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  1. Thanks very much Mike. This is interesting.
  2. This was not part of the original question that prompted my post, but now I'm curious about this: I fully understand the ins-and-outs of equipment grounding with a standard residential 120/240 volt single phase system. Basically you're connecting a wire from the appliance case back to the neutral bus bar in the main panel. (We can skip the details.) And we can do that because the grounded conductor is both grounded and neutral. But what about a 3-phase system where the grounded conductor isn't necessarily neutral? You can't just connect a wire back to this grounded conductor if it's not neutral, right? Or how about in places that use a single phase system that isn't even a grounded system? I don't think that I understand how equipment grounding works in those cases. Any help?
  3. Jim, your reply actually helped me quite a bit to understand this better. But I might not have been clear in my original question, if so I'm sorry about that. I'm not so much interested in some random "neutral" wire running through your house. I'm interested in the grounded service entrance conductor running from the transformer in to your service panel. Would that conductor still be neutral if it wasn't grounded?
  4. Thanks for the reply. I understand that this definition was added in 2008, but nothing physically changed then, right? So if this was a neutral point in 2008 then it was a neutral point in 2007, wasn't it? But specifically to the point, doesn't it look like at the neutral point the vectorial sum of the nominal voltages from the two live phases is zero? But isn't that the case? Isn't the service entrance just a big multi-wire circuit? That seems to be the crux of the issue.
  5. Yes, but that's my point. Or my question. Or something. Grounding has nothing to do with whether or not the point X0 in my diagram is the neutral point. If that's true then the conductor coming from that X0 point is neutral whether or not the system is grounded.
  6. Why? And then let me push back a little bit. From the NEC, the definition of neutral conductor and neutral point are: Neutral Conductor: The conductor connected to the neutral point of a system that is intended to carry current under normal conditions. Neutral Point: The common point on a wye-connection in a polyphase system or midpoint on a single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct current system. FPN (fine print note): At the neutral point of the system, the vectorial sum of the nominal voltages from all other phases within the system that utilize the neutral, with respect to the neutral point, is zero potential. These definitions don't seem to require any type of grounding. At the neutral point of a standard 120/240 system, where our "neutral" conductor attaches at the transformer, isn't the vectorial sum of the voltages from the other phases equal to zero, regardless of whether or not this conductor is grounded?
  7. Would what we colloquially call the "neutral conductor" still be neutral if it wasn't grounded? Steve
  8. The best piece of report writing advice I've come across in a long time comes from this article from The Atlantic magazine from April of this year. https://www.theatlantic.com/ideas/archive/2019/04/what-makes-candidate-authentic/587857/ The article is mostly about politicians trying to sound authentic, but the ideas translate well to many different professions. Basically the idea is that the more authentic you sound the more you're believed. Quote: In a paper published last month in the Journal of Personality and Social Psychology, the academics Rachel Gershon and Rosanna K. Smith described the results of a variety of tests showing that listeners perceived speakers to be less authentic when they were told that the speakers were repeating themselves. Self-repetition, they argue, “confronts observers with the performative nature of the interaction” and challenges our assumption that “social interactions, even those that are typically performed and repeated, are assumed to be unique.” In other words, we’re wired to assume that all speech is extemporaneous. When that assumption is revealed to be false, we penalize the speaker. This is true, the authors found, even in contexts where it makes no sense to expect speakers not to repeat themselves, such as listening to a tour guide or a stand-up comic. End Quote I don't really even know how oral speech and written reports might contrast in this respect. But to me, this helps make the case that referring someone to a "qualified roofing professional" is a bad idea. Referring them to a "good roofer" is a good idea.
  9. Well, several generations of Chicagoans have disagreed. Count me among them. First, if there's a combined storm and sanitary sewer then a backwater valve can actually trap storm water and prevent it from draining out. And you can actually flood your own house by running water when the backwater valve is closed. Second, if the house drain doesn't slope much then a backwater valve can actually put too much resistance onto the sewage flow, slow it down, and cause sludge to build up. Certainly over time this can happen even with good slope. But mostly the failure mode of a backwater valve is terrible. If it fails open then it's doing nothing to help. And if it fails closed then it's trapping all the water in your house and it won't let you flush any of the toilets. An ejector doesn't prevent backups because of the check valve built into it. An ejector (or more properly, an "overhead sewer") functions because the high loop in the discharge line means that the sewer would have to back up not just to the basement floor to flood the basement, but several feet higher than that. And if the sewer is backing up that much then you've got a lot worse problem to think about than your basement. And if an ejector pump fails then you lose the ability to use things in your basement. But you can still run water upstairs and you can still use the toilets upstairs. So the failure mode is much much better with an overhead sewer than with a backwater valve.
