7KW PV with 10KW Inverter

drraptor

I am planning on installing 7KW PV with 10KW grid tie inverter for which I have got quotes from my local solar installers.  I decided on this setup based on my previous 2 years bill and solar installers charging by per watt rate. It is cheaper to get a larger inverter with smaller PV and adding additional panels later on.  I will be applying for Netmetering license too, which takes 1-4months for the approval from the local regulator. 
Inverters to choose from are 

1. Huawei sun2000-10ktl-m0  https://solar.huawei.com/en/download?p=/-/media/Solar/attachment/pdf/eu/datasheet/SUN2000-3-10KTL-M0.pdf (10 years warranty according to 2 of 3 distributors in Pakistan) 

2. Solis-3P10K-4G (5 years warranty) 

3. Other Chinese brands like Goodwe etc 
4. SMA/fornious (almost no local warranty 

Solar panels available are mostly Mono perc 445W or thereabout. Two strings of 8 panels each (most quotes) 

1. Jinko (Mono Perc)https://www.jinkosolar.com/uploads/Cheetah Plus JKM425-445M-78H-D1.2-EN-F35.pdf
2. Candian Solar (Mono perc) https://www.canadiansolar.com/wp-content/uploads/2020/08/Canadian_Solar-Flyer-HiKu5_CS3Y-MS_EN.pdf  and https://www.canadiansolar.com/au/wp-content/uploads/sites/2/2020/05/Canadian_Solar-Datasheet-HiKu_CS3W-MS_v5.59_AU.pdf 
3. Longi (Mono Perc)  https://en.longi-solar.com/uploads/attach/20190829/5d6776668aa8c.pdf 
4. Triana (Mono/ Poly Perc) https://static.trinasolar.com/sites/default/files/MA_Datasheet_Datasheet_Tallmax_PE15H_202011.pdf

My Average consumption was 665Kwh/month for the last 2 years, Location is Lahore, Pakistan. 
Please help me choosing the components. which other devices will be required breakers spd etc etc. 

drraptor

no comments??

BB.

You are 1/2 a world away from most of us... So I do not have much I can add regarding specific manufactures... But with the low prices for solar panels and hardware, expecting that you will be responsible for warranty costs is a good assumption (solar mfg and distributors come and go--Even some of the "good/well financed companies" seem to have failed or exited the market).

GT solar is pretty straight forwards these days.. Well made panels should last 10-20 years pretty easily... If you need replacement/more panels 5+ years down the road--Do not count on being able to match size/wattage/Vmp/Imp with your existing panels. As manufacturing cost reductions and market demands change, available panel models charge too. My 15 year old array of 175 Watt panels--It would probably be more cost effective to buy a whole new set of panels rather than try to replace a few damaged by hail or early life failures (my original panels were probably USD$10 per Watt, now there are panels in the $0.50 per Watt range).

Inverter wise, I would budget for a replacement every ~10+ years... Power electronics (and electronics in general) tend to go out of production in 5+ years (5 year warranty, although 10 year inverter warranty is required for some markets in the USA)--And repairing 5+ year old inverters can be difficult (finding parts/boards, and a facility that can repair them--Let alone if the computer/memory goes bad and no replacement software/memory).

Circuit breakers require a specific chosen GT inverter and array configuration. Also code requirements for your country. In North America, our breakers and wiring following the National Electric Code are for "typical" installations with intermittent/relatively low average current usage. However, solar power (and battery banks) can pull 5+ hours of rated current. Breakers and Fuses for our market generally are specified to not trip at 80% or less of rated current, and will trip at 100%+ rated current (can take hours to trip)... So, for solar/battery/inverter wiring, suggest that if you have a rated current for wiring and breakers of (for example, 10 amp continuous current) of 10a*1/0.80derate=12.5a or ~15 amp minimum breaker/wiring.

You seem to have chosen the array Wattage to meet your average monthly energy requirements and amount of sun for your city--So sizing looks OK.

For solar--Make sure you have no shading at all on your array (at least around 9am to 3pm at least)... Solar electric panels do not work well if there is any shading on the panel(s). Overhead electrical wiring, a vent pipe/chimney, etc. anywhere on the array can pretty easily kill 50% of the array harvest (details do matter--But in general--NO SHADE during harvest time). There is equipment that, in theory, is supposed to help reduce losses from shading--But they add complexity (and costs).

