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Electrical System Installation....school me

bcone1381

PATRON
Michigan
I am starting the installation of the electrical system in my Bearhawk Patrol build. I need help applying my knowledge into the workshop. Book Knowledge and Fabrication knowledge is two vastly different aspects. I want to learn the industry best practice to build this design.

I understand wiring diagrams, fundamentals of size, have chosen a basic wiring layout, done a load analysis, etc. using decades old electrical system classes from college days and recently Bob Nuckolls Aeroelectric Connection. I am using the black lines of Z101B diagram. http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z101B.pdf


For example, lets start with the Master Switch. The red arrow points to the master switch.
Screen Shot 2022-10-19 at 10.17.13 AM.png


When the wiring is done, I want an educated electrical guy to look and say "Wow, Nice job. This will be easy to service in the future when I am 70. This inspires confidence. It's robust. I feel safe flying in this aircraft on a backcountry trip. Very Clean, Very well done.

-Do I first decide on routes that wire bundles will travel?

-Will we plan now for easy removal of a component with a service loop so things they can be removed while sitting in the seat...easy for an old guy to fix.

-Once the routing decision is made, then should I measure the route, and start building the wiring harness on a board with ends of wires 12 inches too long on each end so they can be trimmed and wire terminations installed at the components?

I build at home alone. If this is beyond the scope of the forum, my next idea is one-on-one mentoring. I can and want to pay shop rates for this access.
 

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Some of all of the above! Every wire that has power going through it needs circuit protection with the exception of the one going to your master solenoid and starter solenoid. Those two solenoids need to be as short as possible, basically right next to your battery. You need circuit protection for the control wires for the solenoids as well.
 
Draw up your own diagrams first. And do one diagram for each circuit. Do this as you won't copy any other diagram exactly, so make each one fit YOUR installation.
- Battery/master circuit first as this will provide power to the main bus and to the start relay.
- Next do each airframe circuit. I.e., charging system, starter, lights, etc.
- If you NEED it, tie in an avionics bus to the main bus.
- Don't even think about avionics wiring at this stage.

I'm not a fan of the original Cub diagrams or some of the Aeroelectric stuff as they show switches being used in place of relays in places. I'd recommend using a Cessna diagram as a starting point for the battery and master circuits.

Once you know HOW you are going to wire it, it's easy to pencil in wire lengths and component locations.

As to circuit protection, the master relay needs to be on or next to the battery box to keep the unswitched positive cable as short as possible. And all breakers need to be attached directly to the bus bar in order to protect the entire length of that wire.

Don't share breakers.

Get to really know the wire size charts in the AC43.13.

Web
 
Got it.

There are some circuits that are noisy like P-leads and Antenna Wires. Some are fragile. The CRG-30P install manual says to keep interconnect wires away from the radio stack.

So I am concerned I will have noisy wires running all over and cause problems.

I'm installing a Trig COMM and Trig Xpndr with GPS. So do I just keep the antenna wires away from the sensitive wires? does that seem like it will be robust against problems?

If I run my Whelan LED position and LED strobe lighting wires in a bundle up the door post with the G5 magnetometer and Temp Prob will I have problems?
 
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Can sensitive wires be run near a ground bus forrest of tabs, or is this considered a noisy item that sensitive wires must avoid?
 
Forget about avionics stuff right now. Get the airframe wiring done correctly and the avionics wiring is added 'on top' of that.

Does your engine swing out for maintenance (like a PA18)? if so, make sure all wiring passes through the firewall near the hinge point.

If you are using wire that is so fragile as to require extra special care, choose different wire. I use nothing smaller than 22 gauge wire for single conductor circuits. I go as small as 24 gauge but only with multi conductor shielded wire. This is because the wire is small but still strong enough to not break from vibration and handling during normal operations. Size the wires according to the tables in the AC43 to insure you have the smallest conductor size that will still do the job.

It's a good idea to keep all airframe circuit ground wires connected to one location. When you add your avionics wiring you can then connect those grounds to a separate location to prevent noise issues.

Don't bundle P-leads with any other wires. Keep them separate as they route through the firewall.

Keep the sensor wires for the CGR30P away from the starter cable and the alternator output wire. The high current flow in those wires can make for weird readings from some sensors.

You should not have problems with the GMU 11 and temp probe with LED lighting wires. LEDs pull small amounts of current and should not create interference. That said, keep your CAN bus wires out of the bundles in tight areas like the windshield posts.

Web
 
Every wire that has power going through it needs circuit protection with the exception of the one going to your master solenoid and starter solenoid. Those two solenoids need to be as short as possible, basically right next to your battery. You need circuit protection for the control wires for the solenoids as well.

....but Bob Nuckolls does not protect the master solenoid control circuit.....interesting. Humm...

Draw up your own diagrams first. And do one diagram for each circuit. Do this as you won't copy any other diagram exactly, so make each one fit YOUR installation.
- Battery/master circuit first as this will provide power to the main bus and to the start relay.
- Next do each airframe circuit. I.e., charging system, starter, lights, etc.
- If you NEED it, tie in an avionics bus to the main bus.
- Don't even think about avionics wiring at this stage.

I'm not a fan of the original Cub diagrams or some of the Aeroelectric stuff as they show switches being used in place of relays in places. I'd recommend using a Cessna diagram as a starting point for the battery and master circuits.

Once you know HOW you are going to wire it, it's easy to pencil in wire lengths and component locations.

As to circuit protection, the master relay needs to be on or next to the battery box to keep the unswitched positive cable as short as possible. And all breakers need to be attached directly to the bus bar in order to protect the entire length of that wire.

