Alternator wiring

I'm wiring the electrical system in my Glasair 3, and would like to
know how most builders wire the alternator. It seems every diagram I
get from Bob Nuckolls shows the alternator supply wire (B) connecting
to the input side of the starter contactor. But the wiring diagrams
from B&C show the B wire going directly to the supply or main bus
through a circuit breaker of appropriate amps. The main difference I
see is with Nuckolls method, the alternator has to send it's current
through the battery contactor. Where as the B&C diagram bypasses it
and goes directly to the main bus. Which is better?

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On Feb 18, 12:08 pm, Sliker wrote:
I'm wiring the electrical system in my Glasair 3, and would like to
know how most builders wire the alternator. It seems every diagram I
get from Bob Nuckolls shows the alternator supply wire (B) connecting
to the input side of the starter contactor. But the wiring diagrams
from B&C show the B wire going directly to the supply or main bus
through a circuit breaker of appropriate amps. The main difference I
see is with Nuckolls method, the alternator has to send it's current
through the battery contactor. Where as the B&C diagram bypasses it
and goes directly to the main bus. Which is better?

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The input side of the starter contactor is connected to
the output side of the master contactor, and a heavy line goes from
that same point to feed the bus through the ammeter. Connecting the
alternator to that terminal will run all its current through the
ammeter, which you don't want. The ammeter would show a discharge even
though the battery is charging.
Run the line to the bus, through a breaker. The ammeter will
then read properly, and you will have a protected circuit.

Dan

I'm not sure I am exactly following your descriptions. However one
consideration that may have Aeroelectric Bob running the B lead
through the starter contactor, is the battery can be used as something
of a filter for any alternater noise if the current goes to the
battery then the buss, as opposed to going directly to the buss from
the alternator.

On Mon, 18 Feb 2008 17:41:38 -0800 (PST),
wrote:

On Feb 18, 12:08 pm, Sliker wrote:
I'm wiring the electrical system in my Glasair 3, and would like to
know how most builders wire the alternator. It seems every diagram I
get from Bob Nuckolls shows the alternator supply wire (B) connecting
to the input side of the starter contactor. But the wiring diagrams
from B&C show the B wire going directly to the supply or main bus
through a circuit breaker of appropriate amps. The main difference I
see is with Nuckolls method, the alternator has to send it's current
through the battery contactor. Where as the B&C diagram bypasses it
and goes directly to the main bus. Which is better?

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The input side of the starter contactor is connected to
the output side of the master contactor, and a heavy line goes from
that same point to feed the bus through the ammeter. Connecting the
alternator to that terminal will run all its current through the
ammeter, which you don't want. The ammeter would show a discharge even
though the battery is charging.
Run the line to the bus, through a breaker. The ammeter will
then read properly, and you will have a protected circuit.

Dan

That's what I was leaning towards. I don't think the noise Bob
mentions on the B lead from the alternator is all that bad. In a
composite bird, it might be a little worse than in a metal one, but I
plan to make good grounds. And I can always shield the wire with some
extra shielding. Plus, looking at Bob's wiring diagrams, they all
incorporate a main bus and an essential bus. I'm just going to use one
main bus. If it all fails, I'll get out the handheld and pump the gear
down if the battery can't handle it. His systems have a main bus,
essentail bus, hot battery bus, battery bus, and ground power bus. And
probably coming next is auto load shedding. I haven't seen some of
those items since 737 ground school. One shouldn't have to go to
ground school to check out in a Glasair 3. And spend a day on the
eletrical system alone :-) Although it would be neat to have all that
stuff just to watch people freak when describing it all.

On Mon, 18 Feb 2008 18:25:48 -0800 (PST), Doug Palmer
wrote:

I'm not sure I am exactly following your descriptions. However one
consideration that may have Aeroelectric Bob running the B lead
through the starter contactor, is the battery can be used as something
of a filter for any alternater noise if the current goes to the
battery then the buss, as opposed to going directly to the buss from
the alternator.

That's what he does it for, to reduce the noise from the B lead, from
what I gathered reading his book.
Rich

On Feb 18, 9:15 pm, Sliker wrote:

That's what he does it for, to reduce the noise from the B lead, from
what I gathered reading his book.
Rich

The output side of the master contactor, and input side of
the starter contactor, are wired together and the bus is also
connected to that same point, so it will make no difference at all in
terms of noise filtering. The only difference will be a wrong-reading
ammeter, since the ammeter is installed between the master contactor
and bus, and electron flow during discharge is from the bus, through
the ammeter, and via the contactor to the battery. Connecting the
alternator to this point will have electon flow from the bus, through
the ammeter, to the alternator via that same path, making it show a
discharge at all times when the alternator is running. I don't think
you want that. If the alternator is connected to the bus (through a
breaker), the electron flow runs from the battery (backwards, so it's
charging) to the contactor and, through the ammeter to the bus and
from there to the alternator. The ammeter properly shows a charge,
since the flow is reversed, now. Isn't that what you really want?
Scroll about halfway down this page to the diagram without the
the overvoltage sensor:
http://ronkilber.tripod.com/alternat/alternat.htm
See how the alternator is connected. And see what would
happen if it was connected instead to the contactor.

