Stuart Polansky wrote:
I see now that you have paralleled the output windings. No sweat, but now you must make a ground connection, since this is a separately derived system. The rule is, at the SOURCE of the separately derived system (that is, within the isolation transformer enclosure) you must bond together the grounded and grounding conductors: the white and the green. So, you've used the brown and orange leads as your neutral. 1) Mark them with white tape, to indicate a neutral. 2) Connect a green set of conductors to the brown/orange connection and connect them to the receptacle ground pins. Disconnect 3) Disconnect the building grounds from the receptacle ground pins (that being the green wire from the power cord. 4) Connect a green or bare wire from the green/brown/orange splice to the grounding electrode system in the house. You can make this connection using a ground clamp on the cold water pipe, close to the existing clamp; in the main circuit breaker panel, on the bonding jumper (neutral bar), or spliced with a split bolt connector (commonly called a "bug"), right onto the grounding electrode conductor (wires running from the circuit breaker panel to the grounding means (rods, cold water, etc.)
All of the above is a must and the only challenging part should be the long wire to "ground".
Stuart, I'm not sold on your requirement to have a second ground on the secondary side run all the way back separately. While that would be ideal, I don't think it is a code requirement. What store-bought isolation transformer does this? I would do it if I could, but I don't see it as a "must" do. Bonding the grounded (neutral) and ground on the secondary side, and connecting that bond to the power cord ground, would appear to meet this requirement, at least as far as code.
So instead of connecting the secondary ground to a water pipe, it could be connected to the ground on the primary side. It's the same reference, code wise.
Yes, it's not as good, because there may be more ground noise voltage on the secondary by connecting the secondary ground to the power cord ground.
However, it would help to mitigate some of the inherent ground voltages on the secondary ground resulting from ground currents on the primary side:
1) This one doesn't cost anything. Disconnect all grounds from the chassis. Probably best to disconnect the filter and connections to the receptacles as well. With the transformer powered up, measure the voltage between the detached ground wire in the power cord and the chassis. Reverse the hot and neutral wire connections to the transformer primary and measure again. Wire the transformer for the lowest measured voltage. (Depending on the coil orientation in the transformer, it will induce a current in the chassis that feeds into the ground. So, connect the primary orientation for the least voltage from the power cord ground to chassis. BTW, do this for amps and pre-amps, dacs, etc., too, if they have a three-prong plug.)
2) Move the filter out of the transformer box, to a point closer to your circuit breaker box. This will shorten the ground conductor from the filters for less voltage on the reference do to noise currents. You would need it in a separate chassis, and hardwired to the CB box and hardwired to the cable run to your isolation transformer. Alternatively, move the combined filter and isolation transformer chassis close to your CB panel. This may not keep noise out of the run from there to your hi-fi equipment, but the bulk of the noise comes into your service entrance, anyway, and your ground would be cleaner, being shorter.
If 2) is done, put all the receptacles in another chassis near your hi-fi equipment. Tie each receptacle ground individually to a star ground in the chassis with the power cable ground.
I did not see a fuse in your chassis. You should definitely put one at the power cord entrance!!!! This should be rated no more than the current rating of your transformer.