REFLECTOR: Electrical system

Sun Jun 30 10:43:47 CDT 2013

Dave has a good point. That's why I used "weatherpack" connectors & dielectricgrease for Lots of connections in the bay and up front. 

Kurt

-----Original Message-----
From: Dave T Nelson <dtnelson at us.ibm.com>
To: reflector <reflector at tvbf.org>
Sent: Sun, Jun 30, 2013 9:40 am
Subject: Re: REFLECTOR: Electrical system

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.

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