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A little OT but does anyone have any idea if there is much of a load on the engine with the B/U alternator just spinning w/o being used as primary?
Thinking in terms of HP used. Glenn Wilkinson |
Hp consideration
Hi Glen
I asked that exact question to DIck (Plane Power ) and he said it might be as little as 1 or 2 Hp max so nothing to be too concern about I would say Bruno |
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John Clark ATP, CFI FAAST Team Representative EAA Flight Advisor RV8 N18U "Sunshine" KSBA |
SD-20
Well I finally decided on the B&C SD-20 with their external regulator.
Their special Oshkosh price and the guarranty that it will fit with their oil filter adapter installed swayed me toward them. Now all I need to figure out is how to wire the thing...:eek: Wish me luck Bruno rv4@videotron.ca |
Main & Std By Alternator Wiring
Hello Gents
Well I started installing my new SD-20 Back Up alternator and also review my previous installation of my Main alternator and I hit a wall.. I'm not sure 100 % on how to wire the B leads of both alternator. 1.- Main alternator... If I used Bob Nuckoll's AeroElectric book, in there he suggest ( if I understood correctly) to wire the main alternator B lead directly to the starter main power terminal ( Page 7-13, fig 7-12 ) via either a current limiter or a CB.So this way ,it shorten the large conductor from the alternator B-lead to the bus bar and has some other advantages.. My question is : Is it a good way to wire my main alternator and am I better off using a C/B rather then a current limiter. 2.- Back Up alternator. So far I have install the voltage regulator and some of the wires but I'll like to know how I should terminate the wire from the B lead once I wire it to a C/B?? Do I actually need a C/B or is a current limiter good enough..I think it might be easier to control the alternator via a C/B:confused: Where do I go from there?? Do I go from the C/B to the bus bar or to the alternator shunt?? This is where I hit the wall, I'm just not sure what to do next and I don't want fry anything..:eek: Both Alternator field are wired thru their respective C/B.. Any suggestions are welcome Thanks Bruno rv4@videotron.ca |
Hi Bruno-
I don't have my Aeroelectric book in front of me, but thinking through the logic of connecting the Alternator B lead to the starter main power terminal, this would work if you did not have a firewall mounted starter contactor as Vans shows in their plans. I suppose Bob was thinking this might be a good idea in a configuration where the starter contactor is on the starter itself. Some people wire this way, but most use the Vans recommended firewall mounted starter contactor. Think about it, if you had a starter contactor on the firewall, your alternator would only be supplying juice when the starter contactor is closed. That would not work too well! On your 2nd question, CB vs current limiter is a matter of personal choice. Personally, I prefer current limiters. You will never intentionally open this circuit breaker (it is not a switch) since you always control the function of your alternator by opening and closing the field circuit, which is already a breaker as you mentioned, so that is fine. The CB or current limiter on the B-lead is to protect the B-lead (and the rest of your electrical system) from a dead short. On the other side of the current limiter or the CB you go to the main bus (most people wire directly to the main bus contactor - the side that becomes energized when the main bus switch is closed). If you have an essential bus you may wire instead to the essential bus rather than the main bus - depends on your architecture goals really. Do you have any local builders or A&Ps that can inspect your wiring before powering everything up? That might be a good idea and could help you from "frying anything"! Hope this helps... |
Alternator Wiring
Hi Noah
Thanks a lot for the info, it is greatly appreciated. Reference connecting the B lead of my Main alternator to the starter main power terminal, mine is mounted on the firewall same as Vans. It is power as long as I have power on the aircraft.The way it is wired right now is like this. The battery is connected to one stud of the battery contactor and on the other side of the Battery contactor, there is a wire that goes to the starter main power terminal (this where the cable from the Alt B lead is connected ) and on the other side of the starter main power terminal there is a cable ( # 6 ) that go from there to the alternator shunt. So when I turn the master switch ''ON'', power flows thru the battery contactor to the starter contactor and from there to the starter.. I don't know if it is wired correctly but it does work, I just wanna make sure it is safe the way it is... Regarding the current limiter, should I mount it between the Alternator B lead and the starter main power terminal ? Ref the Back up ALT : Tried to install it today on my -4 but it doesn't work.. There is an interference between the ALT and the B&C o?l filter adapter.. I contacted B&C ( Superb service BTW ) and they are working on a solution that will work with an RV-4..I might have to use a special spacer for the vacuum pump drive like the one use on the RV-10.. I'll keep everyone posted on the results since I'm the first to do this on a -4 apparently. Thanks again Noah Bruno |
Bruno,
You are NOT better off using a circuit breaker. For one thing, it is not desired to run a heavy wire through the firewall to the instrument panel to where a circuit breaker would be mounted. Another reason not to use a circuit breaker is that they have moving parts that can fail. A circuit breaker can nuisance trip. An ANL current limiter will only blow when the alternator or associated wiring shorts out. I suggest that you wire it according to Bob Nuckolls diagrams. His circuits have been perfected and proven over time. There has been some discussion on the AeroElectric list about using a MIDI fuse (which does not cost as much) instead of an ANL. See http://www.matronics.com/forums/view...acf5645e6f6642 and http://forums.matronics.com/viewtopi...bb1782e2726292 Joe Gores |
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