---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 01/15/10: 21 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:55 AM - Re: Question on best use of buttons on stick grip (Ralph E. Capen) 2. 05:16 AM - Re: ebus wire sizing (Robert L. Nuckolls, III) 3. 05:54 AM - Re: Intercom Shields (PaulR) 4. 07:43 AM - Re: Question on best use of buttons on stick grip (Fisher Paul A.) 5. 08:24 AM - Re: Question on best use of buttons on stick grip (D Fritz) 6. 09:26 AM - Re: Question on best use of buttons on stick grip (Dennis Johnson) 7. 09:59 AM - Through-panel ATO fuses (Loman) 8. 10:27 AM - Re: Through-panel ATO fuses (peter laurence) 9. 10:52 AM - Re: Through-panel ATO fuses (Matt Prather) 10. 11:24 AM - Re: Through-panel ATO fuses (a.f.rupp@att.net) 11. 12:32 PM - Re: Through-panel ATO fuses (Matt Prather) 12. 01:31 PM - 28v to 14v (JOHN TIPTON) 13. 01:44 PM - Re: Radio Noise Answer (Robert Savage) 14. 02:07 PM - Re: 28v to 14v (Stein Bruch) 15. 03:14 PM - math (Jesse Jenks) 16. 05:05 PM - Re: Radio Noise Answer (David & Elaine Lamphere) 17. 05:43 PM - Re: Re: Intercom Shields (Robert L. Nuckolls, III) 18. 05:50 PM - Re: math (Robert L. Nuckolls, III) 19. 06:06 PM - AN3115 Pitot Tube Connectors Available (Robert L. Nuckolls, III) 20. 09:06 PM - Re: math (Jesse Jenks) 21. 09:06 PM - Re: math (Jesse Jenks) ________________________________ Message 1 _____________________________________ Time: 04:55:10 AM PST US From: "Ralph E. Capen" Subject: Re: AeroElectric-List: Question on best use of buttons on stick grip I have a different grip - but similar functionality. Hat switch is for trims. Either side of the hat switch are autopilot mode (includes disconnect) and radio swap (activates the comm swap on the PMA7000MS). I use them both frequently. I previously had autopilot disconnect and mode switches on the stick - but found the radio swap more useful - especially since the autopilot mode switch also includes the disconnect function. The autopilot 'off' and mode switches are on the panel if necessary (if there's a failure inside the stick grip). Happy with my setup! Ralph -----Original Message----- >From: DeWitt Whittington >Sent: Jan 14, 2010 3:33 PM >To: aeroelectric-list@matronics.com >Subject: AeroElectric-List: Question on best use of buttons on stick grip > >Fellow Grand Rapids customers: > >We are in the midst of trying to decide what functions to assign to >the buttons on our CS-8 Aircraft Grips from Tosten Mfg. >(http://tostenmanufacturing.com/catalog/aircraft-grips/cs-8-aircraft-grip.html#). >In addition to a 4-way hat switch, this ambidextrous grip has two >face buttons, an index button and a trigger switch. > >We, of course, will use the hat switch for the elevator and aileron >trim. Initially, we thought of assigning the two face buttons (L and >R) to the cowl flap (Open and Close). The trigger switch would be the >Push To Talk and the index button "Acknowledge and turn checklist >pages" for the VP-200. > >However, after receiving suggestions from fellow Subie engine users, >it appears the cowl flap actuator does not deserve such a prominent >position on the grip and would work fine on the panel. There are >other possible uses for the two face buttons if we didn't assign them >to the cowl flap. For instance: > >1. "Swap" button to allow the pilot to switch from the current Com to >the other Com frequency. (Suggested by PS Engineering.) >2. VFR button for GTX 327 transponder (Suggested by Garmin.) >3. Remote Servo Disconnect/Pilot Controlled Steering button for our >Trio Pro Pilot. (Strongly suggested by Trio.) > >Any of you have experience of upside or downside of assigning all >these buttons? > > >Dee Whittington > > >DeWitt (Dee) Whittington >406 N Mulberry St >Richmond, VA 23220-3320 >(804) 358-4333 phone and fax >SKYPE: hilltopkid >GlaStar Sportsman 2+2 #7034, reserved N18TA >Eggenfellner E6 Subaru 3.6L with 2.01 redrive >dee.whittington@gmail.com > > ________________________________ Message 2 _____________________________________ Time: 05:16:14 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: ebus wire sizing At 02:16 PM 1/14/2010, you wrote: I'm trying to get to the point where I can actually run some wires so I feel like I'm getting something done while I continue to learn about and plan my electrical system. I read the section in AEC on wire sizing, but it leaves me feeling like I won't be able to figure this out on my own. I understand that care must be taken here, but in real life