Fremer's Single-leg panel is absolute tweak bs

kingrex said:

I really don’t understand where Erik gets the idea the grounding I did was extravagant. Its code??????? Go read NEC Article 250.

erik_squires said:

Extravagant is the difference between what the NEC would require (minimum 2) and what was installed.

@kingrex only installed one ground rod, 20ft long into the earth. He then tested the rod to soil resistance using the proper test equipment. kingrex met the requirements of 2020 NEC 250.53 Exception.

Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less the supplemental electrode shall not be required.                 

Kingrex's use of the Cadweld System (Trade Name for a exothermic welding process) is unusual for a residential dwelling unit but it is a 100% solid conductivity zero resistance connection of the grounding electrode conductor to the grounding electrode, (ground rod). It will be that way forever... Can't say that about an approved ground rod clamp. Remember the connection is buried in the earth below  grade. How often is the connection checked after it is installed?

FWIW The grounding electrode system primary purpose is for lightning protection. It is the foundation for a good system ground connection to earth for an electrical service.

The lower the soil to electrode resistance the faster a whole house SPD will divert a lightning transient to mother Earth.

Also worth noting 25 ohms is to high of a soil to grounding electrode  resistance. IEEE (Green Book) recommends 5 ohm or less for commercial and industrial facilities. Lightning could care less if it's a residential dwelling.

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@jea48 My mistake then, I thought there were a number ( > 2 ) of rods in the field.

I have two dedicated power lines to my stereo.  One goes to the two mono amps and one goes to the front end.  I had the two circuit breakers adjacent to each other in my breaker box, which means each one was on a different leg.  I took Kingrex’s advice and moved one breaker so that both dedicated lines are on the same leg.  The stereo sounds better now.  (The white wires and ground wires from each circuit are adjacent to each other on their respective ground busses. Ie. I want the ground wires as close together as possible.)  I’m using 10AWG wire and audio grade outlets.

I wonder if the stereo sounds better now because each leg (120 VAC) is out of phase with respect to the other and so now the amps, preamp and source are all on the same phase.

If there's a solid model or reasoning for using only 1 AC leg that is based on math I'd love to see it.

In Fremer’s case the sub panel could have been wired for 120/240V from the start. All the audio equipment still could be fed from one Line, leg. The electrician would have increased the size of the feeders knowing he would be feeding all the branch circuits from just one Line, leg.

If an isolation transformer was used with dual primary and dual secondary windings and the primary is wired for 240V, and the secondary is wired for 120/240V to feed a 120/240V panel unless the transformer is oversized to feed all the audio equipment branch circuits from just one Hot leg to neutral the audio equipment branch circuits would have to fed from both 120V Hot leg to neutral. Therein the loads some what balanced across both 120V legs.

An example, a 7.5KVA transformer is selected for use. The transformer has dual windings. Each winding is good for half of the 7.5KVA rating. 7500VA / 2 = 3,750VA at 120V each. 3,750VA / 120V = 31.25A.

So if the secondary is wired for 120/240V, (two windings are wired in series), and only one 120V hot leg to neutral was used, (Only one 120V, 3,750VA winding), it’s only rated for 31.25A max... If both legs were used to feed the audio equipment the full 7500KVA rating of the transformer would be available. 31.25A on one leg and 31.25A on the other. But the audio equipment would be fed from both legs. Not good for audio equipment that is connected together by wire interconnects... (One Hot 120V leg to the other Hot 120V leg measures 240V.)

If the two secondary windings are wired in parallel the full 7500VA is available.

31.25A + 31.25A = 62.5A Max available.

So in this case the electrical panel would be wired for 120V only.

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