X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 06 Nov 2007 16:28:45 -0500 Message-ID: X-Original-Return-Path: Received: from smtp0.av-mx.com ([137.118.16.56] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2457439 for lml@lancaironline.net; Mon, 05 Nov 2007 20:49:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=137.118.16.56; envelope-from=pinetownd@volcano.net Received: from DennisDell (65-174-0-234.dsl.volcano.net [65.174.0.234]) (Authenticated sender: pinetownd@volcano.net) by smtp0.av-mx.com (Postfix) with ESMTP id 209B21BF2ED for ; Mon, 5 Nov 2007 20:48:28 -0500 (EST) X-Original-Message-ID: <00ca01c82017$1fbdfae0$6501a8c0@DennisDell> From: "Dennis Johnson" X-Original-To: "Lancair Mailing List" Subject: Fuses Vs. Breakers X-Original-Date: Mon, 5 Nov 2007 17:48:25 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00C7_01C81FD4.10C43100" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_00C7_01C81FD4.10C43100 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Hi Valin, I think you might have noticed my Legacy's instrument panel at the = Fredericksburg fly-in. I have only two circuit breakers, one for the = field circuit for each alternator. The breakers are part of the = circuits to shut off the alternators if voltage exceeds limits. = Everything else is protected by fuses, nearly all are automotive "ATO" = type fuses. When I designed the panel, I tried to design the wire sizes and fuse = sizes to eliminate nuisance tripping. (I don't remember the last time I = replaced a fuse in my car.) Therefore, if a fuse blows, I will assume = that there is a fault and I won't reset it in flight. So even if I had = breakers, I wouldn't attempt to reset one if it tripped. Since I won't = replace a fuse in flight, I put the fuse blocks on the avionics shelf, = not accessible in flight. I also attempted to design my panel so that = no single failure will create an emergency, which allows me the = confidence to make the fuses not accessible in flight. =20 Fuses are cheaper, lighter, and easier to wire than circuit breakers. I = use fuseblocks like the ones here: =20 http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?27X358218#FH-12=20 They make very neat, robust wiring. By the way, what is the reason for using breakers for high current = devices like the hydraulic pump if other circuits are protected by = fuses? Fuses are working fine for me. Best, Dennis =20 ------=_NextPart_000_00C7_01C81FD4.10C43100 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

Hi Valin,

I think you might have noticed my Legacy's instrument panel at the=20 Fredericksburg fly-in. I have only two circuit breakers, one for=20 the field circuit for each alternator. The breakers are part = of the=20 circuits to shut off the alternators if voltage exceeds limits. = Everything=20 else is protected by fuses, nearly all are automotive "ATO" type = fuses.

When I designed the panel, I tried to design the wire sizes and = fuse sizes=20 to eliminate nuisance tripping. (I don't remember the last time I = replaced=20 a fuse in my car.) Therefore, if a fuse blows, I will assume that = there is=20 a fault and I won't reset it in flight. So even if I had breakers, = I=20 wouldn't attempt to reset one if it tripped. Since I won't replace = a fuse=20 in flight, I put the fuse blocks on the avionics shelf, not = accessible in=20 flight. I also attempted to design my panel so that no single = failure will=20 create an emergency, which allows me the confidence to make the fuses = not=20 accessible in flight.

Fuses are cheaper, lighter, and easier to wire than circuit = breakers. =20 I use fuseblocks like the ones here:

http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?27X358218= #FH-12

They make very neat, robust wiring.

By the way, what is the reason for using breakers for high current = devices=20 like the hydraulic pump if other circuits are protected by=20 fuses? Fuses are working fine for me.

Best,

Dennis

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