[RE-wrenches] Electricians liability certificate

[Conrad Geyser]

Esteemed colleagues,

 

Having just hired a licensed electrician for our renewable energy company we
find that he cannot use our liability insurance to cover him on pulling
electrical permits here in Massachusetts.  It seems that he has to have his
own certificate despite being listed as an electrician under our liability
policy.

 

Any insights?

 

Thanks,

Conrad

Cotuit Solar

 

  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan
Sindelar
Sent: Wednesday, December 10, 2008 3:16 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] Module Voltage Question for Off-Grid Designers

 

Wrenches, 
Here's an issue I haven't seen directly addressed, and I would like to know
what the rest of you are doing. 
It's getting harder to get 24V nominal modules. Because the bulk of industry
growth is high-voltage grid-tied applications, modules no longer have to be
a standard voltage. Just pick the number of modules to best fit the chosen
inverter's string voltage range.

But for off-grid, the odd cell counts and resulting "nontraditional" DC
input voltages challenge the traditional rules of off-grid design. I may be
fighting a losing battle here, as the industry changes so rapidly and
fundamentally. I have been trying to stay with 72-cell modules for offgrid,
as this most readily combines with existing systems with 36-cell modules
(12V) and 72-cell modules (24V). 

For example, I will use the new Canadian Solar 170-200W modules. They are
60-cell modules, with a Vmppt of around 28 volts - too low to charge 24V
batteries with a standard charge controller. We can use them in any new
systems with an MX60 or similar voltage-converting MPPT controller. Two or
three in series would charge a 24V battery; 3 in series would charge 48V.
Four in series would violate Code, as low-temp voltage would easily exceed
150V. 

Unless 60-cell modules remain a standard in the future, any future array
additions would have to be on their own charge controller, in order to match
a different I-V curve and MPP voltages into the same battery bank. Is this
prohibitive? No, it just runs counter to the longstanding standards of
off-grid design that allow modules to be added in the future: these modules
will not add well to existing systems, and will not easily allow additional
dissimilar modules to be added later. 

I had this same objection to using Day4 modules, although they were better
at 16Vnom. Three made up a standard 48V array, so strings could be combined
with two-module strings of similar 24Vnom modules.

Who else is trying to stay with 24V modules? Anyone still using 12V modules
in off-grid (residential-scale, not little apps) designs? Who has a crystal
ball and knows what modules will be like in 20 years, or even two years? Wat
are the rest of you doing?

Thanks, as usual. 
Allan 
Allan Sindelar 
 <mailto:allan at positiveenergysolar.com> allan_(at)_positiveenergysolar.com 
NABCEP certified solar PV installer 
Positive Energy, Inc. 
3225A Richards Lane 
Santa Fe NM 87507 
505 424-1112 

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