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Schematic Drawings

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stickandrudder1(at)comcas
Guest

Posted: Fri Nov 25, 2011 8:15 am Post subject: Schematic Drawings

Bob, drawing Z-12 shows the conductor from the battery contactor to the  battery bus as being a 12 AWG conductor of 6 inches length or less (rev. K â€“  04/20/05).  I understand the reason for the short conductor is for crash  safety for the always on buss.  However, Iâ€™m using panel mounted circuit  breakers for my three power busses (main, essential, battery) and so adhering to  the 6 inch specification isnâ€™t possible.  What are your thoughts of the  addition of a properly rated circuit breaker or fusible link on the engine side  of the firewall to protect the remaining conductor the length of which I  estimate will be 36 to 48 inches depending on location of the electrical  conductor firewall penetration?   By the way, my Ebus will have one  PMAG (one PMAG, and one conventional mag installation), clock, cabin lights,  fuel boost, and switched Ebus alternate feed on the battery buss.

  

 Thanks

   [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 25, 2011 7:59 pm Post subject: Schematic Drawings

At 10:11 AM 11/25/2011, you wrote:

 	  Quote: 	
		  Bob, drawing Z-12 shows the conductor from the 

battery contactor to the battery bus as being a 

12 AWG conductor of 6 inches length or less 

(rev. K – 04/20/05).  I understand the reason 

for the short conductor is for crash safety for 

the always on buss.  However, Iâ€™m using panel 

mounted circuit breakers for my three power 

busses (main, essential, battery) and so 

adhering to the 6 inch specification isnâ€™t 

possible.  What are your thoughts of the 

addition of a properly rated circuit breaker or 

fusible link on the engine side of the firewall 

to protect the remaining conductor the length of 

which I estimate will be 36 to 48 inches 

depending on location of the electrical 

conductor firewall penetration?   By the way, my 

Ebus will have one PMAG (one PMAG, and one 

conventional mag installation), clock, cabin 

lights, fuel boost, and switched Ebus alternate feed on the battery buss.


	


   If your "battery" bus is on the panel, then it's not a battery

   bus but yet another bus tasked with different loads. Its

   long feeder would be fitted with another battery contactor.



   A battery bus is always hot, drives wires that are always

   hot but protected with fast devices rated below the legacy

   crash safety design rules . . . and located AT the battery.

   Once you depart from this convention, it's some other kind of bus

   that gets treated like other fat-wire fed busses in the

   airplane.

   Bob . . .

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paul.zimmer00(at)gmail.co
Guest

Posted: Sat Nov 26, 2011 7:27 am Post subject: Schematic Drawings

I've changed my Email address that I subscribed to Matronics with, so this may screw up the continuity of the thread.  Please see below.  



On Sat, Nov 26, 2011 at 9:38 AM, Paul Zimmer <paul.zimmer00(at)gmail.com (paul.zimmer00(at)gmail.com)> wrote:

 [quote]

OK.  So my always on battery bus isn't really a battery bus, rather an always on non-battery-bus bus (a lame attempt at humor).  So what to do?   Perhaps if you would briefly discuss the reasons behind the design point for not bringing a non-switched fat-wire into the cabin would facilitate understanding.

   

From a neophyte's perspective (me), given the stated reason for not doing so being crash safety, it seems the concern is one of the fat-wire being compromised in a crash, possibly resulting in a short circuit, in a wire capable of conducting a large number of electrons simultaneously.  Not a good thing when considering all of the bad things that could happen as a result.  Is this is a fair assessment of the concern or is there more to it (you used the phrase "protected with fast devices", the meaning of which escapes me)?

   

If this is the primary design consideration, wouldn't the addition of a circuit breaker (or other device) near the battery accomplish the same thing, as long as the device was sized less than the current carrying capacty of the fat-wire?  The idea of additing another contactor or relay makes no sense if the bus is to be always on, and if it's not going to be always on, then the devices may as well be moved to either the main or essential bus as most appropriate.

   

Thanks once again for your time and insight. 

 

Paul

On Fri, Nov 25, 2011 at 10:56 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

   	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>  

 

 At 10:11 AM 11/25/2011, you wrote:

  	  Quote: 	
		   Bob, drawing Z-12 shows the conductor from the battery contactor to the battery bus as being a 12 AWG conductor of 6 inches length or less (rev. K – 04/20/05).  I understand the reason for the short conductor is for crash safety for the always on buss.  However, I’m using panel mounted circuit breakers for my three power busses (main, essential, battery) and so adhering to the 6 inch specification isn’t possible.  What are your thoughts of the addition of a properly rated circuit breaker or fusible link on the engine side of the firewall to protect the remaining conductor the length of which I estimate will be 36 to 48 inches depending on location of the electrical conductor firewall penetration?   By the way, my Ebus will have one PMAG (one PMAG, and one conventional mag installation), clock, cabin lights, fuel boost, and switched Ebus alternate feed on the battery buss.

   	
 



   If your "battery" bus is on the panel, then it's not a battery

   bus but yet another bus tasked with different loads. Its

   long feeder would be fitted with another battery contactor.

 

   A battery bus is always hot, drives wires that are always

   hot but protected with fast devices rated below the legacy

   crash safety design rules . . . and located AT the battery.

   Once you depart from this convention, it's some other kind of bus

   that gets treated like other fat-wire fed busses in the

   airplane.

 

 

   Bob . . . 



 

 

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[b]

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tomcostanza

Joined: 19 Oct 2008
Posts: 49

Posted: Sat Nov 26, 2011 8:08 am Post subject: Re: Schematic Drawings

 	  Quote: 	
		  Once you depart from this convention, it's some other kind of bus 

that gets treated like other fat-wire fed busses in the 

airplane. 	




Ditto Paul's question.  And does this mean it should be protected?  I didn't want to run 4 branch circuit wires through the firewall, so I put a small fuse panel inside the cabin, fed by a wire connected directly to the battery.  I assume this should be protected.  But Z-11 has a 6AWG wire from the battery contactor to the Main bus and shows no protection.  (I'm soo confused!)



Perhaps a review of "fat wire" protection would be in order.  Or just point us to the relevant section in The Connection. 



Thanks.

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_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project

nuckollsr

Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Mon Nov 28, 2011 11:31 pm Post subject: Re: Schematic Drawings

See paragraph 1357 and 1361 in



http://www.aeroelectric.com/Reference_Docs/FAA/Part23_electrical_A.pdf



These conventions in the certified world are generally promoted in the z-figures by suggesting that battery busses be located at the battery. Protection for always hot feeders not exceed 5A in breaker or 7A in fuse or be fitted with the functional equivalent of a pilot controlled disconnect as illustrated in . . .



http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z32K.pdf



My recommendations are based on what I know I could get certified on an T/C aircraft. Just how far afield one chooses to go in the experimental aircraft world is up to the builder.

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