Dan

On Tue, 19 Feb 2008 09:32:59 -0800 (PST),
wrote:

On Feb 18, 9:15 pm, Sliker wrote:

That's what he does it for, to reduce the noise from the B lead, from
what I gathered reading his book.
Rich

The output side of the master contactor, and input side of
the starter contactor, are wired together and the bus is also
connected to that same point, so it will make no difference at all in
terms of noise filtering. The only difference will be a wrong-reading
ammeter, since the ammeter is installed between the master contactor
and bus, and electron flow during discharge is from the bus, through
the ammeter, and via the contactor to the battery. Connecting the
alternator to this point will have electon flow from the bus, through
the ammeter, to the alternator via that same path, making it show a
discharge at all times when the alternator is running. I don't think
you want that. If the alternator is connected to the bus (through a
breaker), the electron flow runs from the battery (backwards, so it's
charging) to the contactor and, through the ammeter to the bus and
from there to the alternator. The ammeter properly shows a charge,
since the flow is reversed, now. Isn't that what you really want?
Scroll about halfway down this page to the diagram without the
the overvoltage sensor:
http://ronkilber.tripod.com/alternat/alternat.htm
See how the alternator is connected. And see what would
happen if it was connected instead to the contactor.

Dan

That's exactly the way I want to hook it up. Although, I do remember
in reading Bob's book that with that setup he suggests hooking up the
amp meter between the batteries ground post and the ground bus to get
it to read right. But I'm just going to run the alternator wire
directly to the main bus through a breaker and use shielded wire. If
the shield does it's job, the noise should be grounded out. I even
noticed that some of the later wiring diagrams from B&C show the
alternator wire connecting to the starter contactor. So they are in
agreement with Bob on that one. But that's just one way to do it,
there are others. The wiring diagram I like best is the one in The
Sportplane builder and in Firewall forward, by Tony Bengilis. And
thank goodness in his book he shows how to wire my Bendix shower of
sparks mags. That's the only place I've found that wiring diagram.
Although, after looking at it, it's pretty simple. I had thought that
the shower of sparks mags were really modern, until I read a similar
system was installed in the Model A Ford. :-)

Rich

On Feb 19, 10:54 am, Sliker wrote:

That's exactly the way I want to hook it up. Although, I do remember
in reading Bob's book that with that setup he suggests hooking up the
amp meter between the batteries ground post and the ground bus to get
it to read right.

If you put the ammeter between the battery's ground post and
ground, you'd have all the starter current running through it. It
would smoke pretty good. Starters draw hundreds of amps. Grounding the
starter separately would be pretty difficult, since it's grounded to
the engine through its mount, and the engine is grounded to the
airplane as a return path for both the starter and alternator, which
is also firmly grounded to the engine through its mount. The
alternator, though, should have a separate ground wire to keep noise
to a minimum.

Dan

On Tue, 19 Feb 2008 11:14:03 -0800 (PST),
wrote:

On Feb 19, 10:54 am, Sliker wrote:

That's exactly the way I want to hook it up. Although, I do remember
in reading Bob's book that with that setup he suggests hooking up the
amp meter between the batteries ground post and the ground bus to get
it to read right.

If you put the ammeter between the battery's ground post and
ground, you'd have all the starter current running through it. It
would smoke pretty good. Starters draw hundreds of amps. Grounding the
starter separately would be pretty difficult, since it's grounded to
the engine through its mount, and the engine is grounded to the
airplane as a return path for both the starter and alternator, which
is also firmly grounded to the engine through its mount. The
alternator, though, should have a separate ground wire to keep noise
to a minimum.

Dan

Sounds like another reason not to use that alternator wiring method. I
also remember reading about him mentioning using a high amperage rated
shunt for the amp meter when used in that location. The issues seem to
snowball. I have one question, if the B lead were hooked up to the
starter contactor, would reversing the wires on the amp meter make it
read correctly?

On Feb 19, 12:38 pm, Sliker wrote:

Sounds like another reason not to use that alternator wiring method. I
also remember reading about him mentioning using a high amperage rated
shunt for the amp meter when used in that location. The issues seem to
snowball. I have one question, if the B lead were hooked up to the
starter contactor, would reversing the wires on the amp meter make it
read correctly?

Nope. Now it would read "charge" all the time, even during discharge.

The ammeter is an indication of what the battery is doing.
It needs to be wired as shown so that there are two directions of
electron flow so you know whether the alternator is managing to keep
up or not. If the alternator's output isn't wired to the bus itself
rather than the contactor, you'll have no idea if it's working
properly. The ammeter won't be able to tell you anything worthwhile.

Dan