Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Endurance bus switch

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

john(at)johnkeen.com.au
Guest

Posted: Sun Apr 09, 2017 2:03 am Post subject: Endurance bus switch

Hi Bob,

I’m building an RV-7 and tackling the wiring, thank you for sharing the invaluable knowledge in your book.

I’ve been grappling with whether or not to wire the endurance bus directly through the switch or use a relay. The switch is rated at 20 amps but the bus could conceivably see up to 24 amps if everything on the bus was on and drawing its maximum, eg radio transmitting, transponder transponding and GPS charging for example. 



Regards,

John.

 John Keen

0412 141 833

15 Scott St

Scone NSW Australia 2337

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Sun Apr 09, 2017 4:50 am Post subject: Re: Endurance bus switch

The deciding factor is not ampacity because either a relay or a switch will work.  Even if a switch is operated above its rating, it will not immediately self destruct.  For example, if a 20 amp switch carries 24 amps, it might only last 50,000 cycles instead of its 100,000 cycle life expectancy.  It could still outlive the life of the aircraft.

  The important consideration is remote control.  Locating a relay close to the battery allows power to be shut off close to the source.  A small switch and small wires can be used to control the relay.  A government accident investigator once made the comment that the chances of a post crash fire were greatly reduced if the battery had departed the aircraft.  Shutting off electrical power close to the source should also reduce the chances of fire following a forced landing.

  The downside of a relay is that there is one more item to fail.  If you do not install it, it can not fail.  I vote for using a relay.  Your preference may vary.

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 09, 2017 7:07 am Post subject: Endurance bus switch

At 05:01 AM 4/9/2017, you wrote:

  	  Quote: 	
		  Hi Bob,



 I’m building an RV-7 and tackling the wiring, thank you for sharing the invaluable knowledge in your book.

 I’ve been grappling with whether or not to wire the endurance bus directly through the switch or use a relay. The switch is rated at 20 amps but the bus could conceivably see up to 24 amps if everything on the bus was on and drawing its maximum, eg radio transmitting, transponder transponding and GPS charging for example. 	


   The switch 'rating' is largely irrelevant. The

   number is an engineer's guide to service life

   under tens of thousands of cycles at full load.



   Your switch won't see 1000 cycles in its lifetime

   and never under full load.



   Tell us about this 'endurance' bus . . . what

   are your design goals for battery only operations

   and what electro-whizzies are fed from this bus?

   



 

 

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

john(at)johnkeen.com.au
Guest

Posted: Mon Apr 10, 2017 4:44 am Post subject: Endurance bus switch

Thanks Bob,



My design goal for battery only operations is to be able to focus on flying the aeroplane easily to a safe landing at the nearest airfield. As the plane has conventional dual mags and a carb with engine driven fuel pump, and a traditional panel with vacuum AH and DG, I imagine wanting electrical help mainly for navigating and communicating (day VFR). 



This is my list for the endurance bus, the numbers with a ? are current draw that I’ve guesstimated until I have the correct value:



- Panel floodlights x2 (in case day VFR runs out) = 0.15

- Van’s Voltmeter = 1?

- Van’s fuel gauges x2 = 1.5? 

- Dual USB outlet (charges iPad = 0.85 and GPS = 0.5) 

- Transponder Garmin 330ES = 4

- Comm radio (has built-in intercom) Garmin GTR200 = 7.5

- Boost pump = 0.8



Total = 16.3

Better - I had some very round and generous numbers previously giving me the 24! And I’ve taken off the hour meter.



This leaves out the alternator; starting system; nav, landing and interior lights; engine instruments; turn coordinator, flaps and trim; hour meter...



Cheers,

John.

 

  	  Quote: 	
		  On 10 Apr 2017, at 01:05, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  At 05:01 AM 4/9/2017, you wrote:  	  Quote: 	
		  Hi Bob, Iâm building an RV-7 and tackling the wiring, thank you for sharing the invaluable knowledge in your book. Iâve been grappling with whether or not to wire the endurance bus directly through the switch or use a relay. The switch is rated at 20 amps but the bus could conceivably see up to 24 amps if everything on the bus was on and drawing its maximum, eg radio transmitting, transponder transponding and GPS charging for example. 	
   The switch 'rating' is largely irrelevant. The   number is an engineer's guide to service life   under tens of thousands of cycles at full load.   Your switch won't see 1000 cycles in its lifetime   and never under full load.   Tell us about this 'endurance' bus . . . what   are your design goals for battery only operations   and what electro-whizzies are fed from this bus?     

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Mon Apr 10, 2017 6:43 am Post subject: Re: Endurance bus switch

The current draw estimates are way too high.

The voltmeter and fuel gauges combined are probably less than one amp.

The Transponder is 3 amps.

The GTR 200 is probably less than 1 amp except when transmitting.

I guesstimate less than 8 amps total.

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 10, 2017 8:42 am Post subject: Endurance bus switch

At 09:43 AM 4/10/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>



 The current draw estimates are way too high.

 The voltmeter and fuel gauges combined are probably less than one amp.

 The Transponder is 3 amps.

 The GTR 200 is probably less than 1 amp except when transmitting.

 I guesstimate less than 8 amps total. 	


   Generally agree . . . transponder energy draw

   is under 1A except for very short bursts while

   replying . . . so I'll suggest your e-bus loads

   are smaller yet probably 5A or less.



   A simple toggle switch and 10A fuse protection

   for your e-bus alternate feed will be entirely

   adequate.



 

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

john(at)johnkeen.com.au
Guest

Posted: Mon Apr 10, 2017 12:43 pm Post subject: Endurance bus switch

Thanks Joe, Bob!



Cheers,

John Keen

On 11 Apr 2017, at 2:40 am, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 09:43 AM 4/10/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>



 The current draw estimates are way too high.

 The voltmeter and fuel gauges combined are probably less than one amp.

 The Transponder is 3 amps.

 The GTR 200 is probably less than 1 amp except when transmitting.

 I guesstimate less than 8 amps total. 	


   Generally agree . . . transponder energy draw

   is under 1A except for very short bursts while

   replying . . . so I'll suggest your e-bus loads

   are smaller yet probably 5A or less.



   A simple toggle switch and 10A fuse protection

   for your e-bus alternate feed will be entirely

   adequate.



 

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum