Blocking diodes with PVLs [RE-wrenches]

[Bill Brooks]

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Jim,

Basic rule is:

Voltage rating = 1.5 x MaxVoc
Current rating = 1.5 x MaxIsc

The fact that they don't have a specific recommendation is bothersome. I
personally would not put a diode in the circuit that has not be specified by
the manufacturer. This is a liability issue. If they are not going to be
specific, and it is not a listing requirement (they would have to be
specific if it was) then adding a diode that is wrong could obsolve them of
any product liability.

If this is a single or double string going into a SB2500U, there is no need
for blocking diodes. Maybe SIT has some ideas since they do large systems
using the UniSolar laminate.

Bill.

-----Original Message-----
From: Jim Grundy [mailto:eenergy33 at aol.com]
Sent: Monday, September 13, 2004 7:22 PM
To: RE-wrenches at topica.com
Subject: Blocking diodes with PVLs [RE-wrenches]




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Esteemed wrenches,

     Another Diode question that I have posed to Uni-Solar but without
getting an answer.   The PVL manual says "Utility line tie systems 48 volts
and
above:   Blocking diodes are recommended for every series string of
modules....

     Does anyone have experience with this question.   Blocking diodes for
high voltage strings in a grid tie application?   They recommend 8 amp, but
what
type and voltage rating?   Thanks in advance for any insight.

Jim Grundy
NABCEP Certified Solar PV Installer TM
Vermont Solar Plumbing Specialist license # PS-279
Vermont Solar and Wind Partner
Elemental Energy
1750 Clark Rd
East Montpelier, VT 05651
(802) 476-3441 (p)
(802) 476-5680 (f)
(802) 272-8933 (c)


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