---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 12/27/16: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:19 AM - Re: Securing Split PVC Conduit (user9253) 2. 06:44 AM - Re: Re: Securing Split PVC Conduit (Art Zemon) 3. 09:13 AM - Re: Securing Split PVC Conduit (Neal George) 4. 11:31 AM - Re: Securing Split PVC Conduit (Hal Benjamin) 5. 03:07 PM - Re: Securing Split PVC Conduit (Holger Selover-Stephan) 6. 06:25 PM - Re: A couple of questions about Fuses (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:19:26 AM PST US Subject: AeroElectric-List: Re: Securing Split PVC Conduit From: "user9253" Is conduit necessary inside of a channel? -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=464426#464426 ________________________________ Message 2 _____________________________________ Time: 06:44:14 AM PST US From: Art Zemon Subject: Re: AeroElectric-List: Re: Securing Split PVC Conduit When there are sharp things sticking into the channel, yes On Tue, Dec 27, 2016 at 8:18 AM, user9253 wrote: > > Is conduit necessary inside of a channel? -- https://CheerfulCurmudgeon.com/ *"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel* ________________________________ Message 3 _____________________________________ Time: 09:13:47 AM PST US From: Neal George Subject: Re: AeroElectric-List: Securing Split PVC Conduit A dab of RTV? Neal George Sent from my iPhone > On Dec 26, 2016, at 10:05 PM, Art Zemon wrote: > > Folks, > > I am using some split PVC conduit in my plane and two of the runs are pret ty close to vertical, about 4 feet long. Sitting in my garage, with the wire s not yet secured at the bottom, the conduit keeps trying to slide downward i n the 2 inch square channels through which it runs. I think that I ought to s ecure it somehow and wonder if you have any ideas that will keep it in place .. > > Maybe I can wrap a thin cable tie around it and get it to slip into a groo ve? > > Or maybe wrap it with silicone self-sealing tape and the put an AN742 clam p around it? > > Thanks, > -- Art Z. > > -- > https://CheerfulCurmudgeon.com/ > > "If I am not for myself, who is for me? And if I am only for myself, what a m I? And if not now, when?" Hillel ________________________________ Message 4 _____________________________________ Time: 11:31:05 AM PST US Subject: Re: AeroElectric-List: Securing Split PVC Conduit From: Hal Benjamin Hi Art, You could probably use safety wire wrapped around the split loom and hang it using tape to hold the safety wire. Hal Benjamin RV4 Sent from my iPad > On Dec 26, 2016, at 10:05 PM, Art Zemon wrote: > > Folks, > > I am using some split PVC conduit in my plane and two of the runs are pret ty close to vertical, about 4 feet long. Sitting in my garage, with the wire s not yet secured at the bottom, the conduit keeps trying to slide downward i n the 2 inch square channels through which it runs. I think that I ought to s ecure it somehow and wonder if you have any ideas that will keep it in place .. > > Maybe I can wrap a thin cable tie around it and get it to slip into a groo ve? > > Or maybe wrap it with silicone self-sealing tape and the put an AN742 clam p around it? > > Thanks, > -- Art Z. > > -- > https://CheerfulCurmudgeon.com/ > > "If I am not for myself, who is for me? And if I am only for myself, what a m I? And if not now, when?" Hillel ________________________________ Message 5 _____________________________________ Time: 03:07:01 PM PST US From: Holger Selover-Stephan Subject: Re: AeroElectric-List: Securing Split PVC Conduit I=99ve used lacing tape for that purpose in the past. So friendly to do-overs. Holger > On Dec 26, 2016, at 7:05 PM, Art Zemon wrote: > > Folks, > > I am using some split PVC conduit in my plane and two of the runs are pretty close to vertical, about 4 feet long. Sitting in my garage, with the wires not yet secured at the bottom, the conduit keeps trying to slide downward in the 2 inch square channels through which it runs. I think that I ought to secure it somehow and wonder if you have any ideas that will keep it in place. ________________________________ Message 6 _____________________________________ Time: 06:25:59 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: A couple of questions about Fuses In my fused power busses I decided to use LED blade fuses, those whose LED gets illuminated when the fuse trips. Are you anticipating replacement of fuses in flight? It