do I need to do a whole page of algebra for each wire? Is there a quick reference rule-of-thumb chart somewhere? Yes, it's in the chapter on Wire in the 'Connection . . . it's also found at: http://www.aeroelectric.com/articles/wiresize.pdf Can someone give me a best guess on wire size for a 12' e-bus alternate feed wire from my rear mounted battery considering a 6 amp max load (a guess in itself at this point)? Run a 14 AWG for this wire . . . yes, oversized but will accommodate future changes without having to pull new wire. Keeps voltage drop low too. See figure Z-32. While you're at it, how about for the battery contactor wire? Is 22awg still ok for a 12' run? yes Also, I deduced from the chart on Skytec's website that to be safe I would use 1 gauge cable for the battery-starter connection, which appears to be about 15'. Any thoughts on this? Obviously I would rather go a little smaller if possible. I plan to use welding cable. #2 is fine for all runs except those that connect to battery. Drop to #4 for these short jumpers. The last question is; can I run these 3 wires together in the same holes(fat battery, contactor, and e-bus)? don't know why not . . . Bob . . . ________________________________ Message 3 _____________________________________ Time: 05:54:26 AM PST US Subject: AeroElectric-List: Re: Intercom Shields From: "PaulR" Thanks Bob, I had already looked at the pigtail detail, but the connections didn't seem to be working that way. As long as I can stop them just short of the housing for the connector, it will be fine. Thanks -------- Paul Rose N417PR (res) RV-9A Read this topic online here: http://forums.matronics.com/viewtopic.php?p=281601#281601 ________________________________ Message 4 _____________________________________ Time: 07:43:39 AM PST US From: "Fisher Paul A." Subject: RE: AeroElectric-List: Question on best use of buttons on stick grip I too have one of these grips and I like it a lot. I've only got about 60 flight hours so far, but I'm happy with the switch selections: 4 way hat switch - as you stated, aileron and elevator trim Trigger - Push to talk Left top button - Com1/Com2 swap (function of the audio panel) Right top button - Com1 active/standby frequency swap (SL-30) Index button - Trio Autopilot and altitude hold disconnect Obviously it depends on the kind of flying you do, but these have worked ou t well for me. Paul A. Fisher RV-7A N18PF (flying since August 2009) From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectr ic-list-server@matronics.com] On Behalf Of DeWitt Whittington Sent: Thursday, January 14, 2010 14:33 Subject: AeroElectric-List: Question on best use of buttons on stick grip Fellow Grand Rapids customers: We are in the midst of trying to decide what functions to assign to the but tons on our CS-8 Aircraft Grips from Tosten Mfg. ( http://tostenmanufacturi ng.com/catalog/aircraft-grips/cs-8-aircraft-grip.html# ). In addition t o a 4-way hat switch, this ambidextrous grip has two face buttons, an index button and a trigger switch. ... snip... ________________________________ Message 5 _____________________________________ Time: 08:24:42 AM PST US From: D Fritz Subject: Re: AeroElectric-List: Question on best use of buttons on stick grip I have the same sticks in my Velocity (not flying yet) and plan to use one of them as a remote autopilot disconnect.- I've flown many military aircraft and found a remote disconnect on the stic k to be extremely useful when the glass starts to do something you'd rather it doesn't.- With the button on the stick you can both disconnect the au topilot and begin your manual correction with one action. YMMV Dan =0A=0A=0A ________________________________ Message 6 _____________________________________ Time: 09:26:29 AM PST US From: "Dennis Johnson" Subject: AeroElectric-List: RE: Question on best use of buttons on stick grip I've been flying three years with the same stick grip and I'm very happy with it. Here is how I have mine wired: Hat Switch: Elevator and aileron trim Right Switch: Radio frequency flip/flop Left Switch: Chelton audio warnings mute Index Switch: Autopilot on/off Trigger: Push to transmit on radio Some of the switches share a common ground, which reduced the versatility a little. I had to add a relay to control the Chelton mute because merely connecting a pin to ground didn't work. I bought my stick grip from CH Products and the current one from Tosten appears to be similar. A few times I've