400 Amp Service at 200 feet, wire sizes and panel configuration

[Sparky110]

I am putting in a 320 Amp Meter housing, with either a 400 Amp Panel or 2-200 Amp panels, and have to run the service laterals 200 feet....not sure how to do this most efficiently...? Am not sure that 400 Amps are needed, but the owner hopes to add a shop later, and already has two large A/C units and two double ovens planned....everything else is very standard for a 3400 ft house.

 

[ActionDave]

Two 200A is better IMO. 200' feet is not all that far, nothing to worry about.
The owner sounds like he wants something he can brag about so give him what he wants.

Welcome aboard from someone that lives in the same congressional district.

 

[Sparky110]

Thanks!

Thanks!

Dave,
Thanks so much for your reply! So voltage drop is not a problem? I was tentatively planning to run "parallel" 4/0 runs, basically 2-200 Amp runs through a 320 Amp Meter housing with main disconnects at the meter for each panel....yes? I have seen in the forums that 2/0 has also been suggested, but that does not seem right to me. I am planning to set my temporary at the end of one of those runs, but have never seen that done before either. This will be my first job as a new contractor, and I have never done more than a 200 Amp residential service, so I don't want to mess this up. Great to have a resource like this...I have been following some of your posts and already value your opinion....thanks again!

 

[electrofelon]

Dave,
Thanks so much for your reply! So voltage drop is not a problem? I was tentatively planning to run "parallel" 4/0 runs, basically 2-200 Amp runs through a 320 Amp Meter housing with main disconnects at the meter for each panel....yes? I have seen in the forums that 2/0 has also been suggested, but that does not seem right to me. I am planning to set my temporary at the end of one of those runs, but have never seen that done before either. This will be my first job as a new contractor, and I have never done more than a 200 Amp residential service, so I don't want to mess this up. Great to have a resource like this...I have been following some of your posts and already value your opinion....thanks again!

There a few things to be careful of here and we would need some clarification. Is the meter on the house or located remote? Usually the best and cheapest arrangement in your situation is to use 230.40 exception 2 and use two 200 amp main breaker panels. Note that in this case you would need 250MCM (assuming aluminum) between the meter and each panel because they are not main power feeders (or you could use "next size up" rule if load is ok and use 4/0). The conductors on the line side of the meter could be sized to the load. Best and cheapest if you can skip the disconnects on the outside and run service conductors to two grouped main breaker panels. If you dont want the panels grouped or have to go further in to the structure than your AHJ allows for service conductors than you will need disconnects to turn them into feeders, but it can be a hassle to run a 200 amp feeder in RESI because of the low temp rating and ampacity of SER (depending on the situation and what code cycle you are on.)

 

[ActionDave]

Dave,
Thanks so much for your reply! So voltage drop is not a problem? I was tentatively planning to run "parallel" 4/0 runs, basically 2-200 Amp runs through a 320 Amp Meter housing with main disconnects at the meter for each panel....yes? I have seen in the forums that 2/0 has also been suggested, but that does not seem right to me. I am planning to set my temporary at the end of one of those runs, but have never seen that done before either. This will be my first job as a new contractor, and I have never done more than a 200 Amp residential service, so I don't want to mess this up. Great to have a resource like this...I have been following some of your posts and already value your opinion....thanks again!

Thank you for the compliment. Full disclosure, I have never built a 400A service but there a many on this forum that have. Electrofelon gave some good tips.

Here's what I do know - Voltage drop is highly overrated in residences. You do need to do a load calc to see if you can use 4/0 AL. There is a load calculator and voltage drop calculator on Mike Holt's home page under "Free Stuff". But you also have to consider your home owner. Like I said some of them like to brag. You could tell him that 4/0 is the minimum but you are going to use 250 because you don't like to do just the minimum. He may be the type of guy that says, "I like that attitude." or he may say, "Why waste my money then..." That's for you to sort out.

The only way 2/0 makes sense to me is if the conductors are copper.

Setting the temporary at the end of one of the runs seems ok but you have to get into it to work right? That means live work. OSHA had a lot to say about that.

 

[Sparky110]

Thanks!

Thanks!

Wow, guys, really helpful! I think that I was over-thinking this a bit. Yes, 2/0 copper in conduit, because the home owner wants that. With a 200 foot run, he may change his mind, but I will let him decide. Load calc on the house is around 140 Amps, but don't have specs on the A/c's yet. I think that I would like to set one panel inside the house further to shorten almost all of the home-runs, and then set the second at the meter as a main-breaker panel for the future shop. Also, would like to use that second panel for the A/C's to balance the load-per-panel. So two questions.....If I use the second panel for the A/c's, or for that matter just attach it to the house, isn't there a double-service issue? Can't quote the section off of the top of my head, but I thought that you could only have one service per structure? Second, How do you ground these....? I am thinking two separate GEC's run to a universal grounding electrode system. Thoughts? And thanks so much!!

