Wrenches In the event you or some else installed a Class T fuse and you want to protect it a little more from cable stress, installing it inside a PVC C conduit body and cover and fastening the cables to the fuse inside that, this will protect the fuse from stress and metallic contact and you can put a label on it stating size and type. Jerry
On Wed, Apr 26, 2017 at 6:05 PM, Matthew Sirum <[email protected]> wrote: > Greetings William, > > Good point. This is something I always take into consideration. I > have used Class T Fuses in many situations with and without their fuse > holders. In the case of the installation shown in my custom DC Bus > System pictures the wire/cable type and wire management avoid putting > too much physical stress on the Class T Fuses. The #4 AWG conductors > are supported from above and apply very little stress on the fuses > they connect to. The 4/0 AWG cabling is Cobra X-Flex (fine stand, > very flexible) and each of these conductors is secured a few inches > from where they connect to their fuses. Care was taken in making up > these connection and they were all carefully adjusted and inspected to > ensure they would not stress the fuses. I feel really good about how > it all came together. The same care and attention will be needed > whenever these connections are serviced and the fasteners are > torqued/tightened. When well planned and carefully assembled I do not > have concern there will be any issues related to not using the fuse > holder. I also think about this another way as well... Using the > Class T Fuse Holder adds another 2 connections to the circuit. I try > to remind myself that more connections can equal more chance of > issues... Although, if a manufacturer of a Class T Fuse states the > fuse holder must be used with their fuse there could be an NEC > violation by not using it. > > One thing to note about the use of these fuses in this installation is > that they are supplemental over current protection (OCP). Each > positive (ungrounded) conductor connecting to this DC Bus System has a > means of primary over current protection and disconnect on its > opposite end. The battery systems, the charge controllers, and the > inverter/chargers all have circuit breaker disconnects on their > respective positive circuit conductors connecting to this DC Bus > System. I have seen other folks build without having the needed > appropriate means of disconnect and OCP; although most folk are > probably more likely to include the primary OCP, but not consider the > supplemental OCP. The supplemental OCP (Class T Fuses) provide > protection in the event of a fault or short in a circuit between the > Bus System and the other OCP at the other equipment. > > Like many folks I have installed and worked on battery systems where > we install a Class T Fuse directly onto the positive terminal of the > battery bank or via some form of busbar or connector etc. In these > cases not only do we need to take care not to stress the fuse, but the > fuse itself (and added busbar/connector etc) can act like a lever and > along with the mating cable lug(s) create too much stress on the > battery terminal... Potentially damaging the terminal, the inner > battery connection to the terminal, and/or the seal between the > battery case and the terminal. Carelessly tightening the > hardware/fasteners to assemble these items to the battery terminal is > a common way of inflicting damage on the battery as well. I know I > have been involved in some service situations where there was more > stress on the Class T Fuse than I would like to see, but as best I > know there have not been any fuse failures because of it. > > Thanks for bringing up this question! > > Best regards, > > ----MATT > > Matthew Sirum > P.O. Box 1227 > Greenfield, MA 01302-1227 USA > phone: +1.413.773.0611 > email: [email protected] > > > -------- Original Message Below -------- > > [RE-wrenches] Third Radian > > William Miller william at millersolar.com > Tue Apr 25 23:03:03 PDT 2017 > > Matt: > > I have a question for you: I have often considered mounting Class T fuses > directly to a bus bar as you have done. Are you ever worried about > physical > strain on the fuse itself without a fuse holder? > > Thanks again for all of your input. > > William Miller > > Lic 773985 > millersolar.com > 805-438-5600 > _______________________________________________ > 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]. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > >
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