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philperry9
Joined: 23 Nov 2011
Posts: 381
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 Posted: Wed Aug 27, 2014 7:58 am Post subject: Elect Ign - CB in Tailcone? |
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Howdy everyone...
I'm pulling my dedicated wire from the tailcone to the Lightspeed box installed at the panel. In the panel I have a resettable 7.5 amp CB per Lightspeed's recommendations.
However I'm a bit concerned with fire/circuit protection between the battery and the 7.5 amp CB installed 15 ft away. I'm thinking of installing a 2nd CB at the battery that is larger in size - say 10 or 15 amps.
That way, the 7.5 amp CB will provide protection for the Lightspeed, and if the line shorts somewhere in the fuselage, it will pop the tailcone CB and not turn my dedicated wire cherry red and ignite.
Have any of you taken this approach? What size CB did you install and what was your experience?
Phil
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rv10flyer
Joined: 25 Aug 2009
Posts: 364
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| Posted: Wed Aug 27, 2014 8:49 am Post subject: Re: Elect Ign - CB in Tailcone? |
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I have an "always hot" circuit ran from aux bat in the back to my panel accy plug. It is protected at aux bat fuse block with 7.5 A fuse. I think 7.5 A is the max recommended. One definitely does not want unprotected circuits other than right near our batteries and must be as short as possible and very secure.
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Wayne G. |
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rvdave
Joined: 24 Jan 2009
Posts: 191
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| Posted: Wed Aug 27, 2014 8:53 am Post subject: Re: Elect Ign - CB in Tailcone? |
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I'll be using a fusible link from the battery lug per AeroElectric Connection using one size smaller wire about 4 inches wrapped in a firesleeve to protect the wire going forward. .
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Dave Ford
Cadillac, MI |
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carl.froehlich(at)verizon
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| Posted: Wed Aug 27, 2014 9:07 am Post subject: Elect Ign - CB in Tailcone? |
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While not for a LightSpeed ignition install, I had a similar concern about running unprotected wire from the batteries to the panel. I (as most do) have accepted the nice, heavy #2 wire going between the starter solenoid and master relay(s) that is not protected by a circuit breaker. For this unlikely failure scenario however, immediate action procedure to first open both master relays for any electrical fault is the protection. The avionics do not receive any power via the master relays.
I divided my avionics into left and right vital loads. Each half being feed by a #10 wire, connecting to the appropriate left or right battery but with the option to feed either side from either battery using a total of four 30 amp DPDT relays. I installed a single 25 amp breaker at the battery after set of two relays for protecting the left and right #10 wires from direct short. Each load on the panel is protected with a separate, smaller breaker downstream of the 25 amp breaker.
So a component fault will be protected via the specific load breaker. The #10 feeder wire is protected via the 25 amp breaker. In the unlikely event of one of the 25 amp breakers popping then half the panel is still available. I went back and forth several times on not using this 25 amp breaker and just assuming the 30 amp relay that feeds each side would open if I had a hard short on one of the #10 wires. If a 25 amp breaker pops however, there is a major problem that will not be fixed in the air. On the RV-8A I did not use this 25 amp breaker but the batteries were mounted just behind the firewall so the unprotected run was short. I would not accept this as an alternative if the not using these smaller power distribution relays for the panel – just the master relay(s) as their current capacity is so much greater.
For your scenario assuming you are using #18 wire, then a 15 amp breaker at the battery should be fine.
I did wire a 5 amp breaker on the panel (one on each side) for the yet to be delivered six cylinder pMag ignition. As they provide their own power after engine start having a dedicated feed from the batter is not required nor desired. At Oshkosh Brad gave me another promise of “three months and I’m at the top of the list” so we’ll see.
Carl
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Phillip Perry
Sent: Wednesday, August 27, 2014 11:57 AM
To: rv10-list(at)matronics.com
Subject: Elect Ign - CB in Tailcone?
Howdy everyone...
I'm pulling my dedicated wire from the tailcone to the Lightspeed box installed at the panel. In the panel I have a resettable 7.5 amp CB per Lightspeed's recommendations.
However I'm a bit concerned with fire/circuit protection between the battery and the 7.5 amp CB installed 15 ft away. I'm thinking of installing a 2nd CB at the battery that is larger in size - say 10 or 15 amps.
That way, the 7.5 amp CB will provide protection for the Lightspeed, and if the line shorts somewhere in the fuselage, it will pop the tailcone CB and not turn my dedicated wire cherry red and ignite.
Have any of you taken this approach? What size CB did you install and what was your experience?
Phil
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rv10flyer
Joined: 25 Aug 2009
Posts: 364
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| Posted: Wed Aug 27, 2014 9:10 am Post subject: Re: Elect Ign - CB in Tailcone? |
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I think Bob N. uses 2 wire ga smaller for a fuse link. Double check though.
| | - The Matronics RV10-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?RV10-List |
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Wayne G. |
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rvdave
Joined: 24 Jan 2009
Posts: 191
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