[RE-wrenches] Pv i-v analyzers

[Daniel Young]

-	I have the Tri-Ka unit.
-	I probably would not purchase it again unless I planned to make a
business out of advanced troubleshooting.
-	I don't think any other I-V tracer is necessarily any better/worse.
I think you need to pair the features with your goals/needs. I just have not
gotten the use out of our that I had hoped for.
-	Reliability has been great, consistent performance every time it's
in the field. Great memory capacity and battery life. The sensor unit is
handy for doing a standard array health check (gives good/fast cell
temperature and plane of array irradiance to base you calcs off of/ compare
with your onsite monitoring equipment)
-	If you are selling the I_V tracing as a service I believe best
practice for any high accuracy meter is to calibrate yearly/ every other
year (I think it will be in the product manual). I have not had ours long
enough to suspect that it has fallen out of calibration yet. The first trace
I ran was on the array on our office, so as time goes by I plan to test our
array again to see if the meter or array has changed significantly.
-	I think the main negative aspect to I_V tracing in general is the
time it takes. Time is not a big deal on smaller jobs, <500kW. But if you
give yourself an average of 45-60 seconds per string test (that includes
selecting the new string in the device to save the test data under, pulling
the fuse holder of the last string, and inserting the fuse holder of the
next string, with an averaged-out time to switch combiners) and have a 1 MW
array with 180 strings, then you are talking 3hrs/MW of testing time. And
that testing time should be on a day with consistent weather conditions to
ensure accuracy (constant sun at 700 w/m^2 plane of array irradiance or
better, which means you can't plan on starting till late morning, where you
likely get a 3-4hr window for measurements). So you can essentially get
1MWdc tested in a day. If you test in the Midwest, you know your chances of
getting 2-3 good days in a row without some scattered clouds, so you really
have to wait for the right time to go test. It could take over a month to
test a really big project, say 15MW, and that's if you have nothing else on
your calendar and can be on site almost every time you're going to have a
good testing day.

Given the last point above, I tend to be in the camp of monitoring larger
projects on a combiner box level (for central inverters) or string inverter
level (if you design MW's with string inverters like has become more popular
of late). You can usually tell if you have a problem child string with that
kind of granularity, then you could break out the I_V tracer if you need to
dig deeper.

With Regards,

Daniel Young, 
NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90

-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of dana at solarwork.com
Sent: Thursday, November 19, 2015 2:28 PM
To: RE-wrenches
Subject: [RE-wrenches] Pv i-v analyzers

Fellow Wrenches:
If you were going to buy or have bought a PV i-v analyzer:
What product did you purchase?
Would you do so again?
Would you purchase a different product?
How has the reliability been?
Does it need to be sent in for periodic recalibration?
Pluses & Minuses?

Thanks for your input & opinions!


Dana Orzel 208.721.7003
Encourage Free Thinking Self Responsible Free Range Children
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