Technical FAQ

GENERAL

Which elements are automatically verified by SolarAPP+, and which items need field verification from inspector?

SolarAPP+ performs calculations required by code including overcurrent protective devices, wire size, equipment grounding conductor size, PV string voltage, inverter continuous output current, and combined inverter continuous output current based on contractor equipment selections and CEC Database of Approved Equipment list data. Those calculations are weighed against other contractor designations to ensure that code compliance is maintained from the point of interconnection to the utility grid. SolarAPP+ approval document items require the inspector to verify the values on the checklist. Additional items for new sub panels require that raceways be sized according to NEC 300.17 and Chapter 9. The inspector must evaluate conduit fill in the field. The contractor is required to provide conduit fill calculations where requested by the inspector.

Additionally, inspectors are tasked with identifying whether the location of the rooftop system meets prescriptive requirements regarding emergency access pathways and fire setbacks. Inspectors also verify that the work complies with UL standards, manufacturer's instructions, and municipal requirements.

How does SolarAPP+ verify the ratings and certification status of equipment?

SolarAPP requires that the racking system is UL 2703-listed for grounding and bonding requirements in combination with the PV module models specified in a SolarAPP project. SolarAPP now maintains a database of eligible combinations of racking systems and modules per UL 2703. Review this article for more information on that process: https://help.solar-app.org/article/209-ul-2703-database.

SolarAPP+ uses the CEC databases to verify the ratings and certification status for equipment such as Inverters, Modules, Batteries, and Energy Storage Systems. For ratings and certifications that are not a part of the CEC database and are typically only found in installation manuals (Mounting in the sun, fire rating, module attachment placement, etc), the contractor attestation to install the equipment per the manufacturer's instructions is to be verified at inspection. For example, UL 2703 standards for maximum wind uplift is currently handled by attestation from the contractor and also an upload from the contractor of manufacturer's installation manuals. The contractor is also required to attest that they are installing equipment with the same fire rating as that of the roof. A future iteration of our structural database will consider incorporating fire ratings.

How does the CEC database keep up to date and does it remove products from the list with certifications that have been withdrawn?

The CEC Database updates 3 times a month on the 1st, 11th and 21st, with new applications that come in for new products or adjustments to existing products. It does an annual cull of PV module products that have certifications that have been withdrawn.

SolarAPP+ updates to be in sync the day after the CEC is updated. Therefore, the SolarAPP+ is updated on the 2nd, 12th and 22nd of each month, or the next business day after these dates.

(From CEC's website: "[...] CEC staff will be removing equipment currently listed on the photovoltaic (PV) module equipment list for which staff have identified an invalid or expired safety certification. [...]")

How does SolarAPP+ handle or address Unpermitted Structures?

As part of the eligibility checklist, the contractor makes the attestation that they will not install on unpermitted structures. If at time of inspection, it is discovered that they did install on an unpermitted structure, the inspection will fail and the project will not be able to proceed until the situation is rectified.

Does SolarAPP+ enable customizations from the jurisdiction?

SolarAPP+ enables geographic customizations around windspeed, snow load, high temperatures and low temperatures. It also enables customization for the stand alone integration version around what information goes on the Permit and Inspection's job card. The backend code compliance checks take the geographic difference input by the jurisdiction and apply them to the calculations required by the model codes to determine compliance.

Will contractors submit plansets, including site plan and single-line diagrams, for SolarAPP+ submittals?

Traditional site plan and single line diagrams are not included in the SolarAPP+ submittal process. Rather, the longform serves as the contractor's plan document, detailing equipment, circuits, interconnection, site specific data, and compliance with applicable codes and standards. Additionally, SolarAPP+ reduces inspection burden by compiling information regarding the contractor's design and putting it into a standardized inspection checklist format.

What residential projects are eligible in SolarAPP+?

SolarAPP+ can issue permits for residential homes where the project is interconnected at a single service. That service must be less than 400A for the home or individual unit, with a maximum 225 A bus and breaker. If a townhome has its own service, it meets the service requirements referenced, and meets all other IRC code requirements it can be approved within SolarAPP+. This requires that the home has its own meter and is a single-family dwelling, two family dwelling, or a townhome, with less than 3 stories from grade. In a townhome complex, you cannot connect at the switch gear for the community, but rather the individual townhome unit service drop.

ELECTRICAL

How SolarAPP+ verifies the ratings and certification status of: MCI/DC-DC Converters and Rapid Shutdown Arrays.

Since the CEC does not include these rooftop electronics, SolarAPP+ has developed an internal database for MCI and DC-DC converter equipment that captures voltage, amperage, and 1741 listing for the products most used in the market today, based on datasheets, manufacturer published information and National Recognized Testing Laboratory published information.