 

[kwired]

Some thoughts - and replies to multiple posts.

If you run to two individual panels you can not use 310.15(B)(7), neither set of conductors is carrying the entire dwelling load.

If you run a single set of conductors you can use 310.15(B)(7).

I don't see anywhere that allows you to parallel the conductors at the ampacities listed in 310.15(B)(7) either.

If you run to individual panels each set of conductors must have ampacity equal to the overcurrent protection (next size up rule applies as long as calculated load doesn't exceed conductor ampacity).

If you run a single or parallel set of service conductors (in other words connect the parallels together at the load end to effectively make a single conductor), and make taps to each of the panels at the load end, you likely do have less voltage drop - really depends on loading conditions, but for a dwelling- loading generally is on the low side.

If you have two to six disconnecting means and supply them with a single conductor (or an equivalent parallel conductor) that conductor only needs sized to the calculated load. You could have 400 amps of conductor supplying 600 amps of disconnecting means if the calculated load is 400 amps or less.

 

[suemarkp]

Two panels is not a double service issue if you follow the rules of 230.40 exception 2. Basically, a Service is limited to 6 disconnecting handles, and those handles must be grouped. So you can have two 200A main panels are disconnects, but they must be side by side on the same side of the wall. This is where the Service ends and anything past this will be feeders or branch circuits.

There's a lot of way to do this. You can use an outside meter-main with two 200A breakers. You can use two 200A panels inside. You can have two 200A disconnects outside, or a 200A main panel and a 200A disconnect side by side.

You also have multiple methods to ground. If your PoCo allows it, running the GEC from the meter is easiest. You'd run a 1/0 copper GEC (depending on the final size service entrance conductors you choose) to the ground electrode and water bond. If you have a common wiring gutter between the meter and disconnects, you could tap the GEC off the neutral in the gutter. Or, you can use GEC taps from each panel, sized per the conductors feeding that panel, to a common electrode and water pipe. These would be #4 copper if both panels are 200A and fed with 2/0 copper.

 

[dhkane]

I am putting in a 320 Amp Meter housing, with either a 400 Amp Panel or 2-200 Amp panels, and have to run the service laterals 200 feet....not sure how to do this most efficiently...? Am not sure that 400 Amps are needed, but the owner hopes to add a shop later, and already has two large A/C units and two double ovens planned....everything else is very standard for a 3400 ft house.

I know Millbank has the 320A meter housing and is available at 22kAIC.

Going with 2-200A breakers feeding 2-200A panels is a good choice. It would provide the owner with more circuits.

You can also split the A/C units and double ovens separately to each panel. These will be your largest single phase loads.

Future shop later.....go 400A.

 

[electrofelon]

Wow, guys, really helpful! I think that I was over-thinking this a bit. Yes, 2/0 copper in conduit, because the home owner wants that. With a 200 foot run, he may change his mind, but I will let him decide. Load calc on the house is around 140 Amps, but don't have specs on the A/c's yet. I think that I would like to set one panel inside the house further to shorten almost all of the home-runs, and then set the second at the meter as a main-breaker panel for the future shop. Also, would like to use that second panel for the A/C's to balance the load-per-panel. So two questions.....If I use the second panel for the A/c's, or for that matter just attach it to the house, isn't there a double-service issue? Can't quote the section off of the top of my head, but I thought that you could only have one service per structure? Second, How do you ground these....? I am thinking two separate GEC's run to a universal grounding electrode system. Thoughts? And thanks so much!!

It certainly is tempting to have one of those panels at a different location further inside the house. However IMO it is a tough to justify. Add the cost of two 200 A disconnects, more crap on the side of the house, SER is probably out so 2" or 2 1/2" pipe thru the structure....Yes with the two disconnects outside you would only need MLO panels but I think they would be hardly cheaper than a main breaker. May be better off with the grouped 200 MB's and a 100 amp (or 125 if you felt you needed it - 2 pole 125's are generally affordable) sub somewhere fed with SER. Depends on the layout of course and how tight the budget is.....

 

[Sparky110]

Thannks everyone.

Thannks everyone.

