X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rg4.comporium.net ([208.104.2.24] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTPS id 2571556 for flyrotary@lancaironline.net; Fri, 07 Dec 2007 18:26:56 -0500 Received-SPF: pass receiver=logan.com; client-ip=208.104.2.24; envelope-from=Jewen@comporium.net Received: from 208-104-81-95.lnhe.2wcm.comporium.net (HELO engineer1) ([208.104.81.95]) by rg4.comporium.net (MOS 3.8.4-GA FastPath queued) with SMTP id AHJ74607; Fri, 07 Dec 2007 18:26:18 -0500 (EST) Message-ID: <005c01c83928$5cc52c40$6505a8c0@cooleygroup.local> From: "Joe Ewen" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: circuit breakers Date: Fri, 7 Dec 2007 18:24:46 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0059_01C838FE.71CF9FA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Junkmail-Status: score=10/70, host=rg4.comporium.net X-Junkmail-SD-Raw: score=unknown, refid=str=0001.0A090202.4759D5E1.0115,ss=1,fgs=0, ip=208.104.81.95, so=2007-03-13 10:31:19, dmn=5.4.3/2007-11-16 This is a multi-part message in MIME format. ------=_NextPart_000_0059_01C838FE.71CF9FA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable When referring to electrical circuit protection, there are 2 type of = protection: overload and short circuit. With overload protection the = overload protection device can be at either end or anywhere in between. = Since the overload device monitors the current in a conductor and the = current will be the same at either end, it will work anywhere in the = conductor by opening the circuit. Short circuit protection needs to be = closer to the source end of the wire being protected. =20 An example of placing the overload device near the 'bus' would be the = main breaker in a residential electrical service. The main breaker is = located at the distribution bus in the cb panel and serves to protect = both the bus bars in the panel as well as the feed conductors bringing = power from the pole which can be a couple of hundred feet away. =20 I am not suggesting that anyone not put in effective short circuit = protection if they feel it is necessary, just pointing out that overload = protection does not need to be located at the source. Joe ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Friday, December 07, 2007 9:26 AM Subject: [FlyRotary] Re: circuit breakers Bob; My assumption is that the circuits coming off the bus are all = protected near the bus; so putting protection on the feed wire near the = bus doesn't protect anything. But I guess the discussion doesn't mean = much without a larger context. Al G -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of bobperk90658@bellsouth.net Sent: Thursday, December 06, 2007 10:41 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: circuit breakers Sorry that I didn't make my thoughts clear. My thinking is that the = cable is just an extension of the positive terminal of the battery. If there is no possibility of the wiring shorting out to ground, (This = could be what if'this to death) you can protect for the maximum amount = of current your cable can conduct. If there is any possibility that = the cable could be shorted to ground then, yes protect at the source. I = would think that a plastic plane with the positive cable in an isolated = raceway would present itself as a good candidate for the first scenario. = A switched disconnect could be inserted at the battery and remotely and = manually opened for a fill good safety feature . In any instillation = you have a certain amount of unprotected wiring between the battery and = the buss, this only extends that length. In my mind the cable is just an extension of the positive battery = terminal, especially if the cable is sized large enough to carry the = entire load plus 100%. This may go contrary to national wiring code but = if you want control of the operation from the pilot seat then this is = what is needed. Bob Perkinson Bob Perkinson -------------- Original message from "Al Gietzen" = : --------------=20 If you want to protect the wiring from the battery to the buss place = a fuse or CB close to the buss. =20 Bob Perkinson Bob;=20 Not sure I understand that. The protection of the wire should be = near the source, not at the far end. Al ------=_NextPart_000_0059_01C838FE.71CF9FA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
When referring to electrical circuit = protection,=20 there are 2 type of protection: overload and short circuit.  With = overload=20 protection the overload protection device can be at either end or = anywhere in=20 between. Since the overload device monitors the current in = a conductor=20 and the current will be the same at either end, it will work anywhere in = the=20 conductor by opening the circuit.   Short circuit protection = needs to=20 be closer to the source end of the wire being protected.  =
 
An example of placing the overload = device near the=20 'bus' would be the main breaker in a residential electrical = service.  The=20 main breaker is located at the distribution bus in the cb panel and = serves to=20 protect both the bus bars in the panel as well as the feed conductors = bringing=20 power from the pole which can be a couple of hundred feet away. =20
 
I am not suggesting that anyone not put = in=20 effective short circuit protection if they feel it is necessary, just = pointing=20 out that overload protection does not need to be located at the=20 source.
 
Joe
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Friday, December 07, 2007 = 9:26=20 AM
Subject: [FlyRotary] Re: = circuit=20 breakers

Bob;

 

My = assumption is=20 that the circuits coming off the bus are all protected near the bus; = so=20 putting protection on the feed wire near the bus doesn=92t protect=20 anything.  But I guess the discussion doesn=92t mean much without = a larger=20 context.

 

Al=20 G

 

-----Original=20 Message-----
From: = Rotary=20 motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of=20 bobperk90658@bellsouth.net
Sent: Thursday, December 06, = 2007 10:41=20 PM
To: Rotary = motors in=20 aircraft
Subject: = [FlyRotary]=20 Re: circuit breakers

 

 

Sorry that I didn=92t make my = thoughts=20 clear.  My thinking is that the cable is just an extension of the = positive terminal of the battery.

If there is no = possibility of the=20 wiring shorting out to ground, (This could be what if=92this to death) = you can=20 protect for the maximum amount of current your cable can=20 conduct.    If there is any possibility that = the cable=20 could be shorted to ground then, yes protect at the source.  I = would=20 think that a plastic plane with the positive cable in an isolated = raceway=20 would present itself as a good candidate for the first scenario.  = A=20 switched disconnect could be inserted at the battery and remotely and = manually=20 opened for a fill good safety feature .   In any = instillation you=20 have a certain amount of unprotected wiring between the battery and = the buss,=20 this only extends that length.

In my mind the cable is just = an extension=20 of the positive battery terminal, especially if the cable is sized = large=20 enough to carry the entire load plus 100%.  This may go contrary = to=20 national wiring code but if you want control of the operation from the = pilot=20 seat then this is what is needed.

 

Bob = Perkinson

 

Bob = Perkinson

 

-------------- Original = message from=20 "Al Gietzen" <ALVentures@cox.net>: --------------=20


If=20 you want to protect the wiring from the battery to the buss place a = fuse or=20 CB close to the buss. 

 

Bob = Perkinson

 

Bob;=20

Not=20 sure I understand that.  The protection of the wire should be = near the=20 source, not at the far end.

 

Al

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