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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...

Thank you, sir, I'll look into that. Do you have a few best recommended brands running Niagara? On standardizing a brand, we're stuck with what the customer (Air Force Base) has installed in the past, but are trying to establish a best line for future installations; one that's much more open...

HerrKaLeun, having to get certified by the company to buy the software needed to maintain your own property without having to pay that company for a service call is exactly what we want to avoid. In our business (install. & maint.) it's one of the main factors we look at when purchasing...

I see a lot of mention of support. If you're referring to support as in calling in a tech to re-program, this is a big factor we're trying to get away from. We're a contractor and service company, and we'd like to reduce our dependence on outside programmers because until we're a certified...

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

Just to update, we confirmed this weekend it was capacitive coupling. We hooked up the nodes to a light and nothing. I didn't write down the current, but it was minuscule. The AC signal makes sense to me now if it is just "bleeding" through the insulation. Thanks for the insight!

Pride goes before destruction, and a haughty spirit before a fall. Proverbs 16:18 Some people never learn this in their whole life. Be absolutely sure you know what you're talking about and state it politely and humbly knowing that none of us (including yourself) really know anything. Also...

That's interesting. Our runs are only 30 yards at the most, though, and they used single core at install.

Forgot to mention, we did measure amperage from our main 120V lugs to see if it was a short or just high resistance somewhere, and we didn't see anything the clamp on meter could register. We also did an IR scan with nothing to note.

Thanks guys, I like the light and measure current idea. Will try that next time we're scheduled to be out there. The induced voltage was what I meant by the stray DC voltages (anything and everything from other equipment/components to solar flares..), but would we be reading an AC voltage...

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...

As a follow up, in my example you could say that the work input is about 75% of the tonnage of the unit. So the heat rejected in the condenser coil should be about 1.75x the tonnage of the unit. Can anyone add to my confidence by saying they've actually measured this?

Whoops! Forgot about the energy received from the cold space... A better one-word or one-link response would have been 1st law of thermo, but I got it, thanks.

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...

Thanks guys, always important to remember. We have shorting blocks and will make sure to avoid that. And, again, our analyzer needs a dc voltage output like the probes I linked to above. We would chose a 1:1 0-5A probe to measure the current on the secondary of the main CT. Or do you see a...

This bus requires an act of congress to de-energize, so installing more CT's around the bus bar isn't an easy option. Sounds like there shouldn't be much impedance from tapping a 0-5A DC out CT on the main CT's secondary loop. We can try one and see how it goes. Thanks for all the help!

DRWeig, the former. I meant "main" CT loop, which I guess would be the analyzer CT's primary. You have to watch your language here in the EE forums :) stevenal, you caught me. They are transducers similar to these: newark tequipment So they probably just measure potential across a known...

Hi David, I meant clamp onto, sorry (ie to the primary CT loop). I did a little more homework and see the "burden" load is very light, but I'm just unfamiliar of how to translate that to an impedance on the primary CT loop's circuit and if we'll have to re-calibrate all the devices using that...

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...

...and I don't know which transformer it is, but likely a single phase 3kva for the operator cab lighting and an A/C unit, but could also be a 3 phase for the unit's controls (it's a large crane). So it seems like my opened gate on the up slope in my current waveform is the transformer...