Dave, Philosophically, the MRBF fuse should protect the wire from the battery to through the switch to the PowerPost. That wire should be sized to handle the maximum load on the PowerPost. If you run individual wires to each fuse, that fuse should be sized to protect that circuit and its appropriately sized wire.
If you want to check wire size, download Blue Sea Circuit Wizard for your mobile device. http://circuitwizard.bluesea.com/ Remember, the wire run is there and back. I would consider the distance for your circuits to be from the PowerPost, through the fuse, through the user (pump, light, whatever) and then to the ground point. Your ground point may be another PowerPost. In Touche's case, I terminate the individual grounds in the breaker panel on two buss bars. The buss bars are connected by a larger wire to a ground PowerPost. The larger ground wire is sized to handle the conglomerate load of the circuits. Sorry I don't have a circuit diagram. Dennis C. Touche' 35-1 #83 Mandeville, LA On Thu, Mar 12, 2020 at 3:21 PM David Knecht via CnC-List < cnc-list@cnc-list.com> wrote: > Hi Dennis- That makes sense. I also have MRBF fuses on both batteries, so > I could presumably do the same. It would certainly simplify the wiring to > just connect that heavy battery cable at the panel end to a Powerpost and > run from that to the various circuits. I am never confident about doing > fuse issues correctly, so this helps a lot. Dave > > S/V Aries > 1990 C&C 34+ > New London, CT > > > On Mar 12, 2020, at 2:18 PM, Dennis C. via CnC-List <cnc-list@cnc-list.com> > wrote: > > The PowerPost is about halfway between the battery switch and breaker > panel. Less than 3 foot runs each. The PowerPost is essentially fused > because there are MRBF fuse blocks on the battery positive posts. > Therefore, whether the battery switch is on "1" or "2", there is a fuse > prior to the battery switch and therefore the PowerPost. The MRBF fuses on > the batteries serve Touche's entire electrical system except the bilge > switch which is supplied directly from a battery and has its own fuse. > > Hope that clarifies for you. If not, just holler. I plan to be on the > boat this weekend if you need more info. > > Dennis C. > > On Thu, Mar 12, 2020 at 12:49 PM David Knecht via CnC-List < > cnc-list@cnc-list.com> wrote: > >> Hi Dennis- I just wanted to clarify your reply. The Powerpost Plus looks >> like a nice way to distribute power and I had not seen that. Do you have >> that near the main rotary switch or near the breaker panel? I gather this >> is not fused, so if I simplified the wiring by bypassing the fuses and >> putting it near the panel, I would lose the fuse before the breaker. >> In my setup, some power runs from the rotary to the 4 fuses and then to >> the panel. But those wires are not larger than about 10-12G and all the >> same size. There is also a heavy battery sized cable running from the >> rotary switch directly to a bus bar behind the panel. So those circuits >> would only have the panel breakers and no fuse. I don’t know what was >> original and what added later as all that predates my work on the wiring. >> I plan to map all the circuits this week so I know what comes from each >> wire. But that setup does not make sense given what Shawn says about the >> logic of the fuses near the rotary switch being so you could have a long >> run of heavy wire to the panel. Dave >> >> S/V Aries >> 1990 C&C 34+ >> New London, CT >> >> <pastedGraphic.tiff> >> >> On Mar 11, 2020, at 1:59 PM, Dennis C. via CnC-List < >> cnc-list@cnc-list.com> wrote: >> >> Dave, >> >> Piggybacking the supply from one fuse to another is pretty common, >> especially in older boats. Just need to ensure the proper wire size to >> carry the load to all the users. Pre-made breaker panels have a solid buss >> bar which carries the power supply to each breaker. The piggyback wiring >> is philosophically analogous. >> >> Personally, there are better ways to do it. If there's a place for a >> buss bar, you can route the power from the rotary switch to the bar then >> connect each fuse to a connection on the bar. I would not stack a bunch of >> separate wires on the switched connection on the rotary switch. >> >> On Touche', I have a Powerpost Plus, which is on the switched connection >> of the battery rotary switch. That is, when the battery switch is "ON", >> the Powerpost is live. A properly sized wire from the powerpost supplies a >> couple of buss bars in Touche's breaker panel. Each breaker is then >> supplied individually from the buss bar. >> >> Not sure about your comment on a fuse before a breaker. A better pic >> might help. >> >> You should have a fuse at the battery. I have these on Touche': >> >> >> https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A >> >> Dennis C. >> Touche' 35-1 #83 >> Mandeville, LA >> >> >> >> _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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