accidentally hit the frequency flip/flop switch. It would be nice if the left and right switches had ring guards to make accidental activation less likely. I certainly wouldn't want anything on those two switches if accidental activation could jeopardize safe flight. Dennis ________________________________ Message 7 _____________________________________ Time: 09:59:02 AM PST US Subject: AeroElectric-List: Through-panel ATO fuses From: "Loman" I am intent on imitating the RV12 setup where ATO fuses protrude through the panel, like this: http://www.vansaircraft.com/images/RV-12/N412RV/switch_fuse.jpg I found fuseholders that can be panel-mounted close together. I actually bought some. They cost very little and they look great. http://www.littelfuse.com/data/en/Data_Sheets/155ATOPanel.pdf I am using the separate components on the lower half of this datasheet, so that I can crimp in my own wire and be sure it is tefzel of the correct size. I can cram 19 of these into a space 1 in wide by 8 in tall, with labels alongside Two questions: A) can anybody be a devil's advocate and offer a compelling argument against this scheme? B) One downside is that the feed side of each fuse holder needs to be separately wired back to the appropriate bus. Can anybody suggest an approach to achieve this or a fitting or material from which the three buses could be made up? -------- Loman O'Byrne RV-9 builder: Emp Done, Wings Done, Fuse underway Dublin, Ireland Read this topic online here: http://forums.matronics.com/viewtopic.php?p=281655#281655 ________________________________ Message 8 _____________________________________ Time: 10:27:40 AM PST US Subject: Re: AeroElectric-List: Through-panel ATO fuses From: peter laurence Check this site. http://home.earthlink.net/~dswartzendruber/ On Fri, Jan 15, 2010 at 12:55 PM, Loman wrote: > > I am intent on imitating the RV12 setup where ATO fuses protrude through > the panel, like this: > > http://www.vansaircraft.com/images/RV-12/N412RV/switch_fuse.jpg > > I found fuseholders that can be panel-mounted close together. I actually > bought some. They cost very little and they look great. > > http://www.littelfuse.com/data/en/Data_Sheets/155ATOPanel.pdf > I am using the separate components on the lower half of this datasheet, so > that I can crimp in my own wire and be sure it is tefzel of the correct > size. > > I can cram 19 of these into a space 1 in wide by 8 in tall, with labels > alongside > > Two questions: > > A) can anybody be a devil's advocate and offer a compelling argument > against this scheme? > > B) One downside is that the feed side of each fuse holder needs to be > separately wired back to the appropriate bus. Can anybody suggest an > approach to achieve this or a fitting or material from which the three buses > could be made up? > > -------- > Loman O'Byrne > RV-9 builder: Emp Done, Wings Done, Fuse underway > Dublin, Ireland > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=281655#281655 > > ________________________________ Message 9 _____________________________________ Time: 10:52:50 AM PST US Subject: Re: AeroElectric-List: Through-panel ATO fuses From: "Matt Prather" Unrelated to your question.. Is the depicted panel through which the fuses protrude metal? It would seem that it might be quite easy to short one leg of the fuse between the (grounded?) panel and the feeder. Maybe the geometry doesn't allow it, but I would make sure that there is no way for a short to happen there. I like the look. Very slick. As has been discussed at length recently, mounting the fuses in the panel pretty much means that you also have to provide the pilot with replacement fuses, or demonstrate to the DAR that none of the fuses are critical to continued flight. It also means that should someone suffer an electrical malfunction (which might or might not be related to an opened fuse), they may spend time diagnosing the problem in flight instead of flying the airplane - increasing risk. To hijack the topic a bit further I wonder if it might be fairly easy to install a light source in (behind) the panel which would allow inspection of the fuses more easy - directly illuminating the conducting element in each fuse. No active notification, but at least you wouldn't have to pull each fuse to find the blown one. And no circuitry interaction. Regards, Matt- > > I am intent on imitating the RV12 setup where ATO fuses protrude through > the panel, like this: > > http://www.vansaircraft.com/images/RV-12/N412RV/switch_fuse.jpg > > I found fuseholders that can be panel-mounted close together. I actually > bought some. They cost very little and they look great. > > http://www.littelfuse.com/data/en/Data_Sheets/155ATOPanel.pdf > I am using the separate components on the lower half of this datasheet, so > that I can crimp in my own wire and be sure it is tefzel of the correct > size. > > I can cram 19 of these into a space 1 in wide by 8 in tall, with labels > alongside > > Two questions: > > A) can anybody be a devil's advocate and offer a compelling argument > against this scheme? > > B) One downside is that the feed side of each fuse holder needs to be > separately wired back to the appropriate bus. Can anybody suggest an > approach to achieve this or a fitting or material from which the three > buses could be made up? > > -------- > Loman O'Byrne > RV-9 builder: Emp Done, Wings Done, Fuse underway > Dublin, Ireland > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=281655#281655 > > ________________________________ Message 10 ____________________________________ Time: 11:24:21 AM PST US From: a.f.rupp@att.net Subject: Re: AeroElectric-List: Through-panel ATO fuses Use a Waytek fuse that has a LED that lights up when it blows. It looks like the picture has them installed. Al Rupp Lake Placid - ------------- Original message from "Matt Prather" : -------------- > > > As has been discussed at length recently, mounting the fuses in the panel > pretty much means that you also have to provide the pilot with replacement > fuses, or demonstrate to the DAR that none of the fuses are critical to > continued flight. It also means that should someone suffer an electrical > malfunction (which might or might not be related to an opened fuse), they > may spend time diagnosing the problem in flight instead of flying the > airplane - increasing risk. > > To hijack the topic a bit further I wonder if it might be fairly easy to > install a light source in (behind) the panel which would allow inspection > of the fuses more easy - directly illuminating the conducting element in > each fuse. No active notification, but at least you wouldn't have to pull > each fuse to find the blown one. And no circuitry interaction. > > > Regards, > > Matt- > > > > ________________________________ Message 11 ____________________________________ Time: 12:32:32 PM PST US Subject: Re: AeroElectric-List: Through-panel ATO fuses From: "Matt Prather" It's probably not a big deal, but as I said, I'm interested in not having monitoring circuitry interact with the circuit protection in any way. I admit the Wayteks appear to be pretty slick. Regards, Matt- > > > Use a Waytek fuse that has a LED that lights up when it blows. It looks > like the picture has them installed. > Al Rupp > Lake Placid > - > ------------- Original message from "Matt Prather" : > -------------- > >> > >> As has been discussed at length recently, mounting the fuses in the >> panel >> pretty much means that you also have to provide the pilot with >> replacement >> fuses, or demonstrate to the DAR that none of the fuses are critical to >> continued flight. It also means that should someone suffer an >> electrical >> malfunction (which might or might not be related to an opened fuse), >> they >> may spend time diagnosing the problem in flight instead of flying the >> airplane - increasing risk. >> >> To hijack the topic a bit further I wonder if it might be fairly easy to >> install a light source in (behind) the panel which would allow >> inspection >> of the fuses more easy - directly illuminating the conducting element in >> each fuse. No active notification, but at least you wouldn't have to >> pull >> each fuse to find the blown one. And no circuitry interaction. >> >> >> Regards, >> >> Matt- >> >> >> >> > > ________________________________ Message 12 ____________________________________ Time: 01:31:47 PM PST US Subject: AeroElectric-List: 28v to 14v From: "JOHN TIPTON" Hi Is there a simple way of operating a 28v Nav/Com radio from 14v (RV) airplane John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=281697#281697 ________________________________ Message 13 ____________________________________ Time: 01:44:35 PM PST US From: Robert Savage Subject: RE: AeroElectric-List: Radio Noise Answer In my certified airplane=2C I leave an 80 watt heater on and under the pane l in the winter when the airplane is not in use. My reason was just to kee p it a little warmer than