You can also look at "micro inverters" (a single inverter every one or two panels) which can help reduce shading losses--Although there are complexities with micro inverters too (needing a inverter monitoring system, if one fails, having to pull up panels to get to the failed micro inverter to replace, etc.). A single central inverter is generally easier to maintain/service.

If you have lightning in your area--Then using surge suppressor(s) is a good thing. Having suppressors on both the solar input to the GT inverter and on the AC output of the GT inverter is the better solution. These are good suppressors--They help with nearby strikes, but few inverters will survive a direct hit to the array. Using lightning rods to redirect strikes away from the array can help (added expenses and complexity of design).

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=23&productCatName=Surge Protection Devices

Look very closely at the Net Metering Billing rate plan... In the USA, they started out with very good terms for the solar customer (subsidizing GT Solar systems)--Basically, they would pay us back the retail power rate for every kWH we generated... Very easy to "break even" (we could not "make money" selling power to utility).

HOWEVER, as GT solar became more popular, and the politics changed, the rate plans have become much less "GT Solar friendly". We now have time of use (high cost power all they way to 9pm at night--Obviously no sun to generate power), some places have high "GT Solar connection fees" ($48 to $96 per month), and low payments for power ($0.06 per kWH paid by utility vs $0.10 to $0.40 per kWH paid by customer for power). And in some regions, new GT solar installations have been made illegal--Or at the very least, not cost effective (I understand why--Lots of GT Solar, utilities do not make money, and subsidies from state/utilities raise prices and taxes for the non-solar customers and tax payers).

From "your" point of view--A well functioning GT Solar system is "transparent" to you. Your appliances/lights/electronics all work exactly as they have before. And you (hopefully) see a greatly reduced power bill. My electric bill is $10 per month (minimum connection fee) vs $60-$100 per month without GT Solar.

Another thing to be aware of... Standard GT Solar systems have no energy storage--So if you have a power outage, the GT Solar system provides ZERO POWER to your home... Utility power fails, it also fails to your home.

There are various "solutions" for solar and emergency backup power (one is SMA's "secure power" system--It can give you ~1,500 Watts of AC power when the sun is shining--And you can plug a few appliances into the the GT SMA--Another is to go with a battery bank and hybrid GT/Off Grid inverter--Batteries supply energy when the AC mains fail and there is no sun). But that add expense--And batteries are a cost/maintenance issue all of their own.

And my first suggestion... It is almost always cheaper to conserve energy than to generate it. Look at your present power usage. LED lighting, efficient appliances/TVs/Computers. Is your Heating and Air Conditioning system "efficient'. Is your home well insulated (walls, ceilings, windows, etc.)?

It sounds like you have done the research and are probably aware of most of the issues/suggestions I have made... When buying the hardware--Getting good quality is first choice. Second is look at costs... For the most part, a good quality XXX Watt solar panel (crystalline, glass cover, mono or poly crystalline). I would not "pay extra" for PERC or Mono Crystalline panels. In day to day usage, you probably could not measure the extra $$ spent. There are some advantages to Mono and other "high efficiency" panels--That you can harvest more energy from the same square meter space can be worth it to you--If you are limited for space.

Your thoughts?

-Bill

drraptor

I have chosen

•  Candian Solar Mono Perc 440W watts panels 
• Huwaei 10KTL-M0, but waiting for  10KTL-M1 which has battery support.https://suministrosdelsol.com/en/grid-inverter/863-huawei-sun2000-10ktl-m0-three-phasse-inverter.html
• What I should use for routing the wire? UPVC pipes or PVC pipes? 
• ABB AC breakers. The installer is insisting DC breakers are not allowed with Huwaei inverters? but Huawei manual says otherwise 

mike95490

>  What I should use for routing the wire? UPVC pipes or PVC pipes?

You use what your local code says you use.   Mostly, DC has to be in metal conduit. AC  can be in the gray PVC electrical conduit, but exposed areas may need metal too.
 White water pipe is a no-no usually

drraptor

mike95490 said:

>  What I should use for routing the wire? UPVC pipes or PVC pipes?

You use what your local code says you use.   Mostly, DC has to be in metal conduit. AC  can be in the gray PVC electrical conduit, but exposed areas may need metal too.
 White water pipe is a no-no usually

These pics are from the different installation I have visited in the last 1month. 4 different installers. 3 of those used PVCs pipes and only one used UPVC pipes on DC side. what I am looking for a wire duct. what is used for DC side in states? any pics 

solar_dave

I know here in AZ metal conduit holds up the best, the sun just kill plastics.

