Need Help = Z14 Schematic Question
 

I am in the process of wiring up RV10, my electrical skills are very basic, so I try to Buzz\Test each circuit as I bring it on line. Last night got bewildered when I started to activate my Main and Backup Bus.

When I activate the Aux bus contactor, without activating the Main bus contactor or the Bus Cross Feed contactor, I see voltage come alive on Main Bus.

I believe the voltage is coming via terminal 5 on switch 11 and through the warning bulb. (when I remove the bulb, the voltage drops to zero)


Two questions:

1) Is this behavior correct with the schematic or have I goofed up some connections somewhere?

2) If I have not goofed up the wiring and this is the proper operation, seems like if I throw one of the load switches on Main bus (landing light for example) while Main Bus & Cross Feed Bus are not active, it will try to feed this power through Terminal 2 & 5 of switch 11 and probably blow the bulb or two amp fuse?

Not sure of my analysis, would appreciate help & guidance from people more electrically inclined....

Thx

The behavior that you have observed is normal for the conditions that you described.
No, the bulb will not blow. Current is limited by the resistance of the lamp filament.
Too high voltage or vibration can blow a bulb.
But connecting other loads in series with a bulb will not damage it or the fuse.
A 2 amp fuse is too small for a starter contactor.
Replace it with a 5 amp. Notice that Z-14 calls for a 7 amp fuse.

Hi Steve, your wiring diagram image doesn't come through for me.

no image
 

Me neither - I get the standard Google Images grey stop sign.

I was able to get the picture of the schematic before it disappeared. It looked like an unmodified Bob N. Z-14. There are two pages: Z14P1.pdf and Z14P2.pdf
His question pertains to the incandescent lamp connected to terminals 2 & 5 of the starter cross feed switch.
The voltage comes from the auxiliary battery, through the energized aux battery contactor, through the diode attached to the left side of the cross feed contactor, through the coil of the cross feed contactor coil, through the incandescent lamp, through the fuse to the main power bus.

I just tried to update the image link, to the marked up schematic hope it works again now. Google photos is becoming very frustrating....

I see your dwg now
 

I see your drawing from your original post now.

• Seems you said 2 amp fuse in your original post when you meant 7 amp as shown on the dwg.
• Are you baselining Z-14 rev P from http://www.aeroelectric.com/PPS/ folder called "Adobe_Architecture_Pdfs/".
• Will the alternator field CBs really be on the power buses? If not ref Z-13/8.
• I'm planning to have separate switches for start and crossfeed with no crossfeed warn lamp.
  • Edit, I changed plans from Z14 dual batt dual alt to Z101 single batt dual alt.
• I hadn't noticed the aspect of the crossfeed warn lamp powering the main bus. Seems like it would glow and give a false indication if low impedance loads were switched on on the main bus if the main, crossfeed, and aux contactors were off, off, and on as you say.
  • Edit, Bob Nuckolls learned about this issue and added a diode in series with the lamp, not in the latest dwg yet, ref "Z14_SNEAK PATH FIX.jpg" in the folder referenced in the 2nd bullet above.

Even though aux battery voltage can be measured on the main bus under the conditions described by the original poster, very little current can flow through the path that I described in post #6 above. If main bus loads are switched on, the main bus voltage will drop to near zero. So the main bus is not being powered by through the lamp. The O.P. did not mention that the lamp illuminated. It is unlikely that the lamp will illuminate under the conditions described with a diode and contactor coil and main bus loads in series with it.
The voltage measured by the O.P. is to be expected. He did not make a mistake. Z-14 does not have a design error. There is nothing to worry about.
Now, back to building.

I haven't seen the Z-14 in common use for a while. It was used for IFR panels in exp aircraft a while back (like 20 years ago), but these days we have ways to provide backup and redundancy using a simpler single main bus architecture.

That can be accomplished using a combination of EFIS with built-in battery, essential bus architecture, and/or battery backup modules (Like the IBBS).

You haven't mentioned if your RV-10 is for IFR or VFR use.

My suggestion would be to look at a simpler architecture then design in the needed level of backup for your mission. :)

What if one is using EFI with no mechanical fuel pump?