Installing Solar array on carport ! ! !

Batikikik
Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
in General Solar Power Topics #1
I need to install 9,2 KW system on my carport , LongBeach Area , city of LA
dimension of carport is 458inches by 233 inches .
After doing design i got my array 441inches by 231inches .
I am gonna install it with 22degree facing south .
Question , is that ok to "fillup" the carport? city fire department allows you to do that because they do not need any access on carport . Have you guys ever install array on whola carport with 22 degree angle ???

when I raise angle to 22degree i got 7feet standoffs ...I am little bit woried about that because it si too high and I am woring about wind ....
I will be more than happy to know your opinions . Thank you!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Installing Solar array on carport ! ! !

    Who is doing the wind loading calculations for your projects? Normally, it would be done by a licensed professional engineer (PE) to do the structural calculations for your area (based on prevailing wind and weather conditions, snow loadings--if applicable, etc.).

    Solar panels themselves, properly mounted to a pair of rails, will withstand most loadings imposed by weather pretty nicely. Then it is up to the supporting structure design to support the loads (and roof layer underneath/walls/etc.--if the customer wants a "weather proof" car port underneath the solar panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #3
    Re: Installing Solar array on carport ! ! !

    Your city/county permit office will be able to give you the wind/snow loads for your area. Try this document it will help you figure out how to design a system to hold the panels to the roof if you plan on using rails. If you go into certain zones, your loads will be higher due to larger wind forces acting on the panels. I covered most of my roof because the fire departments out here don't have a say. I designed for the worst case + 100%. (safety factor of 2 on top of every thing else)

    www.unirac.com/pdf/ii227.pdf
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Installing Solar array on carport ! ! !

    that's one big carport. with the pvs covering it it almost seems like you could've made a carport roof out of pvs and installed heftier side posts to anchor it all, hence made a structure rather than build one up.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #5
    Re: Installing Solar array on carport ! ! !

    carport is too far from house and already there is existing conduit underground . But the only thing i can not run dc wiring with AC wiring in the same conduit....and I am tring to avoid install one more conduit underground an solutions ?
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #6
    Re: Installing Solar array on carport ! ! !

    enphase micro inverters.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: Installing Solar array on carport ! ! !

    When using Micro Inverters--Check the gauge of the wire run, the typical high line voltage from the utility at the property, and how much current you are going to pump back down that circuit...

    If you have high AC line voltage and add a long run from the home to the car port with significant current--the High Line at the Enphase inverters may be over ~264 volts--and the inverters will fault (we have since found out that the Enphase inverters can be reprogrammed to have a higher line voltage--but don't know the details of that and the legalities).

    With a central inverter, you can place the GT inverter near the power meter/utility drop connection point, and have larger gauge wiring with lower voltage drop--and the central inverter may not fault for over voltage... The wiring from the distant Array to the GT inverter is just designed with normal requirements (Vmp array is within the GT inverter's operational range).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #8
    Re: Installing Solar array on carport ! ! !

    how about mounting the grid-tie inverter near the carport and running a single AC back to the main panel in the existing conduit. However the code guys might have a fit over a power generation line being in the same pipe as a power supply line.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #9
    Re: Installing Solar array on carport ! ! !

    OKay Guys I know about microinverters but my panels are 280watt each and there is not a enpahse microinverter for 280 as i know .

    I am gonna install invereter under carport .and run dc wiring from carport straight to inverter .. but there is not enough space to install all panels on the carport ,so i have to install 6 panels on the rood run separete coduit for dc wiring go to inverter and then come back to the meter(ac wiring) with existing conduit...

    This project is the hardest in my experience :)
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #10
    Re: Installing Solar array on carport ! ! !

    and sorry bb I did not understand what are you explaining me because i couldony understand hats gonna do GT inverter
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    Re: Installing Solar array on carport ! ! !

    Batikikik,

    Basically, imagine you have 220 VAC line voltage at the meter, and you have a 200' run to where you need to run some equipment. And you have a 40 amp @ 240 VAC draw... It would be very easy to see the 220 VAC drop to below 212 VAC and cause the loads to fail unless there is a very heavy gauge cabling running the 200'...

    Well, with your GT inverters--and you have 255 volts high line. The GT inverters output 40 amps and you get another 10 volt rise in the 200' of wiring... Now you have 265+ volts at the inverters (high line plus voltage rise). The inverters will shut down (per UL regulations) at around 260-264 volts for safety. You need heavier cable to reduce the voltage rise due to the 40 amps from the GT inverters.

    One way to avoid the High AC line voltage shutdown is to use a Central Inverter mounted near the meter (no 200' of cable for voltage rise)--And then run the 200' with the Array's DC voltage instead... You have a very wide range of voltage tolerance on the DC inverter input vs normal AC line voltage (200-600 volts or so vs the 238 +/- 11%...).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #12
    Re: Installing Solar array on carport ! ! !

    my 8000sunny boy max input is 10000w DC
    If i have array output 10080w , if i connect that array to invreter , what can be happen , i know its not the right way but have you ever guys try did that ????(overload inverter)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #13
    Re: Installing Solar array on carport ! ! !

    In general, it is not a problem... The GT inverter will limit its input power to its rating (or probably, specifically its output current).

    The one limitation that I am aware of is that you would need to put an input fuse/breaker on the Vpanel input line that is rated for the maximum listed input current of the GT inverter if the Array Isc is over the input current limit.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #14
    Re: Installing Solar array on carport ! ! !

    So can i connect 10080watt array to my 8000sunny boy ?>>>liittle bit mor explanation please
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #15
    Re: Installing Solar array on carport ! ! !

    And I have one more question guys . my panel overhanging the patio , fire department tells me it is ok but I am woried about that and I want to know exact answer ..it is overhanging 7inch on each side
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #16
    Re: Installing Solar array on carport ! ! !

    If you overhang you have to support the end of the rail somehow which means that you need to add structural supports (support beams) off the wall of your house to drive the loads into the wall to hold the end of the rail in position.
    Plus your winds loads increase (about double) since the air can catch a large surface area under the panel. Not a big engineering challenge. But it will add cost and complexity to the system.

    Funny that the fire department is so concerned.

    Have you had the permit office look at your plans? Have you run any stress calculations on the overhang? I had to do a lot of rework of my roof support just to get my panels within 6" of the end of the roof. I can't imagine the work involved with an overhang, let alone convincing the city structural engineering department you've accounted for all the loads.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #17
    Re: Installing Solar array on carport ! ! !

    Yes I understand . Ok I will do design so it will not be overhanging ..
    But you can install panels all over the carport right ? (filled carport)


    This sentence from city
    The filled collector weight does not exceed two pounds per square foot.or three pounds per square foot if the collector is of type which inhibits superimposed concentrated loadings


    Regarding wind load calculation - Its not a a such a windy area and I am gonna install with 10degree tilt angle . . . because of the wind I dont want to install with more tilt angle ..... So with 10 tilt angle I will have 3 feet standoffs , which is not to high for wind calculation (my opinion)...
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #18
    Re: Installing Solar array on carport ! ! !

    Well my system came in at 3.1psf. If I subtract the weight of the Enphase Inverters I'm at 2.8PSF.
    Might want to add up the weight of all your stuff. Making the rafter spacing a little tighter would help there. Its easy to beef up structure you just have to know how to and how much.

    The county should have your wind exposure listed. The loads are dependent on:
    Building Height, Roof Pitch, Exposure Category, Basic Wind Speed, Effective Wind Area, Roof Zone Setback Length, Roof Zone Location, Net Design Wind Pressure, Topographic Factor, Adjustment factor for height and exposure category, Importance Factor. Trust me you come into the permit office with these numbers figured out they'll be real happy to stamp your plans.

    That www.unirac.com/pdf/ii227.pdf document i linked to has a real good basic description of how to do the calculations starting on page 3. Section 1.2. The tilt angle is one of many factors (minor actually). 10 degrees is the same Pnet as 27 degrees or 7 degrees. You have to drop the tilt below 7 degrees to get reduced loads.

    Page 8 has table 5 which will help you figure out the loads. If the permit office doesn't like or believe your numbers they might help you figure out how to make it pass inspection.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #19
    Re: Installing Solar array on carport ! ! !

    Ok it is a carport . It is located in valley not windy area 80mph or less wind speed.458inches by 225 inches ....Height is 12feet....ther is no pith it is flat . So whats the maximum weight i can put on that carport , and whats the maximum tilt angle ???Thank yo very much
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  • mr.radon
    mr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    #20
    Re: Installing Solar array on carport ! ! !

    Look at the blueprints. Most structures can handle an extra 30-40psf. If you don't know how to calculate the margin in the design of the car port take it to an engineer.
    IF not sketch out what you plan on installing and take it to the permit office for a building permit. If the stamp it your fine.
    However, for me at least, I had to draft a scaled print of all the structural elements. Pen and paper would not do. Then they wanted all my calculations. I'm an engineer so this was pretty easy for me.
    If you have the plans for the car port start there.

