[RE-wrenches] Short Circuit Cell Damage

[benn kilburn]

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
beforehandŠ 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  *  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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