[Elecraft] (OT) Grounding Mat

[Don Wilhelm]

But Jim,

The secondary of an isolation transformer is fully isolated - i.e. 
floating AC.  The fact that the neutral of the transformer input side is 
bonded to the green wire ground is quite a different thing.  A proper 
isolation transformer has no relationship to neutral on the secondary 
side - only the safety ground and the voltage across the secondary winding.

Remember the old AC/DC receivers that had one side of the AC line tied 
to the chassis!  Every proper service bench had an isolation transformer 
during that era.

73,
Don W3FPR

Jim Brown wrote:
> On Sat, 27 Mar 2010 09:32:12 -0400, Don Wilhelm wrote:
>
>   
>> An isolation transformer *does* isolate the neutral (and the hot), 
>>     
>
> NO! This is a summary of NEC (National Electric Code) requirements: The 
> NEUTRAL of a transformer on the secondary side MUST be bonded to the 
> equipment ground (steel conduit, the green wire, building structure, etc), 
> and that green wire must be carried from the breaker panel to each outlet and 
> to the transformer.  The neutral conductor that feeds the primary side of the 
> transformer must be bonded to ground at the service for the building (that 
> is, the main breaker panel). And, as we all know, all groundes must be bonded 
> together. Thus, an isolation transformer does NOT isolate either the neutral 
> or the equipment ground. 
>
> What an isolation transformer DOES do is reduce the voltage between neutral 
> and ground to zero. It also shortens the return path for leakage currents on 
> the green wire -- they now return to that transformer, not to the more 
> distant breaker panel at the service entrance. This has the potential to 
> reduce noise current on the shield of signal cables. BUT -- the simple 
> bonding regimen outlined in my Ham Interfacing Power Point is a MUCH less 
> expensive AND more effective solution. 
>
> 73,
>
> Jim Brown K9YC
>   
>