REFLECTOR: Electrical system

Sun Jun 30 10:36:59 CDT 2013

Hi Reiff,

The power and ground bus bars I'm talking about is behind the canard
bulkhead in the area behind the panel - not forward of the bulkhead and
exposed.

In general, for exposed connections, the worry wouldn't be failure due to
shorting from the water, it'd be corrosion.  In general, galvanic corrosion
should be considered, but can be easily controlled with HW store
electrician's grease.  The relays and connections that I do have on the
forward (exposed) side of my bulkhead all have a dab of that stuff (main
contactor, hydraulic pump relays, battery connections, etc.).

I've never seen galvanic corrosion on my homemade brass bus bars & the
bimetal ring connectors I've used.

I've seen the other comments re. use of two alternators, etc. I agree with
the guidance from Richard Gentil - if you've got an electrical problem
you're going to want to land and fix it anyway.  Keeping your system as
simple as possible and building your simple system with reliability in mind
makes much more sense to me than trying to add all kinds of redundancy...
which just gives Murphy more opportunities to ruin your day.  I'd think
really hard before installing a system with two alternators, two batteries,
all kinds of switching relays, lots of extra wiring... failure points...
and things to go wrong.

My two cents.

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

Dave,

Terrific advice! Thanks for all the help.

Did you cover the power buss with anything? Is there any concern of having
a "naked" power buss in the nose? I have an RG, so I'm imagining the entire
inside of the nose will get wet if I take off or land in the rain.

I really appreciate all the info!

Reiff

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Dave T Nelson
Sent: Saturday, June 29, 2013 1:12 PM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Electrical system

This is an excellent area for KISS.... Keep It SIMPLE!

In my installation, I used two connection blocks in the area behind the
instrument panel for both 12V and ground (4 total), one of each flavor on
the left and on the right.  I made them myself by soldering brass screws
into a brass plate.  I then used ring terminals on the wire ends.  The
terminals are then held tight with MS21042 nuts.  The idea is to avoid
having to have wires seeking 12V or ground from having to cross the whole
panel from the left side to the right (or vise-versa).  The ground system
should be simple - everything has only one grounding point (to avoid ground
loops).  On both power and ground, the buss bars are powered (or grounded)
via two wires for redundancy.

I used switch circuit breakers instead of switches with separate circuit
breakers (or fuses).  I wouldn't recommend that... I've had a couple of
them fail.

I used circuit breakers instead of fuses.  My reasoning was that I want to
be able to see at a glance if one had popped (hard to do with a fuse).  I
wish I'd used the type that allow you to pull the end of the circuit
breaker to switch a circuit off.

Don't buy used circuit breakers!

Use real aviation grade wire, not Radioshack junk.

I used, carefully and religiously, a wire size chart.  I've seen many, many
installations where folks use wire of way to low of a gauge (too thick and
heavy).  You'll be surprised how often you can use 20 or even 22 gauge
based on the current requirements.  Make sure the wiring chart you use is
for bundled wire, not single strand.  Make sure you use the right size
terminal for each wire.

I sized the circuit breakers for the load, not for the wire carrying
capacity.  There has been some debate on this, as Nuckolls would size the
fuse/circuit breaker for the wire, not the load.  IMHO I'm trying to
protect the expensive load (radio), and the wire will always be sized with
a much greater capacity anyway... so the wire is protected if I size the
fuse for the load.

Pay attention to wire dress... think about your major wiring lanes... try
to get the wiring to all flow into and out of a lane... which allows you to
secure a bundle instead of trying to secure individual wires.

Ensure you've got wires secured within a few inches of the connection
point.  You don't want vibration load to be taken by the connector.  It
will fail for sure.

If you are handy with a soldering iron, don't be afraid to use it - as long
as you are securing the soldered joint from vibration.

As I said, I chose ring terminals instead of spades... I want to be able to
count on a lock nut for security.  Don't by hardware store connectors -
don't!  Get good quality bimetal crimp connectors (3M makes good ones).
Use a real rachetting crimp tool, not a hardware store special.

I *hate* cable ties... no matter how carefully you cut the ends off,
they'll leave sharp edges that'll get you at some point.  I used nylon wire
tie string instead... it works great, it's easy to use, and it'll never
bite you.

The only relays in my plane are the main electrical and starter solenoids.
I know they've gotten much more reliable through the years, but I'm still
shy of using them.  I don't know where they'd do something that there isn't
an easy way to do without them.

I grew up as a ham radio operator, worked in a TV repair shop through HS,
and as a technician wiring satellites in college.  That (and my BSEE) form
my opinions on this stuff.  I enjoy pulling wire and I believe I'm good at
it.  I'm coming up on 1100 hours on my Velocity, and had 900+ hours on a
Varieze I built first - with zero wiring induced issues.

Happy to discuss if you'd like to call.

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

----- Message from Reiff Lorenz <Reiff at Lorenz.com> on Sat, 29 Jun 2013
09:55:22 -0400 -----

      To:       "reflector at tvbf.org" <             
                reflector at tvbf.org>                

 Subject:       REFLECTOR: Electrical system -     
                basic components                   

I'm starting work on the electrical system. I could use some
recommendations on what to purchase (or how to make) these items and where
you installed them:

      ·         Main bus
      ·         Main ground block
      ·         Firewall ground block
      ·         Avionics ground

I'm going to use the Vertical Power system for switching & circuit breakers
so a combination bus/CB system won't be necessary. Should I just buy some
copper bar and drill screw-holes in it? Is there a good, basic bus product
that works well? Where did you mount it and how did you protect the power
buses from accidental grounding?

Thanks!

Reiff Lorenz, Dayton, OH
Velocity XL-RG, 45% complete
Currently working on: Mounting the battery, main contactor, starter
contactor, and RG control system.

Velocity Owners and Builders Association
http://www.VelocityOwners.com
_______________________________________________
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