200 amp 700 feet

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JDB3

Senior Member
Location
San Antonio, Texas
Before a man buys a lot, he would like an estimate for the additional cost involved for running his total electric home (no plans yet, figure approximately 200 amp load).
Because of certain conditions around this lot, he will need to build approximately 700 feet from where the utility company sets their combination Pedestal/Meter/Breaker enclosure.
The best that I determined is 500 KCmil Al. with 400 neutral. in 3" conduit. {The way their pedestal are setup up, Inches (maybe 5") from the bottom to the load side of the breaker , I will need to set a j-box to the side of the pedestal and connect the 500 to 3/0 copper (tap) to get it under the breaker.

Your thoughts?
 
Z

zbang

Senior Member
Location
Roughly 5346 miles from Earls Court
Price out a pair of 240/480v or 240/600v transformers. It might be cheaper/easier to run a higher-voltage 3-wire feeder (2p + EGC) than to wrestle the larger cable & pipe and run a 4-wire feeder.

Also, can you go direct-burial instead of conduit?
 
ActionDave

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
JDB3 said:
Before a man buys a lot, he would like an estimate for the additional cost involved for running his total electric home (no plans yet, figure approximately 200 amp load).
Because of certain conditions around this lot, he will need to build approximately 700 feet from where the utility company sets their combination Pedestal/Meter/Breaker enclosure.
The best that I determined is 500 KCmil Al. with 400 neutral. in 3" conduit. {The way their pedestal are setup up, Inches (maybe 5") from the bottom to the load side of the breaker , I will need to set a j-box to the side of the pedestal and connect the 500 to 3/0 copper (tap) to get it under the breaker.

Your thoughts?
Click to expand...

Since NEC service sizing is so conservative I would want to know what the heating load is before giving a final answer. I would tolerate ten percent voltage drop from the meter to house if cost was a big issue, however you are not going to save that much even if you go down two wire sizes. Since this is just rough estimating you might as well stick with the bigger wire size for now. I like the idea of the j box beside the pedestal.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
JDB3 said:
Your thoughts?
Click to expand...

There is no right or wrong answer here, it comes down to how little voltage drop the customer is willing to pay for / how much voltage drop they can tolerate.

Some folks will live with lights dimming when the AC compressor starts other folks will not.

The actual load current is also going to be a huge factor, given a 700' run of 500 AL I get the following results

11.87% drop @ 200 amps

9.5% drop @ 160 amps

7.4% drop @ 125 amps

5.9% drop @ 100 amps

4.4% drop @ 75 amps


Now a 200 amp service might never see a constant load over 60 amps but it could see high currents during motor start ups.

Again, it goes back to how much voltage drop can the customer live with. Their answer to that will drive the wire size.

(BTW, it looked like it would take two sets of 900 AL to keep it under 3% drop @ 200 amps. If you really had to meet that transformers would start to look better)
 
Besoeker

Besoeker

Senior Member
Location
UK
JDB3 said:
Before a man buys a lot, he would like an estimate for the additional cost involved for running his total electric home (no plans yet, figure approximately 200 amp load).
Because of certain conditions around this lot, he will need to build approximately 700 feet from where the utility company sets their combination Pedestal/Meter/Breaker enclosure.
The best that I determined is 500 KCmil Al. with 400 neutral. in 3" conduit. {The way their pedestal are setup up, Inches (maybe 5") from the bottom to the load side of the breaker , I will need to set a j-box to the side of the pedestal and connect the 500 to 3/0 copper (tap) to get it under the breaker.

Your thoughts?
Click to expand...
Simple question.
Why Al rather than Cu?
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Is there any way, under current code, that _two_ feeders could be run from the pedestal to the home, one for 'sensitive' low current loads (eg. lights) and one for 'transient' high current loads (eg. motors).

I know in general you are limited to a single feeder, but segregating loads might make sense here, if possible.

I presume that running primary underground to a padmount has already been discarded as a possibility. It really is the best solution, but in some areas the utility makes it very expensive, and in other areas the utility basically pays for it (folded into the electric rates).

I second the query about copper versus aluminum; my understanding was that Al can have reliability problems underground, in that a small nick in the insulation which is not problematic in a dry environment can be a point of severe decay in the conductors. However I've seen no actual statistics on the reliability of Al conductors underground when properly installed, versus the reliability of Cu conductors in the same situation.

