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Author Information Topic:   Service Entrance Sizing
Member

   
Name: Greg Bazar
Email: gregbazar@resurrection.com
Location: Colorado
Title: Not_Listed
In Trade Since: 2000
Registered: May 2001
Total Posts: 9

posted May 22, 2001 at 04:22 PM       Edit/Delete Message
I am installing a service entrance to a residental property. There will be a 550 ft run from the meter pole to the house.

According to my numbers this means I need 4/0 copper to carry the 200 AMP panel. I think this might be too small though.

Is this correct? What gauge Aluminum wire would I need?

Thanks,

Greg

IP: 24.251.14.2

unregistered posted May 22, 2001 at 05:26 PM           Edit/Delete Message
May I ask why you can't have the meter set at the house?

IP: 162.119.240.100

Member

   
Name: Greg Bazar
Email: gregbazar@resurrection.com
Location: Colorado
Title: Not_Listed
In Trade Since: 2000
Registered: May 2001
Total Posts: 9

posted May 22, 2001 at 05:51 PM       Edit/Delete Message
It is a remote location. The utility coop wants to put a pole and transformer near an existing right of way and then have the owner go underground from the pole to the house. They want to put the meter on the pole making the owner responsible for the power to the house.

quote:
Originally posted by DSpark@marioncenter.com:
May I ask why you can't have the meter set at the house?

IP: 24.251.14.2

unregistered posted May 22, 2001 at 06:33 PM           Edit/Delete Message
>making the owner responsible for the power to the house.

Different companies have differing tariffs.
At my residence, I put in an underground conduit, including boring under a road, entirely at my expense. The utility paid for the wire from the transformer to the meter which I located right on my house.

The local rural electrification co-op charges $1 per foot including down their pole and through the property owner's trench to the meter for direct burial cable.

Even if the owner is paying, he should be able to get the meter located near his house so long as it is readily accessible to the meter readers. 550 feet is a long way. He should put a disconnect outside his house for the fire department.

IP: 162.119.240.100

unregistered posted May 22, 2001 at 07:07 PM           Edit/Delete Message
There is already a disconnect outside.
There may be a remote located mean dog in this yard. Meter readers don't get along with dogs. This is why meters are not in junk yards .
I would apply fundamental electrical calculations for designing the service feeder. Factor in the entire loop length, transformer size, and impedance. Use the calculated load figures. Let us know the final resolution.
Good luck: Bennie

IP: 198.81.16.21

Member

   
Name: Steve Mancuso
Email: electric@vermontel.net
Location: Vermont
Title: Contractor
In Trade Since: 1985
Registered: Oct 2000
Total Posts: 1676

posted May 22, 2001 at 07:35 PM       Edit/Delete Message
Greg;
in see this done due to local utilities enforcing overkill on longer secondaries. Their concerns usually end with the first disco.
4/0 cu @550', 200A, 240V , would have a 4.9% drop (11.8v) . the local utilities here would want parrallel 500KCMIL al for this.

My Q to this BB is, can this V-drop calc for the main feeder be calculated according to the load demand calc for the dwelling?
the umph required is a chief component

IP: 205.240.83.181

unregistered posted May 22, 2001 at 08:02 PM           Edit/Delete Message
All the known facts would have to be considered first, unless the peak demand is actually known. You usually have to plug in a house to determine exactly what is necessary for a supply. Load calculations using demand factors, are not a science.
There is a point when increasing the feeder size must give way to moving the source closer to the load, and starting over.

IP: 198.81.16.177

Member

   
Name:
Email: fredwhite@netzero.net
Location: Indiana
Title: Contractor
In Trade Since: 1979
Registered: Nov 2000
Total Posts: 113

posted May 22, 2001 at 08:54 PM       Edit/Delete Message
I have situations where the load to be served(usually grain bins)is located 300-750' from the utility's nearest right-of-way. They are usually willing to bury primary and set a padmount transformer at a reasonable cost. Most times they will spread the cost out over 3 to 7 years, depending on the revenue the customer will generate. I have had situations where the estimated revenue was high enough that the utility waived all or most of the initial costs. I did a custom home last year that was situated 500' off the road. The utility offered to waive all of the costs providing the homeowner installed geothermal or total electric heating equipment and appliances.

IP: 206.148.224.139

unregistered posted May 22, 2001 at 09:02 PM           Edit/Delete Message
If you have a 200 A service and want to be able to utilize it all without excessive voltage drop, then you must have the larger cable.

If the utility is regulated by a PUC, they may be required to provide the wire most of the way. I would check that out too.

