Grid Tie in Tucson Az

[solarix]

Pretty amazing. I'd say you have a service with no main disconnect.
One thing to realize when interconnecting solar is the utility is going to use this opportunity to bring your site up to their current standard. They apparently allowed your service to be this way in back in the seventies, and will allow it forever as long as you don't change anything, but now that you want their permission to add solar, they are gonna want you to bring it all up to date.
You might as well figure on upgrading this service to a solar-ready type breaker panel (if you get a GE one you can reuse the breakers, although all new everything would be prudent). This is going to take a separate permit to have the utility come out and pull the meter, your electrician will have to do the work starting early in the morning and coordinate with the local inspector to check it over and green tag it and then have the utility come back and re-energize it - all the same day.

[posplayr]

Question #1 Is it a relatively simple matter to reorganize the breakers to get a pair of 240V breakers grouped at the bottom of the fuse box?
There is an existing open double at the bottom left with a 15 and 20 amp circuit breakers just above. The 15 and 20 could be moved to two other open slots without regard to phase provide the wire is long enough to support it which it seems it is as everything still stay on the lower portion of the panel.

Yes, move the single breakers up to make room for a double breaker at the bottom left. be careful to relabel as needed.

Question #2 Where is the main breaker? Neither the Main or the subpanel have what I recognize as a Main breaker(my last house had one in Ca and I think they seemed to be common place there). There is a locked box coming out of the ground at the foot of the driveway. I assume this is power as all the other utilities are represented in one way or another outside of this box.

Somewhere in between the meter and the breaker panel, there has to be a main breaker that is readily accessible.
Perhaps in a door below the meter? Need a picture of the meter box.

Follow up to Question #2a

In the absence of a main breaker and the secret lock on the street I'm assuming that the power company has to be called in to switch off the mains inside of that little box.

The main breaker is not going to be locked up.

Follow up to Question #2b

Is it possible to put in a AC disconnect inside of the main panel? The meter and the main panel are separated by little more than 3" of 2" conduit. Basically I'm asking as rewiring the service connection between the meter and the main panel is probably non trivial.

No, it is not OK to put the AC disconnect in the main panel (not listed for that purpose).

TIA.

Here is the deal: You want a 10kW inverter - that's going to take some doing on the interconnect.
10kW / 240V = 41.67A (check inv. data sheet, max amps may vary a bit). Since it is continuous duty, the ampacity is 125% of that or 52A. That means a 60A breaker for the solar circuit. Code requires the backfed current to be less than 20% of the busbar rating. 20% of 200A is only 40A. So you need to either get a bigger busbar (upgrade to 400A panel) or downgrade the main breaker to 175A (good luck finding that in the style for this panel) to give you another 25A, or do a line-side tap (before the main breaker which very few panels are listed for). Any of these options can get expensive - even the derated main breaker requires a separate permit to have the utility out to shut down the service to do the changeout.
The panel may be from the 70's but looks in good condition. First try and find the main breaker and see if a 175A version of it can be special ordered (you will also have to justify to the authorities that your load can be serviced by a 175A main). Next option is to replace the whole panel with a "solar ready" 200A panel that has a 225A busbar. Or if you want future expansion, go to a 400A panel. Either of those options generally cost upwards of $1500 installed.
Or you could back off the solar system size and just use a 7.7kW inverter on a 9kW array which just needs a 40A breaker and no modifications to your panel.

Solarix: Thanks for your reply

This is a picture of the meter and the buried conduit coming up to the meter box. You can see the 4/0 wires coming through another large conduit on the bottom left of the main panel. The meter box doesn't look like something to open. Perhaps it is?

As to the rest, I need to find out what size the breaker is after I find the main breaker. Any clue?

EDIT: I looked closely at the meter box and used a large flat head screw driver to see if I persuade the lid up. It does not give much at all; as if it never was opened. It could have been painted closed, but jamming the screwdriver end under the front lip of the panel did not get a budge out of it at all.

The bottom has two additional knockouts same size as the pipe coming it. It is not moving.

[solarix]

Question #1 Is it a relatively simple matter to reorganize the breakers to get a pair of 240V breakers grouped at the bottom of the fuse box?
There is an existing open double at the bottom left with a 15 and 20 amp circuit breakers just above. The 15 and 20 could be moved to two other open slots without regard to phase provide the wire is long enough to support it which it seems it is as everything still stay on the lower portion of the panel.

Yes, move the single breakers up to make room for a double breaker at the bottom left. be careful to relabel as needed.

Question #2 Where is the main breaker? Neither the Main or the subpanel have what I recognize as a Main breaker(my last house had one in Ca and I think they seemed to be common place there). There is a locked box coming out of the ground at the foot of the driveway. I assume this is power as all the other utilities are represented in one way or another outside of this box.

Somewhere in between the meter and the breaker panel, there has to be a main breaker that is readily accessible.
Perhaps in a door below the meter? Need a picture of the meter box.

