Tandem Breaker Cautionary Tale- Wenatchee and Lake 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.

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.

                             
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.

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.

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…      

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