Grounding Metal Outlet Boxes and Isolated Ground Receptacles

EDIT:

* For 120V audio equipment that is connected together by wire interconnects all audio equipment should be fed from the same Line, leg, in the electrical panel. ALL from L1 or all from L2. NOT from both.

This may not be practical, electrically a good practice, in all cases. Especially where big 120V fed mono amps are used in an audio system. A good example might be a pair of Krell 600 mono amps.

Putting both power hungry mono amps on the same Hot Line, leg, to neutral without trying to balance the load across the two Lines, legs, in the main electrical service panel could stress the electrical service panel bus and main breaker as well placing a large unbalanced load on the service neutral conductor and the power company’s utility power transformer.

It would be less of an issue if the electrical service is 200 amp or even less an issue if 400 amp. If the electrical service is 100 amp then the unbalanced 120V load could/would be a problem. If the house is old and the service might still be a 60 amp that would definitely put a strain on the electrical service.

Technically when fairly large 120V loads are know they should be balanced across the two Lines, legs, in the electrical panel. Only the imbalanced 120V load returns on the service neutral conductor to the utility power transformer. Example: IF all the 120V loads on L1, leg, equal 40 amps, and all the 120V loads on L2, leg, equal 40 amps then zero amps will return on the service neutral to the source. In this case the power company’s utility power transformer. In the case of a sub panel the same thing holds true. Only the imbalanced load returns on the feeder neutral to the main service electrical service neutral conductor.

The balanced 120V loads on L1 and L2 are in series with one another.

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bimmer528 6 posts 12-18-2016 10:34pm

Always follow code first. The use of plastic boxes are not legal in many areas. Nor is armored cable and romex
Given what you posted I’m assuming 1900 4 by 4 deep boxes were used and emt is the conduit. Running a separate ground is pointless. The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box

#6 is overkill. Amplifiers draw between 2 and 4 amps max

depending on what your running I would have ran two dedicated 20 amp on min #10 wire on a shared neutral.

the outlets you bought are good but so is just about any hospital grade. I’d be surprised if a furutech accepts #6 wire.

verify the panel is grounded correct. Tap after your main water shut off and jump to before the shut off valve

cheers

Always follow code first. The use of plastic boxes are not legal in many areas. Nor is armored cable and romex

Given what you posted I’m assuming 1900 4 by 4 deep boxes were used and emt is the conduit. Running a separate ground is pointless. The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box

The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box

depending on what your running I would have ran two dedicated 20 amp on min #10 wire on a shared neutral.

National Electrical Code 90.1 Purpose: -

(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

B) Adequacy. This Code contains provisions considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

FPN: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for increase in the use of electricity.

(C) Intention. This Code is not intended as a design specification or instruction manual for untrained persons.

(D) Relation to Other International Standards. The requirements in this Code address the fundamental principles of protection for safety contained in Section 131 of International Electrotechnical Commission Standard 60364-1, Electrical Installation of Buildings.

FPN: IEC 60364-, Section 131, contains fundamental principles of protection for safety that encompass protection against electric shock, protection against thermal effects, protection against overcurrent, protection against fault currents, and protection against overvoltage. All of these potential hazards are addressed by the requirements in this Code.

the outlets you bought are good but so is just about any hospital grade. I’d be surprised if a furutech accepts #6 wire.

verify the panel is grounded correct. Tap after your main water shut off and jump to before the shut off valve