[RE-wrenches] wrenches] Short Circuit Cell Damage

[bob ellison]

If you cut them during the day, under sunlight conditions it can do bad things to the wire cutters.

 

Been there before,

Bob Ellison

 

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of john
Sent: Tuesday, September 18, 2012 1:43 PM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] wrenches] Short Circuit Cell Damage

 

Mark,

   As far as cutting the jumper for us nightowls, it is easy.  Wait until dark.  The sun actually turns off every day!.
And for the new people on the block, polarity can still be determined after dark.  All you need is a microvolt to get polarity. 


John

CV Solar

-----Original Message-----
From: benn kilburn <benn at daystarsolar.ca>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Tue, Sep 18, 2012 1:48 am
Subject: Re: [RE-wrenches] Short Circuit Cell Damage

Mark,

Shorting the string should not be an issue.  

Unless you work at night, obviously there will be an arc when you cut the jumper, so remember to cover the whole string with an opaque covering beforehand… I think I remember reading that somewhere?!?!  

Or just be careful, try to do it when the irradiance is low (less current), separate the cut wires quickly and make sure you have left enough wire in the box so that you are not working with short (and energized) wires in a metal box. put a wire nut on one wire while you handle and terminate the other.

 

A safer method, if possible, would be to leave an easily accessible module interconnection un-connected until you have terminated the home run (+)&(-), then go back and make the final module interconnection.

 

Cheers,

benn

DayStar Renewable Energy Inc. 

www.daystarsolar.ca <http://www.daystarsolar.ca/>   *  Ph: 780-906-7807 

Construction Electrician Solar Photovoltaic Systems Certified

Certificate # 0007S

HAVE A SUNNY DAY

 

On 17/09/12 9:50 PM, "Mark Frye" <markf at berkeleysolar.com> wrote:

 

Wrenches,

 

True or False: In a nominal sort of grid tied situation with string Voc 

at about 300 VDC and Isc at about 6 or 7 amps......It is OK to install 

modules on a roof in the sun and short the pos and neg together 

indefinitely.

 

In other words modules can handle operating at Isc continuously without 

damage. It is only if you get localized shading AND a failed bypass 

diode that damaging hot spot heating can lead to failure?

 

I am reviewing an installation manual that recommends completing the 

home run by connecting the pos and neg of the string with a single 

jumper cable, folding the cable on itself in order to push it through to 

a j-box and at some point later on, cutting the jumper in the j-box to 

terminate the pos and negs to the home run.

 

I am concerned both about maintaining the string in a short circuit 

condition and cutting the jumper while energized.

 

Any thoughts?

 

Mark Frye

Berkeley Solar Electric Systems

 

 

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