Tom: Here's how I approach this subject:
In general there are two places to insert OCPDs to protect wire and devices: Upstream or downstream. For a vast majority of circumstances, it is preferred to place protection upstream, for obvious reasons. This is not to say protection cannot be placed downstream. This is done for taps and service entrance conductors. The philosophy is to minimize the probability of failure on the upstream side of the protection and the OCPD protects the upstream circuit from downstream faults. I think the same criteria applies for battery lead protection as it does for taps and SE cables: Minimize the risk by keeping leads short and protected from damage. If you follow these practices you can eliminate the need for fuses in proximity to the batteries. William PS: This relates to my complaints about the Sunny Island systems lack of BOS. If you use the Midnite Disconnect, it mounts right under the SI inverter. This can often be too far from the battery bank. Wm Lic 773985 millersolar.com 805-438-5600 -----Original Message----- From: RE-wrenches [mailto:[email protected]] On Behalf Of Tom Ruscitti Sent: Thursday, October 22, 2015 6:27 PM To: [email protected] Subject: [RE-wrenches] Current limiting fuse at battery bank On battery based systems I always install a Class T fuse as close to the battery bank as possible. 690.71(C) is a little vague in requiring a current limiting fuse only where the available short-circuit current from the battery bank exceeds the interrupting ratings of the inverter breaker. Inverter breakers vary in their interrupting ratings and battery banks are big current sources when things go wrong, so it's just a sensible best practice. My question is about service work on systems we didn't install. We're quoting the second job this year for battery replacement where there is no current limiting fuse installed. It's always a tough question to judge what extra work might be required when you touch another contractor's system, but does anyone have an opinion about recommending or requiring the installation of a fuse at the battery box as part of the battery replacement? Thanks, - Tom -- Tom Ruscitti Senior Engineer Taitem Engineering, PC 110 S. Albany Street, Ithaca, NY 14850 Mobile: (607) 220-7022 www.taitem.com _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.htm l List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
