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I've almost finished wiring my Jabiru 3300/CH 750's panel. After studying the Jabiru Engine Installation Manual's wiring diagram, it appears to me that the +12V circuit that excites the alternator (yellow wire at voltage regulator plug) comes directly off the Main Bus and is not fused/breakered.
It also appears that the +12V to the starter switch (to energize the starter solenoid) also comes directly off the Main Bus and is not fused/breakered.
Anyone "been there - done that" and can verify this is correct?
I think it matters little if you connect directly to the battery or the bus - what I'm confused about is whether is necessary or best practice to fuse the yellow/alternator control wire? The 3300 engine installation manual doesn't show a fuse or breaker. Composite Design supplied a wiring diagram for the 3300 showing it attached to the "Accsy" terminal on their Power Panel, which is breakered. I've made inquiries to both Wayne at Composite Design and Jabiru USA - I'll see what the consensus is and report.
The Jabiru Installation Manual diagram also shows the starter switch unbreakered or unfused. Virtually every wiring diagram I've come across for other applications shows it on a protected circuit - I "think" it can momentarily pull about 3 amps.
Major Red Letter day today! I hooked up the battery for the first time (starter cable detached) - Everything powered up fine and no "Magic Smoke" LOL! The EIS read out all my CHT's and EGT's, Oil Temp sensor and OAT all showed the garage was about 55 degrees today The flap motor works and the trim LED's light up (trim motor yet to be connected for testing). So, wiring's about finished and no troubleshooting to do so far!
I followed what I believe are good practices out of the Bob Nuckolls Aeroelectric guides and I have both circuits on either a breaker or fuse. Just for giggles, my overall wiring diagram is attached showing these ciruits. It has served me well for over 200 flying hours now in my Jabiru powered 601XL.
I "think" some of the confusion may have come in because Jabiru USA recommends running the alternator control wire directly to the battery, which would be a short run forward of the firewall. Since I brought the wire to the power panel's bus behind the firewall, I think it only makes good sense to breaker it (and the starter switch as well!).
Thanks for your info!
A little follow-up ... Today I talked to Pete at Jabiru USA. He said that now they actually do NOT recommend running the alternator control wire directly to the battery. If directly wired to the battery, the voltage regulator will draw a very small current even when everything else is shut down, which will eventually deplete the battery if the plane sits idle for a long time.
He said it was "fine" to route the wire through an alternator switch found on a typical split-master switch, or, at least route the wire to the main bus since that will not be energized when the master contactor is off.
As to whether to fuse it or not, he said the current on the wire is very minimal, so it doesn't have to be fused/breakered, but it is OK if you wish to do so. About the only caveat he gave was NOT to put the wire on an ammeter shunt, as this will cause problems for the voltage regulator.
I cannot comment on your proposed placement of the red and yellow VR wires other than to say that Nuckolls's Z-16 diagram works. I have a version of Z16 modified to my situation, but my red and yellow wires VR are just as they are on Z-16. They are butted together coming right out of the voltage regulator to a point upstream of any of the places you mentioned. The battery charges just fine.
Just remember to keep the smoke inside the wires,