[Elecraft] Negative rail grounding

[Jim Brown]

On 4/18/2018 11:10 AM, Michael Blake wrote:
> It seems that my newest Astron SS30 power supply does not allow for the negative post to be isolated from the chassis. The green wire can be disconnected from the chassis but the negative rail of the DC output can not be isolated from the chassis.  The negative rail is firmly connected to the chassis via two of the circuit board mounting screws. Separation would only be possible by using insulating washers and nylon screws.

That's unfortunate, and a good reason to avoid that supply.  It IS an 
absolute requirement of virtually all Electrical Codes (LAW) in North 
America that the Green Wire be bonded to the shielding enclosure 
(chassis).  I suggest that you check that paint is not insulating the 
mounting screws fro the shielding enclosure.
>
> This is not true in one of my older supplies. Has there been an NEC or UL change that requires that one side of the output of a DC supply be grounded?

NEC does not apply to low voltage DC systems.

73, Jim K9YC