Seems like a no-brainer

[maddog808]

Hey all. So I've been reading for many weeks now, and I'm close to pulling the trigger. The amount of information and calculators available to us consumers these days is seriously awesome and at times overwhelming! My situation is as follows:

I live in Gilbert, AZ (Phoenix area) in a 2400 sq ft 2-story home. Our monthly average use is around 1750 kWh with SRP as our POCO. I can fit 28 large panels (39" X 77") on the roof. 14 facing east, 14 facing west, with virtually no shade. According to PVWatts, this will produce 15,000 kWh per year, or $1800 @ $0.12/kWh. I plan on doing all the work myself, with some help from a friend who worked as a PV installer in a previous job.

I've read about optimizers and micro-inverters, and I think I'm going to forego the idea. It seems as though a simple string inverter system makes more sense for my application. I put together a quote on the Renvu website, and it came out to just under $11,500 including freight and tax. The components I used are (28) 370W Peimar Mono panels, (2) SMA Sunny Boy 5kW string inverters, and Ironridge racking. Even if I spend $1,000 at Home Depot and another $1,000 for my friend to help me install everything, I'm looking at around $8,500 after federal and AZ State tax credits.

Like the title states above, this seems like a no brainer, but I'm sure I'm missing something. One thing that comes to mind - do I need to somehow tilt the panels toward the south, which means I'll need to space them apart? The PVWatts calculator asked which way the panels face, and I used 90 and 270 in the model. I didn't see anything in there that would make me think I need to face them south, although I do realize if I had a south facing roof this system would produce more energy.

Please poke holes in my simple plan. What am I missing? Attached is the quote from Renvu, and a view of my roof with the panel layout drawn in. Quick note about the attached Renvu quote: It assumes I'm paying with check or cash, so the price is actually 3% less than what I'll acyually pay. I plan on using a credit card with 18 month 0% interest, and paying off in those 18 months.

Thanks to anyone who's willing to help out a PV newbie!!

Matt

[Mike90250]

1) with virtually no shade. ??? When is the shade. 7am ? noon -3pm ?? This is important

2) with split arrays, they will track fairly closely, but if you find an inverter with dual MPPT channels, you may get a bit more harvest.

3) going DIY. do you have a mentor ? Do codes require rapid shutdown arrays on your structure ? Fire department walkways ?

4) what is roof type, and can your friend easily walk it, or do you need fall protection gear installed for the project ? your wife won't sue you if you fall and break your neck, but your friends wife will, if he falls.

[maddog808]

1) with virtually no shade. ??? When is the shade. 7am ? noon -3pm ?? This is important

2) with split arrays, they will track fairly closely, but if you find an inverter with dual MPPT channels, you may get a bit more harvest.

3) going DIY. do you have a mentor ? Do codes require rapid shutdown arrays on your structure ? Fire department walkways ?

4) what is roof type, and can your friend easily walk it, or do you need fall protection gear installed for the project ? your wife won't sue you if you fall and break your neck, but your friends wife will, if he falls.

Hi Mike, and thanks for the quick reply! I'll do my best to answer your questions.

1) There is no shade where the panels will be installed, other than the inherent shade that comes with east and west facing roofs.

2) I'm interested in more harvest. Would you be able to point me to the inverter with the dual MPPT channels? I'm definitely not stuck on the SMA Sunny Boys in the attached quote.

3) Yes, the plan is DIY. The buddy helping me worked as a PV panel installer in a previous job. He will be my mentor. I need to look into the rapid shutdown, but I do know that the Town of Gilbert is currently following 2011 NEC. I think that means Rapid Shutdown doesn't apply here, but I'm not opposed to installing the components to make it compliant. My attached roof plan has 3ft fire department walkways included at the gable ends, and roof peak.

4) The roof is Spanish Tile, 5-12, 22 degree pitch. Yes, we can easily walk it. I walked it last weekend to get all of the accurate measurements to find out how many panels I can fit up there. We will definitely be using fall protection while working up there.

