PV wire is cable built to live in sunlight, heat, and wet conditions at the DC voltage of an array. Ordinary building cable is built for a different occupancy: often a dry or damp interior, at a voltage and a temperature its own jacket names, behind a wall that shields it from the sun. The copper size can match and the cable can still be the wrong object. The jacket print is the claim. A similar thickness in the hand is not.
| Duty on an array | What the jacket has to show |
|---|---|
| Sunlight for the life of the roof | A sunlight-resistance marking the manual accepts for that exposure |
| Heat and wet service | Temperature and wet ratings printed on the cable, not assumed from the color |
| Array voltage | A voltage rating that covers the DC circuit the design actually builds |
| A hardware-aisle look-alike | Building-wire markings only, which leave it as building wire |
The name on the jacket is the product
Markets use different type letters. One country prints PV wire, another prints a solar-cable designation, another accepts a sunlight-resistant type that predates the PV-wire name. This page will not collapse those into one global permission, and it will not print an ampacity chart. What travels from market to market is the duty. If the manual for the inverter, the module, or the combiner lists the cable types it allows, that list is the list. A cable that is popular, available, or already on the truck joins the list only when its markings are the markings the manual names.
Connectors crimped onto the end do not upgrade the cable they are crimped onto. The connector has a voltage, a current, and a conductor range. The cable has its own. Both have to cover the circuit, which is the matching problem in what a solar cable and its breaker have to match and in solar connector basics. A neat crimp on the wrong jacket is a neat crimp on the wrong jacket.
Wet rating matters on a roof even under a module, because dew, rain blown sideways, and a conduit that fills with water are normal. A cable marked only for dry locations can have the right copper and the wrong insulation once water sits on it for a season. Heat matters because a roof deck runs hotter than the room the building wire was drawn for. The temperature printed on the PV jacket is part of why that product exists. Using the indoor number because the copper is thick enough ignores the insulation that has to survive the deck.
Where ordinary cable still belongs
Building wire has a job inside the building, on the AC side, where the method of wiring and the local rule allow that type. Many solar projects use it there, correctly, and use PV wire on the array. The mistake is to let one spool serve both duties because the color is black and the reel was cheaper. Transition where the design says the transition is, in the enclosure rated for that joint, with the fittings the enclosure manual requires. A splice hidden under a module, taped, is not a transition. It is an unlisted joint in the weather.
Voltage is the other quiet mismatch. Array open-circuit voltage on a cold morning is higher than the operating voltage people remember from a summer noon. The cable's voltage rating has to cover the circuit the designer calculated, including that cold value. This page will not supply the cold-temperature calculation or a maximum length. The module temperature coefficient and the local design temperature are the inputs, and a qualified person runs them. If the jacket's voltage number is lower than that result, the jacket is the wrong jacket, regardless of how easy it is to pull.
Read the full legend before you buy a second spool that looks like the first. Manufacturers change a catalog number and keep a similar print. The sunlight word, the wet word, the voltage, and the temperature all have to be present on the cable that will sit in the sun. A invoice that says solar cable is weaker evidence than the jacket. Photograph the legend and keep it with the module datasheets. The next person on the roof should not have to guess which duty was purchased.
