detailed grounding and power questions

[sound_music]

hi, i've been working on the studio electricity project with an electrician (who has never wired a recording studio), and wanted to verify a few points here on the RSDF. there is some discrepancy between what the electrician is telling me and what my research into the subject is telling me.

so here goes:

1) true or false? technical power (all studio equipment related power) needs it's own separate ground. that is to say that the technical power cannot be tied to the building's general ground that grounds lighting, HVAC, refrigerators, vacuum cleaners etc. a separate physical grounding rod must be put in the ground and tied only to the panel for the technical leg. (FYI, we have 3 phase power in our building, and the technical power has it's own leg and its own fuse panel.)

do i have this right? the electrician seems to think it's ok to run all three legs of our system on the same ground. i think that's true from a safety standpoint, but in terms of potential loops, interference etc, it only seems logical that the technical power needs its own ground. can someone please confirm or correct this!? am i confusing the idea of a separate ground rod with a separate ground panel for the technical power?

2) true or false? all the ground wires from the technical outlets need to be brought back individually to the ground bar in the technical panel. (star system) he cannot daisy-chain them, even if we install a separate ground for the technical power.

the electrician seems to think that if we go to the trouble of installing a separate technical ground (if required--i'm still not sure it is!?), daisy chaining the technical outlets is ok. maybe he's right? to me this would seem to defeat the purpose of a star grounding system... can anyone some shed light on this question?

3) the electrician has proposed some kind of crazy grounding system composed of a galvanized cage, charcoal, multiple copper rods, and salt water!? it sounds awesome to me, but i've never heard of this and wonder if it will really be any better than the good old copper rods all by themselves? any thoughts on this?

4) is it ok to run the technical power wires and lighting power wires alongside one another in close proximity (physically touching), or in the same conduit where necessary? (there seems to be some differing opinion on this between various reference books and what i have read on this forum.)

5) in certain instances it would also be practical for us to run cat-5 and audio cable bundled in the same conduit. this seems ok based on my experience and the little i could find to read on this point, but just want to confirm.

6) this electrician is not familiar with isolation transformers: he's never installed one, and i was planning to put one on the technical leg as i understand they can really help to eliminate potential ground loop problems. but if i've understood correctly this can be tricky because the leg you install it on (technical power) then has to share a neutral with the other legs of the system. can anyone point out a good resource that explains the proper installation of an IT in a 3 phase system? also any quality isolation transformer brands/models/references would be appreciated!

sorry for the long post, and many thanks to anyone that can shed some light on these details! cheers

[sound_music]

ps - if this is all too complicated to attack here in the forums, i'm perfectly willing to hire the electrical design out to a qualified designer. if there are any floating about please feel free to send a PM or email to get more detailed info about our facility that you would need to do a proper quote.

at one point i had intended to do the studio and acoustic design myself as well, but that proved too complicated and time consuming in itself, so i hired an acoustic designer. this electrical portion of the project may end up going that way as well... i'm totally open to the idea. it's actually probably better that way, as i am certainly no electrician, and the one i have available only has experience with normal household and industrial electricity etc. he's a very open-minded guy and very good at what he does, but truthfully i'm not comfortable advising him on such important matters based on my limited understanding of the subject! someone qualified with studio electrical experience would be a welcome addition to the design team!

[gullfo]

The common ground is used to avoid loops across the overall system but you're right on using star grounding for all of the studio wiring even if it eventually ends up on the same ground with the other legs. Not sure about the neutral on the isolation transformer. I suggest finding a competent power engineer to sort this out and get a proper design.

On bundling cables, in practice you can run them together if all the grounds are correct. I tend to keep them separate for ease of maintenance and possible mistakes in connecting them or in the event of an overheating condition on power, noisy equipment etc.