Follow up to Question #2a

In the absence of a main breaker and the secret lock on the street I'm assuming that the power company has to be called in to switch off the mains inside of that little box.

The main breaker is not going to be locked up.

Follow up to Question #2b

Is it possible to put in a AC disconnect inside of the main panel? The meter and the main panel are separated by little more than 3" of 2" conduit. Basically I'm asking as rewiring the service connection between the meter and the main panel is probably non trivial.

No, it is not OK to put the AC disconnect in the main panel (not listed for that purpose).

TIA.[/QUOTE]

Here is the deal: You want a 10kW inverter - that's going to take some doing on the interconnect.
10kW / 240V = 41.67A (check inv. data sheet, max amps may vary a bit). Since it is continuous duty, the ampacity is 125% of that or 52A. That means a 60A breaker for the solar circuit. Code requires the backfed current to be less than 20% of the busbar rating. 20% of 200A is only 40A. So you need to either get a bigger busbar (upgrade to 400A panel) or downgrade the main breaker to 175A (good luck finding that in the style for this panel) to give you another 25A, or do a line-side tap (before the main breaker which very few panels are listed for). Any of these options can get expensive - even the derated main breaker requires a separate permit to have the utility out to shut down the service to do the changeout.
The panel may be from the 70's but looks in good condition. First try and find the main breaker and see if a 175A version of it can be special ordered (you will also have to justify to the authorities that your load can be serviced by a 175A main). Next option is to replace the whole panel with a "solar ready" 200A panel that has a 225A busbar. Or if you want future expansion, go to a 400A panel. Either of those options generally cost upwards of $1500 installed.
Or you could back off the solar system size and just use a 7.7kW inverter on a 9kW array which just needs a 40A breaker and no modifications to your panel.

[posplayr]

Hi all I'm relatively new here but have gotten my feet wet posting a few times. I'm an BSEE/MSECE but not an electrician. I'm not at all convinced I want to even do this work myself (the actual grid connect in the main panel); my main concern is not having a big unaccounted for cost item.

I'm looking to install a 240V Grid Tie Solar system on a large 30'x45' shop detached but 6' from the east side of the attached garage/house. The main panel is mounted on the side of the garage so I'm expecting to drop conduit from the shop roof and bury it to get over to the inverters which will be mounted near the main panel on the side of the garage. It is no more than 30' linear run of wire from the shop roof, to the ground across the walkway and popping back up next to the main panel. Everything else is already buried in this area.

Main Panel: The main panel is very old dating back to 1976 (I wonder what that makes me ) but the electrical seems to have been upgraded when the shop was put in around 2000. The main panel is right next to the meter and is being fed with 4/0 aluminum wire. It seems to be a GE unit but no model number that I can see and the paper labels are unreadable.

Shop Sub-Panel: There is a 240V/125 Amp subpanel in the shop operating of of a ganged pair of 100 amp breaker in the main panel(4 awg wire) but at the moment this seems to bear little impact to the solar connect to the grid (i.e. main panel).

I have some fairly specific questions, but first some basic parameters for the solar.

Looking to install 36 panels at nominal 10 Kwatts and from what I have read with virtually zero blockage (other than clouds) the SMA Sunny Boy would be a good inexpensive choice.

Based on installation descriptions, If I can get away with one higher capacity inverter (like a SB10K v.s. two SB5K) I can avoid a lot of duplicate DC and AC cut-offs and associated conduit. In addition there seems to be limited open breaker slots in the main panel. I think there is enough room for a double breaker.

So it seems I need a pair of 50 amp breakers to tie-in the SMA 240 inverter. I have two open slots in the Main panel but they are not located together. Here is a picture of the beast. I buzzed across a pair of open (but not adjoining) slots and the two open ones have 240V across them.



Question #1 Is it a relatively simple matter to reorganize the breakers to get a pair of 240V breakers grouped at the bottom of the fuse box?
There is an existing open double at the bottom left with a 15 and 20 amp circuit breakers just above. The 15 and 20 could be moved to two other open slots without regard to phase provide the wire is long enough to support it which it seems it is as everything still stay on the lower portion of the panel.

Question #2 Where is the main breaker? Neither the Main or the subpanel have what I recognize as a Main breaker(my last house had one in Ca and I think they seemed to be common place there). There is a locked box coming out of the ground at the foot of the driveway. I assume this is power as all the other utilities are represented in one way or another outside of this box.

Follow up to Question #2a

In the absence of a main breaker and the secret lock on the street I'm assuming that the power company has to be called in to switch off the mains inside of that little box.

Follow up to Question #2b

Is it possible to put in a AC disconnect inside of the main panel? The meter and the main panel are separated by little more than 3" of 2" conduit. Basically I'm asking as rewiring the service connection between the meter and the main panel is probably non trivial.

TIA.