Which switch - master - battery/alternator one position w/ground wire

Fearless · #1 04-24-2010, 03:23 PM

I am designing my electrical system using the Z-11 AeroElectric drawing. I have an internal regulator alternator so I want to wire my master where the alternator is on as well as the battery - not using the S700 2-10 setup that is on the drawing where you turn on the battery circuit in the middle position and turn on the alternator on the next position. I believe this gives me a single pole setup. The drawing has a ground on the 2-10 so what switch would I use in a single pole setup to turn on battery/alternator at one position and have a ground wire running off as well.

apkp777 · #2 04-24-2010, 05:27 PM

You need to be able to turn on the battery separate from the alternator. The S700 or Cessna style master is a good way to go. Why do you want to delete that?

Fearless · #3 04-25-2010, 07:33 AM

I want to wire the alternator to always be on when the battery circuit is on like in an automobile. It the alternator fails then I will turn off the master and switch over to my essential bus and find a place to land. Between my EIS monitoring voltage and the failure light on the alternator I will know it has a problem and switch busses. I have no intention of turning the alternator circuit off and back on in flight and don't want a switch setup that allows that.

apkp777 · #4 04-25-2010, 07:36 AM

Quote:

Originally Posted by Fearless

I want to wire the alternator to always be on when the battery circuit is on like in an automobile. It the alternator fails then I will turn off the master and switch over to my essential bus and find a place to land. Between my EIS monitoring voltage and the failure light on the alternator I will know it has a problem and switch busses. I have no intention of turning the alternator circuit off and back on in flight and don't want a switch setup that allows that.

I understand that. However, your alternator field imposes a load on the electrical system any time the field is energized. Having the ability to isolate that can help you start up with a weaker battery.

Sparky · #5 04-25-2010, 10:41 AM

Mike,

You can do what you want to do by using a 2-3 switch instead of a 2-10 switch. That is how it's done in the AeroElectric Z-10/8 drawing. I am using the Z-10/8 drawing to wire up my RV-7, but I chose to wire up the master switch like the Z-11 drawing using a 2-10 switch, as I want to turn on the battery master and alternator field separately.

By the way, the 2-3 and 2-10 switches are both double pole, double throw (DPDT) switches, but the 2-3 has 2 positions (ON-none-ON) and the 2-10 switch has 3 positions (ON-ON-ON). Their operation is explained in chapter 11 of AerElectric Connection.

Brantel · #6 04-25-2010, 10:54 AM

You can still use the split switch method for versitility and always turn on the alt field before start... If you don't, your battery will be drained much faster when you have the master on for ground testing....

I have a PP alt and they say it is no problem to control the alt with the engine running...

Fearless · #7 04-26-2010, 05:35 AM

Phillip,

You brought up a point I hadn't thought about so I will take that into consideration.

Sparky

I will take a look back in the book as well as take a look at the Z10/8 diagram hoping for clarity.

Brantel,

I have a ND alternator but it didn't come from PP. I got if from where I bought my engine core. You seconded the point that Phillip made.

Thanks guys. There might be some hope to some day getting this plane in the air after all.

Fearless · #8 04-26-2010, 05:36 AM

I meant Tony where I put Phillip