120vac Service upgrade

[tom stratton]

I am currently adding grid power (120/240) to a group of 6 different homes in the same cluster sharing the same 600A main. Each residence is individually metered from a 6 stack meter assembly each with its own disconnect downstream of the 600a main. These homes have been successfully fed trouble free for 12-15 years from PV power. The connected load for these homes ranges from 50-80 amps at 120 volts. Due to significant cost the owner intends to request a variance in the form of a 120 volt 70-80 amp sub service to 1 or more homes based on the fact that that the new service will only be feeding the inverter. However, NEC requires a 120/240v 100A service for all new homes. Further, future residents may desire the use of 220 volt appliances. NEC Calculations demonstrate that these small homes could operate quite nicely at 120/240 volt 50-80amp in the absence of PV power. But the thought of "upgrading" a service to 120v 100a A/C with or without PV power is new to me in 35 yrs in this business. Suggestions on 120vac service upgrade/ PV power?

 

[marinesgt0411]

Re: 120vac Service upgrade

OK I am stupid what is PV power?

 

[davedottcom]

Re: 120vac Service upgrade

Originally posted by marinesgt0411:
OK I am stupid what is PV power?

Photo Voltaic
(Converting solar energy to charge and store electric in batteries to be used instead of utility power)

 

[George Stolz]

Re: 120vac Service upgrade

Originally posted by tom stratton:
Each residence is individually metered from a 6 stack meter assembly each with its own disconnect downstream of the 600a main.

This 600 amp main is after the inverter? Can you build a service there at that central location for the grid power?

Due to significant cost...

What cost? Is the PV giving up?

...the owner intends to request a variance in the form of a 120 volt 70-80 amp sub service to 1 or more homes based on the fact that that the new service will only be feeding the inverter.

I'd tell him the easiest, most correct answer: The service to each individual home will be 240 volts. If he doesn't use a phase, that's peachy keen.

That will whittle down the yacking with the utility, and you're not violating code.

I imagine the expense of a grid-intertied system would actually be more expensive than converting to solely utility power. Those style inverters are expensive.

I guess the big question is, what has prompted this activity? Is the system insufficient, too old, is there new developments being added, etc?

I know very little, don't be misled. I'm just curious as to the details of your predicament.

 

[suemarkp]

Re: 120vac Service upgrade

I'm also curious about the cost issue. What is it you think you must provide that costs too much? I believe you only need to provide equipment (including a disconnect) rated at 100A for 120/240V and service entrance wires rated at 100A.

Correct me if I'm wrong, but I don't think you have to be able to provide 100A to these dwellings as long as you can supply the calculated load.

If you installed a 200A 120/240V service for the whole cluster, you might be able to serve all the houses (about 60A each with 3 using one leg and 3 using another). A single 320A service may be a better choice, as this gives you some margin for growth.