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  #1  
Old 01-19-2021, 04:25 PM
KiloFoxtrot's Avatar
KiloFoxtrot KiloFoxtrot is offline
 
Join Date: Oct 2007
Location: IL
Posts: 58
Default Are all these on firewalls? Ammeter Shunt, ANL current limited, alternator fuse.

I am just now at the beginning of FWF work and I'm installing the master and starter relays. I am still learning about electrical / avionics, and will also review more in the Aeroelectric Connection this weekend. My question is probably simple to most of you guys so any quick guidance is welcomed to shorten my learning curve.

Which of these will I need if I am using a B&C alternator 60amp with an external regulator, and the PC680 battery.

Ammeter Shunt, ANL current limited, alternator fuse.

I have seen pictures of firewalls, but don't see consistency when it comes to these parts being installed on firewalls. What other electrical components will I need to allow space for in FWF planning? Is there something else I am missing. Are some guys just installing these parts behind firewall?
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  #2  
Old 01-19-2021, 04:35 PM
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RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
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Default

Quote:
Originally Posted by KiloFoxtrot View Post
I am just now at the beginning of FWF work and I'm installing the master and starter relays. I am still learning about electrical / avionics, and will also review more in the Aeroelectric Connection this weekend. My question is probably simple to most of you guys so any quick guidance is welcomed to shorten my learning curve.

Which of these will I need if I am using a B&C alternator 60amp with an external regulator, and the PC680 battery.

Ammeter Shunt, ANL current limited, alternator fuse.

I have seen pictures of firewalls, but don't see consistency when it comes to these parts being installed on firewalls. What other electrical components will I need to allow space for in FWF planning? Is there something else I am missing. Are some guys just installing these parts behind firewall?
Location depends on where everything else is.

I would try to have the ammeter shunt in the cockpit if at all possible. There will be TWO (2) wires running to the gauge to tell you current and I like to not have those two wires forward of the firewall.

The Alternator fuse / CB should be the field supply current limiter. I want that in the cockpit so I can take the alternator off line if something goes wrong.

The alternator ANL current limiter is typically on the engine side of the firewall. Again, if it is possible, I would put in in the cockpit to keep it away from the dirty mess that is typically forward of the firewall. IF it requires running the same circuit (wire) through the firewall an extra time, keep it on the dirty side of the firewall.
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  #3  
Old 01-19-2021, 04:48 PM
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Carl Froehlich Carl Froehlich is online now
 
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There is no practical need for an ammeter shunt in our modern panel airplanes. Bus voltage alone is a superb indicator of electrical system health. Ammeters are a leftover from when we did not have accurate/economical volt meters.

I did not put an ammeter in any of my three RVs, and never missed it - or having the clunky thing with big wires hanging on the firewall.

Carl
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  #4  
Old 01-19-2021, 05:38 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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A battery contactor and starter contactor need to be on the forward side of the firewall.
An ANL or similar current limiter is needed for the alternator "B" lead, but it can be located either on the
aft or forward side of the firewall depending on where you want the "B" lead to connect to the electrical
system. Like Carl said, a shunt is not needed. If you really want to monitor the current, consider
a hall effect current sensor which will eliminate 4 high current connections.
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  #5  
Old 01-19-2021, 05:52 PM
John Tierney John Tierney is offline
 
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Location: Vonore, TN
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Here's where I put mine on an RV-7A, based on others examples, and it has worked OK.
The second ANL holder is empty, for a future backup alternator if needed.
I think I got the ANL holders with covers from West Marine.
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  #6  
Old 01-19-2021, 06:28 PM
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Bruce Bruce is offline
 
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Should be on the firewall because of the § 6 inch of wire or less.
All with large gauge wire.
You can see this on the schematics .

Boomer
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  #7  
Old 01-19-2021, 07:51 PM
PilotjohnS PilotjohnS is online now
 
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Location: Southwest
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Default Just me

For me anything that goes thru the firewall has a anl fuse or fusible links prior to firewall. This is because i want the wires to fry on the firewall side and not introduce smoke in the cockpit.
I am using a shunt to measure battery charge and discharge current. I will know right away if my alternator cant keep the battery charged long before the voltage starts to drop. By the time the voltage drops, it is too late to pick a convienent alternate airport; i would need to get down right away. The current shunt allows me to set the G3x to alarm as soon as the alternator craps out ( a technical term).
Here is picture of my firewall in process of being wired.
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  #8  
Old 01-20-2021, 10:29 AM
Ralph Inkster Ralph Inkster is offline
 
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Don't forget about other systems or controls that are vying for space on the firewall. Plan now where that control cable will be routed, or fuel hose that might end up rubbing against a hot 'B' lead, or battery box mounted where its physically impossible to get a battery in & out.

On my first build, I parked a Cherokee 180 beside my project & used it as a template for doing everything FWF.
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  #9  
Old 01-20-2021, 10:37 AM
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bjdecker bjdecker is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
There is no practical need for an ammeter shunt in our modern panel airplanes. Bus voltage alone is a superb indicator of electrical system health. Ammeters are a leftover from when we did not have accurate/economical volt meters.

I did not put an ammeter in any of my three RVs, and never missed it - or having the clunky thing with big wires hanging on the firewall.

Carl
Respectfully - I like having the Ammeter shunt so I can see the state/rate of charge from alternator to battery & rest of bus.
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  #10  
Old 01-20-2021, 03:16 PM
rapid_ascent rapid_ascent is online now
 
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I have 2 of the current shunts in my system. One for the primary alternator and one for the backup alternator. I want to be able to monitor current output to determine what my load is. My view is by the time you can tell that the voltage is low you are already overloading your system in some way. How much do you need to turn off you don't really know. Or if the current is higher than normal but still in the output range of the alternator you can detect that too.

I may be old school about this but the shunts are not that big and they can be installed right next to the protection fuse so its all pretty easy. I wish they still had ammeters in cars too btw, but that's just me.
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