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MSEE, PE -
No but you would be absolutely correct if you did especially when he recommended connecting a Capacitor across an AC Line Circuit. I would call that dangerous, stupid, and wrong. If I were a moderator, I would have banned him permanently for it. Proves he has no clue what he is talking about and a threat to public safety. Like telling kids to play with matches or a loaded gun.
Last edited by Sunking; 12-31-2018, 10:28 PM.MSEE, PEComment
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I wasn't trying to be funny. Just descriptive. No cause for celebration here. Kind of like when someone gets fired for cause. It's for the good of the organization but it's pretty ugly, especially for the supervisor of the person getting the sack who does the dirty deed. Been there, done that twice. Two worst days I ever worked.Comment
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JPM while I understand your POV, he is not on the payroll. In all likelihood you helped to prevent someone from being hurt or property damage.MSEE, PEComment
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R.U.A. I'd like to think I might have. We all do what we think we can. But that's correcting misinformation. There's not much humor in that. I'll continue to do so as I see the need and as my abilities may allow.
Not my call, but I'd have deep sixed him and a few others a long time ago as a public service, as I suspect others would have done to me. Such is the pluralistic situation we have here.Comment
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Get a copy of ASTM E73-13. Probably available at a university library or available for purchase for $48. Tells how to test truss structures for capacity. Also, you say the trusses were prebuilt. You may be able to find a mark on them that indicates the maker. If so, and if they are still in business, you can go to them and request certification. Further, the city B&S dept. should have inspection reports and other files that describe construction details. If prebuilt trusses were used, there could well be a record indicating stress and capacity loading.Comment
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First of all, E73-13 (et seq.) describes methods of static load testing of truss assemblies. It says nothing of ways of determining just what an acceptable load on a truss might be. It says nothing about load capacity of a truss or any other component for that matter - it describes acceptable methods for the testing of truss assemblies only, not limits of determining when a truss has reached its limiting load.
Note too the title of E73-13: "Standard Practice for Static Load Testing of Truss Assemblies" (underline added). The loadings for this (and most any for that matter) application are both static and dynamic, with one of the concerns here being wind loadings that may be different than the original design saw due to the added PV array.
E73-13 refers only to methods to test a truss for static loads, not dynamic either occasional or cyclical.
E73-13 will be of little help for the OP's situation unless any trusses in the structure in question are being proof tested or tested to destruction. I'm also pretty sure the OP doesn't have access to the necessary test equipment even if E73-13 was applicable. In any case, testing to destruction is an absurd proposition, and I'm not sure how a practical an in situ proof test would be.
Furthermore, E73-13 does not speak to other system components the trusses may be attached to.
The OP needs to find out from the AHJ exactly what is needed in the way of any and all documentation and possible calculation and testing to get a residential PV system approved for installation on a roof. The OP may need additional engineering services and/or review and approval from other regulating or interested parties such as a local utility. Until that information has been obtained, and a plan put in place to get such information, all this is little more than mental masturbation.Last edited by J.P.M.; 01-02-2019, 12:46 AM.Comment
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Look. I didn't come to this site to argue or to have a suggestion nit-picked to death. The poor guy is frustrated and seeking some direction. He doesn't appear to be an engineer and is seeking information at a reasonable cost. Even if you are correct in your assessment, so what? It gives him a starting point and that is what he appears to need at this point.Comment
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Please excuse the off-topic post: I am a new member and I want to make a thread about some questions I have, but I do not see any option for making new forum posts, only comments. How can I make a forum topic post?Comment
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No arguments here unless you start them.
So why did you come here ? To send someone off in an inappropriate direction that will wind up with more confusion and another dead end ?
You're a little late to the party. Someone posting to this thread just got a vacation for doing just that. Doing so can be unsafe, costly and wasteful of time and resources. And, I'd add inconsiderate and rude to those looking for opinions but lacking the information and/or experience to be able to separate accurate, appropriate and experiential knowledge from bloviating, ego driven B.S. often shot from the hip with little or no concern as to the consequences.
The information you provided is inappropriate for what's needed. E73-13 describes testing methods for trusses. Period. It is a document that describes a testing procedure.
So what you write ?!?! It gives the OP a starting point to a dead end - that's what. It's a waste of time and resources that will only cause more confusion. The suggestion is a bad one and inappropriate.
That you call my response nit picking says something about your ignorance.
ASTM E73 is not used for design of existing structures, or checking existing structures for loading suitability.
To do that, or actually before that, the OP needs to get to the AHJ and get authoritative direction from them as to what or even if they require not only structural review and confirming detail (perhaps done/sealed by a P.E, maybe not) that renders a recognized competent opinion that the structure is suitable (safe) for the application, but also any other documentation that body requires for conformance to other codes and standards in force.
For structural, such documentation may and often does require estimation of loadings, often/usually using ASCE - 7 or similar recognized standards and other methods. Then, for this application, it looks like an existing structure/design may need to be viewed/reviewed/analyzed in enough detail to determine its suitability for the estimated imposed loadings. The level of detail is often similar from one jurisdiction to another, but sometimes very different. Maybe no checking is required, maybe not. Hence the value of communication between the OP and the AHJ in a professional manner.
I've suggested a couple of times to the OP that he will do himself well to contact the AHJ and find out what's needed, in writing, presented in a way the OP can understand. I believe that will at least produce no worse a result than the OP finds himself in at this time.
I believe doing that in a persistent and professional manner will produce a better outcome than fumbling through some inappropriate ASTM spec that is not only inappropriate, but meant for use by professionals - not homeowners who are probably not - as you seem to write - engineers or designers.
The OP's situation is not unique. There are hundreds if not thousands of similar tales of woe described in these proceedings. FWIW, I don't recall any mention of E73-13 ever being offered as a help.
The formula for probability of a successful outcome in such situations is: Find out what the AHJ requires, then understand what they're telling you, then do it.
FWIW, I'd also suspect most AHJ's don't even know what E73-13 is.
Welcome to the forum of few(er) illusions.
Take what you want of the above. Scrap the rest.Last edited by J.P.M.; 01-02-2019, 06:45 PM.Comment
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Oh, I remember people putting a capacitor across the AC circuit in the EE lab. There'd be a circuit breaker for the bench. Someone would turn off the circuit breaker, put the capacitor leads into the outlet and wait for their victim. The victim would turn on the breaker and "BANG".
It was quite amusing. (yes - stupid, dangerous and wrong - but funny)
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