shunt wiring

[Flyin Farmer]

I received my shunt and capacitor today and noticed the terminals on the shunt are marked 30A and 50MV there are not any instructions included I think the wires from my rectifier would go to the 50 MV terminal and the 30 A terminal to a fuse then to bus bar is this correct and does it make a difference? Thanks

[jrevens]

Hi Greg,

The shunt is not polarity sensitive. The 50MV & 30A markings are just referring to the electrical characteristics of the shunt - they are not identifying the specific terminals that they are near to. I hope that is clear, and helps. It doesn't matter what direction the shunt is installed.

[efwd]

LOL! Do you know how scary this all sounds? I hate electricity. I hope to Heck this Sport Air workshop in October makes this stuff make sense.

[jmodguy]

The shunt is a low resistance path that allows your ammeter to measure a voltage drop. Shunts are wired in series with the circuit you are wanting to measure.
30A is the max current rating of your shunt and 50mV is the voltage drop across the shunt. Using ohms law you can figure the resistance of the shunt by R=E/I or R=.050/30 or around .002 ohms.
Your ammeter will be wired across the shunt terminals. There should be 2 large fasteners (screws) for the aircraft load wires and 2 smaller terminals (screws) for the meter wiring. It is advisable to add a 1A fast blow fuse on each wire going to the meter, just in case...
There are 3 ways to wire a shunt.
1. output of the alternator (measures current from the alternator to aircraft and battery)
2. output of battery (past the master switch) (measures current in and out of battery)
3. before the aircraft load (measures current load of aircraft)
1 and 3 will always be positive current. 2 will show positive and negative current.
Make sure you have a way to protect the terminals of your shunt as they will have full battery current on them when the master is on. Don't ask how I know...

[efwd]

Thanks Jeff. I look at panels every chance I get in an attempt to figure out what kind of stuff I will be wiring into my system. This thing is new to me. Im wondering where I would have learned of this stuff if you hadn't explained it? The Manual doesn't mention this thing to my recolection. Obviously Kitfox can't educate us on everything as they have no idea what we are putting into our aircraft.
Eddie

[Dave S]

Maybe I am a bit of an outlier when it comes to tradition; but, I avoided the whole shunt thing by not using an ammeter. An ammeter, in my opinion, tells a person something (which way the current is flowing and how much) but it does not provide certain useful information like a voltmeter (overvoltage/undervoltage). One of the destructive failure modes, to other equipment, of a regulator is not controlling overvoltage.....a 12 volt system running at 16 V rather than 14 like it should will show a charge on an ammeter like everything is hunky-dory, but it will fry a battery. A voltmeter is a simple hot wire to the charging system and a ground. I think both gauges provide information, just that the voltmeter will be instant and maybe provide a little more direct information. But that's just me