New PV System

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VIC1958

Senior Member
We have our first permit in for a residential roof top PV system install. This is my first review of one and need some guidance. Besides requiring a one line diagram of the install, cut sheets on all related equipment, what other things should I be looking for? Off the top of my head I can think of a few: Structural analysis of the current roof to verify it can handle the array(s), elevations showing where the arrays will be mounted on the roof in relation to ridge and eaves, get FD involved to approve install, get City owned utility involved for possible net metering, others? I understand all components need to be listed/UL listed, does this also include the racking system that supports the panels? Lots of questions, I know. Just want to make sure I am covering my bases. Thanks
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
VIC1958 said:
We have our first permit in for a residential roof top PV system install. This is my first review of one and need some guidance. Besides requiring a one line diagram of the install, cut sheets on all related equipment, what other things should I be looking for? Off the top of my head I can think of a few: Structural analysis of the current roof to verify it can handle the array(s), elevations showing where the arrays will be mounted on the roof in relation to ridge and eaves, get FD involved to approve install, get City owned utility involved for possible net metering, others? I understand all components need to be listed/UL listed, does this also include the racking system that supports the panels? Lots of questions, I know. Just want to make sure I am covering my bases. Thanks
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Are you asking what needs to be included in a design packet? It really depends on your AHJ; in lots of places all you need is a one line and a site plan for the city and/or the utility, but in others you need a structural analysis stamped by a PE. Are you installing the system yourself or are you subbing the job out? Does the installation crew know what they are doing, or do they need the DP to tell them every little thing?

I have produced DP's that were two pages long and others that were 30 pages.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
VIC1958 said:
We have our first permit in for a residential roof top PV system install. This is my first review of one and need some guidance. Besides requiring a one line diagram of the install, cut sheets on all related equipment, what other things should I be looking for? Off the top of my head I can think of a few: Structural analysis of the current roof to verify it can handle the array(s), elevations showing where the arrays will be mounted on the roof in relation to ridge and eaves, get FD involved to approve install, get City owned utility involved for possible net metering, others? I understand all components need to be listed/UL listed, does this also include the racking system that supports the panels? Lots of questions, I know. Just want to make sure I am covering my bases. Thanks
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Requiring a structural engineering stamp on every design is a big burden for installers and I would encourage you to adopt a formula that allows for approval without requiring that. A number of AHJs we work with have standard forms on which we certify that the existing structure meets their required standards, which are pretty much that they meet the current code for rafter spans. In other words, on older homes where we find overspanned rafters, we upgrade by sistering a larger rafter or adding strut or purlin support to a load bearing wall. On homes that meet current code we don't have to. Some AHJs require a section drawing of the attic with dimensioned rafter spans, some just have us fill out a form. The structural PSF load for PV systems is typically under 3PSF which is not that much. We always provide PSF and point load calculations with our plans. Some AHJs have a limit on point loads (e.g. 40lbs per attachment), above which they require an engineering stamp.

Besides a line diagram, our plansets include a site plan, roof plan, and mounting detail, but not an elevation. An elevation is something that we pretty much never do for any AHJ (except one that has a complicated local building height limit ordinance). However we do include a mounting detail that shows whether the modules are mounted flat to the roof, or tilted up, and the height above the roof. A full building elevation is asking too much in my opinion. Things like fire access pathways can be shown on the site plan.

How you involve your fire department is up to them and you. A few AHJs we work with require fire department review, but most simply check for fire setback guidelines at the building department. But since this is your first, you should review with the FD what the requirements are and decide who will approve those aspects.

Racking systems or accessory components may be listed for electrical grounding; most are nowadays, and we don't put lugs on every module for grounding anymore. Other engineering aspects of the racking systems are not subject to UL standards but any reputable racking manufacturer will have specifications and data available for you to check if the product is being used properly. Different rails and systems will allow for larger and smaller spans between mounting points.

Hopefully your local utility has already set up a process for approving net metering that shouldn't have to involve anything besides your normal duties. Large utilities usually just ask for the approved building final before approving interconnection.
 
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TommyO

Member
Location
Sunnyvale, CA
Borrow from another AHJ. :)

ex:
http://santaclaraca.gov/government/...spection-division/information-hand-outs-forms
"Residential Solar Photovoltaic System Guidelines"

If you ask them, most likely they'll be willing to let you copy theirs and adapt it to be your own.

And IMO it's OK to have lower requirements for a small residential PV installation (ex. no stamped structural calcs required if it's <5psf on a roof and <10kW; but require the full engineering for a commercial building install)
Why make the homeowners pay for that if it's really not needed?
Of course you need to balance that with making sure that you're keeping them and their property (and their neighbor's property) safe - but that's one spot where I think you can be more lenient.
 
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VIC1958

Senior Member
Want to thank everyone who has responded, great information. This applicant has submitted very little information and when asked about the racking system, his response, " I am building/designing it myself out of uni strut and bolts". No mention how or what he using he using to mount the racking to the roof. This kind of response has me very leery as to how the rest of the system is being installed and designed. Since this is our first, I want to make sure we do it right and don't miss anything. Might think about sending this out to a third party reviewer.
 
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TommyO

Member
Location
Sunnyvale, CA
VIC1958 said:
Want to thank everyone who has responded, great information. This applicant has submitted very little information and when asked about the racking system, his response, " I am building/designing it myself out of uni strut and bolts". No mention how or what he using he using to mount the racking to the roof. This kind of response has me very leery as to how the rest of the system is being installed and designed. Since this is our first, I want to make sure we do it right and don't miss anything. Might think about sending this out to a third party reviewer.
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At least he's applying for the permit before it's built?

IMO sending it to a 3rd party seems like a prudent choice - "This is the first solar PV we've had here - so I want to get feedback from someone who is familiar with these"
 
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