Bob,
Not a customer, an employee who works for me. She is mid 50's and has
very good hearing. You may be right about sound. I also think there's
a significant portion of psychosomatic in the mix but I wanted to find
out if there were other instances of people experiencing distress from
inverter operation just to rule out the possibility -or take it into
account.
I know that some people are becoming more sensitive to environmental
influences but this inverter is quiet, just the usual fan sound
occasionally. I used to be able to hear the sound of an ultrasonic
alarm system back when I was in my 20's & 30's - now I just hear
ringing in my ears.
Ron
On 4-Feb-10, at 1:30 AM, boB Gudgel wrote:
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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