Articles 225 and 230- Detached Gargae

[Dennis Alwon]

I am looking at a set of plans for a home and a detached garage. The owners want an apartment above the garage on a separate meter. My plan is to wire the garage on that meter however I was curious if we could feed the building with a feeder from the house and have a service for the apartment. IMO, it is compliant. 225 says one feeder and that is what I have- I also have one service so I don't see an issue. Anyone see a problem? Of course I would group the discos.

 

[mopowr steve]

Don't know of any reason you can't. But may require a label defining the source of power locations.

ie. disco1 feed from home panel and disco2 feed from power co.

 

[iwire]

How would a feeder be a separate meter? :?

It sounds like it would be double metered power.

 

[Dennis Alwon]

How would a feeder be a separate meter? :?

It sounds like it would be double metered power.

The feeder would come from the house meter and a new service with meter from the poco would be at the garage also. The meter would be for the apt. and the feeder for the garage

 

[infinity]

If this is a single building won't you end up with both branch circuits (from the service) and a feeder within the same structure?

 

[Dennis Alwon]

If this is a single building won't you end up with both branch circuits (from the service) and a feeder within the same structure?

Yes--is there a section that wont allow this? I would think there is but I don't see it. I see it as a feeder and a service powering the building...

 

[Smart $]

Yes--is there a section that wont allow this? I would think there is but I don't see it. I see it as a feeder and a service powering the building...

Branch circuits in buildings with more than one occupancy?210.25. As long loads are kept on respective supplies, should be good.

 

[infinity]

Branch circuits in buildings with more than one occupancy?210.25. As long loads are kept on respective supplies, should be good.

Isn't that for two dwelling units or common areas?

 

[Dennis Alwon]

Isn't that for two dwelling units or common areas?

Yes but I think one could see justice in that they are two different spaces. The problem is not really that but rather one would consider the service as a feed to the building and then bringing another feed from the house for the other space. IMO, I don't see this as any different then a service with 2 meters on the building. 225.30 seems to be satisfied as only one feeder supplies the building and 230.2 also seems to be satisfied as there is only one service. Not sure if this meets the intent but I see nothing that would not allow this install.

 

[kwired]

One of my concerns with this is the EGC in the feeder will ultimately be bonded to a service on each end and will carry grounded conductor current from either of those services. This defies some of the reasoning why they no longer allow equipment grounding of separate buildings via the grounded conuctor of the feeder.

Other then that I really don't have an answer as to if a service and a feeder as described are allowed to supply a structure.


I will also say if you have a building supplied by a service as well as another source whether it be a generator, PV, etc don't you have a service and a feeder supplying that building?

 

[MasterTheNEC]

Dennis,

My opinion is that nothing would prevent this application except the local AHJ who may see it totally differently. As you stated Section 225 and 230 are totally different and it would appear you (technically) have met (or will meet) those specific applications. What I might suggest is a call to the local AHJ, explain the situation (get them engaged) and then see if their is any zoning issue as well which might prevent the application.

With that said, as long as your labeling is done ( to enhance safety ) and grouping (to ensure added safety) I would be ok with it and after getting the blessing from the local AHJ so they are not confused in your efforts. As for 210.25, just don't violate it and nothing to be concerned about in that area.

Just my thoughts on it.

 

[Smart $]

One of my concerns with this is the EGC in the feeder will ultimately be bonded to a service on each end and will carry grounded conductor current from either of those services. ...

That seems to be the most noteworthy concern to this point in the discussion. My first thought on this issue is going to 250.6(B)... but how would one implement an alteration and still satisfy all intents for grounding?

As a result, IMO, the best method would be to run service drop/lateral to house or garage and put meters and disconnects there, then run feeders as necessary. Putting meters and disconnects on the garage would provide the least controversial application.

 

[Dennis Alwon]

Dennis,

My opinion is that nothing would prevent this application except the local AHJ who may see it totally differently. As you stated Section 225 and 230 are totally different and it would appear you (technically) have met (or will meet) those specific applications. What I might suggest is a call to the local AHJ, explain the situation (get them engaged) and then see if their is any zoning issue as well which might prevent the application.

With that said, as long as your labeling is done ( to enhance safety ) and grouping (to ensure added safety) I would be ok with it and after getting the blessing from the local AHJ so they are not confused in your efforts. As for 210.25, just don't violate it and nothing to be concerned about in that area.

Just my thoughts on it.

