arc fault knob & tube

required a Fed Pacific panel be replaced and the K & T wiring be replaced or protected by an AFCI. At the reinspect the new panel was installed but I was told the AFCI won’t work because of shared neutrals. I am not sure what the repair would be or can the AFCI’s be installed anyway on the 3 remaining K & T circuits ?

I am not sure I understand the term “shared neutrals” appreciate your comments

Forgive me for being blunt, but are you a licensed electrician? Are you otherwise qualified to “require” such things as panel replacements and wiring replacements or installation of AFCIs? I sure hope your reports don’t actually use that kind of language. I’d be pretty ticked off if a home inspector who doesn’t understand “shared neutrals” made expensive electrical “requirements” in a report about my home.

Now you’re in a pickle because you placed yourself in the position of being an expert. They tried your “requirements” and it didn’t work. What you should have done was point out the hazards and defects and “refer” the issue to an electrician.


“The residence is wired with suspect knob-and-tube wiring, which was commonly installed prior to 1950. It is ungrounded and over time the wire’s insulation may become brittle and fall apart or wear thin, resulting in exposed conductors and a risk of shock and/or fire. The hazard is increased by covering it with insulation (a common practice), and incorrectly tapping new wiring into it. We recommend that the wiring be evaluated by an electrician and certified as being safe or replaced.”

A shared neutral is where two circuits share the same grounded conductor and the circuits are on opposite phase legs. A common example would be two small appliance circuits wired with a single three conductor with ground NM cable.

As an electrical contractor, I never installed shared grounded conductors. The problem is that Mr. DYI Homeowner could come along and install tandem breakers to add circuit capacity to the panel then put the circuits sharing the grounded conductor on the same tandem breaker.

When installed properly and left that way, there is nothing wrong with sharing the grounded conductor. The grounded conductor will never carry more current than the heaviest load on either circuit. However, if both circuits are on the same ungrounded bus, the grounded conductor could carry the total current of the two circuits.

If you are interested in learning more about shared circuits, you can sign up for a free electrical course in the Education Center on my website (BestInspectors.Net) that covers the topic. I also do an online class (also free) to go along with the off-line course. The free course also counts toward your InterNACHI continuing education requirements.

A shared neutral is one that is used between 2 circuits that are on opposite legs of the panel. They carry the difference of the current between the 2 hots in a properly wired circuit.

Joe, I think you way over the top with your comments… I did not list my full report in the post but only wanted to get to the issue.

How are we to learn if every question one asks gets a condesending repsonse.

As a home inspector i belive I should require a known problem panel to be replaced ,as noted in our state SOP.

I did refer it to a licensed electrician to inspect and make safe, he left the k&t buried in the insulation and exposed hot ends where he cut some of it off. So much for the Pro’s. now he says it is safe and what am I to do ?

George, do the shared neutrals make a AFCI inoperative or not useable ?

Tell your client that the electrician should put his statement that the system is safe in writing on his letterhead, complete with his license number. I would say, even if the electrician is stupid enough to do that, that I could not endorse the system and the client should seek a 2nd opinion.

Who chose the electrician?

I still say you went overboard by demanding a specific type of repair (arc faults, panel replacements, etc.). No offense intended.

Joe. Seller picked the electrcian. I only required the panel repalcement and the K & T to be out of the insulation and recommended adding an AFCI, but to have a pro electrcian inspect and repair to make safe. I also could not find a permit or state sticker on the new panel and asked for a signed off permit, he is stubbling around to find one he says he has (work was completed 2 days ago) probably bootlegged it in, I forgot to check to see if the utilities meter seal had been broken before I left.

You do a lot more for your clients that I do. I don’t want contractors furnishing paperwork to me. I communicate with my clients only. I would recommend that the client ensure permits were obtained and that the work was performed by licensed contractors. But I certainly wouldn’t do all that documentation checking work for them unless compensated.

Again, if there is a question about it, tell your client to hire his own electrician as any electrician who would say in writing that K&T buried in insulation is safe is incompetent. (There is a difference between competent and licensed.)

I don’t know. I no longer do electrical work and I have not yet been asked to investigate a fire or injury where there were AFCIs installed. To be perfectly honest, I never thought about shared neutrals and AFCIs together until I read your post.

Correct. Here’s a good explanation.

(A common example of a shared neutral is the dishwasher and garbage disposal.)

Ron, with all due respect, I don’t see where Joe was being condescending in his comments. It sure looks to me as though he is trying to look out for you. He was was helping by giving it to you straight. Think of it this way - would you rather be challenged by fellow inspectors who are trying to help you or some lawyer who is out to win a case against you?

