I am going to flirt with disaster and show the licensed and unlicensed electricians/sound persons the basics of tapping feeder wires into venue switch boxes and subpanels. Those of you who do not have a professional license can at least understand what is happening, and what could happen if done incorrectly. So, if you think your ego trumps your unlicensed status, I want you to thoroughly understand people could die (including yourself), if done incorrectly.
Advancing the Venue
I cannot emphasize more that you should always advance the venue before having to do the feeder connections for production power. This is more than just knowing the brand of subpanel to be encountered. Knowing the make of the panel/switch box helps with having the right spare breakers, neutral/ground bus connectors and strain relief panel bushings for your feeders. With advancing the gig, you have the time to ask questions about power, or at least get a feel for how the venue’s electrical system is laid out and what kinds of loads you can apply safely without taking down the location’s electrical supply.
A good example of this is a bowling alley/nightclub that I have frequented for gigs. The subpanel has no master breaker inside, and so I have to go to a master panel in the bowling part of the venue, carefully get my hand between a narrow vending machine/breaker panel gap to flip off the subpanel breaker, and then go back to make the panel tap with my feeder tails. Now when I flip off the subpanel, the stage and surrounding seating goes dark, so I have to be equipped with my mini-mag headband and have everything preplaced to do this in minimal lighting. Then there is the time element, as the bar’s soda system also loses power; and I have to do the work within minutes or thirsty bar patrons and staff lose patience. By advancing this situation, the task gets done within the constraints provided.
Cold Taps
Figure 1 is a photo I took of a typical subpanel with my #2 gauge feeder tails properly tapped into the correct busses. As shown, always attempt to make your feeder connections into unenergized subpanels or disconnect switches (bull switches, company switches, etc.). In electrician parlance, unenergized panels are “cold” if they do not have any supply voltage present. The next best choice is to have the inbound feeders energized, but the master breaker in the subpanel is tripped, allowing the hot wire buss bars to be cold. I still feel very cautious on these semi-cold panels, as I can electrocute myself if I do not pay attention to my hands and the breaker switch positions. And that is why you see me with 600-volt insulated screwdrivers, hex-wrenches, pliers and rubber safety gloves in these situations.
The worst-case scenario for me is a total hot panel, where everything almost has to stay energized while making my connections. I say “almost” because I always trip off the breakers that I will be inserting my red and black (hot) feeders into. In these scenarios, I usually want another person keeping an eye on me for safety reasons, and to make sure nothing distracts me while trying to keep my loose feeder tails from accidentally touching energized metals. I do not care who you are, you still sweat a lot doing these dangerous activities.
Preparations
Besides having the right tools for hot and cold panel/switch taps, it pays to check your feeder tails before the gig. My feeder tails are four-wire, single-phase, with four #2 gauge wires made of many strands of small gauge copper wires in a rubberized black jacket that is weatherproof. They were made to my specifications by J Custom Supply (www.jcustom.com) of Zachary, La., with 25 feet of the four #2 feeders banded and terminated with 1016 female cam-loks on one side, and bare ends with color-coded tape on the tap ends. The electrical code requires these black rubber feeders to have at least three inches of colored electrical tape to indicate the type of feeder wire (green/ground, white/neutral, red/hot and black/hot) as shown in Figure 1.
Most times your feeder tails are in the condition you last left them in. This usually means the bare copper strands are frayed and possibly well oxidized. A good practice is to wrap a loop of electrical tape after removing the feeders to keep the wire tightly bundled. Of course, periodically you must cut off the old frayed wires, and strip off a fresh half-inch of jacketing to start anew.
Another crucial prep-step is to have a couple spare feeder to bus connectors for the correct brand of switch/subpanel. It would be nice if the last person who tapped in left their connectors, but we cannot bank on this charity. Although the connectors are only a buck or two each, having a goodly supply is necessary for bonding your safety ground (green) and neutral (white) feeder tails to the bus bars. In Figure 1, I have two square bus connectors for the Square D panel and they have 3/16” allen (hex) keying for tightening the feeders to the bars.
And no one doing subpanel taps, should caught without spare double pole breakers for the most commonly encountered panels. For me, it means Square D Q0, GE, ITE, and both kinds of Cutler-Hammer 100 Amp circuit breakers. Yeah, each breaker costs about $50 each, but not having them costs more to your production experience. I also keep 50-amp versions as well for smaller club work. It is nice to have switch panels to connect to, since they do not require the breakers to be provided, but about half of my venue taps are on subpanels, and I may get lucky enough to have the spare breakers present for the hot feeders.
The Process
Thankfully, most of the switches panels I tap into have feeder cable strain reliefs, but some do not. Thus, I also carry NM clamp bushings for 1.5”, 2” and 2.5” panel holes to strain relieve the feeders and avoid the sharp panel cutouts from cutting into the feeder jackets. If space permits, I will also wrap shop rag between the feeders and bushing, as a filler to help with function and prevent jacket extrusion when snugged up.
Panel tapping is pretty much used to run feeders through strain relief, snug strain relief, strip feeders as required (~0.5”), and connect them to the ground, neutral and hot breaker busses in that order. Of course, that simple statement is true provided that you have the panel/switch as cold as permissible, and are using the correct tools for the right tasks. One tip I recommend is remove the double pole breaker on subpanel taps for the hot feeder tail connections and make the tail connections outside the box. Then snap-in the breaker back to its location to finish the job. Anything to stay outside a busy wired panel until the last moment.
Once tapped, I recommend making the cam-lok connections to your portable power distribution unit (PPDU) before energizing the switch or un-tripping the breaker. This way you have no exposed hot cam-loks, and the metering on the PPDU can give you the status of your feeder wiring.
I hope this power-tapping dissertation is a thorough enough description of the process. These are the things that go through my head when doing this job, and you can see I am extremely risk-adverse when performing the taps. There are no mentions of sneaking feeder tails into inlet feeder connectors, or using Trico clamps onto hot bus bars. Figure 1 is obviously shown without other wiring to keep the focus on the tails connections.
You can find Mark at marka@fohonline.com
