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  1. I suspect that this building was raised many years ago and the wood frame part was built underneath the original masonry structure. Chicago has a long history of raising buildings, even some very big ones. This city has long struggled with how high it wants its streets to be above the swamp and which direction it wants its river to flow. Also, that mortar joint is done that way so that they didn't have to grind out any old mortar. Probably the mortar was fine but not great and the homeowner wanted to tuck point, for visual reasons as much as anything. I see lots of tuck pointing that'
  2. Do any of you guys know what this is? This is a kitchen cabinet underneath the second (prep) sink in a very large kitchen in a very large house. It's a rectangular plastic piece that's screwed down at all four corners. The scalloped edge is part of a hole that goes through the cabinet bottom to the kitchen floor below. My first thought is that it's part of a system to turn on the sink with your foot that hasn't been completed. Thanks Steve
  3. This document from the U.S. Centers for Disease Control is one of my favorites regarding mold. https://www.cdc.gov/mold/faqs.htm You should take a look at it. A few highlights: So knowing the type of mold isn't really helpful. And this testing seems especially unhelpful because it didn't help at all (as far as I can tell) in pinpointing the source of the water that's causing the mold. So when you tell us how much mold was found, that's not really helpful either, because there's no standard for what's too high. Again the type of mold you may have isn't really imp
  4. This might not be so unusual. In the IBC, table 506.2 lists the allowable floor area of a building based on occupancy type and construction type. If this building is of type III construction (exterior walls built of noncombustible materials) then even without sprinklers it could have a floor area of 16,000 square feet for any type of residential occupancy. So it's not so crazy to think that back in 1974 they wouldn't have required a fire wall anywhere in this building -- if it's type III. If the exterior wall is combustible then you're down to probably a 7,000 square feet limit
  5. So if a manufacturer makes a piece of equipment that uses 14 amps (with a standard 15 amp plug) then how do they ensure that it's only used on an "individual branch circuit"? Just with instructions? That seems awfully tenuous to me. I can see how that might work for something like a clothes dryer or electric range. But I don't see how that works for anything with a standard 15 amp plug, like a hair dryer or toaster oven. The opportunities for the average person to violate the rule are just too great.
  6. I have another electrical question for everybody. NEC section 210.23(A)(1) says that for 15 and 20 amp circuits "The rating of any one cord-and-plug connected utilization equipment not fastened in place shall not exceed 80 percent of the branch-circuit ampere rating." So am I correct that this is a requirement not for the guy running wire through your house, but it's a requirement for the folks making your hair dryer. A manufacturer can't (or shouldn't) make anything with a standard plug for use on a 15-amp circuit such that the appliance is designed to use more than 12 amps. If it
  7. Thanks very much Mike. This is interesting.
  8. 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
  9. 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?
  10. 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.
  11. 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.
  12. 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 nomina
  13. Would what we colloquially call the "neutral conductor" still be neutral if it wasn't grounded? Steve
  14. 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. S
  15. 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
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