A

azonic75

Well Known Member
997a147179.pdf


Haven't deviated to far from a standard z13. Will be using CB's

Very open to comments regarding where I've put various components, product selection ie. batt, alternator, starter.

Batt will be in back and I'm thinking of running ground all the way to the firewall.

To give a bit of backgound the plane will be used for cross country, some IFR (not heavy), and probaby mostly for fun.

Dual G3X system, GX pilot, GTN 650 and Garmin radios/transponder/audio panel. Duckworks lights, LED nav stobe, dual Pmags, AFP boost pump.

Otherwise a pretty spartan craft.

Havent decided on how I'm dealing with a backup attitude indication. Any ideas?

Look forward to any and all comments. I've got a thick skin

Kai

web link to pic if it doesn't imbed -

http://freepdfhosting.com/997a147179.pdf
 
azonic75 said:
997a147179.pdf

Batt will be in back and I'm thinking of running ground all the way to the firewall.

[snip]

Look forward to any and all comments. I've got a thick skin
Click to expand...

Looks very good, Kai. Here's my $0.02:

1. Ground all the way to the firewall is not necessary (and not harmful except for the added weight). Grounding the battery locally (to a longeron for example) is a good way to go.

2. The starter circuit breaker needn't be so large. I'd wager the starter contactor draws less than 5A (we could measure it) so its wire and breaker could be sized accordingly.

3. I'm not up to speed on Pmags, but don't they each require an additional switch for testing?

4. Also, I'm not familiar with your pitot heater but mine requires more than a 7.5A breaker. (Yours may not.)

5. Do youneed to have some means of disconnecting the output of the SD-8 alternator in case of electrical fire? Just asking.

6. With the rear battery, the fat wire feeding the main bus needs to cross the spar. In my '8A I'm planning to feed it from the starter contactor's hot terminal instead. This requires an additional firewall penetration of course.

6. Don't forget spike-protection diodes across the two contactors' coils.

--
Joe
 
I would consider

running the pmags off the essential bus. They don't draw much and having a couple ways to feed these very essential components seems like a good idea...:)
 
My half cent

Joe said:
1. Ground all the way to the firewall is not necessary (and not harmful except for the added weight). Grounding the battery locally (to a longeron for example) is a good way to go.

--
Joe
Click to expand...

Joe is correct. I ran #2 welding cable from the rear mounted battery forward. I considered the same for the ground, but a further review of the Aeroelectric Connection subject matter indicated a local chassis ground is quite sufficient for the battery ground. Sensitive instruments/avionics should all be grounded to a common point to avoid ground loops. I'll have a "forest of tabs" on the firewall for that.

Don
 
Question

Kai and others,

I am helping friends with their RV-10 and your schematic is very helpful.

Quick question:

How much draw can the SD8 handle for the Ess. Bus? I thought 20amps? Will it handle all the items that you have on the E Bus? If not, with everything on, will the system just draw the battery down to a level that it no longer runs individual items or will it cause other issues?

Thanks for the help.

Keith
 
RV8 Battery Compartment

Kai, I'd recommend placing the starter relay behind the firewall. The wire feeding that relay is hot any time the master relay is closed, isn't directly CB protected, and can deliver high current. Putting the starter relay behind the FW lessens the exposure the design has to shorting to ground at the FW.

Here's how it looks on my RV8. Battery compartment just behind firewall contains PC680, Master and Starter relays, B&C regulator, and firewall pass throughs:

BatteryBox01.jpg
 
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Thoughts

Here are some things to think about. I'm am thinking through all these questions as well and this is helpful discussion. So feedback from others would help me as well.

After doing some research, I think the SD8 is good for 8-10 amps (depending on RPM). At this output the components that you have on your ess. buss may draw the battery down quickly. Here are some thoughts on reducing the draw in an emergency.

1)You may consider using the TCW back up batt for the G3X and having their ess. buss CBs pulled in an emergency until the small TCW batt crapped out. This would save you 5-10 amps for other essential needs.

2) You may not need the audio panel on the ess. buss. Some audio panels have a pass through function that allows the pilot to receive and transmit even with the audio panel turned off. You would lose intercom and marker beacon functions, but the G3X would give detailed position info.

Here is some info from the PS Engineering site:
If the PMA8000B is either turned off or the power is lost, the pilot will continue to hear Unswitched audio #1 and be able to continue to hear and transmit on Com 1. When the GMA347 is turned off or if power is lost, Com 1 can still be heard and transmitted on while no unswitched audio be heard. Note: a separate pin (fail-safe warning) accommodates warnings that are directly wired to the pilot's headset in the event of a failsafe mode.

3) The SL30 Nav side could be removed from the ess. buss. GPS and vectors may be easier to use in an emergency.

4) The boost pump could be removed. Slim chance of the alternator and mechanical pump failing at the same time. Then again, you would have it if needed and it doesn't draw unless used.

On the addition side, you may need pitot heat on the ess. buss. Probably wouldn't use it, but may save you if you did.

Thoughts?

Keith
 
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Thanks

Thanks for the feedback, many good points made.


I'll likely move the pmags to the essential buss, and moving the nav component off the essential buss.

I'll keep the boost pump where it is at least for now.

Keeping more than the SD8 can supply on the ess buss is a hedge against failure of the master contactor. I can still turn any of these off manually to keep the batt from running down

Kai
 
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