Bundled conductors on the same circuit: Three separate wires reused as a subpanel feed

[brycenesbitt]

Ok, looking for thoughts on how to approach and understand this installation, including code issues.
The system has been operational for many years and there's no known complaint or disfunction.


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As far as I can tell the electrical system started life in the 1920's with knob and tube wiring to each of eight apartments.
There were probably four Edison base fuses per apartment and 2-4 circuits depending on the unit size.

But what I see today is the apartments each have a subpanel with a few 20 amp breakers.
The old knob & tube branch circuit wires now are bundled together as a subpanel feed.

To restate:
At the service entry point each unit meter is connected to a 30A 120V Square D breaker,
several individual 12 gauge knob & tube wires were ganged to feed a modern 120V apartment subpanel,
then 20A breakers feed each branch circuit.

The neutrals likely come back individually, that's yet to be verified.

 

[petersonra]

Unless there is a problem, leave it be.

Jmnsho.

 

[brycenesbitt]

Unless there is a problem, leave it be.

Insurance company nose poking. Not an option.
Options are to explain it, defend it, modify it or rip it all out.

 

[infinity]

At the service entry point each unit meter is connected to a 30A 120V Square D breaker,
several individual 12 gauge knob & tube wires were ganged to feed a modern 120V apartment subpanel

How many #12's? If it's two circuits you could put two single pole CB's in the panel below the meter.

 

[brycenesbitt]

How many #12's? If it's two circuits you could put two single pole CB's in the panel below the meter.

Could also put a 240V double pole breaker. But is there a specific problem that would solve or risk that would address?
Last thing I would want is a routine breaker trip to trip the main not the subpanel, as that's a callout to the apartment owner.

In terms of ampacity we have two to four parallel #12 wires with a wide separation, for a 30A circuit now.
I'm struggling to find exactly where that's covered in the NEC.

 

[infinity]

In terms of ampacity we have two to four parallel #12 wires with a wide separation, for a 30A circuit now.
I'm struggling to find exactly where that's covered in the NEC.

Parallel conductors must be #1/0 or larger so there is your code violation.

 

[brycenesbitt]

Parallel conductors must be #1/0 or larger so there is your code violation.

Is there a safety violation? This was a permitted job approved by the local AHJ, some decades ago: there's no code obligation to reverse the old AHJ decision.
Could you help me find the #1/0 parallel rule in the NEC for understanding.... but as well is there a safety
reason to be concerned about the use of parallel #12 ?

 

[infinity]

310.10(G)(1)

 

[jaggedben]

... This was a permitted job approved by the local AHJ, some decades ago: ...

If you have documentation that would be the one thing you have going for you.

 

[infinity]

This was a permitted job approved by the local AHJ, some decades ago: there's no code obligation to reverse the old AHJ decision.

I'm guessing they never even looked at it. I can't think of any inspector who would approve the mess in the photo.

 

[brycenesbitt]

I'm guessing they never even looked at it. I can't think of any inspector who would approve the mess in the photo.

I work in an area where the majority of homes and multifamily dwellings are from the knob & tube era.
The pictured main upgrade is not considered a mess here. The old stuff frankly is bulletproof unlike the
crowd that thinks that because NM cable is on the shelf at home depot and their uncle took them on a job once,
they can do electrical now.