I hired an electrician replace my old 6 fuse subpanel with breakers at an existing newer subpanel. I thought I’d get wires running from each circuit to a new breaker, but all he did was wire the six circuits to the old 10 gauge feeder he disconnected from the main (3 on the red and 3 on the black) and then run the feeder to a new junction box where he ran two 12 gauge lines to 2 new 20 amp breakers on the newer subpanel. He says this meets code.

The 6 circuits are the doorbell and 5 knob and tube serving 4 rooms and a bathroom. 11 total outlets, 11 lights, 4 smoke detectors, 1 bathroom fan. Am I right that there should be 6 new breakers, 15 A for the lights and 20A for the outlets?


Assuming the wires are all 12 AWG, this meets Code.

However, current Code requires dedicated circuits to certain rooms and loads, e.g. bathroom receptacles must serve only bathrooms; two kitchen countertop circuits; dedicated washing machine circuit; yadayada. Your setup as it was, with six circuits was Grandfathered, not obliged to be brought to current Code, however, you cannot make things worse. So for instance if one circuit once served a bathroom receptacle and 2 others, and now serves a bathroom receptacle and 5 others, that qualifies as "worse" and is not allowed.

You'll be able to charge a cell phone from any outlet. You'll be able to run a heater from any outlet. Two heaters.. good luck LOL. This is the problem with this setup. Why would the electrician really cheap out on this deal?

I can think of two possibilities. Some people worry about "old" Knob-n-Tube having arcing faults or ground faults. I think Knob-n-Tube is awesome, but discretion being the better part of fandom, I would still put K&T circuits on an AFCI breaker because that will detect most potential K&T problems (as well as most potential Romex problems), and GFCI also because that rounds up the last of potential problems, and allows 3-prong plugs on ungrounded circuits. I suspect the electrician did in fact put them on AFCI, and at $50 each, there wasn't budget for 6 of them. (possibly because you set the budget? ;)

Second, speaking of multi-wire branch circuits, back in the K&T day they positively loved multi-wire branch circuits. That's where 2 hots share a neutral, and this works if the hots are on opposite poles. I presume the electrician did attempt AFCI and/or GFCI. Those require a 2-pole AFCI/GFCI breaker, and the installer may not have been able to figure out the intended MWBC topology, or there may have been illicit neutral-sharing that would prevent an AFCI/GFCI from working. The easy fix is to put all hots which share neutrals (properly or not) on the same single breaker.

Absolutely, if I had done the job, it would have been six circuits, possibly three multi-wire branch circuits and a spare /3 to avoid hitting NEC 310.15b3a limits whilst giving me some expansion room. I'm not even thinking of MWBC because the Knob-n-Tube might have that; I just like how it lets you get 8 circuits within 310.15b3a limits.

I have no idea where you got the notion of a 15A breaker. Breaker size has nothing to do with circuit function. It has to do with

  • the wires downline of the breaker
  • not in this case, but in larger circuits, the type of receptacle
  • not in this case, but in some cases, the instructions provided with the appliance
  • not in this case, but sometimes, motor or welder spec

Not counting wires built into lamps, switches or other appliances... If your wires downline contain any wires which are #14, then the breaker must be 15A. If all wires are #12 or larger, 20A is correct. Any circuit which serves common NEMA 5-15 sockets (you know the one) must be 15A or 20A.

  • Thanks for the reply. I have to say I’m surprised and relieved. – Dylan C. Mar 3 '19 at 16:11
  • @DylanC. I've edited significantly. I just saved mid-write to change computers. It's not illegal (probably), but you're gonna hate it when you start using heaters, laser printers, anything with a lot of draw. – Harper - Reinstate Monica Mar 3 '19 at 16:24
  • New breakers not AFCI. – Dylan C. Mar 3 '19 at 16:32
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    @DylanC. /facepalm I don't believe that's legal if your state has adopted NEC 2014. (Which some states are resisting because they think the AFCI requirements are excessive). This was the perfect time to fit AFCIs. – Harper - Reinstate Monica Mar 3 '19 at 16:35
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    @DylanC. whoops – Harper - Reinstate Monica Mar 3 '19 at 17:04

A picture (likely a bit too late for that!) of the old panel would be helpful. Sounds a bit fishy to me, as bathroom should have at least one circuit by itself (ideally 2 so that lights are separate from outlets) and in any case having so many rooms on one or two circuits really limits usage. Plus if there is any 15A (i.e., 14 AWG) wiring anywhere in the existing circuits you now have a serious code violation/danger.

