I've been told a quick rule of thumb for emergency generator capacity for hospitals is about 6va/square foot. (Obviously, good load calculations and historic measurements are the only way to know for sure.) This is only for doing a preliminary guess at a generator size, accurate load calcs...
We have installed lightning protection components on tall buildings where the cooling tower is the tallest thing on the building. Although it is connected to building steel, you'd rather have a little control over what is struck first and where the current travels. (Not that lightning can be...
I finally got the lowdown from an OSHA officer. They have increased the requirements for Utility workers, but not for the general electrician. Apparently, the rule that workers have to wear "adequate PPE" without really defining that, has been enough to hang people that don't follow NFPA 70E...
AhA! So Subpart V really doesn't cover the average construction electrician! Well that is interesting.
I suppose this kind of work (general electrician type work in buildings, less than 600 V) is only covered by NFPA70E then, and also OSHA's general clauses......
Whenever I think I have this...
You are right, it is moot, however my clients all have their knickers in a knot about it. I want to be able to tell them authoritatively, "Yes, OSHA is going to come down on you with both feet on MM/DD/YYYY because of the new regulations coming on line. Your only hope is to hire me to do an...
>What they are working on now is putting more specific language in their official rules regarding arc-flash. But this probably take years to get through the review/comment process.
Yes, I am trying to find out more about the timetable for that "more specific language".
I realise that OSHA...
I hear rumors that OSHA is going to adopt new standards that specifically mandate PPE for electrical workers, and arc flash safety procedures. Previously, they state that "proper PPE" without any real definition, is required, and they can say "well, NFPA 70E is a recognized standard, maybe you...
The disease is energized work, and the painful cure is to turn the stuff off. Most facilities think they they can run electric power 24/7/365, and that isn't true.
I wish I had good references for this stuff, I put together some of these statistics for an arc flash presentation but don't...
Right - NFPA 70 Table 130.7 rates most energized work on panelboards under 240V as risk category 1. Maybe if one were doing arc flash calculations, you could take the worst case, and if IEEE 1584 doesn't address these panels, you just label them as Category 1.
I was using SKM, and I just assumed some values for a molded case circuit breaker that would be common in such a case, since it was just an excercise. It made me question the 125KVA cutoff, though. Is this really meant to be a cutoff, that Arc Flash Hazards become negligible below 125KVA? I...
I have heard that IEEE-1584 suggests that 208 V systems 125 kVA and larger be evaluated for arc-flash hazard using their calculation method. I was just pouring through this document, looking for this reference. Is this implying that 208V systems under 125KVA do not need to be evaluated? Just...
Arc flash calculation methods always warn the engineer not to use too conservative a number for available fault current. If this number is too high, the arc flash hazard can look confortably low, although the real risk is higher.
However, when I call utilities, they never can provide any...
