Solar flare-up Other Topics, posted by Editor, The Almanac Online, on Oct 8, 2007 at 3:03 pm
On a sunny June day, a pair of Woodside firefighters are up on a roof inspecting the new photovoltaic system on a remodeled house. They maneuver along the narrow strip of rooftop alongside the expanse of solar panels and do what firefighters do best — figure out how they would battle a blaze if the house ever caught fire.
Read the full story here Web Link posted Wednesday, July 4, 2007, 12:00 AM
Posted by Anonymous, a resident of another community, on Oct 8, 2007 at 3:03 pm
The danger in solar photovoltaic modules comes from letting current flow through people (ouch!) or equipment not intended for such flow (such as into a nearby piece of metal structure, where it could arc and be a fire hazard or flow through people from there). The only people-protection in a PV system is the insulation... do not break the insulation if you want to be safe. PV power systems have an automatic shut-off inside the inverter that notices when current has "escaped" the wires it is intended to flow through, and stops that current flow to eliminate a possible ignition source. However, there is nothing that can make a PV module safe to touch once you have broken the insulation... no "rooftop switch" will help. Solution is: don't break the modules, and if you do, stay away from them unless you have electrical protective gear. Rooftop switches are a waste of money, and provide only an illusion of control over the safety of the system.
There is one borderline case where a rooftop switch might help... if a firefighter manages to cut both positive and negative leads and short them together (cut+cut+touch=three faults, which ought to be unlikely). However, the National Electric Code already requires these wires to be inside metal conduit if they are routed inside the house... are they planning to chop through conduits? Most of the wires on the roof are dispersed among the modules. If we have to be worried about such things, then having a switch at the edge of the array would still leave the individual wires on the modules unprotected from wanton axe-work. Fortunately, these days modules have pull-apart connectors, so using their axe to hook the wire and pull the connectors apart to stop the arcing will work right up next to the module, where a switch would be too far away to help. However, I suspect most firefighters would prefer to never touch a PV module... so requiring "access ways" between the panels is much more practical than adding switches that won't help anyway.
Posted by D.W., a resident of another community, on Dec 24, 2007 at 12:37 pm
Being a firefighter, it is absolutely necessary in certain fire attack situations for vertical ventilation (venting through the roof area of a structure) to be performed. While I agree that these solar cells are crucial to reducing emmisions and economy, it is inherently dangerous for firefighter to vent through or around these P.V. cells for many reasons. It is entirely possible to invite an electrical shock or invoke and electrocution (nevermind the shattered glass and possible chemical release). By venting a fire in a different location can cause disasterous effects, redirecting the fire through unburned portions of the structure and potentially onto firefighters or victims. Vertical vent is also necessary to reduce superheated gasses and smoke from collecting, speeding fire attack and victim removal while performing the least amount of damage.
There needs to be a compromise between enviornmental friendlieness, economy, and safety.
Posted by mitch higgins, a resident of another community, on May 26, 2008 at 6:50 am
Don't be fooled by those that say it would be difficult to get a fatal shock from a photovoltaic system. Forget about the ventilation issues for a second and think about this. If there is no roof top disconnect then the wiring from the panels (combiner or junction box on the roof) to the inverter (usually located by the main electrical)is all live when light is on the panels. That is generally 20 to 80 feet or more of wiring in flexible conduit that when cut or folded in half by an unsuspecting firefighgter INSIDE the house or in the attic will cause the circut to complete and give this person a possible lethal 300 to 600 volt shock. Until another solution is devised (remote shunt or fuse) a ROOFTOP DISCONNECT IS THE ONLY SOLUTION that will provide some level of safety.