otherwise and to help reduce any condensation tha t might occur. Maybe the same could help you. I got the heater at the har dware store and it is advertised to be used in boats and motorhomes. Bob > From: dalamphere@comcast.net > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: Radio Noise Answer > Date: Thu=2C 14 Jan 2010 16:08:24 -0500 > phere@comcast.net> > > About a month ago I requested some ideas about what could be causing my K ing > KX125 nav com to have a screeching/hi-freq whistle (in the headsets) eve ry > time I pressed the PTT button (like feed-back) - for the first 5-10min af ter > a startup - on cold mornings. After running for a while - even on re-fuel ing > stops this problem would not surface again. No-one from the group rose to > the challenge - but then again - maybe I didn't give enough data for anyo ne > to form an opinion or theory. :-) > > At first the alternator was suspected - a call to SkyTek resulted in them > sending me a filter cap to put on the output stud of the alternator to > ground. No difference. > > Then the radio's adjustment of side-tone was suspected. Decreased - no > change. > > This morning I finally tracked it down - at cold temperatures (<40) the > problem will show-up. If you take the radio out=2C pre-heat it (I put min e in > my car with the heater going) and bring it up to 70 deg or so=2C put it b ack > in and voila! No whistle at initial startup. > > This problem only showed up when the temps fell this winter. > > Just thought it might help someone else who might experience the same > problem. > > I guess you have to pre-heat radios as well as engines! :-) > > Dave > N365DL > > =========== =========== =========== =========== > > > _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. ________________________________ Message 14 ____________________________________ Time: 02:07:09 PM PST US From: "Stein Bruch" Subject: RE: AeroElectric-List: 28v to 14v You could use a 14V to 28V step-up converter...but they are kind of pricey (hundreds of $$'s). It's what we do with almost every G900X installation in 14V airplanes (as their Comm is 28V to transmit at 16W). Cheers, Stein -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of JOHN TIPTON Sent: Friday, January 15, 2010 3:26 PM Subject: AeroElectric-List: 28v to 14v Hi Is there a simple way of operating a 28v Nav/Com radio from 14v (RV) airplane John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=281697#281697 ________________________________ Message 15 ____________________________________ Time: 03:14:24 PM PST US From: Jesse Jenks Subject: AeroElectric-List: math OK=2C I wanted to at least try to understand the math for my starter fat wi re. Here's what I came up with using Bob's example of wiring a 110V 1500w h eater from page 8-7 in the AEC as a model. On the schematic from Skytec I got 200A @ 12V which is 2400w. At 10v (batte ry voltage) that will be 240A. I calculated starter resistance to be .042 O hms. The wire resistance will be .0023 Ohms for 15' of #2 wire (assuming 0 resistance from airframe ground). This gives a total circuit resistance of .0443 Ohms and a circuit current of 227.27 amps. Voltage at the starter wil l be 9.55V=2C and power at the starter will be 2=2C170.43 Watts=2C for a po wer loss of 9.6% and a Voltage drop of .45 Volts. I did the same calculatio ns for #1 wire=2C and the difference seems minor: .02V and 9.52W=2C or .6% power. So I have two questions=3B Did I do that right? If so=2C is #2 wire accepta ble=2C and what standard are we using for power loss in the starter wire? That's actually 3 questions I guess. Also=2C I realize this only addresses the power loss problem. Wire insulati on heating is the other problem=2C but I assume power loss will be the more restrictive of the two. Thanks. Jesse _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. ________________________________ Message 16 ____________________________________ Time: 05:05:00 PM PST US From: "David & Elaine Lamphere" Subject: Re: AeroElectric-List: Radio Noise Answer Thanks Bob. I'll look into that - sounds like a good idea. Dave ----- Original Message ----- From: Robert Savage To: aeroelectric-list@matronics.com Sent: Friday, January 15, 2010 4:37 PM Subject: RE: AeroElectric-List: Radio Noise Answer In my certified airplane, I leave an 80 watt heater on and under the panel in the winter when the airplane is not in use. My reason was just to keep it a little warmer than otherwise and to help reduce