Dedicated power circuits

I had to have the second phase run at Fremers because I could not get a letter from SqD saying a Square D subpanrl rated 120/240 was suitable for 120 only.

That jogged my memory. Sounds like the Electrical Inspector was using NEC 110.3 (B). Square D manufactured the Load Center to be connected to a split phase 120/240V AC source. The ampacity rating of the neutral bar can be, is, sized smaller for a split phase AC source because as you know the service neutral only carries the unbalanced load back to the neutral of the secondary winding of the power transformer. The neutral bar ampacity rating would not be rated big enough if the panel was connected to a 120V only source. (IF the panel was loaded to its full rated capacity.) There is the problem.

After reading your post I remembered having a conversation with my friend in Texas when I suggested feeding the electrical panel for his audio room equipment 120V only. In my friend’s case the panel was fed from a 15KVA isolation transformer. (Primary 240V, secondary configured for 120V only). I remembered talking to him about the electrical panel and the possible problem with the electrical inspector approving it connected to 120V only. I told him the ampacity rating of the neutral bar would be the possible problem. It depends on how well the inspector is versed on the NEC... He said, can’t I have my electrician just change out the neutral bar? No... Doing so will void the UL Listing. The Electrical Inspector, if his knows the NEC, as well as the electrical panel, will spot the neutral bar was changed out and flag the panel, If the panel was modified it needed to be re-Listed for the modification. No Listing, it can’t be installed. (NEC 110.3 (B) (C) ).

As for the panel for the audio room my friend wanted the best. Money was no object... Imo, a Square D panelboard with QOB bolt on breakers.

His isolation transformer would be 15KVA. At 120V the xfmr was good for 125A. I suggested he over size the ampacity rating of the panel. I can’t remember what I recommended. I do remember the Electrical Inspector passed it being fed 120V only but required the Electrician pull/install a spare conductor the same size as the existing ungrounded conductor for future, possibility of, feeding the panel 120/240V.

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As for Fremer’s video, he made the day of rewiring of the electrical service for his home, I cringed every time Fremer would say "every thing according to code". He said it several times in the video. I was surprised you guys didn’t suggest he stop saying that... As you know Code is bare minimum electrical safety standards... NEC could care less how an audio system sounds. All NEC cares is if it is electrically safe...

Jim

Don't we need metal boxes at each wall outlet and each metal box gets its own ground wire ran back to the panel? These grounds are separate from the romex. 

I don’t like MC cable or wire in a steel pipe.

I agree with your statement for use of steel armored MC cable or loosely pulled conductors in a steel conduit for the reasons you stated in your post dated 02-24-2023.

I do like and recommend 2 wire with ground solid core copper conductor aluminum armored MC cable though. ( MC, not, AC cable. ) The aluminum armor does reject some RF from entering the cable. What I like about aluminum armored MC cable is the Hot, Neutral, and insulated EGC, conductors are twisted in a spiral twist and held firmly, tightly, together by the aluminum armor.

Price for solid core copper 2 wire with ground aluminum armor MC cable is competitive with NM cable in my area. I agree twisting the hot and neutral current carrying conductors together and pulling the EGG along side the twisted pair pulled in conduit is better than AL armored MC but the difference, to me anyway, does not justify the additional cost, especially the labor cost... If cost is no object well then....

Note: MC cable should only be installed by a licensed electrician that has experience removing the armor from the wire for termination.

Jim

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For anyone interested:

Power Distribution and Grounding of Audio, Video and ...

Read pages 4 and 8.

Closely read pages 11, 12, and 13.

For Isolation transformers read page 19.

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I have dedicated circuits but still they don't address the noise issues which are a shared problem with everything else on the panel.

So I Think it should be recommended to additionally install a Power conditioner of quality that does not impede the flow of electricity.

This combo of Power conditioners and dedicated circuits seems optimal. I use a Transparent Power isolator which I use to plug in my amplifiers.

Additionally now that people have 10 gauge dedicated circuits they need to replace all the power cords what's 10 gauge Power cords. Doesn't this make sense?