Here is an example of a replacement I had to do because of the sun.

drraptor

I haven't seen this material here in Pakistan. On side note you are running 2 inverters? 

New_Mexico_Will

Although you should not use white PVC, if you do, it's a good idea to paint it.  It has no UV inhibitors, so the sun will degrade it quickly.  Any paint will do.

solar_dave

drraptor said:

I haven't seen this material here in Pakistan. On side note you are running 2 inverters? 

yes 2 inverters which run to the AC combiner that ultimately run to main panel breaker.

drraptor

New_Mexico_Will said:

Although you should not use white PVC, if you do, it's a good idea to paint it.  It has no UV inhibitors, so the sun will degrade it quickly.  Any paint will do.

Does UPVC has any UV inhibitors? does it work well under sunlight? 

mcgivor

The white UPVC conduit pictured is what's typically ised in Thailand and seems to be resistant to UV, it is however significantly different to what's available or used in North America, in industrial applications in Thailand, electrical metallic tubing, EMT, is more common, likely so in Pakistan as well.

As an electrican from Canada, the practices I see in developing countries, in non industrial applications, would never be acceptable in more developed countries, but it is what it is, less regard for user safety, or lack of rule enforcement in domestic installations. Looking at the first 2 pictures for example the bend radius of the connectors would be unacceptable in North America and probably exceeds 360° total bend between junction boxes making it impossible to pull the conductors, but rather pull as you go.

Not being critical of the practices, just pointing out to those who may not have not seen what exists elsewhere in the world, how things are done.

drraptor

mcgivor said:

The white UPVC conduit pictured is what's typically ised in Thailand and seems to be resistant to UV, it is however significantly different to what's available or used in North America, in industrial applications in Thailand, electrical metallic tubing, EMT, is more common, likely so in Pakistan as well.

As an electrican from Canada, the practices I see in developing countries, in non industrial applications, would never be acceptable in more developed countries, but it is what it is, less regard for user safety, or lack of rule enforcement in domestic installations. Looking at the first 2 pictures for example the bend radius of the connectors would be unacceptable in North America and probably exceeds 360° total bend between junction boxes making it impossible to pull the conductors, but rather pull as you go.

Not being critical of the practices, just pointing out to those who may not have not seen what exists elsewhere in the world, how things are done.

According to this website, it is UV resistance https://fusionaus.com/products/upvc/. but it depends on the amount of TiO2 
https://medium.com/@jamex_upvc/what-is-upvc-how-upvc-is-made-and-also-its-advantages-d46f215ad567
Bend radius what is the best/ recommended practice?   

mcgivor

The bend radius is irrelevant in your situation, the rules that apply to North America are to satisfy local electrical code requirements, if there are rules to follow in your circumstance, follow them, but I'm confident there are no such rules in residential applications as there is nobody overseeing the installation.

drraptor

mcgivor said:

The bend radius is irrelevant in your situation, the rules that apply to North America are to satisfy local electrical code requirements, if there are rules to follow in your circumstance, follow them, but I'm confident there are no such rules in residential applications as there is nobody overseeing the installation.

All local laws are mentioned in the following links 
http://www.lesco.gov.pk/Registration/NetMetering.asp
Application is only approved after the visit by the local inspection team. 

drraptor

what exact model of DC breakers I should use in this system? The inverter used is Huwaei 10KTLM1 and Panels are Candian solar CS3Y-490W http://www.vicoexport.com/wp-content/uploads/2020/05/Canadian-Solar-HiKuPro_CS3Y-MS_475w-495w-Vico-Export-Solar-Energy.pdf 

mike95490

The forum sponsor/host site carries the Midnight DC breakers  https://www.solar-electric.com/mnepv.html
150VDC, switch duty rated.  ( you can turn the strings off and on in daytime and figure out which string behaves different than the others for troubleshooting )

drraptor

mike95490 said:

The forum sponsor/host site carries the Midnight DC breakers  https://www.solar-electric.com/mnepv.html
150VDC, switch duty rated.  ( you can turn the strings off and on in daytime and figure out which string behaves different than the others for troubleshooting )

those are single-pole breakers. I have two separate strings and I think would need 4 pole breaker. 

mike95490

if you are not in a lightning prone area (florida) you usually don't need to switch the minus leads, just the plus.

Most combiner boxes are set to only handle the + leads (some have MC4 connector stubs) and the bus bar is often marked +