[sound_music]

hi glenn, happy new year! thanks for looking in on the thread.

so in your opinion a second physical ground rod for the technical power is unnecessary, but the technical ground wires do in fact need to be brought back to the ground bar individually. cool.

regarding bundles in conduit (or without conduit), were you talking about the power wires or the audio/digital cables? my hunch is that for the audio and cat-5 cabling it would be ok to bundle them up snug and run them together, as there's so little current running though them the effects would be negligible. but i see your point about keeping them separate for future replacement etc--very practical. i'll try to keep them separate where possible. i would guess that the bigger potential problem area is running the tech and lighting power cables together. there's only one or 2 spots in our design where that may be practical though--i can probably find a way of keeping them apart or at least crossing at 90 degree angles in most instances.

the question about how to install an isolation transformer on the tech leg on our 3 phase system is the biggest hole in my info right now... hopefully someone else will set me straight on that point.

that, and the idea of using balanced power on the tech leg (noise floor 10db quieter is appetizing!)... if anyone can point me in the direction of balanced power resources or references would be much appreciated as well.

[sound_music]

so i spoke with jim brown in california today about some of this stuff, wow does he ever have it together! he straightened me out on a couple of key points (that i understand a bit better now), but quite a bit of it went over my head as well.

so i'm definitely looking for someone to help with the electrical layout/design, that conversation really sealed it for me. i'm way out of my depth on this electrical stuff!

pm or email if interested

[Speedskater]

I thought that Jim Brown was located in Chicago:

The Audio Systems Group, Inc.
4910 N Wolcott
Chicago, IL 60640

Jim Brown is the AES committee chair on EMI/RFI interference.

His best paper on audio and AC power wiring:
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

Some of his other papers:
http://www.audiosystemsgroup.com/publish.htm

[sound_music]

nope he's in california. (not that it's relevant)

he's a very, very, knowledgable guy on this subject. and a class act.

i'm trying to figure out if i can afford his services! (for the moment it doesn't look doable unfortunately for me)

[Soundman2020]

First, a caveat: I live in Chile. Electrical code here may well be different from electrical code where you are, so DO NOT do what I do, unless your code allows it and your electrician fully understands what he is doing.

I design and install video post production facilities, so I run into many of these same issues. Here's my answers to your questions (keeping in mid the above caveat):

1) true or false? technical power (all studio equipment related power) needs it's own separate ground.

True. I always get one phase dedicated to technical power, and that phase gets its own physical ground. That ground should also be bridged to the neutral bar in the distribution panel.

2) true or false? all the ground wires from the technical outlets need to be brought back individually to the ground bar in the technical panel.

True. Full star ground. Don't let your electrician skimp on this: you'll be sorry later if you do!

3) the electrician has proposed some kind of crazy grounding system composed of a galvanized cage, charcoal, multiple copper rods, and salt water!?

It might well work, but is probably over kill! I normally get my electrical contractor to lay out a grid of copper rods, about 1.5 m long, driven into the ground in a grid pattern, and interconnect with thick copper conductors. Your one-and-only ground connection can tie into this grid at an point. The size of the grid I leave up to the contractor, but they normally end up at least a couple of meters square, with at least 4 rods (one in each corner), and sometimes as many as 16.

4) is it ok to run the technical power wires and lighting power wires alongside one another in close proximity

Yep. They are all on the same phase, after all, and they all come form the same panel, with the same neutral bus, so there's no reason why they should not run in the same conduit. HOWEVER: I seem to recall that code does not allow that in some places, and you HAVE to run heavy and light circuits in separate conduits.

5) in certain instances it would also be practical for us to run cat-5 and audio cable bundled in the same conduit.

Iffy.... Theoretically it should be OK, but I do like to take care of my audio cables! I'd keep them separate if you can.

6) this electrician is not familiar with isolation transformers: he's never installed one, and i was planning to put one on the technical leg as i understand they can really help to eliminate potential ground loop problems.

Then maybe you should switch electricians, to someone who DOES know how to do it right, and also follow code?

Anyway, one more time; take the above with a pinch of salt! It may or may not be OK for you. Your expert electrician and your local code will decide. We are on 220v 50Hz power here in Chile, and our code is rather different from yours.