  10. In my experience, nobody with any authority in Chicago will notice -- let alone care -- that your installation doesn't match the plans. Chicago has combined storm and sanitary sewers -- all the rain water goes out the same pipe as the poop water. So Chicago used to have terrible problems with sewer water backing up into basements when it rained hard. So to fix this problem, about 50-60 years ago builders stopped connecting any basement floor drain directly to the sewer. They all went to an ejector pit, or sometimes just a basic sump pit if it was just for laundry discharge. This has been the standard in Chicago for many decades. Even now, although Chicago has made great strides in stopping the sewer backup problem, all new construction that I see has an ejector system (an overhead sewer), regardless of whether or not the house drain can discharge by gravity to the city sewer. It's just what everyone does all the time. Even in the suburbs of Chicagoland this is pretty much all I see -- ejector systems. I saw two new construction houses in Naperville this summer and they both had ejectors. And nothing that I see prohibits this. The code that Mike Lamb posted describes what has to be done if the building drain can't discharge by gravity. But it doesn't prohibit using an ejector if you want to protect yourself from sewer backup. Probably your plumber thinks an ejector is required because it's all he sees. But I'd say that your architect is correct that a gravity drain meets any code requirement. I can imagine that some home inspector might see this when you go to sell the property and think it's weird that there's not an ejector and warn his client. But that's the only reason you might want to go the ejector route. Steve Nations
  11. I inspected a small condo today, about 800 square feet. Now my client is upset that I didn't measure the size of the unit and give her the square footage. She doesn't seem to think that she can adequately gauge the cost of the condo without knowing the square footage. This seems like a job for (if anybody) an appraiser. But her agent seems to agree with her that I should have done it. Her father is also claiming that when he's bought property the inspector measured the square footage. I've never heard of anything like this and I think it's ridiculous. Am I missing something here? Is it a common thing for home inspectors to measure the size of a property? Does anybody actually do this? Are they just confusing my role with that of the appraiser? Thanks Steve Nations
  12. I think you should use boiler plate content. Why waste your time writing the same thing over and over? I don't get that. "I saw signs of extensive mold beneath the roof sheathing at the north side of the attic." What signs did you see? The mold itself? That's not a "sign" of a problem. That's the problem. I think you should be more direct about what you saw. "There's a lot of mold on the roof sheathing in the attic." From a technical standpoint, when I see a lot of mold in the attic it's almost always caused by a particular problem and not just a general humidity issue. Mostly it's a wet crawlspace. So I tell my clients to fix the water problem in the house that's allowing the attic to become too humid. I'm confident that I can usually identify what that water problem is. I think it's great sending your client to EPA for more information about mold remediation, but isn't there a specific website that you can direct them to?
  13. Kurt, I'm with Marc here in not understanding what you mean by needing thermal mass. The concept of mass wall doesn't have much use in Chicago, where winter temperatures get low and stay low. So thermal energy is always going in only one direction -- out. A good and proper amount of insulation isn't going to perform any differently with 3/4 inch drywall or 1/2 inch drywall or even 1/64 inch drywall (assuming such a thing existed), as long as the drywall is airtight.
  14. That's one way to put it, I suppose. But the intention is to not have any induced flow in the secondary loop when that loop is supposed to be off. The intention isn't to not mess up the flow rate when that loop is active. No, I don't think that's right. The secondary loop might be quite large and need a big circulator. You'd simply size the secondary loop circulator for whatever flow and head loss requirement you have -- big or small.
  15. My bible for this stuff is "Modern Hydronic Heating" by Siegenthaler. When you have two closely spaced tees on the primary loop there is very little pressure difference between them. And that's what you want. If the tees are far apart then there's a pressure difference, and that pressure difference will induce flow between the points through the secondary loop. To minimize turbulence in the flow you want at least 8 pipe diameters of straight pipe in the primary loop before the first tee, and at least 4 pipe diameters of straight pipe after the second tee. In Kurt's picture it looks like the primary circulator is bigger than the secondary, so you won't get the short circuiting. But Siegenthaler says that if the closely spaced tees principle is done right the primary circulator doesn't need to be any bigger than the others -- just sized right.
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