    Mind you all the points you attach to the roof has to go into beams not the roof sheathing. Plus the support rails can only attach to the solar panels in certain zones. So if a rail doesn't line up with a rafter you have to add perlins or figure some other method of backing the roof's sheathing up.
    Then the distance between support is predicated to the loads the panels will see.
    I posted my plans to give you an idea what I had to draft up to get my permit.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #21
    Re: Installing Solar array on carport ! ! !

    In many cities/counties--You will need to have a licensed structure engineer (PE) sign-off/wet seal stamp on the solar array/mounting drawings for building department approval.

    This is not usually something that you can do yourself (or should do, if you do not have the the training/experience).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #22
    Re: Installing Solar array on carport ! ! !

    Yes I know that guys , that Itisnot something so i can do myself.
    This is my first time doing job on carports . I think I can do drawings and go to the city if they approve it is fine , if not I think they will tell me what to do .
    But because of the weekend (city hall closed) thats why I decided to ask this question in this forum .
    So what do you think for that carport (I am gonna install 2000pounds) whats the maximum tilt angle and what specificatians are prsenting ???
    Carport size-464*242
    Array size- 462*241
    Thank you!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #23
    Re: Installing Solar array on carport ! ! !

    Are you planning on tilting the whole array, or several tilted rows (sounds like your plans was to tilt the whole array)?

    If you have several tilted rows--Then at 20 degrees you are approaching a ground coverage ratio of 0.6 for a 96% shading factor (100% is no shading).

    So with tilted rows, you are able to use less of the roof space (because tilted panels in front shade panels in rear).

    Lots of issues to balance here...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #24
    Re: Installing Solar array on carport ! ! !

    I am planing to tilt whole array... because of the shading I dont want to install rows... but I have no idea which is the best way in this situation
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #25
    One Array or several rows?

    On carport which is the best way to install array???
    1.With 24 degree tilt severeal rows ?
    2.with 6 degree whole array ?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #26
    Re: Installing Solar array on carport ! ! !

    Go ahead and keep the related posts together in one thread... It is much easier for everyone to follow and reply.

    I guess the question comes down to how much power a flat, vs several rows tilted, vs entire array tilted will cost, what it looks like to the customer, and other limitations (tilted rows require a larger foot print--Sounds like area is limited on top of the car port).

    In some cases, you just have to do a paper design of all your options, run up the costs, estimate the kWH per month/year from each design, and run the stuff by your customer.

    The service stations in our area are mounting solar arrays on their flat canopies and store roofs--All are tilted at ~30 degrees and two to three rows deep (typically). Does not look great--but heck, it is a gas station.

    Do you have any software that can estimate your production based on ground coverage, array tilt, etc. for your various mounting options?

    -Bill

    PS: I should add that I live father north--so "flat" and near flat arrays are not ideal energy producers. Vs you guys in the Los Angeles area.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #27
    Re: Installing Solar array on carport ! ! !

    No I dont have that kind of software ...
    So whats you r suggestion ?
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #28
    Re: Installing Solar array on carport ! ! !

    I have no shading on caport it is 100% insolation over there , can you tell me pleas percentage of shading if i will put my panels like this .
    Ok I am gonna install panells horizontal south facing , panel wide is 39inches . when i give them 34degree tilt(to get best sun) it means panel on the carport will occupay 32,3inches (cos34degree=0.8290), length of tha carport is 228 inches .it means 228/32,3=7 It means I can install 7 rows . This is the first option installing 7 rows , what s gonna be shading ??by percentage
    2nd option I can install 6 rows so i will have little bit space between rows which will be about 5 inches between rows in this case I think I will have no shading about 100 % . So can you tell me please shading perecentages on both situations .....thank you somuch , I appriciate your time
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #29
    Re: Installing Solar array on carport ! ! !

    This is getting beyond my limited knowledge and tools to help you with those calculations... I would be doing little more than guessing based on the links I have already provided you.

    You are probably looking at professional solar / architectural planning tools and those are not going to be cheap to purchase. You might find somebody who you can contract with to make those calculations for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #30
    Re: Installing Solar array on carport ! ! !

    But what do you think ....I think If i will install rows with 34 angle degree and 6inches between distance , shading factori will be not less than 90%
    What do you thing ?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #31
    Re: Installing Solar array on carport ! ! !

    I just don't know.

    If you have partial shading of panels--you run the risk of dropping a whole lot more than 10% power (Vmp falls below minimum required by inverter, seasonal sun position--micro inverter vs central inverter, etc.--all sorts of variables).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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