meltedfire
New User
- Location
- Bastrop County, Texas
- Occupation
- Utility Engineer
Hi all,
New to the forum although have been lurking as a reader for some time.
A friend of mine asked me to help design a power distribution system for his 40 acre ranch. He doesn't want to put Poco poles all over the place and wants to keep a single handoff from the POCO if possible. Being a DC buy, I naturally started to think 480/240 system so that I can step him down as necessary for loads at different places in the property. This is all single phase - there is no 3phase available at the property. In essence, he wants an on-property intermediate voltage system to drop off to different locations as necessary.
POCO indicates to us that we can have single phase up to 800amp@120v services (100Kva transformer) and they are able to hand us 480V at 200amp (single phase - 2x 240v legs instead of 2x 120v legs).
His loads are:
400Amp service at House (divided into 2x 200amp panels) - current fed with a 50Kva 240/120 from POCO.
200Amp service at Guest House (1x 200amp panel - current fed with a 15kva 240/120 from POCO.
he wants to add a
100-125 Amp service at Barn 1 (600 feet from Guest House)
200 Amp service at Storage Bldg (650 Feet from guest house)
50-60Amp service at each of the Gate and Storage Barn (400-600 feet from main House)
I come to the forum because traditionally this is easy - take in 1000A or larger service at primary 3ph and step it down to 120v everywhere - do this every day. But this one is distributed and making me second guess the design.
My design is - so far -:
1) Let POCO upgrade service to 200a@480v (100kva transformer gives me 800 amps of total 120v capacity) at the Main House
2) Install a basic 480V 1ph panelboard at the handoff from Poco with 4 distribution breakers - 50A@480V each: 1-2 facing the House, 3-4 facing North and South feeds to other areas on the property.
3) Install 2 25kva 480/240 x 240/120 single stepdown transformers at the house to feed the 2 existing 200a panels.
4) Run 250MCM/250MCM/4/0 in conduit underground to the South destinations (Guest House, Barn 1, Storage Bldg -the furthest point is 800 feet away from the distribution panel)
5) Tap the 250-250-4 at each location to put 480/240 x 240/120 stepdowns of 15kva (at Guest House), 15Kva (at Barn 1), and 25Kva (at Storage Barn).
6) (future) Run 250-250-4 in conduit underground to the North destinations (Gate/Storage Barn) with 5kva transformers at each little site.
That puts 115 kva of transformers behind a 100kva Primary feed, which I should be fine doing considering this is agricultural and residential application?
Have I missed anything here? Do I need a primary disconnect at the Poco handoff? They will CT meter on the pole so no meter can required.
Thanks! (Not sure if I'm in the right forum, this may be a calculations question - if so, mod please feel free to move.)
jwb
New to the forum although have been lurking as a reader for some time.
A friend of mine asked me to help design a power distribution system for his 40 acre ranch. He doesn't want to put Poco poles all over the place and wants to keep a single handoff from the POCO if possible. Being a DC buy, I naturally started to think 480/240 system so that I can step him down as necessary for loads at different places in the property. This is all single phase - there is no 3phase available at the property. In essence, he wants an on-property intermediate voltage system to drop off to different locations as necessary.
POCO indicates to us that we can have single phase up to 800amp@120v services (100Kva transformer) and they are able to hand us 480V at 200amp (single phase - 2x 240v legs instead of 2x 120v legs).
His loads are:
400Amp service at House (divided into 2x 200amp panels) - current fed with a 50Kva 240/120 from POCO.
200Amp service at Guest House (1x 200amp panel - current fed with a 15kva 240/120 from POCO.
he wants to add a
100-125 Amp service at Barn 1 (600 feet from Guest House)
200 Amp service at Storage Bldg (650 Feet from guest house)
50-60Amp service at each of the Gate and Storage Barn (400-600 feet from main House)
I come to the forum because traditionally this is easy - take in 1000A or larger service at primary 3ph and step it down to 120v everywhere - do this every day. But this one is distributed and making me second guess the design.
My design is - so far -:
1) Let POCO upgrade service to 200a@480v (100kva transformer gives me 800 amps of total 120v capacity) at the Main House
2) Install a basic 480V 1ph panelboard at the handoff from Poco with 4 distribution breakers - 50A@480V each: 1-2 facing the House, 3-4 facing North and South feeds to other areas on the property.
3) Install 2 25kva 480/240 x 240/120 single stepdown transformers at the house to feed the 2 existing 200a panels.
4) Run 250MCM/250MCM/4/0 in conduit underground to the South destinations (Guest House, Barn 1, Storage Bldg -the furthest point is 800 feet away from the distribution panel)
5) Tap the 250-250-4 at each location to put 480/240 x 240/120 stepdowns of 15kva (at Guest House), 15Kva (at Barn 1), and 25Kva (at Storage Barn).
6) (future) Run 250-250-4 in conduit underground to the North destinations (Gate/Storage Barn) with 5kva transformers at each little site.
That puts 115 kva of transformers behind a 100kva Primary feed, which I should be fine doing considering this is agricultural and residential application?
Have I missed anything here? Do I need a primary disconnect at the Poco handoff? They will CT meter on the pole so no meter can required.
Thanks! (Not sure if I'm in the right forum, this may be a calculations question - if so, mod please feel free to move.)
jwb