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That's great! Thanks for you response. That is good information.

I just wanted to know where this was all coming from.

Per IEEE 1584, "The study must take into account all sources, including utilities, standby and power generators, and large motors—those 37 kW (50hp) and larger that contribute energy to short circuits." My understanding is that Martin Technical is considering contributions of 75hp or "greater,"...

So it sounds like they applied a safety factor to IEEE's recommendation of 50hp limit and went with 75hp. Thanks tem1234 for pointing out the standard.

I've read (at the Martin Technical website, http://www.martinarcflash.com/labeling.htm) that they do not consider Arc Flash Analysis of motors 75hp or less contribution. I cannot find any information other than their website to substantiate why or what standard they are following that would...

Your'e right Zogzog. No hard feelings. I appreciate your candor. It's not that I don't like/want to troubleshoot, but on the flip side, when production is shutdown due to downed equipment, sometimes you need to reproduce a blown fuse for those standerby lookyloos that have all the answers to...

Thanks all for the replies. I was trying to capture the event that sometimes a fuse just blows out of the blue and there are no signs of symptoms for those who are questioning the cause of the fuse blowing. It is easy for me to understand this just happens occasionally (e.g., old/faulty...

I am searching for the words, in the AEH, NEC, IEEE, etc., that give guidance that it is acceptable to replace a blown fuse once before commencing troubleshooting on the condition that the replaced fuse does not immediately blow following replacment. I am being asked to show proof of this...

Where can I get some information on good plc I/O connection practice? My question is basically whether I should be connecting my I/O's to an isolated common or should the modules be independently common of each other? The reason I am asking is because I found that the (-) output 0-10Vdc...

dpc--I absolutely agree on all accounts, but in an industrial environment I can not rely on others to be aware of my cable concerns or of necessarily performing voltage checks on spares. There are literally hundreds of temporary power cables, as well as control cables, which are not typically...

HCBFlash--Can you elaborate a little more on the problems that arose when "taped off ends" weren't insulated very well and what kind of trouble you experienced with wet conductors? I am trying to convince others of this issue, but I am not getting the agreeable response as I would have...

I am getting conflicting discussion regarding grounding unused/spare conductors in a cable. My VFD manual Power Wiring section says unused wires in a conduit must be grounded at "both" ends to avoid possible shock hazard caused by induced voltages. Now granted I am universally trying to apply...

I'm not sure how I got onto this specific forum, but thanks for responding anyway. I'm using an Allen-Bradley 700-CFB310D and a 700-CFB220D to be exact. I would call it a multipole mechanical relay.

I am designing a control circuit that will provide control contact for a 120VAC and the other contact will control a 24VDC circuit. Has anyone done this and, if so, should I be concerned? To throw another variable into the design, the control circuit will be adjacent to a VFD which I am more...

Thank you all for your advise on the matter. A little more background, the motor is a fan motor and the controller is a VFD. The reason I was questioning the conduit vice cable is because the cable is rated for all weather use and would be out of the way of any harm. I'm just trying to...

I need to connect a 10HP, 3ph motor to contoller box. Do I have to use conduit or can I use cable? The run is less than 10ft. Am I bound by NEC 400.7 Uses Permitted? because it is not specifically Not Permitted per 400.8. I just find it hard to believe that this would not be allowed.