Can I do this

[Jerseydaze]

Bring a service to a detached garage then feed a home from detached garage? If you can how do you handle water grounds?

 

[david luchini]

Yes, you can do that. The house would be a building supplied by a feeder per 250.32. The water pipe would be part of the required grounding electrode system at the house.

 

[augie47]

I might add, any water lines at either/both locations would be subject to 250.53 or 250.104

 

[Volta]

And in my opinion, if your service ends in a main breaker sub-feed panel, from which the feeder to the house is connected to the load ends of the busbars, and any other other circuit is fed from that panel, you would no longer comply with 315(B)(7) for undersized conductors, as that portion would not be a 'main power feeder'.

120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.
For individual dwelling units of onefamily, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an
equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

I did one last month: 4/0 AL to the garage service, and 250 kcmil AL to the house. I am not saying it makes sense in every application, but I cannot find the text that allows the 4/0 to continue after some load diversity has been removed.

 

[Article 90.1]

Check with your utility CSR first, because around here the electric bill would be calculated at a commercial rate for any meter that does not supply power to a dwelling unit first.

 

[kwired]

And in my opinion, if your service ends in a main breaker sub-feed panel, from which the feeder to the house is connected to the load ends of the busbars, and any other other circuit is fed from that panel, you would no longer comply with 315(B)(7) for undersized conductors, as that portion would not be a 'main power feeder'.



I did one last month: 4/0 AL to the garage service, and 250 kcmil AL to the house. I am not saying it makes sense in every application, but I cannot find the text that allows the 4/0 to continue after some load diversity has been removed.

Why you say that?

The feeder to the house is feeding the entire dwelling load, just like 310.15(B)(7) requires.

If the dwelling plus the garage comes to over 200 amps of load calc, then your service is too small.

Even so, 4/0 aluminum is still acceptable on a circuit with 200 amp overcurrent protection, as long as the calculated load does not exceed the conductor ampacity of 180 amps.

 

[Jerseydaze]

Ok next question my plan is to bring 200 amps into garage and have 2 disconnects 1-50 amps 1-150 amps the existing main panel iin home is 200 amps do I need to separate grounds and neutrals ? do i need to change 200 amp breaker in home to 150 amp ?

 

[kwired]

Ok next question my plan is to bring 200 amps into garage and have 2 disconnects 1-50 amps 1-150 amps the existing main panel iin home is 200 amps do I need to separate grounds and neutrals ? do i need to change 200 amp breaker in home to 150 amp ?

Is no requirement to do it that way, but is no code violation either as long as the calculated load for the house can be covered by 150 amps.

With multiple disconnecting means in the garage you could still have less than 200 amp service conductors even though the mains are 200 amps, all depends on total load calculation. With a single service disconnect you would need 200 amp service conductor if you have a 200 amp main.

see 230.90 and exception 3.

You could have a 2000 amp main in the house and still supply it with only 150 amps of feeder capacity if that is all that is required for load calculation.

 

[Jerseydaze]

Ive never understood this why would I want to put say two biger breakers then the service mains can handle what if in the future they add a hot tub ? I understand i can do it I just dont see why Id want to .

 

[kwired]

Ive never understood this why would I want to put say two biger breakers then the service mains can handle what if in the future they add a hot tub ? I understand i can do it I just dont see why Id want to .

It doesn't come into play all that often with 200 amp or less service.

Where it comes in real handy is situations where you maybe have 600 or more amps of service conductor with calculated load being less than the service conductor but the mains add up to more than the service conductor ampacity.

I am installing a new service to a school building right now that will have 800 amp service conductors, mains will consist of two 400 amp breakers and two 150 amp breakers. Total load calculation was only around 600 amps though. An 800 amp main lug I line panel cost much less than one with a 800 amp main.

 

[Dennis Alwon]

If your mains are at the garage then you need a 4 wire to the house. Separate equipment grounding conductor and neutral plus you need grounding electrodes (usually rods) at the house as well as at the garage.

 

[kwired]

If your mains are at the garage then you need a 4 wire to the house. Separate equipment grounding conductor and neutral plus you need grounding electrodes (usually rods) at the house as well as at the garage.

A way around needing the separate equipment grounding conductor for the feed between the two is if you came to building one with service conductors, made splices or taps outside the first building and then continued service conductors to second building. Then both buildings are supplied by service conductors.

Grounding electrodes are needed at both buildings either way, only exception would be if the second building were supplied by an individual branch circuit instead of a service or feeder.