What types of combiner panels can be used within SolarAPP+?

As of September 2021 SolarAPP+ allows: PV only combiner panels, ESS only combiner panels, PV and ESS combiner panels. We constantly look to expand to capture more technology out there to allow more systems.

How does SolarAPP+ verify the ratings and certification status of combiner panels, load centers and busbars?

There are currently contractor attestations that gather the amperage ratings and state equipment certifications. These ratings are then run through SolarAPP+'s calculations to ensure code compliance and listed on the Inspection's Checklist to be verified in the field by the inspector.

How are rooftop DC combiner panels restricted to ensure safe installations?

SolarAPP+ compatibility is limited to a maximum of 2 parallel DC strings being combined. SolarAPP+ does not allow DC combiners that require fusing. If a contractor feels the need to differ from this, they would be required to go through the traditional permitting routes.

How is SolarAPP+ ensuring that the rooftop equipment is appropriately verifying bonding/grounding requirements?

Contractor attests to the listing of the racking system under UL 2703 and compatibility with the PV modules is verified at time of inspection through the installation manual that was uploaded by the contractor during the SolarAPP+ application process.

How does SolarAPP+ verify the ratings and certification status of backup initiation devices (ie. Microgrid Interconnect Device and Automatic transfer switch)?

There are currently contractor attestations as well as uploads that gather the amperage ratings and equipment certifications. These ratings are then run through SolarAPP+'s calculations to ensure code compliance and listed on the Inspection's Checklist to be verified in the field by the inspector.

How does SolarAPP+ verify the ratings and certification status of Hazard Control Systems listed under UL 3741?

When a contractor chooses to use a Hazard Control System certified under UL 3741, they are required to upload the UL 3741 certification, install per manufacturers instructions, and provide documentation at inspection. At install the inspector is required to verify that the (PV Hazard Control) equipment listed in the UL 3741 manufacturer's instructions matches the installed equipment.

Can the SolarAPP+ approve a project with a service upgrade that requires the contractor to trench? What about a meter spot relocation or service change from overhead to underground fed?

The SolarAPP+ does not allow any contractor trenching per the eligibility checklist, at this time. Utility trenching, meter relocation, and service change-outs are at the purview of the utility and not governed by SolarAPP+ approval. At Inspection, Inspector can confirm that no trench was done by the contractor, and fail the inspection with a correction to re-permit through the traditional permit process should a trench be found.

How does SolarAPP+ handle conductor and/or OCPD sizing for relocated branch circuits and subpanels?

The OCPD is attested to be sized according to the code requirements around calculated backup loads. Based on the corresponding OCPD size, as well as Code required ampacity adjustments based on site conditions indicated by the contractor, the conductor size is calculated accordingly.

How does SolarAPP+ handle load calculations for derating the main breaker?

When contractor indicates that a main breaker derate is being performed, SolarAPP+ requires contractor to enter calculated load demand from load calculation according to the code. The load demand value that is entered will be checked against the new main breaker rating selected. Upon request at inspection, contractor will need to provide load calculation to justify the size of the new main breaker.

How does SolarAPP+ verify the need for AFCI breakers when circuits are extended more than 6ft per NEC article 210.12(A)?

A specific checklist item regarding AFCI breakers per article 210 is added when a contractor designates that relocated loads will be extended greater than 6ft per NEC article 210.12(A). Inspector to verify the use of AFCI breakers.

Why can the sum of the generation sources OCPD ratings be greater than the limit imposed by the 120% rule? For example, provided that the breaker rating is sufficient for the PV, a 50 A PV breaker can be installed on a 200 A busbar with a 200 A main breaker.

The Code does not enforce any limit on the ratings of the OCPDs, it only looks at "the sum of 125 percent of the power-source(s) output circuit current", therefore SolarAPP+ performs the 100% rule and the 120% rules checks using the power sources output circuit current and not the rating of its OCPDs.

Why does SolarAPP+ allow a contractor to select an overcurrent protection device rating that greatly exceeds the size required to account for 125% of the maximum inverter continuous output current?

For inverter output circuit overcurrent protection, the code specifies the minimum value for the OCPD as 125% of the inverter continuous output. The code does not specify a maximum value for the OCPD of a current limited source, like a PV inverter. As long as the circuit is properly sized for the ampacity, it is code compliant. The combined inverter output is 125% of the continuous output current and it is used for interconnection calculations and ampere rating comparisons. For example, contractors may oversize an OCPD in order to serve downstream loads in association with a backup panel. In these cases, the circuit ampacity is based on the loads served and the circuit ampacity must be equal to greater than 125% of the maximum combined inverter output current.

