How hot does an amp shunt get?

[Jch]

I have a Dynon Flight dek 180 in my new build and I installed an amp shunt so the Dynon could read the amperage. I fabricated a thin plastic cover to protect the shunt from a loose wire short, but before I get the engine started for the first time, I wonder how warm/hot the shunt will get and whether it could melt the plastic cover. Does any one have any knowledge/experience with this? JCH.

[cgruby]

It's been my experience that a shunt shouldn't get hot at all. It's simply a very small resistor that is calibrated so that the voltage drop across it is directly proportional to the current flow through it. The voltage is then sent to a meter which is calibrated in amps as opposed to voltage.

One way to find out is hook everything up, turn on the juice and put your finger on it.

Cheers,

[Jch]

Thanks, I thought it would be easier to change now before I permanently attach the boot cowl but I will check it after firing up the 912 the first time.

[n85ae]

If it get's hot the smoke coming from other places should likely lead you to the
problem ... :)

They don't normally get hot, unless a zillion amps go through them.

Regards,
Jeff

[SilverFox1]

Some energy will be dissipated in the shunt. The actual watts (power) dissipated by the shunt can be calculated by multiplying the resistance of the shunt in OHMS times the current flowing through the shunt in AMPERES. The resistance of the shunt will be very small (less than one OHM) and the current can be read from the panel that is getting the signal (voltage) from the shunt. The shunt itself should have its resistance value on it. Hopefully the shunt has been properly sized (resistance value) for the expected load (current flow) and the power dissipated by the shunt should be less than one watt. Another thing to consider is the placement of the shunt in the circuit. If there are instructions as to where to put the shunt then follow the instructions--in any case the shunt should not see the current to the engine starter. As for your concern about heat--I like your idea of protecting the shunt from an accidental short but at the same time you need to allow for some air flow to remove any heat being generated. As a final note, remember that depending on where the shunt is located in the system the shunt and the connections to and from the shunt may see all of the charging and or battery current (except the starter) so the connections to the shunt must be able to handle this current and those connections warrant frequent inspection for tightness and any sign of heating.