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battery contactor vs starter contactor wiring

 
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stephencliverichards(at)g
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PostPosted: Sat Oct 08, 2016 11:02 am    Post subject: battery contactor vs starter contactor wiring Reply with quote
I would say for safety if starter solenoid was switched on negative side any grounding fault would energies solenoid with positive switching a ground would blow fuse a connection to another positive less likely.
With battery solenoid if switched positive it would require a fused positive supply from battery to switch to solenoid, any ground fault would blow fuse and de energise solenoid, with negative switching any ground fault will retain solenoid, if on switched side it would energise solenoid but this should not cause any danger unless you happened to have crashed.
Clive

From: Ken Ryan (keninalaska(at)gmail.com)
Sent: ‎08/‎10/‎2016 19:13
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: battery contactor vs starter contactor wiring
Reviewing 13/8 I notice that the battery contactor jumps power from the big terminal and then switches the coil ground, but the starter contactor switches coil positive. Why do it differently on one than the other?

Ken

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ceengland7(at)gmail.com
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PostPosted: Tue Oct 11, 2016 12:58 pm    Post subject: battery contactor vs starter contactor wiring Reply with quote
IIRC, the mstr technique saves a return wire (local gnd for switch on the 'ground' side of the coil).

The start contactor typically has one side of the coil grounded inside (2nd small terminal goes high when start is activated) , so requires switching the hot side.
Can't swear to it, but there may be a writeup about it in 'the book'.
Charlie


-------- Original message --------
From: Kent or Jackie Ashton
Date:10/11/2016 3:30 PM (GMT-06:00)
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: battery contactor vs starter contactor wiring

--> AeroElectric-List message posted by: Kent or Jackie Ashton <kjashton(at)vnet.net>

The difference is the fuse.  In both of them, grounding the coil circuits actuates the solenoids but there is no fuse on the battery contactor circuit.  If you visualize the starter contactor wired the same way as the battery contactor, you would have to bring the output side of the actuating coil back to the cockpit to the starter switch and thence through a single dedicated fuse.  Wiring it the way it is allows you to use a fuse or CB in the fuse panel. 

Just a guess.
-Kent
Quote:
On Oct 11, 2016, at 2:15 PM, Ken Ryan <keninalaska(at)gmail.com> wrote:

I haven't seen any responses to this. Did I ask a dumb question?

<snip>
Reviewing 13/8 I notice that the battery contactor jumps power from the big terminal and then switches the coil ground, but the starter contactor switches coil positive. Why do it differently on one than the other?
<snip>

On Sat, Oct 8, 2016 at 9:44 AM, Ken Ryan <keninalaska(at)gmail.com> wrote:
Reviewing 13/8 I notice that the battery contactor jumps power from the big terminal and then switches the coil ground, but the starter contactor switches coil positive. Why do it differently on one than the other?

Ken



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stephencliverichards(at)g
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PostPosted: Tue Oct 11, 2016 1:13 pm    Post subject: battery contactor vs starter contactor wiring Reply with quote
Ken I did send this resending Clive

From: Stephen Richards (stephencliverichards(at)gmail.com)
Sent: ‎11/‎10/‎2016 22:07
To: Stephen Richards (stephencliverichards(at)gmail.com)
Subject: RE: AeroElectric-List: battery contactor vs starter contactor wiring


From: Stephen Richards (stephencliverichards(at)gmail.com)
Sent: ‎08/‎10/‎2016 20:01
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: RE: battery contactor vs starter contactor wiring
I would say for safety if starter solenoid was switched on negative side any grounding fault would energies solenoid with positive switching a ground would blow fuse a connection to another positive less likely.
With battery solenoid if switched positive it would require a fused positive supply from battery to switch to solenoid, any ground fault would blow fuse and de energise solenoid, with negative switching any ground fault will retain solenoid, if on switched side it would energise solenoid but this should not cause any danger unless you happened to have crashed.
Clive

From: Ken Ryan (keninalaska(at)gmail.com)
Sent: ‎08/‎10/‎2016 19:13
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: battery contactor vs starter contactor wiring
Reviewing 13/8 I notice that the battery contactor jumps power from the big terminal and then switches the coil ground, but the starter contactor switches coil positive. Why do it differently on one than the other?

Ken

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