Some of your loads - smoke detectors, bathroom fan (assuming it is only an exhaust fan and not a heater/fan) and doorbell use very little power. But receptacles for the rooms could use and should be able to use a lot of power. Two heaters at the same time are guaranteed to cause problems if they are on the same circuit. But also a hair dryer in the bathroom plus a few hundred watts elsewhere - e.g., computer, laser printer, vacuum cleaner - all running at the same time will either cause nuisance trips of a breaker (because what used to be two separate 15A (or 20A) circuits are now one 20A circuit that gets overloaded with normal usage) or cause a fire hazard because some of the existing wire (previously on a 15A fuse) is now overloaded for the wire but not overloaded enough to trip a 20A breaker.

What the electrician should have done is to either splice all the circuits from the old fuse box (using it as a big junction box) to 6 new circuits in the breaker box or reroute the circuits directly to the breaker box, bypassing the fuse box. Which option would have been best/cheapest depends on the specifics of your particular installation.

The only exception, in my mind, is that the smoke detectors, as a well-known low-power item, could have been combined with another circuit. However, that was likely already the case because wired smoke detectors (or actually, any residential smoke detectors) didn't exist in the days of knob & tube wiring. So they must have been added at a later time, almost certainly piggybacked on an existing circuit.


AFCI is required in most areas, including California, for most circuits when upgrading. It is particularly helpful for knob & tube and other older wiring as it can help catch certain types of problems before they would result in a house fire. Since your electrician did not, as noted in comments, install AFCI breakers for the "6 circuits that became 2" then that is another sign of a big problem.

Being lazy (not moving as many wires means less work) and/or cheap (fewer breakers = less spent on parts) isn't necessarily bad - you may have even indicated to the electrician that the cheapest solution would be the best. However, a licensed electrician has a responsibility to do all work according to local code requirements. Squeezing 6 circuits down to 2 may be OK - and in fact may have saved a lot of money if your breaker panel was nearly full. But ignoring code requirements for AFCI (and perhaps GFCI too if the bathroom receptacles aren't already protected) is a real cause for concern as these requirements are, by and large, based on real safety (human & property) issues.

  • What you said the electrician should have done is what I was expecting. The are only two white commons in the old box. He said if he ran 6 circuits there’d be too much common which could cause problems. Thanks for the AFCI tip. – Dylan C. Mar 3 '19 at 16:25
  • Harper's comments about MWBCs are quite possibly correct. But that would cut 6 separate circuits down to 3 MWBCs, which would mean 3 common (neutral) wires, not 2. Something doesn't add up. – manassehkatz-Moving 2 Codidact Mar 3 '19 at 16:28
  • The 2 commons are from the old knob and tube, returning one on each side to the old fuse box with 5 blacks. – Dylan C. Mar 3 '19 at 16:46
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    It's entirely possible you didn't actually have 6 circuits with those 6 hots. I regularly have MWBCs where there's 1 neutral, and 4 hots. Hot 1-2 go up pipe 1 with the neutral... hots 1A-2A go out pipe 2 to the switch and comes back as a switched-hot 1S and 2S and go back out pipe 1. Those 4 hots land on 2 breakers, since I use breakers that take 2 hots. – Harper - Reinstate Monica Mar 4 '19 at 2:16
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    Thanks to both of you gents, manassehkatz and Harper for your help. – Dylan C. Mar 4 '19 at 2:17

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