Solar fire raises questions about panel safety
Apr 12 - McClatchy-Tribune Regional News - Eric Wolff North County
Times, Escondido, Calif.
A small house fire caused by a solar panel in San Diego last week
exposed a potentially dangerous flaw in the building codes of many
cities across California, which is pushing for tens of thousands of
homeowners to install the generating systems on their rooftops.
Experts say that in most cities, installers are not required to place a
switch on the roof to cut power from panels in an emergency -- leaving
firefighters unable to put out certain fires and helpless to stop
dangerous amounts of electricity from flowing along wires as long as the
sun is shining. Temecula, which requires a separate shut-off, appears to
be the sole local exception.
Amy Pavis had a solar-powered electrical fire on her Lake Murray-area
home on Wednesday, and it wouldn't go out.
Fed by electricity from her rooftop solar panels, the fire smoldered for
hours despite repeated applications of a household fire extinguisher and
the efforts of the San Diego Fire-Rescue Department. Only after an
electrician arrived to cut the wires leading from the panels were the
flames put down for good.
Pavis was home with her two children Wednesday when a painter
she'd hired came in reporting "a funny smell." Soon he returned to
report smoke coming out of the inverter box, the unit that converts DC
power from the solar panels to AC current for the house.
Pavis flipped the cutoff switch to disconnect the power and began
calling electricians. After five declined to help, she reached Mark
Snyder, a Poway-based master electrician and solar installer.
"While on the phone with Mark, the converter box caught fire," Pavis
said.
One of the painters emptied a fire extinguisher onto the box, keeping
the flames down until the San Diego Fire-Rescue Department arrived. But
all the firefighters could do was keep the fire down to a smolder.
Finally Tom Doherty, an electrician dispatched by Snyder, arrived on the
scene wearing a fireproof suit and gloves insulated against 1,000 volts
of electricity.
"When I hit it with a screwdriver, it started arcing and started to burn
again," Doherty said.
Doherty reached in and cut the wires from the panels. With its source of
energy throttled, the fire went out. The fire department estimated the
damage at $4,000.
Doherty and Snyder said that if Pavis hadn't been home, or if the
workers hadn't noticed the smell, the flames would have heated the metal
casing until, eventually, the frame of the house was ablaze. Snyder, who
has investigated electrical fires for 25 years, said he's seen 50
solar-fed fires like this one, and on five occasions there was major
damage.
Snyder said the fire illustrates a clear failure of building codes
governing solar installations, especially given the proliferation of
residential solar arrays.
Spurred by state and federal incentives, an appetite for carbon-free
energy and a desire to protect themselves against electric rate hikes,
California homeowners have been installing solar panels in increasing
numbers. San Diego County issued 432 permits for solar installations
between July 2008 and June 2009. In the nine months since then, it has
issued 760.
Nearly all of these installations include two switches next to or even
inside the inverter box: one that cuts AC flowing into the house, and
one that cuts the DC current flowing down from the panels. Pavis had an
older inverter with the DC cutoff switch in the box, which exacerbated
the problem. But Snyder thinks even the two-sided set up is inadequate.
He argues there should be a way to cut DC power right up on the roof, as
close to the panels as possible.
"When you throw the breaker in the house, it should cut power on the
whole system," he said.
San Diego County follows the state's building codes, which do not
require such a switch. In the region, only Temecula has such a
requirement, Snyder said.
Charlie DeHart, a battalion chief in Temecula for the California
Department of Forestry and Fire Protection, said the stricter rule is
preferred because firefighters can effectively cut power from the
panels. Outside of Temecula, they have to be wary.
"We can safely kill the interior side of the structure, and our folks
are still safe," he said. "If they have to go on the roof, they have to
know to be careful, unless they have that cutoff switch."
But some industry experts said that's exactly the problem.
Sue Kateley, the executive director of the California Solar Energy
Industries Association, a trade group, said DC cutoffs create danger
because they mislead firefighters.
The solar panels remain energized as long as the sun is up, and they
even retain some electricity when it's dark. Putting a cutoff on the
roof only neutralizes the wire running from the panels to the inverter
box, but it doesn't eliminate the danger to firefighters.
"It's that perception of safety we want to avoid; they think they're
safe, when there's potential from getting a shock, and falling off the
roof," she said.
Requiring DC cutoff switches remains a subject of debate among
electrical engineers nationwide.
Gig Conaughton, a spokesman for the San Diego County Department of Land
Use and Planning, said the county monitors the national discussion
carefully.
Yet no national requirement appears to be on the horizon.
"There's no national movement for DC cutoff switches on the roof," said
Bill Brooks, an engineer and electricity consultant who has worked
extensively on national electrical standards.
Kateley said there are other solutions to the problem of energized solar
cells, but she didn't provide examples. She said the real lesson of last
week's solar panel-sparked house fire is that homeowners need to have
their systems inspected on a regular basis, to make sure nothing needs
replacement or repair. But she also conceded that data on solar panels
and safety is still coming in.
"The challenge is, until we had enough systems out there, if we had an
incident it was so actuarially insignificant," she said. "There was no
generic problem."
In the meantime, Pavis said she isn't sure if she wants to continue
being a solar guinea pig.
"I had them cut all the wires to both of the panels right now until we
find out what the heck is going on," she said. She said it had been a
stressful day. "It wasn't fun."
Call staff writer Eric Wolff at 760-740-5412.
(c) 2010,
McClatchy-Tribune Information Services To subscribe or visit go to:
www.mcclatchy.com/
|