Parallel 800 amp service

[10uhcplz]

I have an 800 amp service on a house. We are installing an 800 amp service disconnect that will feed 4 - 200 amp panels. The way it is wired now one parallel feeds 2 - 200 amp panels and the other feeds the other two. It was previously fed underground from the pad mount transformer to the house without a main. The conductors used was direct burial 350 mcm aluminum. Isn't that a little small? The power company is telling me that it will be ok to use 350 mcm copper from the transformer to the service disconnect. I'm thinking 400 at least....maybe even 500 mcm considering the distant from the splice to the termination point in a trough just above the 4 - 200 amp panels in the basement. That's probably about 175 feet of 350 aluminum ( in parallel). All terminations are going to be made in the transformer. Utility out to the 800 amp main and then, from the main back into the transformer, spliced and then on to the house. LOL!!!!....Is that clear as mud? LOL!!!!!
Is this proper and are they right or even close on the wire size?

 

[augie47]

Little fuzzy to me
Where is the 800 amp main located (at the house ? At the transformer ? Other ?)
What conductors are you supplying and what conductors is POCO supplying ?
(may determine applicable Code)

 

[10uhcplz]

LOL.....sorry. Main is located at the transformer. All I'm providing is the wires I'm re-directing to the main and then back into the transformer for splice back to the house. I will be using insulated splice bars. Not sure who provided the conductors to the house originally.....suspect that the power company did. That customary on this type of application around here.

 

[Dennis Alwon]

Are you saying that you have 4 runs of cable to the house and they terminate in 4 separate enclosures?????

 

[augie47]

I'm afraid I see a problem.
Why are you adding the main ?
If I understand you correctly, one conductor (per phase) feeds two 200 amp panels, the other 2 other panels.
If that's correct you don't actually have a parallel feed as they don't connect (together) at both ends.
With the original arrangement, if the conductors were POCO supplied, they decide the size.
Regardless of who supplied them, with no main ahead of them and more than one set of OCPs on the end, they could be sized by the calculated load.
By adding the main, because of 225.30 you will need to make it a single feeder and protect the conductors in accordance with 310.16.

 

[iwire]

In my opinion before we can really decide anything we would need to know with absolute certainty where the "Service Point" is in this installation. Without firm knowledge of that we are just guessing.



Article 100

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

 

[10uhcplz]

Here's the deal. We are installing a 60 kw generator. The pad mount transformer is about 175 feet from the house. Originally there was no main breaker (although I think there should have been). The secondary feeding the 4- 200 amp panels in the basement of the house is unprotected. They are terminated in a trough above the panels. One set of conductors in one 3 inch conduit feeds panels A and B......the other feeds panels C and D.
The generator is at the same location as the transformer, as well as the 800 amp ATS. This is because of gas location and distance from the transformer to the house. We now have to have an 800 amp main. So.... I'm feeding from the transformer to the main, to the ATS, and then back into the transformer to splice back into the conductors going to the panels in the house.
We're going to have to join all the panels together at the trough to make the parallel proper under one main......right?
Then there is the wire size......

 

[augie47]

In order to comply with 225.30 I would say you will need to parallel the existing conductors and tap to your 4 panels at the house.
The conductors would need to be protected according to their ampacity.

I do see another problem, however, in that, if you are under the '08 Code, you need to address 702.5. With the remote generator feeding an ATS supplying all 4 panels that may involve some load shaving, etc.

 

[kwired]

You may be better off to leave service as it is and make one of the panels a standby power panel and only feed loads out of it that you wish to have on the generator. Transfer switch will have to be at the house of course. 60kva is 250 amps. If you have less than 200 amps of load to run off the generator you will only need a 200 amp transfer switch instead of an 800 amp, and you will not need to shed the load of the other panels because they are isolated from the generator.

With your original proposed idea I would still do a load calculation to make sure 800 amp service equipment is what is actually needed, you may be able to use 400 or 600, but now you may have a problem with adding future load if 400 or 600 is acceptable now.

 

[10uhcplz]

The house doesn't have anywhere close to an 800 amp load, but, it does have 4 - 200 amp mains which would determine the service size. This is an exsisting house....I'm working with what I have to work with. This is something that is very common.....buy a bunch of panels for spaces when the actual load don't reflect the service size. According to the load calculations this house would do nicely on a 400 amp service. All gas heat, gas water heaters, and gas cook stoves.

 

[augie47]

As kwired mentioned, if you don't take future load into consideration, the fact that you have (4) 200 amps panels does not dictate your service size.
The conductors from your metering point/transfer switch only need to be large enough to carry your calculated load, not the sum of your panels.

If your calculated load is great than 60kw, then 702.5 may still be an obstacle.

 

[kwired]

Do you already have the equipment you mentioned in the OP?

If I were doing this I would find out what the HO wants to be able to run when on standby power and size a generator to feed that and with any luck it will be a 200 amp or less load so that one of the 200 amp service entrance conductor sets can be the utility supply and install a service rated automatic transfer switch and supply one of the original 200 amp panels from that. You may even be able to do the job more than once and still be less than using any 800 amp equipment.

I have done the same set up described on a new home before. 4 - 200 amp panels for entrances because it cost less than 400 amp disconnect plus wireway and taps and eventually feed the same 200 amp panels.

One of them I installed a breaker feeding a main lug panel with enough room for an automatic transfer switch between them. All circuits that the owner desired to have on standby power someday when he wants to install a generator are fed from this panel and will be easy to put the transfer equipment in the space left for it.