any condensation that might occur. Maybe the same could help you. I got the heater at the hardware store and it is advertised to be used in boats and motorhomes. Bob ________________________________ Message 17 ____________________________________ Time: 05:43:27 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Intercom Shields At 07:52 AM 1/15/2010, you wrote: > >Thanks Bob, I had already looked at the pigtail detail, but the >connections didn't seem to be working that way. As long as I can >stop them just short of the housing for the connector, it will be fine. Don't make them TOO short . . . or all the same distance outside the housing . Stagger 'em so they don't make a big lump. Bob . . . ________________________________ Message 18 ____________________________________ Time: 05:50:25 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: math At 05:05 PM 1/15/2010, you wrote: >OK, I wanted to at least try to understand the math for my starter >fat wire. Here's what I came up with using Bob's example of wiring a >110V 1500w heater from page 8-7 in the AEC as a model. >On the schematic from Skytec I got 200A @ 12V which is 2400w. At 10v >(battery voltage) that will be 240A. I calculated starter resistance >to be .042 Ohms. The wire resistance will be .0023 Ohms for 15' of >#2 wire (assuming 0 resistance from airframe ground). This gives a >total circuit resistance of .0443 Ohms and a circuit current of >227.27 amps. Voltage at the starter will be 9.55V, and power at the >starter will be 2,170.43 Watts, for a power loss of 9.6% and a >Voltage drop of .45 Volts. I did the same calculations for #1 wire, >and the difference seems minor: .02V and 9.52W, or .6% power. >So I have two questions; Did I do that right? If so, is #2 wire >acceptable, and what standard are we using for power loss in the starter wire? Don't worry about "getting it right" by calculation for cranking circuits. Temperature rise is not part of the concern for VERY light duty cycle loads . . . i.e. seconds per flight cycle. Voltage drop studies at very high currents demand that you also consider internal resistance of the battery and voltage drops across contactors. This is mostly an academic exercise unless every system drop is accounted for. 2AWG has be PLENTY big for cranking with rear mounted batteries in light airplanes for decades and hundreds of thousands of aircraft. The overall system losses due to resistances is more than you really want to contemplate . . . fortunately it's not significant in the grand scheme of things. 4AWG jumpers to batteries for ALL installations is to accommodate ease of maintenance and reduction of stresses on battery terminals. Bob . . . ________________________________ Message 19 ____________________________________ Time: 06:06:29 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: AN3115 Pitot Tube Connectors Available Packing "stuff" up for move to M.L. I find four AN3115 electrical connectors heated pitot tube. http://www.aeroelectric.com/Pictures/Connectors/AN3115_Pitot_Tube_Heater/AN3115-1.jpg These are new old stock and sell in the $55.00 range from other suppliers. I have 4 connectors to offer to members of the List at $30.00 each postage paid. Put an order in at: https://matronics.com/aeroelectric/Catalog/AECcatalog.html and put "AN3115-1 connector @ $30.00/pp" in comments box at bottom of the form. Bob . . . ________________________________ Message 20 ____________________________________ Time: 09:06:37 PM PST US From: Jesse Jenks Subject: RE: AeroElectric-List: math 2AWG has be PLENTY big for cranking with rear mounted batteries in light airplanes for decades and hundreds of thousands of aircraft. The overall system losses due to resistances is more than you really want to contemplate . . . fortunately it's not significant in the grand scheme of things. 