>>> I rather expect it to improve the stability of my engine instruments
>>> when this earth is properly installed ! 12 or 14 amps through 22AWG
>>> will have heated it up a LOT ! And increased its resistance (I think)
>>
>> Richard,
>>
>> Please let us know if the heavier earth wire does in fact improve the
>> stability of your engine instruments. It is from things like this that
>> we learn. I suspect this might be a good example of a ground loop
>> situation but with my limited knowledge ......
>
> Folks, we don't use #22 wire to carry up to 20 A; it will get hot to the
> point of insulation failure. But nor can there be any ground loop if
> no device's ground wire is connected at the regulator. Nor does the gauge
> of the wire have any appreciable effect on RFI or EFI issues.
>
> Regards,
> Fred F.
"Folks, we don't use #22 wire to carry up to 20 A"
Exactly so - IF we know the wire is to carry 20A. My point was that NOWHERE
is the capacity required for this wire mentioned. It is just shown as an
earth the same as the earth on the starter solenoid (which takes maybe 1A
for a very short time).
To honest it should melt as act as a fusible link at 20 A ! (See
AeroElectric Bob's book - he suggests using a wire numerically 4 larger to
act as a fusible link to protect any one cable). I am surprised my 22AWG
wire didn't burn out if the full 19A from the alternator at full charging
rate ran through it. However it would have got hot, and increased its
resistance and probably reduced the current in it.
It could however explain how, when the engine is warm and idling the oil
pressure is shown as 3 bar, and then if you rev up the engine the gauge
shows only 2.5 bar !
These gauges are not very accurate, what they show (or what you want them to
show) is a steady reading - any change (especially in flight) needs to be
investigated.
I have made up the 12AWG cable to replace the existing cable. I will report
back after I have fitted and flown it.
Ground loops are something completely different !
Richard
Richard F.W. Holder 01279 842804 (POTS)
Bell House, Bell Lane, 01279 842942 (fax)
Widford, Ware, Herts, 07860 367423 (mobile)
SG12 8SH email : rholder@avnet.co.uk
Europa Classic Tri-gear : G-OWWW, EGSG (Stapleford)
PA-28-181 : Piper Archer : G-JANA, EGSG (Stapleford)
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