ECN Forum Forums Code Related Discussion NEC & other Code issues Grouping of Service Disconnects

A Commercial Building has two separate services of different characteristics. One is 120/240V. single phase for power and lighting. The other is 230V. three phase, three wire for air conditioning load. Would it be NEC compliant to have one service located at opposite ends of building from each other. <B>The single phase service is existing</B>. The three phase service is new, to be used for HVAC equipment only. Lastly, the Electric Power Company directed the electrician to install the new service away from existing service. Approx. 50 ft.

Frank,

All the "Dual Services" I have seen over time were right next to each other [physically!].

I imagine you are describing a system which is derived from a 4 wire Delta [could be closed, could be "Vee"] Transformer bank from the Utility guys. That's the norm of the ones I have encountered. They are as follows:

The 1 phase 3 wire service is separately metered and contains the Grounded Conductor. The 3 phase 3 wire service is separately metered and in it's own gear, as is the 1 phase 3 wire [in it's own gear / separate meter]. Each of these services are fed from the same 4 wire Delta network.

The gear I worked with / around was physically bolted together and bonding jumpers installed [sometimes ] between the sections - as well as within the gear. All bonded to the GES in the 1 phase 3 wire section.

Since they are both fed from the same system, the 3 phase 3 wire section bonds to the system "Neutral", in order to complete the requirements of a Grounded Conductor's action [AKA Ground Faults / Sparks be - a flyin', balls 'O fire, yadda, yadda, yadda].

The only thing I could see being a problem is bonding the Grounded Conductor in two individual services within the same "Area". I am referring to the current loads running on cold water pipes, in the rebar, under the slabs, etc.

If the 3 phase 3 wire system is derived from a separate Transformer, or bank of pots [either from one stand alone 3 phase 3 wire xformer, or 2-3 individual 1 phase xformers connected as 3 phase 3 wire only] and the 1 phase 3 wire system is not a part of the 3 phase system, then there will not be as much of a Grounding Electrode / Grounded Conductor bonding problem.

Now, as far as "Spotting A Meter", the local Utility Design Engineer[s] would be the ones to ask for an accurate answer. If they will allow meters in separate locations, your 1/2 the way home! Then see what the AHJ has to say about that setup. If both agree - your in! If not, back to the drawing board! [AKA both services in same location].

Is there some unresolvable restraints occuring, which is why you + PoCo want to locate the new 3 phase service away from the existing 1 phase service? Like size of the room, etc.??

If it's just to accomidate feeding 3 phase loads easier, maybe you could subfeed from the service and place it next to the 1 phase guy.

If there was a little more information, maybe someone [or I] could give more accurate answers [boy, if that's not redundant ].
I'll browse the NEC articles 200 - 230 and see what they say.

Scott SET

Scott,

I agree, two services of different characteristics feeding the same building are usually installed next to one another. A person at my workplace asked me about the possibility of the said services being separated as mentioned in post. He already installed the new service. He installed it that way because it was closer to the large air conditioning equipment on that side of the roof. The local Electrical Inspector wants the service disconnects grouped together. What do you think about 2002 NEC section 230.2(D)and (E). (E) deals with identification on services using a permanant plaque. I'm probably grasping for straws.

I guess my basic question is: Is there ever a case where there could be a single phase service on one side of a building and a three phase service on the other?

Frank,
I don't see anything that says you have to group the service disconnects when you have multiple services to a building. 230-2(e) certainly implies that they are not required to be grouped. 230-70 only requires that all of the disconnects for "a" service be grouped. It does not require multiple services to be grouped.
don(resqcapt19)

I know of a few buildings where services with different characteristics have been located as far as 300' apart.
We normally have are directed by the Utility Planners as to the location of the meters. Maybe you can get the PoCo and the local inspector to hash this out between themselves, and you won't have the headache yourself!

The other service can be 15' apart. No closer on a bldg. But then again in a gear room I can have up to 6 main switch's with tons of modualar metering and a seperate emergancy service meter does not count on the six operations by hand rule. " just jumped in here ! "

Gary, Out here (SoCA), they can be as close together as you want them, and are often directly adjacent to each other.
On a 120/240-1Ø, 240-3Ø setup, this can eliminate the need for the power co to install 2 separate drops.

Keep in mind Art 250 requires a common grounding electrode system for all services to a building.