So I had the 200 foot measurement from the homeowner, who is now saying it is 300 feet. Geez. I am trying to get him an accurate number, although I think he is pretty committed to me doing the work. So, in order to keep that 300 foot cable (which I will measure tomorrow myself) as cheap as possible (and especially if he is still committed to copper, which I actually feel good about for the future...comments?) I am thinking that an extremely detailed and accurate load calc would probably save thousands literally. I have done load calcs quite a few times in the far past, but not recently, and never in a situation where I was actually planning to hit the load calc very closely with my SEC size. Any ideas as to pitfalls and dangers associated with this? SER is a possibility for the internal panel, but actually was thinking of burying PVC in the foundation as it is not poured yet and it is a slab foundation. maybe a very good point about more crap on the building. I thank you each for your responses, as each one has been very helpful and opened up other options that I was not considering.

 

[GoldDigger]

So I had the 200 foot measurement from the homeowner, who is now saying it is 300 feet. Geez. I am trying to get him an accurate number, although I think he is pretty committed to me doing the work. So, in order to keep that 300 foot cable (which I will measure tomorrow myself) as cheap as possible (and especially if he is still committed to copper, which I actually feel good about for the future...comments?) I am thinking that an extremely detailed and accurate load calc would probably save thousands literally. I have done load calcs quite a few times in the far past, but not recently, and never in a situation where I was actually planning to hit the load calc very closely with my SEC size. Any ideas as to pitfalls and dangers associated with this? SER is a possibility for the internal panel, but actually was thinking of burying PVC in the foundation as it is not poured yet and it is a slab foundation. maybe a very good point about more crap on the building. I thank you each for your responses, as each one has been very helpful and opened up other options that I was not considering.

Why does the homeowner object to Aluminum? Properly specified and installed it can just fine, and could allow him to get a lower voltage drop at a lower cost.

If you will use the PVC in the slab for actual service entrance conductors, make sure that the concrete is thick enough over it for it to be considered outside the house.

 

[kwired]

So I had the 200 foot measurement from the homeowner, who is now saying it is 300 feet. Geez. I am trying to get him an accurate number, although I think he is pretty committed to me doing the work. So, in order to keep that 300 foot cable (which I will measure tomorrow myself) as cheap as possible (and especially if he is still committed to copper, which I actually feel good about for the future...comments?) I am thinking that an extremely detailed and accurate load calc would probably save thousands literally. I have done load calcs quite a few times in the far past, but not recently, and never in a situation where I was actually planning to hit the load calc very closely with my SEC size. Any ideas as to pitfalls and dangers associated with this? SER is a possibility for the internal panel, but actually was thinking of burying PVC in the foundation as it is not poured yet and it is a slab foundation. maybe a very good point about more crap on the building. I thank you each for your responses, as each one has been very helpful and opened up other options that I was not considering.

Have you mentioned even an approximate cost difference between copper and aluminum for that length at 400 amps? It may make him decide pretty quick which to go with.

 

[kwired]

Two panels is not a double service issue if you follow the rules of 230.40 exception 2. Basically, a Service is limited to 6 disconnecting handles, and those handles must be grouped. So you can have two 200A main panels are disconnects, but they must be side by side on the same side of the wall. This is where the Service ends and anything past this will be feeders or branch circuits.

There's a lot of way to do this. You can use an outside meter-main with two 200A breakers. You can use two 200A panels inside. You can have two 200A disconnects outside, or a 200A main panel and a 200A disconnect side by side.

You also have multiple methods to ground. If your PoCo allows it, running the GEC from the meter is easiest. You'd run a 1/0 copper GEC (depending on the final size service entrance conductors you choose) to the ground electrode and water bond. If you have a common wiring gutter between the meter and disconnects, you could tap the GEC off the neutral in the gutter. Or, you can use GEC taps from each panel, sized per the conductors feeding that panel, to a common electrode and water pipe. These would be #4 copper if both panels are 200A and fed with 2/0 copper.

2/0 copper can not be used, to be able to use 310.15(B)(7) the load on the conductor must be the entire dwelling load.

 

[Sparky110]

Update

Update

Apprised of the costs, the homeowner has opted for 4/0 AL. Thank you all for your help. I will save this to favorites for the future. Great resource. :thumbsup:

 

[Sparky110]

2/0 copper can not be used, to be able to use 310.15(B)(7) the load on the conductor must be the entire dwelling load.

So 4/0 AL cannot be used either, then, correct? Although if the load calc for the dwelling could be used on only one of the runs, the other run could be a future panel to feed the shop and other things like pumps, sheds, etc. Am I getting that right, or am I missing something? I am about to do a voltage drop calc on the 4/0 AL, and may see that the dwelling load does not work with that size wire. Seems like that load calc must needs be extremely accurate. Competitor is telling homeowner that it can be done, and I would love to agree, but just a bit more cautious, I guess. Would love input on this further.