How does SolarAPP+ enforce the separation and location of ESS units as required by the July 1st 2021 amended California Residential Code and the 2021 International Residential Code?

Where applicable, the SolarAPP+ fire bulletin requires that ESS units are installed in accordance to the 2021 IRC guidelines. All of the requirements around location, separation, individual and aggregate energy ratings are listed in the corresponding Fire Bulletin.

How does Solarapp+ ensure available fault current does not exceed equipment short circuit ratings

Fault current reduction is achieved by decreasing the wire gauge and/or increasing wire length. Since multiple wire length and wire gauge pairs can be used to achieve this, SolarApp+ presents a table 29 in the long form with various wire size and wire length combinations to achieve the desired available fault current.

How does SolarApp+ verify Isc and Voc compatibility for Inverters

SolarAPP supports 4 different inverter architectures, the verification process is different for each of them:

AC Modules
- Not required, AC modules have the inverter and module assembled by the manufacturer.
String inverters with DC-DC converters (SolarEdge)
- Only SolarEdge is allowed in this category and they regulate this through max string length of optimizers. Only module optimizers are allowed. To guarantee the appropriate use of SolarEdge inverters, we decided to add a compatibility check to the system to prevent SolarEdge on architectures without DC-DC converters.
Microinverters and String inverters without DC-DC converters
- A couple of questions are included in the permit form:
- What is the maximum input DC open circuit voltage (Voc) of the microinverter?
- What is the maximum input DC short circuit current (Isc) of the microinverter?

The two questions above will be verified against SolarAPP calculated values and have inspection items requesting verification of the values.

Why does a 125% safety factor not added on the Module Isc?

Per NEC 690.8(A)(1)(1) code, adding a 125% safety factor to the “Module short circuit current with average high temperature correction” is already performed for wire sizing, but this derate is not applied to optimizers and MCIs. The UL 1741 standard (under which all relevant MLPE and inverters are listed):

“2.1.32 MAXIMUM INPUT SHORT-CIRCUIT CURRENT (Isc MAX) – Absolute maximum prospective short circuit current that a DC port of the DUT is rated to have connected to it.

Note: This could be the short circuit from a PV array, battery or, energy storage device. For a PV source it would account for worst-case conditions of ambient temperature, irradiance, etc. For NEC compliant installation, this Maximum Input Short Circuit Current rating equates to 1.25 × Isc of the PV array.”

SolarAPP uses equipment which are compliant with UL 1741 and the safety factor is already incorporated in this rating.

STRUCTURAL

Does SolarAPP+ inspection checklist show the structural inputs and outputs for structural verification?

The weight of the PV system is part of the longform output, the submitted project will not pass if the weight is greater than 4 psf.

The following items appear on the inspection checklist:

“Maximum spacing in inches between adjacent attachment points of the mounting system”
“Attachment points of the mounting system are staggered”, Yes or No
“The distance from the module back sheet to the roof surface does not exceed 10"
“Quantity and spacing of structural attachments match the installation instructions per manufacturer.”
“The roof structure appears to be structurally sound, without signs of alterations or significant structural deterioration or sagging.”

What happens when an existing roof requires structural enhancements?

The contractor can only move forward by answering “Yes” on the following attestation: “Does the roof structure appear to be structurally sound, without signs of alterations or significant structural deterioration or sagging?” In addition, the inspection checklist has the following requirement: “The roof structure appears to be structurally sound, without signs of alterations or significant structural deterioration or sagging”

Do mobile/manufactured homes qualify for SolarApp?

No. Manufactured homes, mobile homes are currently disallowed in SolarApp. They are governed by Health and Safety code and HUD and excluded due to weak framing of a structure.

FIRE

How is SolarAPP+ ensuring that the rooftop equipment is appropriately verifying fire class requirements?

Contractor attests to the listing of the racking system under UL 2703 and compatibility with the PV modules is verifying the specific module fire type at time of inspection through the installation manual that was uploaded by the contractor during the SolarAPP+ application process.

How will inspectors verify Fire Setbacks without the use of a planset?

The SolarAPP+ determines the percent of roof covered by solar panels based on the total planview array coverage area and the contractor's attestation of total roof surface. SolarAPP+ then asks whether or not sprinklers are present in the home. Based on these two items, the SolarAPP+ will output the appropriate Fire Bulletin to signify which fire setbacks should be enforced. These setbacks will then be verified by the inspector in the field at the time of inspection.