Don't share breakers.

Get to really know the wire size charts in the AC43.13.

Web

Web, you prompted me to draw additional wiring diagrams of each circuit in the area of my boot cowl area. This is helping me to organize

Regarding an Avionics...I wont think about wiring them, butI think about an unmolested area to accommodate them. Like this is causing me to run the CAN BUS down the left window post and the lights down right.

RE Avionics Bus.bus.....I don't want one. I have the CGR-30P engine monitor, a G5, single and Xpndr. No navigation....I'm going portable. I'd like to know if the CGR-30P will brown out when I start the engine. EI says it takes 15 seconds to boot up. What is the industry experiencing? Nuckolls has an optional brownout circuit that can power an avionics but during start, but I lean towards simple.

I'll be double checking wire sizes against AC43.13.
 
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Master relays do not require breakers/fuses due to the way they are connected. The relay coil is powered by a short jumper from the 'hot' battery connection. The master switch is on the ground leg of the coil. If it was 'shorted' to airframe ground, the only problem would be the relay would not shut off with the master switch. No way to burn any wires.

The only avionics you have are the com, transponder, and intercom (?). The CGR30P and G5 are instruments and need to be connected to the main bus. If you do not use an avionics bus, make sure you switch your stuff off before starting the engine, or they will get spiked every time you release the key on start up.

You'll need to run nav/strobe wires up each side but LEDs won't interfere as they draw small amounts of current. The only coax cable you'll need to worry about is the com antenna cable. Route that up the right windshield post so that you can route the mic/audio wiring up the left side. Don't worry about the transponder coax as it will route down under the floor.

As for rebooting the CGR30P, you'll have to try it and see. Should not be a problem if you keep the battery cables and bus feed cable fairly short and keep the grounds clean. I would not do anything special unless it becomes an issue.

Web
 
How did the install end up? I have the CGR-30 as well. Not completely installed yet


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The installation, except for the CGR-30P, is 95% completed. I just have to finish an antenna installation and install the wire harness between the ELT and its panel switch. Is there anything you want to know? I voiced a concern in Post #7 wondering if the CGR-30P browns out during engine start. I got good feedback that the CGR-30P stays on during start.

As I said in post #1 I designed my system IAW Bob Nuckolls book, using almost all B&C products. The routing of my wire bundles vastly avoids running a possibly noisy circuit near a sensitive circuit. A noisy circuit could effect reading on a sensative circuit via electromagetic interference (EMI). A sensitive circuit is anything avionics related (including CRG-30P). Everything possible noisy is bundled together, like lights, Ignition, power supply and alternator regulation.

I contracted with Wireweinie to build my avionics Wire Harnesses. That saved me in more ways than just time. Using good folks in our industry to help build complex items builds relationships making life more pleasing and learning happens.

The CGR-30p will be wired when I finish the firewall forward.
 
Just recently got my CGR-30P installed. No brownout or dimming during start.


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Speaking of master relays, and starter relays, do we have anything newer and better than this 1930s tractor stuff we’re using?


These things are heavy and they take an amp or more just to keep the relay open. Surely somebody has come up with a solid-state relay that is better.

Help

Bill
 
Speaking of master relays, and starter relays, do we have anything newer and better than this 1930s tractor stuff we’re using?


These things are heavy and they take an amp or more just to keep the relay open. Surely somebody has come up with a solid-state relay that is better.

Help

Bill

iu
Light weight and low current draw.
 
I think I have a reasonably safe idea to eliminate the master relay. Using two independent start relays (one is built into the skytec 149nl starter) should provide safety in a hung starter scenario but no master relay pulling current in flight. Using a 20 amp switch breaker for the master switch.

I'm sure many will say this is a bad idea. It is certainly not traditional, but traditional is big heavy, high current draw lights, avionics and instruments. Those are not what we are dealing with any more. Seems reasonable to re-think electrical design. Gliders have done simple systems for years. My system is very similar to a glider system with a starter added.

Bob Barrows doesn't use any external solenoids or relays for his simple Bearhawk electrical system with starter.


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Speaking of master relays, and starter relays, do we have anything newer and better than this 1930s tractor stuff we’re using?


These things are heavy and they take an amp or more just to keep the relay open. Surely somebody has come up with a solid-state relay that is better.

Help

Bill

Sometimes simple is better. A typical master or start relay isn't much heavier (if at all) than a solid state relay with the heat sink necessary at high current rates. The typical master/start relays are much cheaper also. If you are running battery power only, then the operating current may be an issue, but not with a charging system. If you are running battery only AND have something like a starter installed, then consider the old school cut off switch like in Pete shows in post #15. That is both the lightest weight and least current draw (0.0 amps) of any choice. And if you need to, you can operate the lever with a linkage or cable, just use your imagination.

But remember, being able to cut off battery power AT THE BATTERY is not just a convenience, it is a safety item. This is true whether you are talking large starter cables or smaller bus feed wires. Even the old clock circuit was circuit protected right at the battery.

Web
 
Has anyone tried one of these to replace master relay for experimental? these things are used on race cars and hold up well to vibration/abuse. For a simple system with starter, it seems this for the master relay, then using the starter relay built in to the Skytec starter (with removed jumper wire) would work.?IMG_0512.jpg
 

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That switch with a battery placed under the front seat would be easy to maintain, durable, and resilient. The switch placed next to the battery would be an easy install. Downside is ergonomically high risk to forgetting to turn it off. Maybe a hardwired red beacon will mitigate that risk.
 
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