I just found out that the apartment is not even allowed but they are planning to put it in afterwards. I will not get involved in that but I will put the entire building on one meter and have no feeder back to the house..... I was more curious about doing the other install and I am not really planning to do it.

 

[Cavie]

Homeowner metering the apt in the future and charging the tennent is not allowed either.

 

[fmtjfw]

Any other thoughts?

Any other thoughts?

I am looking at a set of plans for a home and a detached garage. The owners want an apartment above the garage on a separate meter. My plan is to wire the garage on that meter however I was curious if we could feed the building with a feeder from the house and have a service for the apartment. IMO, it is compliant. 225 says one feeder and that is what I have- I also have one service so I don't see an issue. Anyone see a problem? Of course I would group the discos.

This is actually pretty interesting (ignoring the zoning issue).

230.2 Number of Services. A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D).

230.2 (B) Special Occupancies. By special permission, additional services shall be permitted for either of the following:
(1) Multiple-occupancy buildings where there is no available space for service equipment accessible to all occupants

230.2 (E) Identification. Where a building or structure is supplied by more than one service, or any combination of branch circuits, feeders, and services, a permanent plaque or directory shall be installed at each service disconnect location denoting all other services, feeders, and branch circuits supplying that building or structure and the area served by each. See 225.37.

225.37 Identification. Where a building or structure has any combination of feeders, branch circuits, or services passing through it or supplying it, a permanent plaque or directory shall be installed at each feeder and branch-circuit disconnect location denoting all other services, feeders, or branch circuits supplying that building or structure or passing through that building or structure and the area served by each.

225.37 Exception No. 2: This identification shall not be required for branch circuits installed from a dwelling unit to a second building or structure.

The two requirements essentially say the same thing, I think, it would be nice if they used the same words. I'd probably ignore the exception and put a plaque up any away.

Now the service at the garage/apartment needs to meet all the requirements for grounding and the feeder/branch circuit from the other building needs to meet all its grounding requirements.

If we use ground rod(s) at the home and at the garage/apartment building, we can connect the two with #6 AWG copper wire and treat the rod(s) at each other building as supplemental grounds. The #6 can also serve as the grounding connection between the home and garage. (The wire would need to be larger if the GEC for the feeder size requires it.)

I would mount the apartment service disconnect and the garage feeder/branch circuit disconnect adjacent to each other and interconnect the four grounding wires (from rod(s), from feeder, to service and feeder disconnects). I would interconnect the grounding and neutral only in the service disconnect.

 

[GoldDigger]

And, needless to say (but saying it anyway) the two sets of neutrals will remain isolated from each other throughout the structure.

 

[Smart $]

...

Now the service at the garage/apartment needs to meet all the requirements for grounding and the feeder/branch circuit from the other building needs to meet all its grounding requirements.
...
I would mount the apartment service disconnect and the garage feeder/branch circuit disconnect adjacent to each other and interconnect the four grounding wires (from rod(s), from feeder, to service and feeder disconnects). I would interconnect the grounding and neutral only in the service disconnect.

And, needless to say (but saying it anyway) the two sets of neutrals will remain isolated from each other throughout the structure.

As mentioned previously, there is no way that I can think of to comply with all the grounding requirements and prevent grounding from being a parallel path for neutral current. While some say neutral current through grounding is not objectionable current on the utility side of service disconnecting means, for the case proposed in the OP, it will be on the load side of the house's service disconnect.

 

[Dennis Alwon]

I wonder if you ignore some of art 250 and install 4 ground rods and not connect them together- 2 for the feeder and 2 for the service. Would that not keep from getting a parallel path

 

[david]

I guess I do not read it this way at all

Article 230 general requirements deal with a building being supplied by a service and only one supply is allowed with exceptions

Article 225 part II states in general one supply with exceptions

Both articles limit the building to one supply not withstanding the exceptions.

 

[Smart $]

I wonder if you ignore some of art 250 and install 4 ground rods and not connect them together- 2 for the feeder and 2 for the service. Would that not keep from getting a parallel path

No. Under current code, we are required to run an EGC with the feeder from the house, which gets bonded to the garage GES along with the apartment service. The feeder EGC is effectively bonded to the neutral of both services. Even under older Code where the EGC was not required for a feeder to a separate structure, the neutral (grounded conductor) was still required to be bonded to the structure's GES, so the feeder neutral would end up being the parallel conductor.