Eric, this is very interesting that the foil (Faraday shield) used in
this way would help that situation !
A Faraday shield using aluminum foil will only shield electric fields
and not magnetic fields of course
so something interesting is going on here. SO, the foil was not
grounded in any way ?
The mechanism should hopefully become obvious after some thought and
experimentation.
We will definitely be looking into your fix.
Than you !
boB
On 12/16/2020 3:36 PM, Eric Smiley wrote:
Season's Greetings Wrenches
We have been attempting to use MidNite SOB's with Sol-Ark inverters
this year. In Canada we only need one SOB per string since our Code
requires Rapid Shutdown for PV source or output circuits more than 1
meter from the array.
However, not all the SOB's were closing the circuit when we had two
strings on one MPPT - both when we combined two strings on the Sol-Ark
PV input terminals or when we used MC4 Y connectors outside the
Sol-Ark to combine two strings. MidNite had no solution for this back
during the summer and tech support there only suggested that we had
configured the system incorrectly or that we shouldn't combine strings
that way. This array also had a very long underground run between the
array and inverter. So, at that time, not knowing if it was distance,
interference from something else or gremlins, we just took out all the
MidNite equipment and installed a DC SunVolt Rapid Shutdown box.
Diagnosing the problem was a challenge since only one of the parallel
strings on each MPPT was not producing power at any given moment.
Also, everything worked fine while I made voltage and current
measurements but when I pushed the coil and wires into the JB I lost
half my solar power.
Anyway, today I solved the problem on a new system I was commissioning
by wrapping the SOB Transmitter coil, with the positive conductors
passing through it, in aluminum foil.
I hypothesized that with the coil on the positive conductors, the
negative conductors, which were very close to the coil, all of which
was inside a metal junction box, were picking up a signal from the
coil and this was interfering with the signal on the positive.
It's a bit cludgy, but shielding the coil seems to be the solution.
I'd love to hear if anyone else has had this problem and/or solution.
Eric Smiley, MASc
Project Manager, North Island
E: [email protected] <mailto:[email protected]>
T: 1-888-386-0116 ext 702 (toll free)
C: 250-703-6004
W: viridianenergy.ca <http://www.viridianenergy.ca>
<http://www.viridianenergy.ca/>
RENEWABLE POWERNOW
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