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Tandem Breaker Cautionary Tale- Wenatchee and Chelan Home Inspection

Tandem Breaker Cautionary Tale- Wenatchee and Chelan Home Inspection

Most people have seen these little half sized breakers sometimes referred to as a tandem, double, half wide, skinny or wafer breakers.

                      Tandem Circuit Breaker               Cutler-hammer Circuit...  


They can be an approved breaker for the use in the electrical panel if they meet a couple criteria.

One is that the panel is rated for their use and two they are installed in the proper location as prescribed by the electrical panel manufacturer.

Electrical service panels will have a design for how many total circuits can be in the panel. For example if the panel has xxxx4040 in the part number this indicates 40 spaces and 40 circuits. But if the panel has a xxxx2040 in a part number usually indicates that there are 20 full width spaces and 40 circuits are allowed- meaning that 20 tandem/skinny/wafer (40 individual breakers/circuits) are allowed.

Now some manufacturers will have xxxx3040  number which has 30 full sized breakers and there will be a designated area where tandems/skinny/wafer breakers are allowed on the bus.

                             Tandem Breakers Allowed in these positions
So that is a quickie background on when and where tandem breakers may be used.

But there are more precautions that must be watched out for as in this scenario.

First... this specific panel is a xxxx4040 panel. Indicating that the use of tandem breakers are not allowed. So the use of the tandem is not approved for this panel.

                                                  No tandems allowed in this service panel

But we have a little more fun here… in this panel this specific tandem breaker is installed in a multi-wire branch circuit. This now kicks up the situation a bit. This mean the neutral (white) wire is being shared between two circuits.

                                                 Tandem breaker in a Multi-Wire Branch Circuit

Since the tandem breaker is installed on one leg (or bus) of the panel(In a normal multi-wire branch circuit the neutral wire is shared between two legs and will cancel each other out like a 240v circuit). So instead of having the circuits cancel each other out they now become accumulative and can overheat the neutral wire.

Let’s use a common example the dishwasher and disposal on a multi-wire branch circuit. For this example the dishwasher is 11 amps and the disposal is 8 amps. Since these two appliances are on two separate legs (busses) they would have a canceling effect, 11 amps – 8 amps would leave 3 amps potential on the neutral wire.

But if they are on the same leg then it would be 11 amps + 8 amps for 19 amps and this will start to overload the neutral wire which will heat up and can lead to fire.

Using your disposal to rid you of some food scraps is okay, but burning down your home would not be good.

If you do not fully understand the electrical system it is best to leave it to the professionals.

“We cannot solve our problems with the same thinking we used when we created them.”

Albert Einstein


NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Orville, Cle Elum, East Wenatchee, Quincy and many more…      

Your Wenatchee and Chelan Professional Home and Structural Pest Inspection Service

17 commentsDonald Hester • April 25 2012 06:25AM

Comments

Thanks Don, Very informative. This is something I never would have thought of.

Posted by Wayne Jackson, North Idaho Realtor, Serving Coeur dnullAlene and Hayden Lake (Lakeshore Realty 208-714-4109) about 2 years ago

Wayne, Thank you, sometime a good though can have some unattended consequences.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

Good info, Donald.  We run into them all the time.  I'm amazed at how many electricians I see put both legs of a 220+ circuit on one of these, and then they can't figure out why their circuit isn't doing what it's supposed to do.  I guess they don't fully understand how the phases flow down the box.

Posted by Mike Cooper, Your Winchester, VA Real Estate Pro (Winchester Real Estate Sales, Cornerstone Business Group Inc) about 2 years ago

Mike,

 Sometimse just because you know does not me you know better ; ) 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

aMazing what some pee pul will do with theyr electricitee

and Panels.

Posted by Anthony Daniels, SF Bay Area REO Specialist (Coldwell Banker) about 2 years ago

Anthony, This is true, sometimes you think it is a simple thing then it you find that simple thing has more complexities than you first think.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

Don it will be a good day for wiring when multi-wire circuits go away.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) about 2 years ago

Don -- you mean that there shouldn't be three wires going out from the circuit breaker?

Posted by Steven Cook, - Pierce, King, Kitsap, Thurston, Mason Counties (No Longer Processing Mortgages.) about 2 years ago

Charlie, If I had it my way they wold go away. I still have to convince a few more electricians ; )

 

Steve, no... no... not good. There are ways to make three wires work but his ain't one of them. We get to see all kinds of fun stuff out there in the world. 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

Looks like they installed an oversized neutral to try to "cover" the extra load?  Would not be surprised if that was not the thinking.

Great post Don.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 2 years ago

Electrical is nothing to mess with if you're not sure what you're doing.  Taking shortcuts can create problems and no one wants a fire.   Thanks for bringing this to our attention so we know what to look for.

Posted by Doug Bullwinkel, NMLS #281609 (Vitek Mortgage Group) about 2 years ago

Great post.  I find a heck of a lot more scorched neutrals than anything else.

Posted by Reuben Saltzman, Minneapolis Home Inspections (Structure Tech Home Inspections) about 2 years ago

Unfortunately that is allowed. I talked to an electrician friend of mine about it, he said its a dumb idea and he never does it. Good enough for me. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 2 years ago

Jay, That is actually a 240 circuit just below this tandem.

Doug, There are many out there who think they are electricians. 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

Reuben, In this one the neutral looked okay but this home was lived in by a little old lady so probally was not getting tested much.

Jim, I think that in this scenerio first you would have to properly size the neutral to be correct. The NEC states that in a single phase 3 wire config. that they should be on two poles, I think this infers two legs.

 If your electrician can provide some info that states other wise I would love to know. 

 I am not a big fan of multi-wire branch circuits in residential. Multi-wire and back-stabbed eceptacles should just go away ; )

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

Don, You misunderstood, I am agreeing as does the electrician, a single neutral for two circuits is a bad idea.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 2 years ago

Jim, Sorry for the confusion. My bad ; )

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 2 years ago

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