Separate Earth Ground For L.E.D Price Signs

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Robert Beagle

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The manufacturer of the L.E.D price signs are having some problems with the signs and do not want to warranty the product unless it has a separate earth ground specific for the sign installed, with resistance to ground at 10 ohms or less and the ground rod installed within 25' of the sign ,connected to a lug inside the sign provided for that purpose.

As the signs are grounded per code, Is this additional ground going to do anything?
Will this provide protection from a static charge to the circuit boards?

Could this be an attempt to redirect attention from the product to the installer?

Robert
 
Could this be an attempt to redirect attention from the product to the installer?
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That's what it sounds like to me.

Just how are you supposed to prove a 10 ohm ground impedance?

What if you can't get 10 ohms even with multiple ground rods?

If it were me, I would not use the product as it sounds like they are trying to get out of the warranty.
 
I am always suspicious of any manufacturer that requires a dedicated ground rod for their equipment. I strongly supect that they do not understand grounding & bonding or how to protect their electronics from real world conditions. I could understand better if they required the grounding electrode system to be less than 10 ohms. Even then they ask for something that may cost more than their sign... Maybe they could learn something from the people that make traffic lights.
 
091127-2001 EST

Is the data displayed on the sign sent to the sign by some directly connected serial or parallel path.? If so, then probably there needs to be DC isolation in this communication path to eliminate ground path noise problems.

A local supplemental ground rod to earth is most likely only a marginal solution, if it does anything.

.
 
How are the signs mounted, are they on poles? If so then how high?

Could the supplemental ground be for lightning induced currents protection?
A low impedance path for Overvoltage protective devices referenced to earth.

Otherwise I would expect an LED sign design to be fairly robust.
 
gar said:
091127-2001 EST

A local supplemental ground rod to earth is most likely only a marginal solution, if it does anything..
Click to expand...

Say you acheive the 10 ohms or less with a ground rod at the sign. Then suppose the grounding electrode system at the service is 50 ohms. Lightning induced current will now seek out the sign.
 
Robert Beagle said:
As the signs are grounded per code, Is this additional ground going to do anything?
Will this provide protection from a static charge to the circuit boards?
Robert
Click to expand...

A grounding electrode system that is adequate for a power circuit is more than adequate as a static electricity grounding system. So long as a properly sized EGC is present, then their is no need for a supplemental ground rod.

Do they provide a terminal for an EGC next to the one for the GEC ?
 
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