620 VDC [RE-wrenches]

[Joel Davidson]

<x-flowed>

Bill,

Please vet your guidance with other PV professional before you advise AHJ 
what lowest temperature to use. Temperature records have a lot of  variation 
and some errors. For example NREL, weather.com and NOA are fairly consistent 
for Phoenix (-8.3, -8.0, -8.3), but they show Los Angeles 
as -5.0, -2.0, -8.9. I'm reminded that the spinach "super food" myth started 
with a typo. See http://www.uams.edu/news/medical_myths/ Sorry Popeye fans.

Joel Davidson

----- Original Message ----- 
From: "Bill Brooks" <billbrooks7 at yahoo.com>
To: <RE-wrenches at topica.com>
Sent: Thursday, June 26, 2008 10:36 PM
Subject: RE: 620 VDC [RE-wrenches]


>
> Joel,
>
> While I don't disagree that some modules are not optimal for some 
> inverters,
> the idea that all AHJs insist on using all-time low as a guide for "lowest
> expected ambient temperature" is a myth. There is no guidance in the code 
> on
> the subject. That is precisely why we intend to add guidance. Until now,
> when asked what to use for the number, my response is that all-time low is
> the most readily available appropriate number.
>
> Bill.
>
> -----Original Message-----
> From: Joel Davidson [mailto:joel.davidson at sbcglobal.net]
> Sent: Thursday, June 26, 2008 6:43 PM
> To: RE-wrenches at topica.com
> Subject: Re: 620 VDC [RE-wrenches]
>
>
> The NEC is very specific about 600 volts DC and AC in Chapter 1, paragraph
> 2. The 600-volt Rule is that fundamental. Almost all AWJ and Code Priests
> interpret Article 690.7 "lowest expected ambient temperature" as the 
> lowest
> temperature recorded by their chosen Weather Scribes even if that low
> temperature only happened once many years ago. From a practical 
> standpoint,
> some solar modules can not be used optimally with some inverters. Every 
> time
>
> I get a good module/inverter match, the manufacturers change specs,
> availability, price, or all three.
>
> ----- Original Message ----- 
> From: "Drake Chamberlin" <Drake.Chamberlin at redwoodalliance.org>
> To: <RE-wrenches at topica.com>
> Sent: Thursday, June 26, 2008 12:37 PM
> Subject: 620 VDC [RE-wrenches]
>
>
>>
>> Hello Wrenches,
>>
>> Some inverters are able to withstand voltages above 600 VDC.  The
>> Solectria 95KW can take up to 620 VDC without harming the electronics.
>>
>> If we size a system so that the record low temperature is gives a voltage
>> of under 620 VDC, a viable system can be installed.  There is a question,
>> however, about the Code compliance of this, since building wire is rated
>> at 600 volts.  Higher voltage wiring is available, but will likely not be
>> cheap or convenient to use.  Also, what about 600 V modules and PV cable?
>>
>> Since this is DC, there are not any cycles to create a voltage peak.  A
>> 600 VAC RMS nominal system can have (if my calculations are correct) a
>> peak voltage of close to 850 volts.  Also, system voltages can range up 
>> to
>
>> 10% from the nominal, resulting in voltages of as high as 660 VAC RMS on
>> 600 volt systems.
>>
>> The question is, "can we have a system with a possible low-temperature,
>> open circuit voltage of 620 VDC with wiring and modules rated for 600
>> volts?  Can the other 20 volts be considered within the nominal range?
>>
>> Thanks,
>>
>> Drake
>>
>> - - - -
>> Hosted by Home Power magazine
>>
>> To send a message: RE-wrenches at topica.com
>>
>> Archive of previous messages:
>> http://lists.topica.com/lists/RE-wrenches/read
>>
>> List rules & how to change your email address:
>> www.mrsharkey.com/wrenches/etiquette.php
>>
>> Check out participant bios: www.mrsharkey.com/wrenches/
>>
>> Moderator: michael.welch at homepower.com
>>
>>
>>
>
>
> - - - -
> Hosted by Home Power magazine
>
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: 
> http://lists.topica.com/lists/RE-wrenches/read
>
> List rules & how to change your email address:
> www.mrsharkey.com/wrenches/etiquette.php
>
> Check out participant bios: www.mrsharkey.com/wrenches/
>
> Moderator: michael.welch at homepower.com
>
>
> - - - -
> Hosted by Home Power magazine
>
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: 
> http://lists.topica.com/lists/RE-wrenches/read
>
> List rules & how to change your email address: 
> www.mrsharkey.com/wrenches/etiquette.php
>
> Check out participant bios: www.mrsharkey.com/wrenches/
>
> Moderator: michael.welch at homepower.com
>
>
> 


- - - -
Hosted by Home Power magazine

To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at re-wrenches.org

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------


</x-flowed>