diy solar grid tie

[john95]

@billy:

I pay about 125.00 not in summer. In summer I pay about $180 for the hot months. 4 AC units that keep us cool & EV.

[billy1]

Hey John, I'm curious to know which EV you have, yearly mileage, and yearly kWh your electric utility bills you for jus the EV.

[billy1]

I created a spreadsheet with various options when I was evaluating which to go with.

I had 285's and 260's and 300's as various options. And projections of how much of the electric bill they would eliminate. And how many months until the "breakeven" point.
For me, the 285's were a good point in the price/capacity curve.
If I had more roof space, 260's would have been just as good, and I probably would have gone that way. (I'm somewhat glad they didn't fit though. Looking back it would have meant even *more* mounting points and racking to get setup. And that took quite a bit of time.)

If you have a south-facing roof or even better, a south-west facing roof, with being in PG&E, you will want to go TOU.
TOU makes the calculation of how much $ are saved for a given array size more difficult. (or what array size gives you $0 bill)
You can download your green-button data from PG&E and do a spreadsheet to calculate - but it will be a bit of a PITA.

While you're doing your planning you need to evaluate how you're going to tie into your current service.
1> do you have a large enough service to do the backfeed?
2> Is your main breaker panel an end-feed panel or center-feed?
3> What is the "120% rule" and does it apply to your situsation?
4> What size breaker do you need for the backfeed?
etc.

Good luck.

Hey foo1bar, I got to a point where I need to understand my main breaker.

1. I have plenty of room left on my 200 amp main breaker for the back feed, I'm using 140 amps of 200 amps. I think I need 30 amp breaker for PV and I will add a 50 amp breaker for 14-50R outlet for a EV in the future. That would bring me to 220 amps total I believe.

2. Not sure end fed-feed or center-feed, If the take the panel service cover off it will be clear right?

3. So it should be 240 amps for my 120% rule?

4. I believe I need a 30 amp breaker for my PV system


It's going to be Solar World 285 watt and Enphase m250 15 each

IMG_20160927_152934.jpg IMG_20160927_152949.jpg

[billy1]

So for 2 rows of 6 panels 20' rails and one row of 3 panels 10' rails. If my rafters are every 2' how many flat tile hooks do I need?

[sdold]

Did you do the uplift calcs? What did you come up with?

[billy1]

ICalcs looks like a windows program. I have linux and chrome os pc's. I just looked at unirac builder I'm thinking a roof hook every 48" ? (rafter is every 24")

[sdold]

It depends on wind zone, exposure category, the pullout strength of the mount, the framing method and species, snow load, rail manufacturer requirements, etc. ASCE 7-10 along with wind speed and snow load numbers from the Building department will get you going. On mine, I got the wind speed/snow load requirements from the city, designed to the next higher wind speed, and chose the number of mounts to satisfy the uplift loads plus a generous fudge factor. Be aware that there might be fire setback or even seismic requirements. That's why it's important to have a conversation with the building inspector early on.

[billy1]

I just spoke to the building inspector in person in Vacaville and he said due to a city ordinance passed last November, he cannot answer any of my questions and the city would rather I pay someone to install. Talk about being in a rock in a hard place, that explains why the inspector didn't return my voicemail and email. He did suggest I look online for "how to install solar" to get a template for the paperwork to submit and to read title 24. I'm still scratching my head because cities in general can add special requirments, but my city refuses to tell me what they are. I did speak to 3 separate installers in the past month and they all said with micro inverter setup, they can run the wires directly into the main service panel without a separate disconnect and and that the fire setback is 3 feet on left, right, and ridgeline.

[foo1bar]

I'm still scratching my head because cities in general can add special requirments, but my city refuses to tell me what they are.

Probably they aren't refusing to tell you - you just didn't ask that *specific* question.
"Hi, I'm Bill Smith. I need to know if Vacaville has any amendments to the electrical code or if it's just the vanilla California Electrical Code".

What you probably asked was an open-ended question that is essentially asking the building inspector for advice - and they can't/shouldn't give advice.
What they should do is tell you "Item X is not up to code because of Code section Y"
The general assumption is that the builder generally knows what he is doing, and will get things mostly right - and the inspector is just there to catch mistakes that can happen.
It's not the inspector's job to give advice - especially on things where it may not even be a question of code.

I'd start by figuring out what you're going to do.
Create detailed plans of what you're doing. You'll need both mechanical plans and electrical plans.
The mechanical plans you will need to calculate that your fastening to the roof is sufficient. (I used IronRidge racking and used their tool to figure what was sufficient number of fastening points, etc. ) You'll also need to figure out what conduit is needed / how the wires are getting to the roof.

The electrical plan you can probably find a number of sample plans and adapt them to your needs.

Once you have the plans made including various details on fastener method, grounding methods, etc, you can take your plans to the building dept. You will review the plans with their plan reviewer who will hopefully say "This all looks good." Or he/she will ask that you add additional details. Or point out issues with your plans that you'll need to address.

