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Topic: Dealing with broken neon tube

Jim Spohn
Film Handler

Posts: 95
From: Bakersfield, CA, USA
Registered: Jan 2003

posted 06-21-2004 01:21 PM

When by-passing a section of neon tubing you need to assertain what percentage of the total neon tubing is being by-passed. For example if there are two tubes 10' long and you are by-passing one of them then you are taking 50% of the tubing out of the circuit. Neon lighting tube will take all the current you can give it, getting brighter and brighter but the tubing is also getting hotter and hotter as the current increases. The transformers are current limited to the correct amount of current for the amount of footage of tubing they supply. If you by-pass a large percentage of the tubing, you are in effect raising the current on the remaining tubing, therefore increasing the heat of the glass. The problem with increasing the glass temperature is that the wire leads on the end of the tube (that go thru the glass) expand at a lessor expansion co-effecient than does the glass, as the glass expands greater than the wire, the seal is lost and the atomsphere will leak into the tube and at first there will be flickering and then complete failure. The bottom line is that if you are going to by-pass at all do it only on a small percentage of the total tubing OR you will send the good tubing to an early grave. I would think that 25% would be a good fugure to stay under and that might even be pushing it.... enough rambling...I hope this helps... Jim

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Bobby Henderson
"Ask me about Trajan."

Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001

posted 06-21-2004 05:17 PM

That's true, Jim. But the more likely problem to occur when taking too much neon out of a given circuit is the penalty the ballast itself suffers. You're more likely to roast a transformer when it doesn't have a comfortable length of glass to power. And then these days the old fashion transformers are disappearing. Everything is going to ground-fault design. In a new neon installation (that is wired for UL Listing or at least National Electric Code compliance) ground fault transformers will be in use. If everything isn't hunky-dorey, the neon may just flip off the power.

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