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Tap dancing around double lugs

 

I am sure that most real estate agents have heard the term “double tap” so many times that I am likely to lose most of you due to not being able to bear having to hear about them even one more time.

But!

Hang in there--because this will be a slightly different conversation about “double taps.”

Service PanelFirst of all I need to clear up a “technical issue.”  Technically an electrical installation that is generally referred to as a “double tap,” by many home inspectors and the general public, is really a “double lug.”  In electrical installations a double tap is an entirely different thing and is typically a point where wires are spliced together---not typically related to two wires placed under the same screw terminal---as is a double lug (or multiple lug as the case many be for more than two wires).

Now the average real estate agent’s eyes will start to glaze over when the inspector goes into his or her spiel to their mutual client as to what is wrong with double lugging.  The discussion will revolve around how when two wires are placed under one screw it is hard to be certain that equal pressure is being applied to both wires.  If there is not equal (enough) pressure on one of the wires then there is the possibility of arcing at the connection.  No one should need any education regarding the problems with arcing of electrical connections---unless of course you are doing welding and then arcing can be very useful.

The correction is remarkably simple and typically takes less time than it does to go through the whole process of making the agent’s eyes glaze over.  It is a repair that can usually be done when the electrician is at the home doing something else.  Correction is as simple as taking the two wires off the breaker and wire-nutting them together with an additional wire that is then run to the breaker.  As a side note, there are some breakers that will allow two wires to be properly connected to them, but for our discussion here, we are going to ignore them. 

Of course the bigger problem with double lugs is that they are an indication that the service panel may no longer be adequate to accommodate the electrical needs of the home---that or Uncle Homeowner was too lazy to go and buy another circuit breaker.  So what turns into a 2 minute fix turns into a complete service change to the home.

There is one type of double lugging on circuit breakers that deserves more immediate attention than the typical installation of two same gauge wires under the same screw.  It is not to hard to get one’s brain around the notion that two wires of different gauges (thicknesses) will very likely not have equal pressure on each wire.  An even worse variation of this theme is when the wires are different types---as when one is solid wire and one is stranded type wire.

In the picture below we see three circuit breakers---the top two have double lugging. 

 double lugs

The top breaker has two wires of the same gauge under one screw.  The middle breaker has two wires under the same screw but one is solid wire and the other is stranded. 

Where as you would have to be very unlucky for the top breaker connections to be a problem, with the lower breaker you would be pressing your luck and an arcing condition would be much more likely.


Charles Buell, Real Estate Inspections in Seattle

 

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Seattle Home Inspector

 

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Comment balloon 21 commentsCharles Buell • January 13 2013 07:54AM

Comments

Great photos and descriptions of what you see on the inspection Charles, it sure helps to get a good clean look at the problem. 

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) almost 6 years ago
This issue does seem to come up frequently - thanks for a really good description of what it's about, why it's a problem....and what needs to be done. Good stuff!
Posted by Nancy Conner, Olympia/Thurston County WA almost 6 years ago
Really great explanation! I appreciate the education!
Posted by Francine Viola, In Tune with your Real Estate Needs - Olympia WA (Coldwell Banker Evergreen Olympic Realty, Olympia WA) almost 6 years ago

Charles,

Great post, I do have a question would it be better to add a subpanel,or new Larger panel

because the need for circuits has outgrown the capabilities of the old panel?

Ricky D

RD House Real Estate & Property Management INC

Seattle,WA

WWW.RD-House.com

Posted by Ricky D. Sadler, Trusted Senior Property Advisor & Marketing Expert (Real Estate Marketing Experts &Trusted Senior Advisors on Property Management services, Rentals Leasing, Landlord Tenant ) almost 6 years ago

Tom, I think it makes it easier to understand when you can actually see the stranded wire and solid wire under the same screw---even though the same gauge

Nancy, thanks---glad to be of help

Francine, thanks---glad you liked it

Ricky, I guess that would depend on how much you were adding.  Because this is an older service anyway, in this case I recommended upgrading to a larger service.  In some instances a sub-panel could suffice.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 6 years ago

Charles -- this is a great explanation of double lugging.  Thank you for the very informative photos and accompanying information.

Posted by Steven Cook (No Longer Processing Mortgages.) almost 6 years ago

But some arcs are really pretty - a long home run, a rainbow, or a touchdown pass, for instance.  In a panel box it would be hard to see with the cover on.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 6 years ago

Oh, if I have been called a lug more than once, does that make me a double lug?  Next time I'm out there you can tap dance around me...

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 6 years ago

"Double taps" I think are made more into mountains than they deserve. The problem I find more often is when tandem breakers are added to avoid the double connection. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) almost 6 years ago

Great post.  Thanks for the clarity on the issue and the photos. Will know what I am looking at next time on an inspection.

Posted by Susan Jackson (America's Network Realty Group, Inc) almost 6 years ago

Good morning, Charles. Very good point! I see this more than I care to especially on older properties...

Posted by TeamCHI - Complete Home Inspections, Inc., Home Inspectons - Nashville, TN area - 615.661.029 (Complete Home Inspections, Inc.) almost 6 years ago

Charles, I was not aware of the different terminology. thanks for the clarification and additional information.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA almost 6 years ago

Steven, thanks

Jay, as long as I don't have to lug you around :)

Jim, well the tandems can be a proper repair if the panel is rated for them.  I often find the tandems in slots not rated for them.  Then again some panels are rated to take tandems in every slot.

Susan, glad to help

Hey Michael T, long time to see!  So nice to see you back.  Lots of older properties end up with this issue for sure.

Michael S, while the terminology might be considered minutia, it is good to be able to communicate accurately.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 6 years ago

Here the wire nut connection inside the panel is just as much an issue as the double tap or double lug. The code is interpreted as requiring connections in a box outside the panel and new leads run into the panel, resulting in no wire nuts or marretted joins in the panel itself and only one wire under the lugs.

Note: same code, just interpreted or applied differently.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) almost 6 years ago

@Robert, is that a Canada thing?  Here a double tap is actually the proper correction to a double lug.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 6 years ago

Ok, I admit it...my eyes did glaze over, but I forced myself to keep reading because I always enjoy your posts! The last photo and explanation made it all clear to me! Now, I understand!! Thanks, Charles!

Posted by Nina Rogoff, Sells Real Estate! (RE/MAX Executive Realty) almost 6 years ago

Luckily no glazing over for me. Just the realization that I've been calling it a double tap instead of a double lug. I wonder why even the electricians down here are using the wrong term.

Posted by Michael Therriault, The name to remember when you want it done right. (Michael Therriault Contracting - M.T. Contracting) almost 6 years ago

Nina, I knew they would :)

Michael, I used to as well until I was corrected by the WA State head electrician.  It has become pretty standard---not sure it can ever reverse itself :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 6 years ago

Here we are taught to call it a double tap, which describes the action of tapping or drawing power twice from the same breaker. This is not acceptable practice (at least for us).

The entomology of double lug, I believe, is referring to the equipment itself, which physically has positions for placement of two leads.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) almost 6 years ago

Robert it is mostly semantics but the NEC actually talks about taps as being splices that are not under attached lugs.  So two wires under a lug would be a double lug---not a double tap.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 6 years ago

What you and the NEC are referring to as taps is what we call joints, usually marretted or having a wire nut. Even if the semantics or word usage is different, the conditions described are not to code because they creat risk conditions.

As you say it, double lugs, is two circuits branched from the same breaker, and for us that is not to code even if the wire types and size match.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) almost 6 years ago

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