I'd recommend watching some videos, doing some reading, and you may even want to do some installing as a volunteer. Before I did my install I spent a Saturday volunteering for Sunwork out of Milpitas. Job site was in Sunnyvale. They do have some jobs farther north - and there might be a similar non-profit nearer to you.

[foo1bar]

Hm - looks like I found Vacaville's CEC amendments.

http://www.codepublishing.com/CA/Vacaville/

http://www.codepublishing.com/Ca/vacaville/Vacaville14/Vacaville1420254.html#14.20.254

[sdold]

Maybe this will help: http://vacaville.granicus.com/MetaVi...&meta_id=61839

Foo1bar's advice was good too.

The questions you should ask them are about the code version followed, wind design speed used for the structural calcs, and possibly if an engineering stamp is required, although I might first submit my plans with thorough engineering on my own to see if it flies. They have the state-mandated "checklist" on their website, which basically says it must meed electrical code requirements and have sound engineering behind the structure from the panels all the way to the ground.

If you can't get any of the info, maybe just design it for 100 mph wind, no snow load (unless you're on Mt. Vaca) , CEC 2016, and see how they like it. Get it as absolutely correct and complete as you can before submitting so they take it seriously

[J.P.M.]

Maybe this will help: http://vacaville.granicus.com/MetaVi...&meta_id=61839

Foo1bar's advice was good too.

The questions you should ask them are about the code version followed, wind design speed used for the structural calcs, and possibly if an engineering stamp is required, although I might first submit my plans with thorough engineering on my own to see if it flies. They have the state-mandated "checklist" on their website, which basically says it must meed electrical code requirements and have sound engineering behind the structure from the panels all the way to the ground.

If you can't get any of the info, maybe just design it for 100 mph wind, no snow load (unless you're on Mt. Vaca) , CEC 2016, and see how they like it. Get it as absolutely correct and complete as you can before submitting so they take it seriously

Perhaps this has already been addressed, but an often forgotten part of the wind/seismic/external loading design is to check what the array is attached to (usually a roof) to make sure it too will handle the imposed additional loads and loading combinations, including imposed moment loads, particularly the uplift from wind, and especially if the array is not parallel to the roof.

An example, if a bit off this application: I once had a new engineer under my supervision who designed a lifting lug that was good for 10,000 lbm dead lift or so (as I recall), but it was welded to a 3/16" st. stl wall of a vessel that would have failed on lift even though the vessel only weighed about 3,000 lbm or so. The lug was adequate for the lift, but where it was attached (the vessel wall)would have failed. That, BTW, is why is an example of why they're called EIT's (engineers in training) and working under P.E.s.

For this wind loading, a bit of overdesign is OK, but I'd not, for example, use a 100 MPH design speed in a 70 MPH zone, so you don't wind up with more overdesign than practical, as a small example: with required screw embedment that's more than the rafter depth, and never without checking the other required design criteria such as exposure factor, importance factor, etc. per the ASCE specs.

Overdesign is a poor excuse used by the ignorant to make up for sloppy engineering that can lead to expensive and perhaps (but in most situations, unknown) cases of possibly unsafe designs.

[sdold]

Overdesign is a poor excuse used by the ignorant to make up for sloppy engineering that can lead to expensive and perhaps (but in most situations, unknown) cases of possibly unsafe designs.

I agree, but in my case it was a good thing to do because of the way uplift loads would actually be carried. The way I calculated it for the AHJ, a mount point's uplift is shared equally between two screws, but in an actual uplift, it's initially carried by one screw, and there is an additional moment that is applied because of the shape of the tile hook. So the load is first applied to one screw, and then about the time that screw has backed out a couple of threads (which is all it takes to destroy the load carrying capacity of that screw/thread combo), the second screw begins to carry a load.

In other words, I don't think the second screw carries a tension load until the threads in the first screw have failed. I could be wrong about that, but I don't think I am.

The engineering examples I saw from the tile hook company didn't take this into account, but since I know how things work and knew that the two screws wouldn't be acting perfectly "in parallel", I kicked it up from 85 mph to 100. This had the dual effect of a) Decreasing the load carried by each mount, and b) Giving the AHJ the impression that it was solidly engineered. So in a case like this one, it is OK to do what I did. IIRC the loads at 85 mph can now be carried by a single screw with 150% margin, but I'm not positive. I think that is what I was shooting for.

Steve

[sdold]

Perhaps this has already been addressed, but an often forgotten part of the wind/seismic/external loading design is to check what the array is attached to (usually a roof) to make sure it too will handle the imposed additional loads and loading combinations, including imposed moment loads, particularly the uplift from wind, and especially if the array is not parallel to the roof.

It has, that's what I was referring to when I said that the array must "have sound engineering behind the structure from the panels all the way to the ground".

[J.P.M.]

It has, that's what I was referring to when I said that the array must "have sound engineering behind the structure from the panels all the way to the ground".

Understood. Just reconfirming.

J.P.M.