isolated ground

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Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
This is an ongoing argument I have had with an audio contractor. A true isolated ground originates at the exact point where the neutral and the ground are bonded together, period. This is different than a "dedicated ground wire", which is what many Engineers, datacomm, cash register and audio people really want when they ask for one. It is pretty rare that an isolated ground is actually necessary.

The purpose of an isolated ground is to provide a clean reference "0" volts for computers and such that use multiple voltages for their operation. This is usually done on the load side of equipment power supplies nowadays. In a standard ground installation there is often 1-2 volts potential between the ground and the neutral. This can mess with sensitive equipment and cause parity errors, and slow downs due to the equipment having to correct the errors. I have repeatedly seen Point of sale equipment specifying Isolated ground receptacles without a corresponding detail of the isolated ground bond. When challenged they answer with a request for a dedicated ground instead. Dollar General's are an example, along with many restaurants, which often go in little cubbyhole build outs.

I doubt this clears up your problem but should give you an idea of what to do next.
 
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