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Re: the physics of a neon sign
>I do use conventional transformer loading
>tables, as a first approximation. Generally, if I don't like the code, I try
>to get it changed, and have done so. I knocked my head on these old metal
>outdoor signs at first and eventually had to admit that I had a lot to learn
>from their time tested strategies. My view is that there is a lot to be
>learned from the past, that does not need reinventing, and there is a lot of
>old technology that can be updated with new technology to benefit. A
>combination of the best of old and new, that's the best approach.
I think the NEC has very little to do with reliability for neon signs...
it's purely an attempt at safety... there may be gobs of GTO at high
potential, running thru 3/8" conduit, just waiting to arc thru. Though
the sign will invaribly fail in short order, the arcing will (hopefully) be
contained, and you'll be left with a buzzing, flickering sign instead of a
fire.
The older, metal signs did rely on physics. Fewer components (and of them,
rugged and simple in design), and inch or more of air as HV insulation,
ventilation of the trans. compartment, etc.
A look thru the Neon Installation Manual reveals a very different picture.
Some installations are hopelessly complex. There are hundreds of individual
components: GTO inside GTO-Sleeving inside conduit, PK housings with
complex strain-relief mechanisms and gaskets and conduit-plug-assemblies
with o-rings, rubber boots that attempt to make a "water tight" seal around
the entire electrode and GTO, and more and more. The backs of some of
these signs look like a conduit octopus.
It makes me wonder if _anything_ from the lessons from the past are being used.
-John