Hi,
Need some help interpreting the NEC as well as some help with general engineering sense.
We're interpreting NEC 2014 725.48 that power and control conductors for the same equipment can share a raceway:
725.48 Conductors of Different Circuits in the Same
Cable, Cable Tray, Enclosure, or...
Hello,
Interested in opinions of the top/best BAC system manufacturers out there today (Johnson, ALC, etc.). My personal key factors are programmability/maintainability, component interchangeability, technical support, and reliability.
Thanks in advance
We have several nodes in a simple 120V relay control circuit that are floating w.r.t. everything else. The voltages we're seeing is anywhere from 20-70VAC from the nodes to our neutral. At this point we concluded that voltage to ground on these nodes should see only minuscule DC voltage and...
I'm still relatively new to the field, but for a while now I've wondered how manufacturer electrical data seems to defy the law of conservation of energy for A/C units.
For example, a 20 ton split system we just put in has a published MCA of approx 60 amps. That equates to about 50kva, which...
Hello,
Researching what effect piggybacking another CT onto an existing CT might have. We have 300:5 CT's for 12.47KV 3MW generators that we'd like to tap onto with an analyzer's CT's. I'd like to learn how much of an effect the analyzer's CT's would have on the signal out of the 300:5's...
Hello,
I've read through several articles on transformer inrush, but I'd like to poke around the great EE minds here to see if I can get a physical explanation of why transformer inrush is only one direction (or polarity), (see the example waveform we captured in the link).
Much appreciated
The ASHRAE estimate for heat gains from electric motors seems very high. For the motor and driven equipment in room equation, they're saying all the real electrical power put into the motor is converted to heat??? What about the energy transferred to the driven equipment? Anyone else think...
Hi,
Been reading a few threads about using fan laws, but I think they're incorrect and I need some reassurance.
If you have a fan and change its speed while keeping the same pressure change over the fan, then you can use the 1st fan law. But if you have it connected to a ducting system, you...
Hi,
Looking for opinions of Chiller manufacturers. Who has the most reliable brand these days? I'm looking at an air-cooled in the range of 60 tons. Part availability, and maintainability are also important, but mostly looking at reliability.
Thanks
Hi, I'm trying to obtain info for a cooling load calculation of a below ground (above ground, really just bermed) building. The walls (dirt) are at 45 degrees, several feet on the roof. I'm going to adapt using the radiant time series RTS method just plugging in appropriate sol-air temp...
Hi Sparkies,
If you would, I need help finding a paper or book (or your experience) on the degradation effects of primary injection circuit breaker testing. Surely there must be something out there?
Thanks,
fiberstress (gearhead)
Hello,
I have a 480/277V PDU with an onboard transformer that steps down to 208/120V, and then branches into 2 panels (or 3, I’m not sure) supplying 208V L-L/ 120V L-N (3 phase of course).
We need to add two new circuits for two AC units that run on 208V and need 50A breakers each. We're...