The closer they put the transformer to the house, the less voltage drop will be experienced.

IP: 162.119.240.100

unregistered posted May 22, 2001 at 09:07 PM           Edit/Delete Message
This is good, Fred. I am forever amazed at the power suppliers marketing tactics.
I have a book describing how the utility companies used to give away incandescent lamps, to encourage power consumption. Now in many areas they are buying back power contracts.
Our rates are going up 250% soon, The largest hydro-plants in the US are on the Columbia River. Three of them within an hour of Portland. I worked on all three of them.
The old worm turns, where are we headed?

IP: 198.81.17.174

unregistered posted May 22, 2001 at 09:35 PM           Edit/Delete Message
I wired a new home in this area a few years back with a 400 amp. 2, 40 circuit 200 amp. SP. panels inside , meter on side of house.In this county the power co. supplied the secondary conductors from their utility pole to the house we furnished the conduit all the counties around here are different on what they furnish on a service.

But anyway they pulled 4/0 alum. triplex in each 2-1/2 sch.40 PVC conduits.
This service was a little over 500 ft. can't recall the exact length but both of these panels are loaded pretty good and never give any problem as far as blinking lights Ect. I also was unsure about the 4/0 but I figured the utiliy engineer knew what he was doing, but if you are funishing the wire wouldn't hurt to go to 500 MCM if you don't care to go the extra cost. Another thing is you wouldn't have but one conduit this way.

IP: 152.163.207.177

unregistered posted May 23, 2001 at 01:42 AM           Edit/Delete Message
On the last custom Residential job we had [the one for our General Contractor's new house- which they decided to sell now!! but that's another story ], we put in one of those 400 amp max / 320 amp continuous meter main panelboards [this one was Square D Homeline - first time using the Homeline stuff]. It's the one with two separate 200/2 - 22KAIC breaker frames for the mains, plus a 200 amp 30 space bus kit, which is fed from one of the two main breakers.
Not a bad panel, except the weak way the grounded conductor was "Bonded" to the enclosure through only a 10/32 screw [I supplimented that bond with a few lugs, then routed the GEC through them uncut, then terminated to the grounded conductor's bus - now a fault in the system doesn't have only that 10/32 screw to flow through!!].

Anyhow, this project was an existing house with overhead feeders and an old 100 amp FPE service. The 400 amp service is kind of overkill, but the capacity is there if anyone needs it!
The new feeder was installed underground in a 5" PVC duct.

Never got an actual SCA quote from SCE, but I had given them [plus Building Dept.] my figures using Point-to-Point method [Gary's gonna kill me for that one! - just kidding]. This was done just because I'm so used to doing it!!

To sum it up finally , the transformer is pole mounted - right at the rear corner of the lot. Transformer is 25 KVA, 2.35% Z.
SCE installed two 4/0 XHHW al, one 1/0 XHHW al for the feeders. Length of feeders is <150'
Calcs out like this now [with the 1/0 and 4/0 al]:
KVA load on 25 KVA transformer = 31.0 KVA across 4 customers [124% load - just barely upto the 130% max limit SCE has].
Voltage drop = 0.8%
Flicker Factor = 4.6% [two-4 ton A/C units].
SCA = <22KAIC rating of main panel [looks like it wouldn't even exceed 10KAIC - even with full motor contributions].

Scott SET

IP: 207.214.187.241

Member

   
Name: Steve Mancuso
Email: electric@vermontel.net
Location: Vermont
Title: Contractor
In Trade Since: 1985
Registered: Oct 2000
Total Posts: 1676

posted May 23, 2001 at 04:16 PM       Edit/Delete Message
Scott;
this 'flicker factor' is interesting !

IP: 205.240.83.181

unregistered posted May 23, 2001 at 09:30 PM           Edit/Delete Message
The main reason we go to a 400 amp. service is for the extra breaker capacity not the current capacity the new larger homes usually require more than 42 circuits.

IP: 64.12.102.158

unregistered posted May 23, 2001 at 09:55 PM           Edit/Delete Message
Many in the trade, are under the impression that the size of the service equipment sets the criterion for load calculations and wire size.
The supply side is always based on the calculated load. There is no overcurrent protection on the supply side. The main overcurrent device, or devices, only protect load side systems. They may limit the load on the supply side, but can not provide overcurrent, or short circuit protection.
The supply side conductors are not required to have the ampacity of the main breaker.
I know I will get trashed for this statement, but I am a veteran, not a virgin

IP: 198.81.16.189

Member

   
Name: Greg Bazar
Email: gregbazar@resurrection.com
Location: Colorado
Title: Not_Listed
In Trade Since: 2000
Registered: May 2001
Total Posts: 9

posted May 24, 2001 at 12:39 AM       Edit/Delete Message
Well we re-measured the run and it will be 375ft. Given this what do you folks think about using 4/0 for the service entrace? By using 4/0 I would get a 3.75% voltage drop. Cost is an issue and I can get the 4/0 for about half the price of the next bigger wire sizes.