- Stuart -

[sound_music]

hi soundman2020, thanks so much for your replies! great info there.

i ended up hiring an electrical designer in the neighbourhood (not far anyway, in portugal), and he has been great so far. he has done many studio and theater installations, and all kinds of technical facilities throughout europe and the middle east. my electrician on site will now only be executing the blueprints that come from lisbon.

the electrical project is well underway, i'd estimate we're nearly 1/2 done the design at this point. we should be installing the grounding rods + grids on monday or tuesday.

there are a couple of points i'd like to clarify with you:

a) it seems there are a few different ways of achieving the technical ground. all of our grounding will in fact be tied to the building. (via the neutral bar i believe... as you suggest.) he's created a ground "zone" that encompasses the entire floor surface of the building, with grounding rods in all 4 corners of the property, and 2 additional 1m2 copper grids with 4 rods each under each of the main rooms, all tied together with 3.5mm copper tape. my question is as follows: this seems like ALOT of rods! we have good soil here in casablanca... would like to hear your opinion on this. we may install only 1 grid at first and then test to see if we get the result we're looking for (less than 1ohm) with only 1 grid (8 rods).

b) regarding your response to question #4 above, i think we've misunderstood each other. our technical power is on a separate phase from the lighting--so they are not on the same phase as you suggest. with this clarified, do you still think it's ok to pass technical wiring and lighting wiring in the same conduit if necessary? (we're not that far along in the actual design yet--i will of course be running this idea by the electrical designer as well--just curious as to your opinion.)

cheers, and thanks again for your informative post.

[Soundman2020]

On the grounding issue: I'd go with whatever your expert electrician recommended: If he thinks it is necessary to do all that, then that's what I'd do. It doesn't sound unreasonable, and he's the guy who looked around and saw the actual conditions. It sounds like your guy knows what he is talking about, so I'd go with whatever he recommends. It might be a bit of overkill, but with grounding I'd rather go overboard than come up short!

so they are not on the same phase as you suggest. with this clarified, do you still think it's ok to pass technical wiring and lighting wiring in the same conduit if necessary?

In that case, I think I'd go with separate conduits. I'm not eve sure what code allows, but from both an interference and a safety point of view, I reckon I'd keep things separate. Conduit isn't THAT expensive anyway! What does your electrical guy suggest?

Glad to hear that it's all coming together well! Of course, you know the rule here: "No photos means that it didn't happen"! So how 'bout some pics????


- Stuart -

[sound_music]

lol, we haven't installed any of the electrical project yet, we're just in the midst of slugging it out on the design end... so you're right--it hasn't happened yet! but i will post a few pics next week when we lay down this crazy grounding scheme... promise!

[Soundman2020]

Great! One last thought: oversize your conduit, and keep the bends wide! I don't know how many times I've heard a customer say "Please can we run a new circuit for our ultra-new super duper thingy whatsit gadget.", only to find that all of the conduits are already packed to the brim, or the only one with space left in it has a very tight kink way down there somewhere, and you can't even get the fish ape past it! Do yourself a favor, and whatever size conduit your electrician recommends for each run, ask him to up-size it to the next dimension, or run an extra one next to it. Also insist that all bends must be much larger radius than the minimum that code allows.

The slight increase in cost now can save you many hours (and dollars!) a couple of years down the line... Installing extra conduit now is a few cents per meter in cost. Ripping things out two years from now to re-do it is thousands of dollars....

- Stuart -

[sound_music]

totally agree about oversizing the conduit slightly and using wide angles for ease of future maintenance and upgrades. i had a discussion on the subject with both the electrical designer and the acoustic designer recently, we are all in agreement that we will be running everything separately. the AD wants to be sure we don't lose too much isolation with all the conduit we will be running, but he as given us a few good methods to minimize loss, so it should be cool.

[sound_music]

here's a few pics of the ground install, as promised!

for some reason the uploader tool ordered the pics in reverse, so start from the bottom of this post if you want to see them in chronological order...

[Soundman2020]

Looking interesting! You do also have rods in there going down vertically, correct?

- Stuart -