620 VDC [RE-wrenches]

[Joel Davidson]

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Drake,

Uni-Solar and other amorphous silicon solar cells have a flatter IV curve 
than crystalline silicon cells which requires a wider inverter input voltage 
window. This means that it is difficult to design a Uni-Solar PV system for 
places like Boston where cell temperatures can range from -25C to +70C. Cell 
temperature right before daybreak is almost always the same as ambient 
temperature unless the building leaks a lot of heat.

Joel Davidson

----- Original Message ----- 
From: "Drake Chamberlin" <Drake.Chamberlin at redwoodalliance.org>
To: <RE-wrenches at topica.com>
Sent: Friday, June 27, 2008 8:35 AM
Subject: RE: 620 VDC [RE-wrenches]


>
> Thank you all for your input.  It appears that this is an area that needs 
> work in the Code.  I'm looking forward to Bill's new temperature guidance 
> being implemented.
>
> With the particular system we are considering, we would be using Uni-Solar 
> laminates that will adhere directly to a metal roof.  Is there anyway we 
> can get credit for the building heat that will never let the modules get 
> down to the ambient?
>
> Drake
>
>
> At 11:39 PM 6/26/2008, you wrote
>
>>Joel,
>>
>>What does 600-Volts nominal mean to you? As Drake pointed out, 600Vac has 
>>a
>>peak voltage of 850V. Any momentary exceeding of 600V, when using 
>>reasonable
>>statistical design numbers, will be momentary at best and have no affect 
>>on
>>the equipment unless the equipment is faulty to start with.
>>
>>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]
>>
>
>
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