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Re: More Info

Posted By: SVP Neon Equipment
Date: Monday, 15 September 2008, at 12:19 p.m.

In Response To: More Info (Tom H.)

> Mark , here are the specifics you requested
> . I'm using your brand of elec's , I don't
> have the model # now , but they're the small
> 12mm. glass jacket with a 1" or so
> shell , rated for 30 m.a. , matching the 30
> m.a. tranny's my customer is using . The
> install is somewhere in the NE corner of
> Ohio , so it does get pretty cold , 0*F ,
> during the winter . Again the question is ,
> do I need to compensate for the extremely
> short units by increasing the filling
> pressure . Thanks .


The simple answer is yes, you should use more gas pressure in shorter units. But the amount to overfill is widely opinionated. Some recommend 1 to 2mm more gas pressure regardless of how short the unit is, while others recommend 1mm more gas for every foot under a certain length of glass. The latter can add up to an enormous amount of gas pressure for a 10mm tube less than 1 ft. in length.

What it boils down to is, the more gas that you use in the tube the longer the unit will last and the less gas used the shorter the life of the unit will be. But you can go too far in either direction, and these days it may even depend on what type and brand of transformer is used. So I should have also asked if conventional or solid state transformers will be used. With conventional trans. you can get away with more as they do not respond to over/under fill in the same way as solid states do.

With that said, and trying not to drag this out too long, this is what I recommend. Again, others may have different opinions and if solid state trans. are going to be used you may also want to contact the specific trans. mfg. to get their opinion.

Conventional transformers: Your 10% to 20% over fill is a little low. For 10mm units 6" to 16" in length with a short electrode, I would use 4mm to 5mm more gas pressure (30% to 40% more). Be sure to check the transformer load with a meter. Obviously you will not be able to run as many feet with a given size transformer with this much over fill.

Solid state transformers: Your 20% is probably about right. This would be 15.6mm, or 2.6mm more than normal. You can round it up or down: 2mm or 3mm over fill. Be sure to check with the specific transformer mfg. for their input on over filling units by this amount and if they have other recommendations for their transformers.

As a side note, a larger electrode will also help short units last longer, but of course they will be more difficult to process completely with units as short as you mentioned. (An induction heater comes in quite handy for situations like this). Regardless, with units this short they will not last as long as units that are 6-8 ft. long.


SVP Neon Equipment

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