Electronic Transformers 2

In our last column (SB Jan 07, page 34) we commenced a discussion of some of the changes in power technologies for the electric sign industry and the impact electronic ballasts and power supplies have on energy consumption and lighting efficiencies for neon and fluorescent fixtures.

To recap, we discussed the physical differences between new solid state transformers and the old “brick bat” ferro-magnetic/core and coil transformers; the solid state transformer’s relationship to the emergence of Secondary Circuit Ground Fault Protection; and some of the changes in thinking needed to implement these components into our neon displays.

The reason we felt this was so pertinent and timely has to do with the resurging attention being placed on an ever-increasing desire for a “greener” culture along with less dependence on foreign oil. In soliciting solutions for those problems, we have been turning more and more to electronics in all its various forms (i.e., LEDs and their drivers, electronic ballasts, solid-state transformers, etc.). However, most of the hold-ups, when it comes to these components blending into our industry’s niche, have stumbled due to the lack of knowledge when dealing with the idiosyncrasies of these drivers and power supplies.

In looking at electronic power supplies we have to understand that this relatively new electrical transformation method is far different from its elder ferro-magnetic cousins, which we had the opportunity to become accustomed to over many decades. Instead of using iron cores containing multiple windings and shunts, the newer technologies are pulling us almost totally into the world of silicon chips. The difference is that these newer power supplies operate on principles of high frequency. This high frequency can normally radiate from the conductors it travels through and these radians are some of the issues we have to be extremely cognizant of when designing or installing such a system.

A REFLECTION FROM YESTERYEAR

In the mid-1990s, when the pillars of high-voltage neon transformers were still the ferro-magnetic “brick-bats”, I sat in on a seminar that was presented to fire marshals, electrical inspectors and fellow electric sign crafters. In this seminar it was pointed out that the secondary leads traveling to and from an electronic transformer could not be encapsulated within the accepted trade standards of Electrical Metallic Tubing (EMT) or flexible metal conduits.

Electronics, with their radio-type waves and all their associated properties, are way out of their element when it comes to metal of any kind. He also pointed out that a conductor transporting electronic current couldn’t be laid in or within a close parallel proximity to any type of metal. He showed how a high-voltage conductor could pass directly through a piece of metal with adequate spacing. He then showed conversely how the moment that home or returning run was laid against a metal surface or near an open channel, for example, the “cross-talk” (the tying together of high frequency radians) could not only be problematic but also exert very destructive forces onto any system.

These are issues we have discussed within this column previously. One of the most pronounced examples we used was how a national clothing retailer was having constant problems with their hanging interior signage. From what I have observed since, most of that particular retailer’s newer stores have totally eliminated luminous tubing and now use Edison screw-type lamps, which can be replaced by any of their employees.

HANDLING THE DIFFERENCES

There is a lot of confusion regarding these electronic components. For years I have emphasized the use of metal and glass components. Metal is a great equalizer when it comes to grounding and, when it comes to protecting conductors, this will almost always be my first material of choice. Also, while metal conduit can act as a compliant grounding means, I would still advocate running solid green copper grounding conductors as an added safety precaution.

When we finished our last column regarding newer sign branch circuits we asked you to consider newer energy saving measures along with electronic drivers that are accompanying some newer light forms. How does that tie in with our wiring methods? Well, for one thing we have to start introducing some components that previously we really didn’t take the time to cover.

Those would be organics (plastic).

SECONDARY RACEWAYS & METALLIC COMPONENTS

If you want to configure and install a remote solid-state (electronic) signage power system (and we should really be working toward that type of approach for many applications if additional energy usage is of concern), then we have to go out of our way to either eliminate our solid-state components’ proximity to any type of metal, or at least isolate them.

I’ve always emphasized a belief in using EMT and flexible metal conduit and still feel as committed on those components as ever.

However, in the sign section of the National Electrical Code (NEC), Article 600, we are not restricted to metallic raceways. In fact, in 600.32(A)(1) Installation, we are told that we can install our high voltage conductors “…in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, liquidtight flexible nonmetallic conduit, flexible metal conduit, liquidtight flexible metal conduit, electrical metallic tubing, metal enclosures, or other equipment listed for the purpose…”

However, I would advise caution, in this particular article, with the “…other equipment listed for the purpose…” issue. While this statement blankets a multitude of sins, trying to figure out and research every particular intended purpose can be daunting and potentially end up with an installation that might be seriously compromised.

What I want you to glean from this NEC test is that among other mentioned components, the terms liquidtight flexible nonmetallic conduit and rigid nonmetallic conduit come to the forefront when designing our newer systems. With electronic power supplies these nonmetallic conduits are the components that we must use.

Also, concentrating on what we’ve been saying, anything metallic can assist in destroying an electronic based lighting system. For example, our old standby metal electrode housings (PKs, etc.) have stated on each and every barrel that those components must be used with metal conduits. Therefore, not only are those components not code compliant for use with the conduits we must use in an electronic system, but also those electrode receptacles would become one of the destructive points in an electronic (high-frequency) power system.

What about our secondary raceway connectors and fittings? Again, everything that we design for these newer electronic systems, besides being code compliant, must contain as little metal as possible. Therefore, listed organic connectors and fittings are called for. If, in our design process, we can specify and have fabricated listed individual nonmetallic channel letters, then that just becomes one less troublesome spot whose substitution will increase the longevity and make our display far less problematic.

If we look back at some of the signage we have peered upon over the years, it quickly becomes apparent why these newer power supplies have taken so long to start ebbing their way into our mainstream installations.

FORGET GROUNDING? NOT

We have spent a majority of our time trying to explain how to eliminate or greatly reduce the amount of metal present when dealing with electronics. I hope that this isn’t, upon first observation, construed as a sanctioning of the elimination of grounding or bonding practices within our systems. It’s not.

However, as we commence to eliminate metal components from our displays, the amount of items that need to be grounded or bonded becomes that much less. For example, if we have a nonmetallic conduit emerging from a nonmetallic shape or channel letter, the criterion for ground/bonding becomes that much less. By the NEC 600.7(C), small metal parts not exceeding 50 mm (2˝) in any dimension, not likely to be energized, and spaced at least 19 mm (3/4˝) from neon tubing, shall not require bonding.

Therefore, it is now becoming very conceivable that we could possibly put together an entire remote channel letter sign or design and not be required by the code to have any type of grounding or bonding on the secondary side of the installation.

We have brought up a lot of new points for many to consider. However, we have a lot more to cover regarding these power supplies and a lot more to cover in just the way we deal with letters or designs that are metal in nature.

Until next time…

(Click here to read Part 1 of this article series.)