A module fire classification describes the panel’s tested fire performance. A roof-system fire rating applies to the specified combination of panels, mounting hardware and roof covering. A panel’s rating alone does not establish the fire rating of the installed rooftop system. Research presented by the U.S. Department of Energy found that module-only classifications were not reliable predictors of the combined module-and-roof rating.[1]
The Class A, B and C terminology below refers to the U.S. roof-fire classification framework. Projects elsewhere must follow the standards and building rules adopted in their location.
Module vs. System Ratings
| What to check | Module-level assessment | Roof-system assessment |
|---|---|---|
| Test scope | The module’s construction and fire performance | Modules and mounting hardware used with the specified roof covering |
| Information on documents | A module fire-performance Type designation, or other fire-classification information, depending on the certification | A system Class A, B or C rating with installation conditions |
| What affects applicability | The certified module model and construction | Eligible modules, rack configuration, roof covering, slope, clearances and any required accessories |
| What it establishes | Module-level performance within the certification’s scope | The roof-mounted combination’s rating within the listed installation conditions |
UL 61730 addresses PV module safety. Older documents may refer to UL 1703, which included module fire characterization and system fire classification provisions. UL 2703 covers mounting systems and their applicable evaluations. Check the actual certification and installation instructions rather than treating these standard numbers as interchangeable.[2][3]
What Class A, B and C Mean
ASTM E108 evaluates roof coverings exposed to fire from outside the building. Its tests assess flame spread, fire penetration through the roof deck and the production of burning material under specified conditions, including a 12 mph wind, approximately 19 km/h.[4]
| Classification | Test exposure | Meaning for selection |
|---|---|---|
| Class A | Severe | The highest of these three roof-fire classifications |
| Class B | Moderate | Does not satisfy a requirement for Class A |
| Class C | Light | Does not satisfy a requirement for Class A or B |
These are external-fire classifications, not hourly fire-resistance ratings. Class A does not mean that a roof is fireproof, that its components cannot burn or that the PV installation cannot develop an electrical fault. ASTM E108 expressly excludes determining performance against fires originating inside the building.[5]
Why the Installation Changes the Rating
Mounting panels above a roof introduces a space where flames and heat can interact with both surfaces. System testing addresses that combination. Changing the rack, roof covering or mounting geometry can put the installation outside the conditions covered by its rating.[6]
There is no universal 15 cm clearance that makes every system Class A. The permitted clearance and slope range come from the applicable listing and installation instructions. Install fire shields or skirts when those documents require them; do not assume every Class A system needs the same accessories.
Installation example: Suppose a particular listing specifies a minimum clearance of 150 mm. An installation at 120 mm falls 30 mm below that requirement. The original listing cannot establish the rating for that configuration unless another approved provision covers it. This is an illustrative example, not a general clearance requirement.
The roof itself also needs checking. A metal or tile surface does not tell you everything about the assembly beneath it. Underlayment and deck construction can be essential to the roof’s classification. UL identifies underlayment as a significant factor in many burning-brand tests over combustible decks.[7]
What to Check Before Ordering
Record the full model number when comparing Tongwei solar modules. Wattage, frame appearance and single-glass or double-glass construction do not establish the system fire rating. Use the matching product documentation and obtain any missing certification details before finalizing the installation.
| Document | Details to match | Question to resolve |
|---|---|---|
| Module certification and installation manual | Exact model, applicable fire classification or Type, and installation restrictions | Does the documentation cover the module being supplied? |
| Mounting-system listing and manual | Eligible module models or Types, roof conditions, clearances, slope and required parts | Does the proposed combination fall within the listed scope? |
| Roof assembly documentation | Covering, underlayment, deck and applicable fire classification | Does the existing or proposed roof match the documented assembly? |
| Project requirements | Required roof and PV-system classifications under locally adopted rules | Does the documented installation meet the project’s required class? |
For the installation record, retain document revisions, equipment labels, relevant clearance measurements and photographs of required shields or skirts. If a contractor proposes a substitution, ask for written confirmation that the replacement is covered by the applicable listing. Equal power output is not evidence of fire-rating compatibility.
Rack-Mounted PV and Solar Roofing
Rack-mounted panels sit above an existing roof covering. Building-integrated photovoltaics, or BIPV, may replace that covering, so the roofing function must also be evaluated. UL identifies UL 7103 for BIPV systems, UL 61730 for module safety and UL 790 for roof-covering fire tests among the relevant standards.[8]
Do not assume that solar roofing always needs one extra fire-resistant layer. An NREL installation study documented different underlayment arrangements: one product required a separate fire-resistant slip sheet, while another achieved its specified roof classification with a single underlayment layer. The required build-up belongs to the particular roofing system.[9]
Common Purchase Questions
Does Type 1 Mean Class A?
No. A module Fire Type identifies a construction and fire-performance grouping used in system evaluation. It is not an A–B–C ranking. Check whether the mounting-system documentation covers that Type and the proposed roof configuration.
Does an Existing Class A Roof Stay Class A?
A Class A roof rating does not, by itself, establish the rating of the roof-mounted PV combination. Obtain the applicable PV system classification and confirm that the installation conditions are met.
Can a Replacement Panel Keep the Original Rating?
Possibly. A replacement may already fall within the mounting system’s approved module or Type scope. Check that scope before ordering. A different brand does not automatically require retesting, and matching wattage does not automatically make the replacement acceptable.
Does Class A Cover Electrical Fire Prevention?
No. Electrical protection, wiring and shutdown requirements need separate review. ASTM E2908 addresses practices intended to reduce fires originating in PV source circuits, including the distinct challenges posed by DC arcs.[10]
Need documentation for a Tongwei module?
Include the module model, project country, roof covering, proposed mounting system and required fire class in your inquiry. Ask for the available certification and installation documents for that model.
Request Module Documentation