Please let me know if you have any more questions or suggestions for me. I'm not opposed to switching gears, and I'm not in a huge hurry. I'd like to get it installed by end of year to get the full 30% federal tax credit, so I have a few months to figure things out.

Thanks again for your help,
Matt

[NEOH]

1)

2) with split arrays, they will track fairly closely, but if you find an inverter with dual MPPT channels, you may get a bit more harvest.

With the two (2) Sunny Boys as quoted, the East array and West array will already track independently.
And each Sunny Boy has multiple MPPT inputs to further sub-divide the East array and West array from 14 PV Panel strings each into 7 PV Panel strings, each
... assuming min / max voltages are OK.

[NEOH]

Hey all. So I've been reading for many weeks now, and I'm close to pulling the trigger. The amount of information and calculators available to us consumers these days is seriously awesome and at times overwhelming! My situation is as follows:

I live in Gilbert, AZ (Phoenix area) in a 2400 sq ft 2-story home. Our monthly average use is around 1750 kWh with SRP as our POCO. I can fit 28 large panels (39" X 77") on the roof. 14 facing east, 14 facing west, with virtually no shade. According to PVWatts, this will produce 15,000 kWh per year, or $1800 @ $0.12/kWh. I plan on doing all the work myself, with some help from a friend who worked as a PV installer in a previous job.

Matt

Are you getting the "-40" Model SMA Inverter?
Will NEC 2017 Module Level Rapid Shutdown apply to your home?

Are you using one Inverter for the East array and one Inverter for the West array?
Are you then sub-dividing each of those into 2 MPPT channels x 7 PV panels per channel ?
Have you verified your min / max voltages?
What size Main Panel ?
How are you doing the AC Breaker connections?
What size wire and voltage drops.
Do you need a "fireman" shutoff?

[khanh dam]

your biggest headache will be the permitting process.
Never EVER tell the permit office you will be having someone do the electrical for you, auatomatic fail in most places, unless your friend has a Electrical license.
Some cities will require you take an elelctrical exam to work on your own home
other cities require a refundable "deposit" of $2000 or more for larger scale projects
Some states like florida require you submit electrical diagram for approval by state agency with hundreds in fees
I would install the panels NOW while you do not need to obey 2017 NEc rules sinc eyou said 2011 was in effect 2017 will cost you another $3000 in electrical components. Just when solar was getting cheap these stupid rules had to take effect and add to the cost. !

[maddog808]

Are you getting the "-40" Model SMA Inverter?
Will NEC 2017 Module Level Rapid Shutdown apply to your home?

Are you using one Inverter for the East array and one Inverter for the West array?
Are you then sub-dividing each of those into 2 MPPT channels x 7 PV panels per channel ?
Have you verified your min / max voltages?
What size Main Panel ?
How are you doing the AC Breaker connections?
What size wire and voltage drops.
Do you need a "fireman" shutoff?

Hey NEOH,

Thanks for helping out. See below for answers to your questions:

1) The model quoted in the attached pdf from Renvu is the SB 5.0-1SP-US-40, with "3 MPPTs (100V minimum voltage) w/ Opti Track Global Peak". I'm not married to this inverter, and I'm open to better suggestions by more qualified and experienced folks here on this forum.

2) Gilbert, AZ adopts the 2011 NEC, so I believe the 2017 Rapid Shutdown doesn't apply to my home. I'll be calling the AHJ office tomorrow morning for further clarification.

3) Yes, the plan was to use 1 inverter for each array. I will sub-divide each into 2 MPPT channels if this will benefit the output, or make the install easier/more affordable. I haven't really looked that far into it yet. This is one of the reasons I finally posted here, to get into the details more.

5) I have not verified my min/max voltages. Could you point me in the right direction for this?

6) My main panel is 200A

7) I have not gotten a electrical design yet, so I'm not sure about AC Breaker connections, wire size, voltage drops, etc. I was planning on getting the design from the company I choose to purchase the equipment from (Renvu, Go GreenSolar, etc). Is it better to go through someone else for electrical design?

8) According to everything I could find about the Town of Gilbert Fire Code, I couldn't find anything regarding a "fireman shutoff". The attached pdf only references markings and pathway requirements.

