Multi-wire Circuits the Movie

Multi-wire circuits can be confusing to people. 

How multi-wire circuits function, and problems related to them, are important to understand for electrical safety.  In a multi-wire circuit, the neutral (grounded conductor) is shared between two circuits.  Most circuits have their own neutral.  Generally speaking, multi-wire circuits perform just fine as long as the rules of installation are not violated.

Each leg of the multi-wire circuit must terminate on a different bus bar. 

Because bus bars are 180 degrees out of sync with each other, the neutral current can travel on the neutral wire safely.  If they were to terminate on the same bus bar, the current from the two circuits gets added together.  This is because the circuits are no longer 180 degrees out of sync with each other.  Wiring the circuits this way can result in overloading the neutral.  The amount of current leaving the breaker however, would not be more than normal and the circuit breaker would not trip even with the overheating wire.

The following read-along, video-blog attempts to discuss some of these issues.  Please pause or rewind the video where necessary to suit your own level of understanding and learning curve.  The demonstration board is set up to do many more experiments than what this post is about, so pay more attention to the overlays in the presentation and ignore all the rest.  Perhaps some of the other components will show up in a future post.

Charles Buell, Real Estate Inspections in Seattle


What the heck is an AFCI?

It seems like just yesterday that AFCI (Arc Fault Circuit Interrupter) type circuit breakers became required on 120 volt outlets in bedrooms.  It was the year 2002, and there was incredible gnashing of teeth over them.

afcibreakerThere were many who thought they were useless, a waste of money and a burden to the consumer.

There were also complaints of nuisance tripping, after all, what is one to think if every time you plugged in your vacuum and turned it on the breaker tripped.  Certainly there were some bugs to work out and pretty soon it became clear that if the vacuum was tripping there was in fact an issue with the vacuum and not the breaker–the breaker was just doing its job.  Of course some motors were not designed to not emit the kinds of signals that indicated an arcing condition to the brain of the AFCI and adjustments to both the brain and the motors had to be done.

Another issue with the AFCI’s was that it took a couple of years to get even electricians on board as to what an “outlet” was.  Some electricians and even jurisdictional inspectors interpreted the code requirement that all “bedroom outlets” be AFCI protected to mean “receptacle outlets.”  That however, was not what was intended.  An “outlet” can be defined as any place electricity is accessed.  Like lights, smoke alarms, the fans in hydronic heaters or gas fireplaces etc.  Anything that utilizes 120 volts and is located in the bedroom is supposed to be AFCI protected.

I still routinely find some of these 2002 houses with only the receptacles on the AFCI circuit.  By the next code cycle this was clarified and we started to see “all” bedroom outlets on the AFCI circuits.

There was always some question about the efficacy of these early AFCI breakers because they did not provide protection of the wiring for both parallel arcs and series arcs.  A justifiable complaint in my opinion since series type arcs are perhaps one of the most likely causes of electrical fires (like what would occur at a loose connection) and they required relatively high levels of fault current to activate the devices.  But they did pave the way for the “combination type” AFCI that could detect both series arcs (loose connections) and parallel arcs (line to neutral–short circuits).

In 2008 (with a start date of June, 2009) the combination type became required instead of the branch feeder type and they became required in more locations in the home than in just the bedrooms.

Some States, like Washington State, in their infinite wisdom (never underestimate wacky), decided to maintain the requirement for them to only be in bedrooms and amended the NEC to that effect.  This amendment was ignored by the larger cities, like Seattle, Bellevue and Renton where the full requirement of the 2008 National Electrical Code is enforced.  In brand new construction in Seattle, it is now common to run into service panels with many of these AFCI breakers–instead of just the bedroom circuits.  Now, as of 2014, AFCI’s will be found protecting the outlets in kitchens, laundry rooms, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas.

All of this represents some problems for the home inspector—we have to be conscious of the jurisdiction we are inspecting in.  Of course inspectors have always had to take the jurisdiction they are inspecting in into account.

How does the inspector share this information with their client?

