claycookiemonster
Well Known Member
The VPX manual says a shunt is optional and all information can already be read through the VPX. Any advice on the need for an Alternator Shunt in this situation?
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Alternator Shunt with VPX and Dynon Skyview?
- Thread starter claycookiemonster
- Start date
dmattmul
Well Known Member
Disclaimer
First, I have Garmin G3X and because of my EFI system the alternator is not wired into it. (Stein suggested that I don't do this) I understand not an apples-to-apples comparison or close. I can see how many amps the VPX is drawing but only when I bring up the VPX menu. (This is only done to troubleshoot an issue) VPX communicates with the EFIS in a very limited manner. (Example since the flaps are controlled by the VPX the EFIS does not know the position) Yes you get a display showing flap position on the EFIS but it is just a display. You can't set any alarming to go with it. Maybe Matt B can explain this better than me. You really need alternator output not bus usage to understand if you have a failed alternator and that requires a shunt on the B lead. I'm glad I have B lead shunts to tell me within seconds I have had an alternator failure.
Just FYI and may NOT apply to your Dynon system.
First, I have Garmin G3X and because of my EFI system the alternator is not wired into it. (Stein suggested that I don't do this) I understand not an apples-to-apples comparison or close. I can see how many amps the VPX is drawing but only when I bring up the VPX menu. (This is only done to troubleshoot an issue) VPX communicates with the EFIS in a very limited manner. (Example since the flaps are controlled by the VPX the EFIS does not know the position) Yes you get a display showing flap position on the EFIS but it is just a display. You can't set any alarming to go with it. Maybe Matt B can explain this better than me. You really need alternator output not bus usage to understand if you have a failed alternator and that requires a shunt on the B lead. I'm glad I have B lead shunts to tell me within seconds I have had an alternator failure.
Just FYI and may NOT apply to your Dynon system.
supercub1999
Member
claycookiemonster
Well Known Member
I need to take a step back...
Basic question time.
A "Shunt" is a device placed into a circuit with a known small resistance so that voltage drop across this device may be measured?
It may also operate as a fuse if overloaded, though that is not its primary function.
While many functions of shunts have been taken over by the VPX system and it's not strictly required, a shunt may still be installed if desired.
If a shunt is installed in an electrical system otherwise controlled by a VPX, that reading will be given special prominence in EFIS displays which may make it easier to monitor than the other electrical displays already in the VPX.
If, after taking all of this into consideration, a shunt is desired in a VPX system, the recommendation is to install it in position "A" as shown on page 32 of the Aircraft Wiring Guide.
Close?
Basic question time.
A "Shunt" is a device placed into a circuit with a known small resistance so that voltage drop across this device may be measured?
It may also operate as a fuse if overloaded, though that is not its primary function.
While many functions of shunts have been taken over by the VPX system and it's not strictly required, a shunt may still be installed if desired.
If a shunt is installed in an electrical system otherwise controlled by a VPX, that reading will be given special prominence in EFIS displays which may make it easier to monitor than the other electrical displays already in the VPX.
If, after taking all of this into consideration, a shunt is desired in a VPX system, the recommendation is to install it in position "A" as shown on page 32 of the Aircraft Wiring Guide.
Close?
That's exactly how I connected the Dynon supplied shunt
claycookiemonster
Well Known Member
Ok, continuing with Shunt position "A". I have a backup alternator. Both alternators go through their own ANL fuse before being joined by a copper bar which is then wired to the starter contactor (aft battery).
So, to achieve shunt position "A's" desired goal of reading alternator output no matter which alternator was operating, I'd have to position the shunt between the copper bar connecting both alternators and the starter contactor?
So, to achieve shunt position "A's" desired goal of reading alternator output no matter which alternator was operating, I'd have to position the shunt between the copper bar connecting both alternators and the starter contactor?
