Nik:
Ian Woofenden mailed me the same letter which has apparently been
circulating on the internet of late. Ian asked for my response for a
potential column or at least a reply to a letter to the editor for Home
Power. Below is what I wrote back. If I missed any points, I appreciate
any feedback from my colleagues.
There are valid concerns, in my opinion, that exist about fire fighter
safety. Unfortunately, the letter you forwarded is only partly
rational. In California, there are competing Fire Departments that are
attempting to create regulations for PV installs to accommodate fire
fighter safety concerns. The two top agencies are the Cal Fire and the
LAFD. Preliminary documents from both agencies are on our web site under
resources: http://mpandc.com/resources/resources.html They are near the
top of the list.
The implications of the roof edge set backs are severe. We did a quick
analysis of the 20 jobs we did previous to the issuance of these
preliminary standards and, of the residential jobs, about 90% would be
infeasible with the new setbacks.
One of the agencies, I recall it was the LAFD, allowed quick release
hardware to suffice if minimum setbacks could not occur. We created some
concepts for quick release mounting and presented them to DPW, but they
never contacted us back. As more and more jurisdictions require setbacks,
I am hoping some manufacturer can take these concepts and create a product
that will allow installations closer to the roof edges than either of the
above requirements would allow.
This is a topic that will be very important in the next year. Thanks for
brining it up.
William Miller
Ian:
The firefighters letter states facts for the most part. The two areas I
disagree with is the length of time that a PV feeder remains energized
after being tarped and the presence of PV feeder voltages at night. The
time required for covered PV modules to de-energize should be no greater
than five minutes by statute and confirmed by independent lab
testing. After sunset PV voltage will not be present.
The 2005 National electrical code addresses these safety issues as related
to fire fighters by requiring the PV feeders either have a disconnect
located prior to the feeder entering the building envelope or the feeders
need to be inside a metallic conduit. I believe future code editions may
further improve safety by requiring minimum spacing below roof surfaces for
this conduit to be installed.
Firefighters can be assured of safety from PV voltage hazards if they
follow two rules (in addition to turning off any disconnects provided): 1.
Do not break the modules, and 2. Do not cut through metallic conduits. I
can not comment on the likelihood of electrocution by voltages following a
stream of water, but I am sure there is information out there on this issue.
Ian, I hope this answers your questions. Please feel free to reformat this
to fit your needs. If my name will be on it, run it by me for review.
William Miller
At 01:07 PM 1/5/2009, you wrote:
I just got this email forwarded from a coworker that volunteers as a
firefigher. Your comments are welcome:
Forwarded Message:
At this past Monday's Twp. Chief's meeting, I went to the presentation put
on by the State of NJ last night at Amwell Valley Fire concerning solar
panels and the danger they present to the Fire Service.
The presentation lasted for about 2 1/2 hours and was what I believe time
well spent. It really opened my eyes to the potential danger and problems
they will be for us for any dwelling fire we will encounter where they are
present. I'm going to attempt to give everyone a quick snapshot of what
was covered.
The thing to know with solar panels are that they cannot be shut down -
they are ALWAYS ENERGIZED. And they are energized with up to 600 volts of
DC current. For example, you cannot put an ax through them to open up a
roof to vent - your putting the ax through 600 volts. If fire is
infringing upon solar panels on the roof it will compromise the integrity
of the panels. You then have 600 volts of live electrical energy - and
what don't you do when you have live electrical energy? - you don't put
water on it. Even if the roof burned through and the panels fell into the
structure, unless the panels were destroyed (de-energized) by the fire
and/or falling into the structure, they can still have the potential to be
live,they have to be treated as such and have the potential of 600 volts
of DC current.
A basic solar system consists of: The solar panels themselves; a
combination box; a disconnect box; and a inverter. The panels all feed
into a combination box. The combination box (which is almost always
located on the roof) takes in all the energy and sends it to a disconnect
box. The disconnect box takes the energy and then sends it into the
inverter which converts the DC current into AC current. From there the AC
energy "pushes" into the structure's normal electrical system.
The combination box has fuses in it that come from the solar panels
themselves. If you access that box, you can pull all the fuses inside and
"kill" anything after the combination box. But remember the panels are
still live and have up to 600 volts in them. If you "kill" the energy at
the disconnect box - anything up to that box is still energized - the
solar panels, the combination box, the line going from the combination box
into the structure and into the disconnect box are all still
energized. The power company pulling the meter for normal service has no
effect whatsoever on the solar panel system - it is all still live and has
up to 600 volts of DC current. The only "good" thing when it comes to the
disconnect box and the inverter is that they need to be co-located with
the normal service panel for the structure and each should be marked as
appropriate.
Even if it's nighttime and the solar panels have not been exposed to
direct sunlight for several hours, they still are energized and can kill
you. It is estimated that the panels would need to be covered with an
opaque tarp for 7-10 days before the panels will "de-energized" down to
minuscule levels. (although the handouts specify that this is an option
for safety steps - it is not accurate per the presenter)
In closing there are people who have greater minds and resources than we
do in developing a process to safely handle fires which may involve these
systems - such as the NFPA, OSHA, etc. Per the presenter, the situation -
and these organizations, are now starting to become aware of the potential
problems. So far in the State of NJ, there is no recorded injury to a
Firefighter being caused by coming into contact with a solar panel
system. Ironically, New Jersey comes in 2nd when it comes to solar panel
system installations in the nation, behind Califorina.
The final question which was asked really put things in prospective -
someone asked that since Califorina is number one when it comes to Solar
Panel Syatem installations, "...what do their Firefighters do when a
structure fire involves these systems?" Answer was "... they let it burn!"
Please, I'm not suggesting that we adopt this strategy. But the reality
is - I really don't have an answer and it seems as if the Fire Service
industry, nor the Solar Panel Companies, don't either.
Just - please be aware and please be careful if you roll up to a structure
where a solar panel system is installed - bottom line, if can kill you.
<End Forwarded Message>
Is this even possible? "Even if it's nighttime and the solar panels have
not been exposed to direct sunlight for several hours, they still are
energized and can kill you. It is estimated that the panels would need to
be covered with an opaque tarp for 7-10 days before the panels will
"de-energized" down to minuscule levels. "
And are there documented cases where firefighters let a house burn because
it had PV on the roof?
Thanks again,
nik
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