happens that I have a couple of circuits which require a 1A fuse, but there are no 1A LED blade fuses. Therefore, in these circuits, either I use a normal (non-illuminated) 1A fuse, or I go for a 2A illuminated fuse. I used to sell 1 and 2A ATC fuses but never with failure annunciation. If your appliance is 'dead in the water', little lights on the fuses are of marginal convenience. What happens if I decide for the latter? Do I get less protection? Is that particular device more prone to be fried? "Less" and "more" are hard to quantify. What we do know is that legacy wire protection philosophy is based not upon wire size but the robustness of the insulation. You can purchase 22AWG wires with recommended maximum operating temperatures all over the map . . . generally no lower than 80C but some as high as 180-200C. In EVERY case, it is not the wire at-risk for failure due to effects of current flow . . . it's the INSULATION that drives the numbers on max recommended temperature rise. Wrestling with the consequences for choosing 1A vs 5A protection on a 22AWG wire is not particularly difficult. See http://tinyurl.com/zrmkoz6 That image demonstrates that loading a 22AWG wire at 20 amps does not produce a free-air temperature rise that places the Tefzel insulation at risk for failure. Now, for the second question, in a broader perspective: I have heard dozens of times that a fuse (or other protection device) is there to protect the wire and not the device at its end. Absolutely . . . However, the size (in A) of the fuse is determined by the device in use (you read in the installation manuals that "to protect this device, you should use a 3A fuse or circuit breaker"). People who write installation manuals are almost never system integrators. Frequently they are not talented writers either. The installation manuals should speak to continuous and intermittent current drain values. Intermittent values should also be quantified with a typical duration. It's up to the system integrator to supply a source of energy that is (1) not at risk for tripping its feeder protection. (2) sizing the wire such that its temperature rise does not exceed ratings for the proposed insulation. Allowances must be made for areas where the wire may traverse an elevated environmental temperature. Further consideration is made for loss of cooling the wire is bundled. (3) The final consideration evaluates potential for loss of appliance performance due to voltage drop when the run of wire is particularly long. Lear got bit in the cushy behind when they discovered an unacceptable loss of performance for a pitch trim system because motor current ran the length of the aircraft four times! While the wires were not over-heating, the voltage drop under certain conditions produced unsatisfactory trim performance. I got to design a solid state fleet retrofit trim controller. My boss was really happy with that one . . . got a big raise. He paid for my flying lessons accompanied by a generous flying budget from the rental fleet at United Beechcraft. I know that this depends on the power (W) that is used by the device when working, and that both the wire and the fuse must be sized accordingly. I also know that if we use a thinner wire, it will get very hot and eventually melt. But what about using an higher A or a lesser A fuse? What are the physics involved? The copper wire is never at-risk except conditions where ship's batteries can drive a hard-fault of hundreds if not thousands of amps. So in the photo example cited above, I COULD consider running a 20A appliance through a 22AWG feeder protected with a 30A fuse . . . as long as the feeder length wasn't so long that voltage drop becomes an issue. When selecting wires and protection, you're never wrong with the "legacy pairs" of 22AWG/5A, 20AWG/7A, 18AWG/10A, etc. etc. These are very conservative pairings. An installation manual should read something like, "Supply DC power at 11-15 volts with a continuous demand of X.X amps and a 10% duty cycle of Y.Y amps." After that, it's up to the system integrator to meet that requirement. I would never have attempted to qualify a product that begged for EXTERNAL overcurrent protection beyond that normally supplied with the recommended wire size. If you've got a 22AWG feeder to a device where 3A protection is suggested, 5A protection is not out of line. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.