Return-Path: Received: from spdmgaab.compuserve.com ([149.174.206.135]) by ns1.olsusa.com (Post.Office MTA v3.5.3 release 223 ID# 0-64832U3500L350S0V35) with ESMTP id com for ; Sun, 23 Jul 2000 11:02:11 -0400 Received: (from mailgate@localhost) by spdmgaab.compuserve.com (8.9.3/8.9.3/SUN-1.9) id LAA02889; Sun, 23 Jul 2000 11:08:30 -0400 (EDT) Date: Sun, 23 Jul 2000 11:08:04 -0400 From: James Frantz Subject: Essential bus Sender: James Frantz To: "Neal Garvin" , Marve Kay Message-ID: <200007231108_MC2-AD2B-B82B@compuserve.com> X-Mailing-List: lancair.list@olsusa.com Reply-To: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> >Hamid mentions in a post to the Lancair List tonight that all relays should have diodes protecting them. In the main/essential bus system that we both have in our airplanes that use the small relay for the essential bus, did you use any diodes with the essential bus relay?< Yes, I used transorbs on many of the relays that I considered critical. Hamid is correct that relays will weld shut thus the reason to carefully size them. Too big and the contact will not self clean, too small and they eventually weld shut. Transorbs help prevent the contact damage and welding as the relays are opened especially when the relay is used to turn off inductive loads. >Did you wire your relay so that the essential bus can be powered via a rocker switch with the relay coil unenergized? (i.e. if the relay fails in the NC/unenergized position, the essential bus gets power by turning on a switch).< I could not find a small double throw mechanical switch that would handle the current required for the essential bus and match the looks of my other switches. So, I used pretty switch that activates a properly rated relay. The essential bus is normally powered by the radio bus. If power to the radio bus is interrupted either by failure of any number of parts or by me turning off the radio bus switch the essential bus is not powered. To get power to the essential bus, I have to switch the emergency bus switch on which activates a relay and the essential bus is powered directly from the battery without going through the master relay. A big part of the essential bus is that it can get its power directly from the battery without any parts inbetween and can be isolated from all the other buses should there be a fault on any of them. In an emergency, the essential bus should be able to get power without the master relay on. I check this prior to every IFR departure. For example, you have electrical smoke in flight and you turn off the master switch which solves the smoke problem. Do you have enough to keep flying IFR? Maybe but difficult without an essential bus that meets the above criteria. I'll submit the electrical pictorial schematic for my Lancair to Marve for inclusion in the LNN. I tried to incorporate all the best from the AeroElectric publication and my own experience for an IFR X-country machine. Jim Frantz >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>