|
I have been testing my wiring harness from the
EC2. I found a behavior that I did not expect. The manual drawing
(EC2 manual) show a single injector supply that splits at the Injector primary
and secondary disable switches. On my installation, I have 2 separate
feeder circuits, supply Primary comes from battery 1, and supply Secondary
comes from battery 2. I did this for redundancy. If I had a failure
such as a short to ground in either circuit, its related overload should trip,
but the other circuit should remain active.
While testing the injector circuits, I noticed what
I would term an abnormality. With both injector disable switches in the
enable position, I turned on the power for the primary circuit (I have LED
indicators on all circuits that annunciate power present) and the secondary
circuit also showed power present even though the power switch for the secondary
circuit was off. The same is true when the secondary circuit is engaged
and the primary is off.
Initially this led me to think I had miss wired
something in the circuit. After checking out the wiring, I found no
issues. So I took a closer look at the wiring diagram in the manual.
It turns out the power was being back feed through the injectors to the opposite
circuit. On the 20B version of the EC2, the injector control lines for
each rotors injectors are junctioned going into the EC2. For example the
Rotor 1 Primary and Secondary control lines are junctioned into a single input
point at the EC2.
I can see several situations where this may lead to
undesirable operation. For example, if the Primary circuit had a hard
short to ground, it would take out the primary circuit's overload (CB or
Fuse.) Since the primary and secondary circuits are electrically connected
on the control line, the other circuit would also trip. Another situation
that could occur is a medium to high resistance short. Current would then
flow uncontrolled through the unaffected circuit's injector to the affected
circuit's injector then to the resistance short. This could keep both
injectors on 100%. While this situation is unlikely, it seems
possible.
I believe the 13B version uses separate
control lines for each injector, so this in not likely to be an issue on the 13B
version.
It appears that isolation diodes are needed to
prevent these possible problems. Before making any changes I have to look
the circuit over more closely, as well as a call to Tracy on the next service
day. My question to the group, especially anyone with a 20B, is am I
looking at this wrong?
Thanks,
Joe
|