Dan Fink said:
"That's a tricky situation. There are only two possibilities for what's
causing the problem; sound or electromagnetic radiation"
I'm betting that it's sound. Remember how you could hear televisions
singing
away at 15 kHz ?? That still gives some people headaches.
How old is this customer ?? I'm guessing he's young because it's most
likely because he
can hear the inverter switching. We just can't normally hear
them.... The FX/VFX
inverters switch at around 20 kHz which some people can still hear.
Especially younger ones
with better hearing.
It's probably the transformer windings and iron acting as a
speaker/transducer.
High frequencies are very directional so will usually respond well to a
thin wall of
padding between inverter and the rest of the inside of the house or cabin.
That should help reduce the acoustical output.
boB
Dan Fink wrote:
Joel --
Good points. In a recent newspaper article in Boulder, CO about a
really bad PV install, the direct grid tie inverter was mounted right
on the outside of the wall from the homeowner's bed. They finally had
to have it moved--mostly because of buzzing, but EMF was a concern
too. It was basically less than a foot from the guy's pillow.
Also, I forgot to mention that there are fairly inexpensive EMF meters
available from the same places that sell DIY shielding materials.
The biggest source of EMF at *my* house is actually the E-Meter
measuring amp-hours. It even interferes with my handheld ham and fire
department radio FM communications on 2 meter.
DAN FINK
Renewable Energy Consultant
Joel Davidson wrote:
Ron,
Electromagnetic fields are produced any time you have current flowing
through wire. They are low frequency waves that drop off rapidly
proportional to the distance from the source. Inverters,
transformers, fluorescent light ballasts, motors, clock radios, power
blocks, microwave ovens, kilowatt hour meters, service panels all
emit EMF. There is no
practical way to block EMF. It passes through almost everything
including walls and even lead. There is no U.S. safety standard for
EMF. Some say 8 milligauss or more is dangerous and 2.5 milligauss or
less is safe.
I went through our home about 10 years ago using a borrowed
milligauss meter (thanks David Katz). Our utility meter service had
significant EMF, but that was not a problem since it is mounted on an
outside wall and there is a closet between the living space and the
meter. The EMF had fallen to below 2 milligauss between the wall and
the closet door. The bedroom clock radio was the second largest EMF
source in our home. Moving the clock 1 foot away from the bed to the
other side of the night stand brought the EMF levels under 2
milligauss. Our SW4048 inverter emitted a field that fell to a safe
level 2 feet from the inverter.
I tell people not to put their bed against the wall where their
utility service panel or inverter is mounted. I also tell them that
the Japanese did a 2 year study of school children riding the Tokyo
subway (big EMF emitter) and found that there was no danger.
Some sounds that most of us take for granted can cause physical
discomfort and even pain. SW4048 and other transformer and electrical
and electronic buzzing can be annoying. Also certain wavelengths and
intensities of light can cause pain and injury.
Joel Davidson
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