-Jon
 
kwired

kwired

Electron manager
Location
NE Nebraska
winnie said:
Is there any way, under current code, that _two_ feeders could be run from the pedestal to the home, one for 'sensitive' low current loads (eg. lights) and one for 'transient' high current loads (eg. motors).

I know in general you are limited to a single feeder, but segregating loads might make sense here, if possible.

I presume that running primary underground to a padmount has already been discarded as a possibility. It really is the best solution, but in some areas the utility makes it very expensive, and in other areas the utility basically pays for it (folded into the electric rates).

I second the query about copper versus aluminum; my understanding was that Al can have reliability problems underground, in that a small nick in the insulation which is not problematic in a dry environment can be a point of severe decay in the conductors. However I've seen no actual statistics on the reliability of Al conductors underground when properly installed, versus the reliability of Cu conductors in the same situation.

-Jon
Click to expand...
You can run 1 to 6 separate sets of conductors connected together at the supply end to 1 to 6 separate service disconnecting means. If the building is supplied by a feeder - the general rule is only one feeder is allowed to supply the building.

Getting the primary and transformer much closer is the best option. I'd still look into what that may take if they will do it. Even if you run some large conductors you may take care of the "running voltage drop" but still may have some rather significant voltage sags when a larger motor is starting. POCO's around here just won't leave a customer having to run secondary conductors that far for the most part. They may charge them to bring primary closer but won't tell them they can't have it closer.

Small nick in underground aluminum can be an issue - one has to handle it carefully when installing it. It is tough enough you don't have to be extremely careful, just be smart when handling it. Copper is subject to damage as well, it just takes longer to fail when there is damage to insulation.
 
N

NewtonLaw

Senior Member
Location
Honesdale, PA USA
More Questions...

More Questions...

JDB3 said:
Before a man buys a lot, he would like an estimate for the additional cost involved for running his total electric home (no plans yet, figure approximately 200 amp load).
Because of certain conditions around this lot, he will need to build approximately 700 feet from where the utility company sets their combination Pedestal/Meter/Breaker enclosure.
The best that I determined is 500 KCmil Al. with 400 neutral. in 3" conduit. {The way their pedestal are setup up, Inches (maybe 5") from the bottom to the load side of the breaker , I will need to set a j-box to the side of the pedestal and connect the 500 to 3/0 copper (tap) to get it under the breaker.

Your thoughts?
Click to expand...

Are you saying the actual deversified load comes to 200 amps? If so, are you putting a 400 Amp service in? If you load is truly 200 amps, running 1000 MCM aluminum would get you down to about 5.4% voltage drop along the 1000 MCM conductors. This assumes 75°C, with a power factor of 1.00. You get about 7.1% voltage drop, 75°C cable temperature and a 90% power factor.

As others have pointed out, the true demand loading may be a lot less than 200 amps. An off peak electric home I put in had the highest recorded demand of 32 kW, about 131 amps. This was a heat pump, electric water heater and electric hot water storage for on peak heating to a 2500 square foot home. Thus my question about the 200 amp load level. So if you demand load is closer to the 131 amp level, 1000 MCM in PVC, 75°C temp, PF=100%, will get you to 3.5% voltage drop. 500 MCM to about 6.5%.

Also, all of this assumes phases and neutral are the same size and type of conductor.

Hope this helps.
 
J

JDB3

Senior Member
Location
San Antonio, Texas
zbang said:
Price out a pair of 240/480v or 240/600v transformers. It might be cheaper/easier to run a higher-voltage 3-wire feeder (2p + EGC) than to wrestle the larger cable & pipe and run a 4-wire feeder.

Also, can you go direct-burial instead of conduit?
Click to expand...

VERY rocky conditions.
 
J

JDB3

Senior Member
Location
San Antonio, Texas
This "possibly" will be a normal house, around 2.000 square feet, total electric. Guesstimating that the load will not be more than 200 amp at any time, it will be a heat pump HVAC system. I have not been to the location yet, but the power company will just set their pedestal/meter socket/breaker at the road, then the rest is up to the owner. :roll:
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
JDB3 said:
This "possibly" will be a normal house, around 2.000 square feet, total electric. Guesstimating that the load will not be more than 200 amp at any time, it will be a heat pump HVAC system. I have not been to the location yet, but the power company will just set their pedestal/meter socket/breaker at the road, then the rest is up to the owner. :roll:
Click to expand...

I would have to turn everything on at one time to get 150 amps and before long the range or oven would be cycling. The water, garage and house all cold with heat pump and well on.

In reality it will never see a 100 amps. We are 2k+ Sq ft with a full basement, all electric.
 
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