I'll be calling SRP & Town of Gilbert tomorrow to get more details regarding requirements, permits, etc. So far, everything I've read online lead me to believe I'm ok to self-install, and won't need a permit from Gilbert. Then SRP will accept a "Cerificate in Lieu" of the AHJ electrical inspection. More to come on that. I'm hoping azDave will chime in. I've seen a few of his posts where he talks about his PV install here in Gilbert, AZ.

[maddog808]

your biggest headache will be the permitting process.
Never EVER tell the permit office you will be having someone do the electrical for you, auatomatic fail in most places, unless your friend has a Electrical license.
Some cities will require you take an elelctrical exam to work on your own home
other cities require a refundable "deposit" of $2000 or more for larger scale projects
Some states like florida require you submit electrical diagram for approval by state agency with hundreds in fees
I would install the panels NOW while you do not need to obey 2017 NEc rules sinc eyou said 2011 was in effect 2017 will cost you another $3000 in electrical components. Just when solar was getting cheap these stupid rules had to take effect and add to the cost. !

Hello khanh,

I'm hoping I won't need a permit here in Gilbert. I'll know more once I speak to them tomorrow.

Thanks,
Matt

[khanh dam]

5) I have not verified my min/max voltages. Could you point me in the right direction for this?

https://www.sunnydesignweb.com/sdweb/#/

best thing to do is call their tech support phone number and get them to walk you through it. Do not bother leaving a message, they will never call you back. but they are pretty good at answering the phone most of the time.

1 877-697-6283

[Mike90250]

When you call the factory, you need to have on hand, your location average summer highs, winter lows, and the all-time-record-low. These temps affect the string voltages, and you need to chose the number of panels in a string to never exceed the Voc on a cold morning. There are voltage ranges where the MPPT works, and then a wider range when the inverter works, but optimum MPPT activity ceases.

[khanh dam]

this is power I got using your equipment closer to 14, not 15kWh ( only 360W panels were available , not the 370w so maybe that is the difference)

Month	Energy yield [kWh]
1	587
2	761
3	1156
4	1497
5	1757
6	1834
7	1720
8	1557
9	1209
10	845
11	563
12	496
	13982kWH/year

[khanh dam]

gilbert az.png

[khanh dam]

your voltage will be fine. these newer inverters are very VERY flexible. looks like you can use anywhere from 4 to 19 panels per string. Older inverters needed a minimum of 6 or7 panels per string. above sunny design was based on a 30 degree tilt. not sure what actual will be.

[khanh dam]

SQUARE-D DU221RB AC Disconnect, NEMA3R, 30A 240VAC,
2-Pole Unfused, Hub
Won't you need a 60A disconnect? each inverter requires a 30a fuse x 2 = 60amp disconnect I think.

[azdave]

I'm hoping azDave will chime in. I've seen a few of his posts where he talks about his PV install here in Gilbert, AZ.

azdave here in Gilbert...

I did a turnkey system with Harmon Solar and they took care of working with SRP, my HOA and the Town of Gilbert. I have 2-strings of 13 panels all facing south with no shade except 1 hour on early winter mornings so not really an issue. I have a single inverter in the garage. SRP is all I use to gather data. No need for anything deeper than that. I compare my strings by glancing at the inverter display any of the 4-5 times a day I walk past it. The string wattages are always on display and I see quickly they are within 5-8 watts of each other.

I don't have much to add at this point. I have the most ideal situation I could hope for at my place installed in 2014. Simple string inverter with 26 panels facing south. I'm on SRP's basic plan and grandfathered until 2034 (if I live that long). I can use power anytime I want. No TOU hassles and my energy is banked in only one bucket. I've had no net billable energy for the last 3 years as I become even more energy efficient. I get about $100 per year account credit when SRP zeros my accumulated reserves in April each year. My energy cost for all of 2019 will be $164 or about $13 a month. I paid $11,150 for my system after all rebates and incentives and then after that got a free spare ABB inverter and $360 account credit for participating in an SRP advanced inverter study.