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ANL Current Limiter to protect 10 AWG Wire

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LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Sun May 04, 2008 4:05 am Post subject: ANL Current Limiter to protect 10 AWG Wire

I need some guidance.



I want to use 10 AWG wire from my SD-20 alternator to feed my endurance bus.

I would like to use an ANL current limiter to protect the wire.

B&C sells a 40 amp ANL and Bussman makes a 35 amp ANL (does anyone have 

a source for this 35 amp ANL)

The wire table (Fig 8-3) in the connection suggests 30 amp protection 

for 10 AWG wire.

Is 35 or 40 amp protection on this wire acceptable?

Would I be better off using a 14 AWG fusible link?

In addition in this circuit I want to use a S704-1 relay that is rated 

at 20 amps, do I need to protect the relay?  The maximum loads off the 

relay are well below the 20 amps, but if it does see excessive currents, 

how does it fail?



Larry Rosen

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Larry Rosen
#40356
N205EN (reserved)
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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 04, 2008 6:56 am Post subject: ANL Current Limiter to protect 10 AWG Wire

Larry:  

   

There are two reasons to use the fuse.  One is to protect the wire...  The other is to protect the alternator.  Putting a 35 or 40A fuse of any kind on a 20A alternator doesn’t give the alternator any protection from over draw or short circuit.  To protect the wire place the fuse (no more than 20A) as close to the alternator as is feasible.  If you want 20 A protection and think you might come across short spikes use a 20A slo-blo fuse.  

   

The relay you have chosen is rated at 20 A.   I would go with a bigger (higher capacity) relay.  If your aircraft is not certified (AB) I would check out a relay used for RV batteries.  They are usually around 30 A.  However those relays are rated to switch that current.  Each time the relay is either opened or closed under load there are little sparks that slowly eat the contactors  inside the relay.  The relay is more than able to handle 20 amps continuously.  If the relay is over driven it will melt.  

   

Noel  

   

   

--

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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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