New Home

[moresi]

I have a great project that I am about to start. It is a time and materials new resi. home - big money - approximately 6000 sq./ft. Unfortunately it starts asap and the cold weather is here. I am trying to configure the service and any insight to an easier way would be appreciated. Will be underground service - 400 amp (2 200 amp panels / 320 amp can) which will need to go to panels in mechanical room which is at opposite end of home from where service entrance will be. I am planning on one of two scenarios - #1= 320 amp meter main on service pedestal (fed via 2 sets 4/0 AL) at property line with 2 200 amp breakers and 2 sets of 4/0 AL run underground to 2 200 amp panels located in mechanical room. In this scenario I will hit ground rods at meter main and have a #4 CU ground wire run with each set of conductors to their panels. At panels I will hit each with #2 Cu to water main and also hit UFFER ground to one of them. My second scenario consists of me mounting a 320 amp meter can on outside stone face of house supplied by 2 sets of 4/0 AL. Then supply each 200 amp panel in mechanical room with a separate underground run of #4/0 Al grounding service at this point.
So what is the verdict? House is one level and over 160' long built into side of mountain.

 

[satcom]

No contract? that may be your biggest problem.

 

[RH1]

Well, he's doing it T&M which means he's not taking any risks. I'd say in this scenario, not having a contract is not particularly alarming. I'd rather all my jobs were T&M.

 

[moresi]

I have my bases covered as far as contract and getting paid - that is all set.

Does my service scenario agree with you all or might some changes be needed?

 

[satcom]

I have my bases covered as far as contract and getting paid - that is all set.

Does my service scenario agree with you all or might some changes be needed?

Why are you going underground to get to the sub panels? I am just trying to get a better idea of what you are doing. T&M with a contract is goog, yup it is all about getting paid.

 

[augie47]

Depending on your local or POCO rules, if you mount the meter base on a pedestal and continue your runs outside to the house, I see no NEC reason for you to have breakers at your meter (as long as you comply with 230.70)
With those long runs you might need to give consideration to larger conductors due to voltage drop.

 

[moresi]

POCO will require a meter socket with CB protection. This is standard requirement for our area. I am just trying to get a good feel for the design of the 2 sets of conductors and associated grounding so that I can spec. it out prior to digging. I was planning on upsizing my 4/0 given the long runs. thanks for tip. As far as why i am doing this install as noted - 1oo% finished basement area with only mechanical room being allowed for electrical equipment placement. I find the underground approach to be most efficient way to get there.

 

[dbuckley]

Running two sets from one meeter on the property line is the better approach - because of volt drop considerations. Fluctuations on one set will be reflected less on the other.

 

[augie47]

other than the location of the meter, I don't see the difference..sorry

 

[-marty]

Most of the poco's in my area would require a disconnect on the outside of the house. This is probably for the fire dept. This arrangement required a ground rod at the house, then I went from the outside disconnect to the ufer and water line, and gas piping. I did a 10,000 sq foot house and wished I would have put a panel on each floor instead of grouping them together in a mech room. The house was also t&m, I made the calcs and ran a 200 amp service based on the drawings, problem is the project grew and grew. You know, two washers, two dryers, two dishwashers, and on and on. The 200 amp service has never been a problem. I didn't have the option of a 360 amp service and a 400 amp would have required a ct can. There was so much glass I just couldn't fit it with in the poco requirements. Keep track of how many times the wife makes you change something so you can give the list to the husband when he wonders why the price is so high. Pay close attention to the details. I asked the cabinet maker how tall the vanities would be. They were increased from 30 inches to 36 inches after rough-in. What a pain. Hope this helps.

 

[jzadroga]

Just something to keep in mind. I like to run to a 400 amp meter main with parrallel 4/0 copper. Then to a 400 amp disconnect in the basement. from there I run to two 200 amp panels with mains. Under all of this is a 12x12 trough that is 8 feet long. I drop from each panel to the trough for wiring. I know some think its to expensive. But more than once I have been asked to add a generator to the house. Beside this is t&m so I assume they want a better than average instalation. With this set up all I have to do is install a transfer switch in the extra space I leave for the purpose and wire it between the 400 amp disconnect and the 200 amp panels. the whole set up looks very clean.

 

[benaround]

moresi,

Be careful on the proper size of your feeders, can't use 310.15B6 table for your feeders,

I'm not sure if you can use that table for parallel conductors, anyone know for sure on that.

 

[moresi]

Here is wher I am at. Had site visit at property today and even though snow is about to fly digging starts Monday.

My load calcs. for house put me at 189 amps with gas for dryer and cooktop. I can get away with a 200 amp service but I feel that a 400 amp service is better suited to this house and future expansion. I will be setting service on a pedestal next to underground xformer (apprx. 25') I plan to have a Millbank metermain which has 2 200 amp mb's and feed each 200 amp panel from this metermain. Considering voltage drop from metermain to house I will be installing 250mcm AL to feed panels (maybe Cu - if so 3/0) In everyones experience - do you prefer to install conductors in seperate conduits or upsize to one large conduit to bring both sets of conductors into house? Obviously I will be upsizing conductor sizes for derating purposes if this is the case. My plan is to stub incoming lines into a trough at base of panels and then feed the panels. This service will also allow me to install a sub in the second mechanical room as well as garage. I appreciate the insight but am curious why310.15(B)(6) does not apply to this install. Am I missing something?

 

[moresi]

Also-

Regarding parallel conductors - the only point where I will be using parallel conductors is to feed the meter pedestal. Because I am hitting my main overcurrent at the meter my conductors from that point on are on 2 seperate 200 amp protected circuits. Each panel inside the home will be a main breaker 200 amp panel. I believe all this should be fine with the AHJ.

 

[bradleyelectric]

I appreciate the insight but am curious why310.15(B)(6) does not apply to this install. Am I missing something?

If I am understanding your question we are talking about the feeders from the service to the sub panels. Because they are not service conductors.

 

[moresi]

Correct- The feeders from the service to the sub panels. Service located on a pedestal outside house and panels located in mechanical room inside house. In our area there has been some disagreement over proper way to install such a service. We opten see metermains installed on pedestals outside of homes and then feeder supplying house panel. Some electricians have run 3 wire from these metermains with no grounding conductor while others run 4 wire with a grounding conductor. I have often argued that the later of the two is illegal and the grounding conductor is required in this run. I do not know how they have passed. Now looking at my scenario where I have a 400 amp service which goes to two 200 amp panels in house I am required to ground the meter main with #2 Cu and drive 2 rods. I am then required to hit both my panels inside the home with my uffer ground as well as bond my water piping. I want to ensure that my installation is in agreement amoingst others as we have some differing opinions amongst local electricians. This size service is not somehting we see much of in these here parts.

 

[AV ELECTRIC]

I would put a 400 meter main combination on the house if it will work out with the stone work talk to the stone contractor to see how this will work out cosmetically. Talk to the owner to see if this will work for them. Hopefully most of your major circuits are on this side of the house if so maybe run a 100 amp sub in the mechanical room you can run it underground and take car of the other half of the house. run pvc back to poccos connection from your meter main combination ask them on size and sweep diameter. stub out spare future conduits ask owner what plans they have for future pool, spa, ect. Just an opinion. t @ m give you alot of flexibility .

 

[benaround]

moresi,

Re: 310.15(B)(6) Table, can only be used on feeders suppling the entire load of the dwelling. (2) 200a feeders split the load. Read the section before the Table carefully.

 

[moresi]

I must admit, now I am confused. These feeders are supplying the entire load of the single family dwelling. It has always been an accepted practice to use 4/0 AL for a 200 amp feeder or to paralell for a 400 amp service. I see this as all being acceptable to 310.15(B)(6)

 

[LarryFine]

These feeders are supplying the entire load of the single family dwelling.

They're saying that, with a split service like this, each 200a portion only serves half of the total load. In other words, each half is disqualified as serving the entire load by the existence of the other.

It has always been an accepted practice to use 4/0 AL for a 200 amp feeder or to paralell for a 400 amp service. I see this as all being acceptable to 310.15(B)(6)

Personally, I also consider the practice still acceptable, but the NEC's position that it isn't has been made clear. If your inspector still accepts it, be grateful. And be discreet.