Wiring Question for Guitar Store

[Ben Abuya]

Hi guys,

We're in the midst of renovating a new guitar store in Haifa, Israel. It's about 40 sq. meters total floor area, but the guitars and amps will be in a rectangular room about 35 sq. meters (see graphic). The ceilings are quite high, about 5 meters tall. We will be playing high-end guitar and bass amps at high volumes.

We're working from a plan designed for us by a local acoustic advisor, which I'd be glad to post details of if anyone's interested. What I'm not clear on is how to do the electrical wiring in a way that will minimize problems like hum, noise and interference.

The idea is to keep all the amps plugged in, while only a few of them (maybe 3-5) will be switched on at any point in time, and only one or two will actually be playing at any given time. They'll be plugged into sockets at the rear of the acoustic risers (wooden risers filled with mineral wool). These are the green rectangles in the graphic. Each rectangle represents 6 outlets. The orange squares in the front of the risers are double outlets for effect pedal power supplies. The red rectangles are XLR connectors for patching in mics for live performances.

We talked with our electrician and he recommended installing a 3-phase system (25A x 3), putting all amps on one phase, all lights on another, and HVAC on the 3rd. He wasn't familiar with star grounding systems, but said he could direct wire each outlet bank to the service panel. Our budget for the electric wiring is about $2,500, but flexible. I'm not sure how much that helps because a lot of it is labor, which is cheaper here. Israel has about 60% of the per-capita GDP of the US.

Here are the main questions I have. I'm not an electrician, and I actually don't have a lot of electrical understanding yet. First, a few points about Israeli electricity:

a. We have special plugs here, so receptacles are a localized market, although Gewiss makes an Israeli version.
b. We run 230V, 50Hz. Three-phase is very common.
c. Everything is done with plastic -- plastic conduits, receptacles, junction boxes.
d. Construction is generally (and in our store) concrete.
e. It's very common to install 6-receptacle strip units, which come internally wired with a single connection to live, neutral and ground.

Questions:

1. I've read the articles on balanced power, and they represent it as the ideal solution. I also read that power is not balanced in North America, but is it balanced in Europe? How can I check if my power is balanced?

2. If it is balanced, or if we install a power balancer, is it still necessary to use star configuration grounding?

3. If we use standard 6-receptacle strips, is it necessary to connect the ground from each individual receptacle directly to the star hub, or can the single ground out from the strip be used. Wiring each ground directly will be a lot more work for the electrician, and he even mentioned something about individual ground wire running not being to code. Is it important for the effect pedal receptacles to be star grounded, too?

4. Is the plan the electrician had about using one phase of the power just for the amps a good one. Will this cause problems due to the phases not being load balanced? If so, is there a better way? Bringing in 3 individual phases maybe?

5. Is there any risk of all the cabling under the risers causing an antenna effect and messing with guitar pickups or with the XLR cable signals?

6. What are the other solutions, like AC line filters and isolating transformers for? How well do they work?

7. Our electrician mentioned something about Lightning Arresters (I think that's what they're called in the States). It sounds like a heavy duty surge protector that would vaporize in the case of a lightning strike and break the circuit to the equipment. It would cost about $250. Is this kind of thing necessary? How about other kinds of surge protectors?

It was really hard finding good electrical info for studios until I found this particular forum. Thanks a ton in advance!

[Aaronw]

Hello Ben,

This is a bit out of my realm of knowledge on Int'l power, but I'll drop a PM to Steve (Knightfly) and see if he may have a minute to chime in here and give some feedback.

Aaron

[Ben Abuya]

Thanks, Aaron. After mulling this over the past few days, I don't think we're going to have the budget for power balancers or line filters, so the main questions I want to focus on are whether it's critical to connect each receptacle ground straight to the star or if it's ok to just connect the whole 6-receptacle strip to the star; and whether all the cabling under the risers will cause any electromagnetic interference problems.

Thanks again,
Ben

[knightfly]

Ben, according to this

http://ita.doc.gov/td/industry/otea/ecw/is.html

your power system is NOT balanced - the neutral is grounded. For 3-wire plugs apparently one is a (grounded) neutral, the second is hot (220 volts, 50 hZ) and the third is a groundING conductor.

The difference between groundED and groundING is normally defined as this -

neutral, which is a return line, is usually grounded somewhere but is NOT used for safety.

Ground (groundING) means that this is NOT a current carrying wire, but is only for safety so the chassis of a device is safely at ground potential.

If your strips aren't very long between receptacles, a single ground where they plug into the mains should be fine in most cases. By your comments, I'm assuming you're using the 3-prong system?

As to EMI, this will increase due to higher current and closer proximity to signal wires (guitar cords) and also due to longer than necessary wire lengths - so I would (if this is a "stage" type of riser, where amps are placed near the wall and players/guitars are NOT) place all your electrical supply wiring as close to the wall as practical, use as short a wires between receptacles as possible, and keep FX boxes/guitar cords as far AWAY from the power grid as possible.

Also, if your amps have ground lifts or power polarity switches, make SURE they are all set the same and do NOT lift the grounds - this is just asking for death, especially if there will be mics involved for singing.

Even if there are no mics, having two guitar players on stage with their guitar hardware at a 220 volt difference will make for some interesting pyrotechnics

HTH... Steve