 

[ActionDave]

Have you looked at 240.4? A good load calc is important. 4/0 AL is possible.

Allowances for voltage drop are not required by the NEC and highly overrated when it comes to services.

 

[kwired]

So 4/0 AL cannot be used either, then, correct? Although if the load calc for the dwelling could be used on only one of the runs, the other run could be a future panel to feed the shop and other things like pumps, sheds, etc. Am I getting that right, or am I missing something? I am about to do a voltage drop calc on the 4/0 AL, and may see that the dwelling load does not work with that size wire. Seems like that load calc must needs be extremely accurate. Competitor is telling homeowner that it can be done, and I would love to agree, but just a bit more cautious, I guess. Would love input on this further.

If you are supplying individual disconnects with individual conductors your conductor ampacity must be equal or greater than the overcurrent protection - next size up rule applies to 800 amps and under.

If you have the allowed two to six disconnecting means, then you can tap them off a conductor with ampacity equal or greater than the calculated load.

4/0 aluminum is good for 180 amps. It can be used on a circuit with 200 amp overcurrent protection as long as the calculated load is not over 180 amps, because of the next size up rule. If it were to have 181 amp of load then a larger conductor must be used.

You can not use two runs of 2/0 copper to feed 2- 200 amp circuits because of the mentioned fact that neither one of the sets will feed an entire dwelling unit.

I also don't think 310.15(B)(7) would allow paralleling two 2/0 copper conductors and calling the net result a 400 amp conductor.

You however could parallel two runs of 2/0 copper effectively making them a single 350 amp conductor, and then tap two to six disconnecting means from it as long as the calculated load is not more than 350 amps. All two to six disconnecting means could add up to well over 350 amps and it is still compliant if load calculation is 350 or less.

If you were supplying a two family dwelling you could use 310.15(B)(7) and supply each dwelling with 2/0 copper and install 200 amp service disconnect for each dwelling because each set is supplying the load of an entire dwelling unit.



Knowing the rules sometimes helps you find ways around problems. If one already had two sets of 2/0 installed and was red tagged, a way around not replacing all the conductor could be to make them so they are parallel and still feed two 200 amp disconnects as long as the load calculation is under 350 amps.


Confused yet?

 

[Sparky110]

ActuinDave and Kwired

ActuinDave and Kwired

Guys, I am so much clearer on the rules now than when I started this little exercise. I understand now how the competition has come up with their number, and it is legitimate. If I get the job (and my hesitation may have lost it for me) I will have this forum and the lot of you to thank for doing it right AND understanding why I am doing it in such and such a fashion.....Can't thank you enough, and just for fun will repost if I get the job or not. If I don't, at least I won't need to hesitate on the next one! So I am going to put together a price based on a 320A Meter/Main with 200A disconnects, and two 200A panels driven by 4/0 AL paralleled. The 200A Panels will essentially be sub-panels, and I may move one inside, if the SER option is available and cost effective. At least one of the panels will be set outside at the Meter/Main to drive the future shop. Thanks again, and I will let you know if I get it, just for curiosity's sake.

 

[kwired]

Guys, I am so much clearer on the rules now than when I started this little exercise. I understand now how the competition has come up with their number, and it is legitimate. If I get the job (and my hesitation may have lost it for me) I will have this forum and the lot of you to thank for doing it right AND understanding why I am doing it in such and such a fashion.....Can't thank you enough, and just for fun will repost if I get the job or not. If I don't, at least I won't need to hesitate on the next one! So I am going to put together a price based on a 320A Meter/Main with 200A disconnects, and two 200A panels driven by 4/0 AL paralleled. The 200A Panels will essentially be sub-panels, and I may move one inside, if the SER option is available and cost effective. At least one of the panels will be set outside at the Meter/Main to drive the future shop. Thanks again, and I will let you know if I get it, just for curiosity's sake.

If this meter main is not on/right at the house, you still will need both main house panels grouped together. Plus I somehow missed that this is a feeder and not a service. You will have to parallel the run if it is a feeder. 225.30 only permits a building or structure to be supplied by one feeder or branch circuit. By joining the conductors together at both ends, they are considered one conductor, if they are not joined together at both ends they are not parallel conductors per definition and are considered multiple conductors - that is where the violation of 225.30 would be. You can still have up to six disconnecting means, and must group them together, but you have to supply it with a single feeder.