Solar PV Basics for Trade Service Reference

Why this matters

Solar PV (photovoltaic) is increasingly common on residential roofs. Roofers work around it; electricians service panels with solar tie-in; HVAC techs encounter battery + load-management systems. The non-solar tech who understands the basics works safely + advises customers correctly. This is the field card.

Components of a residential PV system

Solar modules (panels): convert sunlight to DC electricity. Typical residential 300 - 450 W per module; 20 - 40 modules per home.

Inverter: converts DC from panels to AC for the home grid. Two configurations common:

• String inverter: one large inverter for all modules; modules wired in series.
• Microinverter (one per module): converts at each panel; more flexible for partial shading.

DC optimizer (Tigo, SolarEdge): hybrid - module-level optimization but string inverter conversion. Compromise between cost + per-module performance.

Combiner box / DC disconnect: combines multiple strings of panels; provides shutoff.

AC disconnect: required between inverter + panel; service-disconnect for first responders.

Critical-loads sub-panel (with battery): backed-up circuits when grid is down.

Battery storage (optional): stores excess for use at night OR during outage. Tesla Powerwall, Enphase Encharge, Generac PWRcell.

Monitoring: app showing production + consumption; per-panel diagnostics on microinverter systems.

Rapid shutdown requirement (NEC 690.12)

Modern residential solar requires rapid shutdown - within 30 seconds of a signal, the DC voltage outside the array must drop below safe levels. Achieved via:

• Microinverters (each module shuts off at AC side)
• Module-level shutdown devices (Tigo, SolarEdge optimizers)

Important for first responders during fires: turn off the AC disconnect + the DC side becomes safe within 30 seconds.

Roof considerations (for roofers)

Penetrations: solar mount attachments penetrate the roof. Proper flashing critical (similar to vent stack flashing). Old attachments leaking are a common roof leak source for solar-equipped homes.

Weight: typical modern panels ~2.5 - 3 lbs/sq ft installed. Most residential roofs handle this; some older structures need engineering review.

Roof age + remaining life: panels last 25+ years. If the roof underneath is older than the panels' life, the roof needs replacement BEFORE solar (otherwise removal + reinstall mid-life adds cost). When working on a customer's roof:

• Solar present + roof aging: customer should plan removal + reroof + reinstall when roof needs replacement
• New install with old roof: red flag to discuss with customer

Shading: panels in shade for hours of the day = lost production. Tree removal OR pruning may be part of the conversation.

Electrical interconnect

Behind-the-meter (most residential): solar AC output ties to the home's main panel via a backfed breaker OR a line-side tap.

120% rule (NEC 705.12): solar breaker + main breaker can't exceed 120% of bus rating. A 200A main panel + 200A bus can have 40A solar breaker (200 × 1.2 = 240; 240 - 200 = 40A available).

Line-side tap: bypass the panel limit by tapping ahead of the main breaker. More install work; allows larger solar systems.

Supply-side disconnect: required for line-side tap.

Net metering + grid interconnect

Most residential solar is grid-tied:

• Produces excess during the day → exports to the grid → credit
• Consumes from grid at night / cloudy / overload moments
• Net of the two is the customer's billing basis

Net metering rules vary by state. Some pay retail rate for exports; some pay wholesale ("avoided cost"). Some have time-of-use exports.

Battery considerations

Adding a battery to an existing system:

• AC-coupled (battery connects via inverter to AC bus)
• DC-coupled (battery shares DC path with panels)
• Required for blackout backup (grid-tied solar typically shuts down during grid outage for safety)
• Critical-loads panel + battery = limited backup during outages

Without battery, grid-tied solar doesn't help during outages - it shuts down automatically.

When solar PV is on the roof + non-solar work is happening

Roofer doing work near solar:

• Solar installer handles panel removal + reinstall (typically separate crew)
• Communicate scope: which panels need removal? When?
• Document panel position before removal
• Coordinate timing - don't open up the roof + then wait for solar crew

Electrician at panel with solar tied in:

• AC disconnect is downstream of solar; opening it shuts off solar's grid connection but the panels are still active in daylight
• DC side downstream of rapid-shutdown device is energized
• 1,000V DC OR more available on older systems; can be lethal
• Treat anything DC-side OR upstream of the AC disconnect as live unless verified
• Use rated PPE + tools for DC voltage

HVAC at outdoor unit near solar conduit:

• Be aware of conduit routing; avoid damaging during work
• Tag the line if it must be temporarily moved

Common issues service techs encounter

Lower-than-expected production:

• Shading (tree growth over years, new construction nearby)
• Dirty panels (dust, pollen, bird droppings)
• Failed microinverter on one module (others compensate but total drops)
• Inverter fault (replace; under warranty often)
• String fault (open connection in series chain)

Inverter showing fault code:

• Grid voltage out of range (utility-side issue; rare)
• DC voltage out of range (panel issue, faulty optimizer)
• Temperature fault (location too hot OR fans failed)
• Communication fault (monitor app shows offline but inverter working)

No production from one or more panels (microinverter system):

• Individual microinverter failed
• DC connector loose
• Module damaged (cracked glass)

Roof leak near solar attachment:

• Flashing failure
• Mount sealant degraded
• Re-flash work (specialist; not typical roofer scope without solar credentials)

Refer when

• Solar-specific install or service (specialist contractor required in most states)
• Rapid shutdown device replacement
• DC-side work (lethal voltages possible)
• Inverter replacement
• Battery service (high-voltage DC + thermal runaway risk)

The roofing + electrical scopes overlap solar but don't fully replace solar specialist work. Refer to a solar installer for solar-specific work.

Customer expectations

When customers have solar:

• Production varies seasonally + with weather (visible on the app)
• Cleaning panels annually OR semi-annually marginally improves output
• Battery extends backup capability but adds significant cost
• Some warranties cover labor; some only parts
• Net metering policies change; the deal at install may differ from today

Cross-trade techs can answer general questions + refer specifics.

References

• NEC Article 690 (Solar Photovoltaic Systems)
• NEC 705 (Interconnected Electric Power Production Sources)
• UL 1741 (inverter standards)
• IEC 61215 (PV module standards)
• IREC, NABCEP, SEIA installer + safety guidance
• Manuall internal: Net Metering + Billing, Breaker + Panel Reference