"""""Unless you do the test with the actual wiring and fault it repeatedly to adjust everything it is NOT going to work""""" """"This is a very application dependent item, not anything a lab can do for you. """" It�s like beating a dead horse.... This will be the last time I am going to try to explain this to you because I am not getting it through to you. I guess square D, engineering firms and hospitals do this kind of thing for fun and like to spend 7, 10 or 20K on things that don't work. You are only talking in opinion. Please provide your comments with some articles that a selective coordination study is bogus from a reputable source? You say you have seen all these issues but provide not details as to the specs or conditions it was under. It�s almost an insult and as if you�re saying the engineer who performs these studies is performing a job that serves no purpose. What else are you stating that can't be duplicated at a test site???? You can get the resistance of the wire, the temp, weather conditions, motor torques, load, time ran, splice types, terminations, age etc. During the study the engineer should get plans that show your entire setup. If there is something odd then they will review that and take it further into consideration. If someone doesn't do a spice correctly that is an incorrect installation, but if you take into account the available AIC at the site and spec your breaker correctly it will open without damage. The amount of time and calcs is why it cost thousands and thousands of dollars. Let�s take one common sense note, if it�s BS then why does the code require it in certain instances? Once again the study will take into effect the amount of available current and if done correctly will match the equipment to this. You say that a lab can't duplicate the field conditions???. Some labs test some of their gear at 200% in some instances. Take a look at MGE gear and see what they do upon testing/commissioning. So if you are in the field and a splice fails or a phase to phase short and the breaker blows off the wall or does something off normal then you better start looking at who designed it or setup the settings, because in MOST (not all) cases it wasn't correctly installed to handle the fault. Please before you go any further please read the link I added. It is an example of a study and it is from cooper/bussman. Look at page 1 number two on "SHORT CIRCUIT STUDY" I do hope you understand this better and that this helps clear things up for you. """"""Ever seen conductors move under fault current? You should see power lines jumps. """"" I have a lot of experience in high voltage and yes the air can become a conductor. Where are you going with this? Here is a link that might be useful: READ THIS LINK! Example of a study and what it includes

Will a circuit toner signal be attenuated by a transformer? If so, would turning off the power and attaching the toner to the doorbell leads help locate the transformer? Before ripping into any drywall, why not check all accessible junction boxes first? Often (not always), the transformer is not given its own box and just attached to a box that is close to the door switch-bell line. That box should still be accessible and you should be able to tell the one that has the transformer by looking from inside the box. BTW, this is the exact reason that before drywall is installed, I take extensive pictures including closeups of any junction box. Each picture covers around a 4' x 10' section, with closeups being as close in as possible to have the junction box (and incoming wires) fill the field of view.

The house is a small (1100sf) single story "all electric" ranch style vacation home built in 1970. It has baseboard electric heat, electric hot water heater and an electric stove. The panel box is an ITE brand with a 200 amp main breaker. The wiring in the house is copper. There is 12 -15 breakers in the box. They are all pushmatic style. Many of them are 240V because of the electric baseboard heater circuits. What concerned me about the humming noise is I don't remember hearing it when the electric hot water heater was wired directly. I only noticed it after I installed the clock timer switch in the circuit. It may have been there before and I just didn't hear it. I also don't hear humming coming from any of the other breakers. That's what made me wonder if I should replace this breaker or if the time clock had anything to do with the noise.

not to shoot down the transformer idea making the noise, but is your furnace by chance electric? I myself have an electric furnace in one of my houses that makes a buzzing noise. It comes from one of the double pole breakers in the furnace unit. Some breakers just make a buzzing noise. I haven't tired replacing the breaker because I don't care that much since the noise isn't that loud and there's no harm from it buzzing at all.