4AWG jumpers to batteries for ALL installations is to accommodate ease of maintenance and reduction of stresses on battery terminals. Bob . . . Thanks Bob. I need to start looking in my inbox before I hit send. Jesse > _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. ________________________________ Message 21 ____________________________________ Time: 09:06:39 PM PST US From: Jesse Jenks Subject: RE: AeroElectric-List: math From: jessejenks@hotmail.com Subject: AeroElectric-List: math OK=2C I wanted to at least try to understand the math for my starter fat wi re. Here's what I came up with using Bob's example of wiring a 110V 1500w h eater from page 8-7 in the AEC as a model. On the schematic from Skytec I got 200A @ 12V which is 2400w. At 10v (batte ry voltage) that will be 240A. I calculated starter resistance to be .042 O hms. The wire resistance will be .0023 Ohms for 15' of #2 wire (assuming 0 resistance from airframe ground). This gives a total circuit resistance of .0443 Ohms and a circuit current of 227.27 amps. Voltage at the starter wil l be 9.55V=2C and power at the starter will be 2=2C170.43 Watts=2C for a po wer loss of 9.6% and a Voltage drop of .45 Volts. I did the same calculatio ns for #1 wire=2C and the difference seems minor: .02V and 9.52W=2C or .6% power. So I have two questions=3B Did I do that right? If so=2C is #2 wire accepta ble=2C and what standard are we using for power loss in the starter wire? That's actually 3 questions I guess. Also=2C I realize this only addresses the power loss problem. Wire insulati on heating is the other problem=2C but I assume power loss will be the more restrictive of the two. Thanks. Jesse Thanks Bob=2C I already see that I made some poor assumptions and omissions in my math attempt. I forgot to include the resistance of the battery=2C and I guess calculating the starter's resistance is not as simple as dividing Volts by Amps as in the case of the heater. I thought I had it figured out=2C but now it seems complicated again. Thanks for "individuals willing to share a career's worth of experience". It seems that sometimes people size the wire simply based on the Volts=2C current draw of the device=2C and the length of the wire. You give some lengthy example calculations that go deeper to include resistance of various devices in the circuit. How do i know when it's ok to "grab any wire chart and hook things up accordingly"? I hadn't noticed Z-32 before. Is that the standard for a rear battery? I hadn't considered using a relay. If the bulk of the ebus load is resistive=2C shouldn't a switch be able to handle the 10 amps that the #14 wire can cary? Wouldn't a relay just be another possible point of failure? I'll go that route if it's necessary=2C but I would rather keep it simple at this point. Ok=2C I'll use #2 wire to the starter=2C but why #4 at the battery? That seems strange. Won't that negate the benefit of the longer piece of #2? Let me guess at your answer: Is it because you're worried about fatiguing the battery terminals and the voltage drop of those short pieces of #4 is not very significant to the overall circuit=2C and the temp rise is not really an issue? Is fatigue as much of an issue with more flexible welding cable? The picture I have in my mind though is those pieces of #4 acting like a tr affic-jam to electron flow. is that incorrect? Jesse At 02:16 PM 1/14/2010=2C you wrote: I'm trying to get to the point where I can actually run some wires so I feel like I'm getting something done while I continue to learn about and plan my electrical system. I read the section in AEC on wire sizing=2C but it leaves me feeling like I won't be able to figure this out on my own. I understand that care must be taken here=2C but in real life do I need to do a whole page of algebra for each wire? Is there a quick reference rule-of-thumb chart somewhere? Yes=2C it's in the chapter on Wire in the 'Connection . . . it's also found at: http://www.aeroelectric.com/articles/wiresize.pdf Can someone give me a best guess on wire size for a 12' e-bus alternate feed wire from my rear mounted battery considering a 6 amp max load (a guess in itself at this point)? Run a 14 AWG for this wire . . . yes=2C oversized but will accommodate future changes without having to pull new wire. Keeps voltage drop low too. See figure Z-32. While you're at it=2C how about for the battery contactor wire? Is 22awg still ok for a 12' run? yes Also=2C I deduced from the chart on Skytec's website that to be safe I would use 1 gauge cable for the battery-starter connection=2C which appears to be about 15'. Any thoughts on this? Obviously I would rather go a little smaller if possible. I plan to use welding cable. #2 is fine for all runs except those that connect to battery. Drop to #4 for these short jumpers. The last question is=3B can I run these 3 wires together in the same holes(fat battery=2C contactor=2C and e-bus)? don't know why not . . . ...Bob ========= _________________________________________________________________ Your E-mail and More On-the-Go. 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