Obviously it will vary depending on the house.  A pre-2002 house is pretty simple, we can ignore the issue (not a good idea in my opinion) or we can inform our clients that the overall fire safety of the home can be improved by the installation of AFCI breakers.  This of course is going to be greatly affected by the existing condition of the wiring in the home.  For example some panels won’t have room for them and of course if the house has an old fuse panel it becomes even more complicated.  Certainly in the context of a service change they should be added and the older the wiring is, the more benefit that can be derived by their presence.

For houses built between 2002 and 2009, the inspector might want to consider recommending upgrading the older style “Branch/Feeder” type AFCI’s to the safer  “Combination Type” AFCI’s.

Obviously the client would not be “required” to upgrade, but I still consider it a good recommendation–and then let the client decide.  I also like this approach because there were some recalled breakers during this time period that will automatically be eliminated if they are upgraded.

For a much more enlightened and thorough treatise on AFCI breakers please visit Douglas Hansen’s, AFCI’s Come of Age.


By Charles Buell, Real Estate Inspections in Seattle

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Replacing receptacles is going to be more expensive from now on!

AFCI Receptacle

AFCI Receptacle

Someone recently asked me what to do about three prong receptacles that have been installed in ungrounded circuits in older homes.  It is VERY common to see this in older homes and solutions did not use to be all that problematic.  One could either take out the receptacles and replace them with GFI type receptacles or return them to 2 prong type receptacles.

But today, it could mean that $3.00 receptacle is now a $3,000 receptacle.

Depending on what cycle of the electrical code is in effect in your area, this still could be easy–or, as is the case in my area, it could be quite difficult/expensive to address.  At the very least it is going to result in quite a learning curve for homeowners and anyone involved in real estate transactions.

For areas that follow the 2014 NEC, as Washington State does (along with 14 other states as of this date), it is not so much complicated as it is expensive when you start messing with the older receptacles–especially in ungrounded wiring systems.

Currently, if you want to change a receptacle, and it is in an old two wire circuit (ungrounded), your options are to change it to a new two prong type receptacle, or to a Tamper Resistant GFCI type receptacle, if it is to be installed in an area that requires Tamper Resistance (the vast majority of locations in the home and outside the home currently); AND, if the replacement is in a location that currently requires AFCI protection, one of the means of providing AFCI protection must be installed.

If someone has already improperly changed the receptacles to three prong type (non GFCI), what exactly would the “repair” be? The repair would be to replace them in accordance with current standards, just the same as if they had never been messed with.

In a sense it would have been better to have left them alone. 

In some cases sellers that have improperly changed out receptacles may be on the hook for expenses they might not have incurred had they left the circuits alone.  It is quite common in the context of putting homes on the market, to “spruce up” the look of the home with shiny new receptacles.

If the receptacle is being replaced in a three wire system (has a ground wire), then not only must it be replaced with a three prong receptacle that is Tamper resistant (if in an area that requires them) but if that receptacle is also in an area that currently requires AFCI protection then either the receptacle or the circuit itself must be AFCI protected.

“Older homes are statistically more vulnerable to electrical fires. Extra protection for older homes is provided by the gradual replacement, over time, of non-AFCI-protected receptacles with new AFCI-protected ones.”

This gets really complicated if there is no more room in the electrical panel for installation of the AFCI breakers.  There are AFCI type receptacles (Like the one in the picture above and they look much like a GFI type receptacles) that can be used, but they cost almost as much as a circuit breaker and you might need a lot more of them.  They also only protect the circuit from the point where the receptacle is first installed, whereas the entire circuit is protected by the breaker in the panel.

What I am getting at, is that it is completely possible, that in order to upgrade a few receptacles, you might end up having to upgrade your entire electrical service, install a bigger service panel, or add sub-panels to gain space for the AFCI breakers.  It could even mean rewiring your home as the safest and most cost effective road to take.

Whatever the solution is, it could turn that $3.00 receptacle into a $3,000 dollar receptacle, and why it might be the most expensive receptacle you have ever purchased.

For those of you that still have knob & tube wiring or other ungrounded wiring systems—the handwriting is indelibly written on the wall.


By Charles Buell, Real Estate Inspections in Seattle

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