Washington’s SOP is very much like other state and organization SOPs. I’m not saying you are wrong but I cannot find anywhere in the SOP or the law that gives home inspectors the authority to require anything. A provision granting that kind of authority would have profound implications. I would think that it would be challenged by the entire real estate and construction communities and local building regulation departments. Here are some relevant excerpts from the WA SOP:

WAC 308-408C-020 Ethics—Statement of purpose.
The home inspector must:

(4) Perform services and express opinions based on genuine conviction and only within the inspector’s area of education, training, or expertise.

(6) Not provide services that constitute the unauthorized practice of any profession that requires a special license when the inspector does not hold that license.

308-408C-030 WAC 308-408C-030 Exclusions and limitations.

Inspectors are not required to:

(1) Determine the condition of any system or component that is not readily accessible; the remaining service life of any system or component; the strength, adequacy, effectiveness or efficiency of any system or component; causes of any condition or deficiency; methods, materials, or cost of corrections; future conditions including, but not limited to, failure of systems and components.

(2) Comment on the suitability of the structure or property for any specialized use, compliance with codes, regulations, laws or ordinances.

(9) Offer or perform any act or service contrary to law.

(10) Offer or perform engineering services or work in any trade or professional service other than home inspection.

I am not trying to give you a hard time or trying to be argumentative. I get o nthe message board when I have some time (or don’t much feel like working) to help other inspectors. As your fellow InterNACHI members, we would be remiss if we were not to challenge you about a practice such as requiring things in your inspections.

As I said earlier, I am not saying that you are wrong but, I’d also sure be surprised to learn that you are right. If you are wrong, hey, it’s no big deal. We all learn by having open and honest discussions. That is not to say that there are not people who get on the board just to stir things up. In fact, I limit my participation on message boards for that very reason. In this instance though, I don’t think anyone is trying to do anything but help. One thing you might want to consider is starting a new discussion thread in the ethics section. You will probably attract the attention of other Washington inspectors who can share their thoughts on the subject.


Ron was referring to a section of the Washington State SOP that states:

 (h) **Report** on any circuit breaker panel or subpanel known within the home inspection profession to have safety concerns.

As home inspectors, there is nothing we can REQUIRE.

Thanks Stephen. I knew “Report” was in the SOP but I was looking for anything that said that the inspector had the authority to require anything. Ron had used the word “Require” in his original message. My concern for Ron is that he could get himself into a bit of trouble if he implies that he has the authority to require an update. I don’t mean to split hairs about the meanings of words but we provide mediation services and we frequently see big disputes grow out of the meaning of a single word or phrase.

thanks all for your comments, as I mentioned early on I did not post the full content and extent of my report and I guess I needed to, I wanted to try to get to a short answer to a question. I appreciate Joe’s comments but I still feel they were too strong and can scare away newbies from asking questions. I thought that was how we learned. I know we cannot and I do not REQUIRE any thing only recommend. And in this case I had recommended a professional evaluate etc and he did not perform so I was a bit frustrated. for both yours and Joe’s benefit I did take a 7 hour electrical course today from one of the writers of the code check books, but I am still a bit confused on shared neutrals.

next time I will PICK my words more carefuly as I see they are read as a technical statement rather than a general questions which is fine and I should clarify that in the intial post.

Ron, you are welcome to attend my online electrical class December 2nd. It is free and will count toward your InterNACHI continuing education. The online portion of the class is two-hours. You should read the offline portion in advance of the class to get the most of the class and to qualify for four continuing education hours. The way it works is that attendees come to the class with questions about the offline material. We usually go into depth on two or three topics. I try to leave time at the end to cover things that are not in the course materials but that inspectors need help with.

The topic of shared neutrals is one that comes up often. I have a few diagrams that you can look at and I can do sketches during the class to illustrate points.

My approach to teaching electrical is a little different from other courses you may have taken. I don’t like to go into building codes until I am confident that the underlying concepts are understood. Only then, will I explain how the codes address these things. I would also rather have you leave the class with a clear understanding of something that you have been struggling with than to throw a whole bunch of stuff at you and have you leave not really understanding any more than before the class.

If you are interested in attending the December 2nd class, please let me know in advance. Space is limited. If I have more than I can accommodate, I’ll schedule a second session.

Details are posted here:

I also post a message on this board a week or so before each class. The class is free to all InterNACHI members.

Answering the technical question: yes it is possible to install an AFCI on legacy multiwire branch knob & tube circuits. This requires a (previously) rare Double-Pole Combination AFCI such as the Siemens Q220AFCP. I’ve had electricians and inspectors claim this device does not exist… but look for yourself, it does, and works.

But be warned:* it may not be possible to get it work in a particular house, due to the many chances for interconnected neutrals with K&T*. But if it does work, it can protect against a big fear with K&T: insulation degradation where wires enter metal junction boxes.

I’m in California where K&T may be insulated over by code, but sometimes insurance does not cooperate.