What do you think?

Thanks,

Greg

IP: 24.251.14.2

unregistered posted May 24, 2001 at 01:39 AM           Edit/Delete Message
> By using 4/0 I would get a 3.75% voltage drop.
I think that (3.4% = 8.2 V on 240 V) is too much drop at the service entrance.

If operating cost is an issue, the extra investment for heavier conductors might pay off in less energy wasted to resistance over the years.

If your peak load is really 100 amps now and forever, and you are using copper 4/0, and you don't have long runs to major loads after the main panel, then I think you are okay. You'll have more like a 2% drop normally.

IP: 162.119.240.100

Member

   
Name: Greg Bazar
Email: gregbazar@resurrection.com
Location: Colorado
Title: Not_Listed
In Trade Since: 2000
Registered: May 2001
Total Posts: 9

posted May 25, 2001 at 10:39 PM       Edit/Delete Message
Just talked with a Colorado Electrical inspector. For that run he figures 4/0 Aluminum is enough. I have bough the 4/0 copper anyway, since I got it for $0.62 / ft!

Thanks for the input guys.

Greg

IP: 24.181.187.136

unregistered posted May 28, 2001 at 08:25 AM           Edit/Delete Message
Steve,

Sorry not to give you any reply here! I've 'a bean 2 dan-g-y bizzy [I've been buzy]

SCE listed flicker factor per 2-4 ton AC units, so that's got to be how much the lights will flicker when the ACs kick-in.

Sounded like this to me, how about anyone else??

I never dove into that one, but it's on my "To-Do" list [which is below my "Honey-Do" list ]

Scott SET

quote:
Originally posted by electric@vermontel.net:
Scott;
this 'flicker factor' is interesting !


IP: 207.214.185.69

unregistered posted May 29, 2001 at 07:56 PM           Edit/Delete Message
quote:
Originally posted by gregbazar@resurrection.com:
I am installing a service entrance to a residental property. There will be a 550 ft run from the meter pole to the house.

According to my numbers this means I need 4/0 copper to carry the 200 AMP panel. I think this might be too small though.

Is this correct? What gauge Aluminum wire would I need?

Thanks,

Greg


Greg;
I agree 550 feet is an awfully long run. I would first get in touch with the planning department at you serving utility and see if they cant get a ' tad ' closer like 500 feet closer. Generally for a residence the code allows you to use no. 2/0 cu for a 200 amp service and a number 3 or 2 on the neutral and of course an EGC of number 4 copper, otherwise the cost of such a long run would almost be prohibitive. If this is a feeder then all conductors must be insulated.
If you must proceed with the 550 feet, then I would do a serious load calculation to see exactly how much power you really do need and also include any future expansion, ie A/C if not already included, then see if you can downsize the neutral to cut down on the cost. Since this is a residence you will have no continuous loads. I certainly would not go any bigger than 4/0 copper and I would certainly try to downsize the neutral.
Good Luck.

IP: 64.12.101.157

Member

   
Name: Greg Bazar
Email: gregbazar@resurrection.com
Location: Colorado
Title: Not_Listed
In Trade Since: 2000
Registered: May 2001
Total Posts: 9

posted May 30, 2001 at 10:47 PM       Edit/Delete Message
Well,

It happens that a store was going out of business in Denver. I got my 4/0 wire for $0.62 / ft. Hot dog!

Thanks for you help all.

Greg

IP: 209.179.158.123

Member

   
Name:
Email: tmlett@hohi.net
Location: Texas
Title: Not Listed
In Trade Since:
Registered: May 2001
Total Posts: 111

posted May 31, 2001 at 12:34 AM       Edit/Delete Message
An interesting calculation would be to the farthest outlet to see if it exceeds 5%. Remember that the 3% for branch circuits and the 2% for feeders, (5% for them both) is a code suggestion only not a rule!
I agree with whoever said the only way to get a true reading would be to know the peak demand, and that is almost impossible to get.
I challenge anyone to show me anything that has a peak demand larger (excluding additions) than the code calculated load. I'm not saying it hasn't happened, I have just never seen it!

IP: 66.25.24.45

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