds 800A, you now require the full OCPD worth of ampacity of the conductors. Everything else still works the same, in the line of reasoning for how you scale circuit sizes. You determine a combination of identical wires in parallel that add up their ampacity to the size of the circuit you need.

Metering equipment is also an essential difference. 400A circuits and less, usually have self-contained metering, where the full circuit amps pass through the meter jaws, directly through the meter globe. Over 400A, you have instrument metering instead. CT's are instruments, along with their counterpart, PT's (potential transformers) for voltage. 480V and less, can easily be measured directly by most meters, so it's less common to see PT's in addition to CT's. The typical CT cabinet has a removeable busbar between two multi-lug terminal blocks for each phase, and a terminal block for the neutral. The busbar passes through the opening of the CT, and the CT measures the magnetic field around the busbar. It produces a corresponding representative current, that the meter can then use for indirectly measuring the power. The meter then multiplies by the configured CT ratio to figure out corresponding current and power. Milbank has regional catalogs that show what equipment is approved for use in utility territories.

A non-intuitive principle for CT's, is shorting, rather than opening, their output lead circuit. Meter sockets can be ordered with test switches built for this purpose. I.e. shorting the CT's, and opening the voltage taps, whenever you need to remove the meter globe. Never let CT leads stay open, as they are a step-up transformer for voltage (as consequence of being a step-down transformer for current). The excessive voltage can damage the CT.

The utility has their own standards in their construction handbook (commonly called a greenbook or bluebook) on the sequence of the meter, relative to the main disconnect, as a function of the specifics of the service. Such as nominal voltage, and whether metering is self-contained or instrument-based. Generally speaking, simpler services tend to be hot sequence, while more power/equipment intensive services tend to be cold sequence. Additionally, you'll also have location constraints on where the equipment can be (grouping, maximum CT extension length, etc).

 

[curt swartz]

I would verify if the utility has and rules about the number of load conductors in the CT cabinet. My utility does. If you are breaking it up into 180 amps feeders you will have at least 5 or more.

I know in many areas of the county it common to build a service like this out of components but in my area it pretty standard to use a free standing switchboard with Pull Section, CT-Meter Section, Main & Distribution Section. I would never try to build a service like this. Large loads such EV's, Pool's and resistive heat would be fed from the service instead of lower amp feeders. shared with small loads.