25 kW inverter [RE-wrenches]

[Matt Lafferty]

Sunshine Wishes to all Wrenches,

RE:  Oregon LRET limited to 25 kVA.
http://licenseinfo.oregon.gov/index.cfm?fuseaction=license_seng&link_item_id
=1684

Matt's Perspective:  
For Inverter based PV systems, the answer is simple:  Sum of Inverter
Maximum Power ratings.  
For non-inverter based PV systems, there is no reactive power, and therefore
there isn't a kVA rating... Oooops!  <Would somebody please run over the the
CCB and close that door?>

Paul Israel has the correct answer.  More importantly, he has the right line
of thinking for his answer.  The responisible line of thinking.  Bravo to
Paul!

This is a Contractors' License issue.  There is a reason for it, whether or
not you agree with the reason(s).  If you want to work on systems that have
kVA ratings larger than the limit, get the appropriate license or wait until
the limit changes upward to a rating more to your liking. (In the meantime,
you could submit a motion to modify the classification...)

Think about it this way:  It is not reasonable to require a Contractors'
License board in one state to base the kVA limits of a given classification
on some ever-changing incentive-program methodology that is based and
maintained in and by another state and may be subject to withdrawal at some
time in the future.  To think otherwise is foolish. 

I can hear the sand in the gears now as some poor clerk at the OR CCB tries
to answer this question... "OK. Let's see here... The classification limits
work to 25 kVA. (Fact)  You want to calculate this based on this PTC
(non-nameplate) value from this website here then multiply by some
efficiency number from this website here then by the number of inverters
then by the number of modules which gets you to some # of WATTS. Is WATTS
the same as kVA?  I'll have to get back to you."

<NOTE>  If this methodology has not yet been defined at the OR CCB, I hope
that one or more of our mature Oregon bretheren will take it upon themselves
to gently submit this recommended definition:  kVA shall have the same
meaning as 1,000 Volt-amperes, or 1,000 watts, or 1 kilowatt. RE systems
utilizing inverters shall have their kVA ratings calculated based on the Sum
of the Maximum Power Output ratings of the inverter(s). RE systems that
utilize direct current only shall have their ratings calculated based on the
Sum of the Maximum Power ratings of the PV modules (panels).

If you are one of the 15 LRET's and want to push the envelope, do so at the
peril of many, not just yourself. The 25 kVA limit was negotiated.  Some of
the contractors on the "other side" of 25 kVA are most likely to be watching
for just this thing.  In Oregon's case, it will be relatively easy to track
down via Rebate Program statistics.  Much blood over "classification" has
been shed in CA. Unnecessary blood in my opinion, but this industry did not
move proactively in time to avoid it. I'm hearing the early sounds of a
3-years-later echo coming from OR here...  

Welcome to rebates!  Please don't be greedy!

Be thankful that Oregon has a Limited Renewable Energy Technician
classification that allows non-Electrical Contractors to even do this work
and that it isn't limited to 10 KW.  Many states don't.  Bravo Oregon!

Peace and Sunshine! See you all at Country Fair.

Matt Lafferty

-----Original Message-----
From: Paul Israel
Sent: Thursday, June 12, 2008 1:18 PM
To: RE-wrenches at topica.com
Subject: RE: 25 kW inverter [RE-wrenches]


Wrenches,  

1.  Most Utility Interconnection Applications use the inverter nameplate to
determine system size for interconnection. 

2.  The NEC uses it to size the OCPD.

3.  The manufacturers vary as to which inverter can handle power above the
nameplate rating.  Some will process the extra power others will not.
However, by the time we follow the manufacturers or figure for ourselves how
much wattage the inverter can efficiently process we are probably darn close
to the rated nameplate.  Time, that stringent beast, will limit it anyway.

4.  Oversizing an inverter for future expansion would limit us to installing
a 25kW inverter.  Installing a 50kW inverter and then putting 25kW of panels
would be questionable at best.  A loophole that would be quickly closed.

Hey, let's just change the law!

 

 
Paul N. Israel, President


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