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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3666
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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I recently installed a 30-amp interlock breaker in my

Customer Question

I recently installed a 30-amp interlock breaker in my breaker panel for my portable generator.
I planned on using 2 Murata Power Solutions ACM20-2-AC1-R-C meters to measure volts, amps, watts and Hz to monitor L1 and L2 from the generator. The meters use 2-18 awg leads to monitor the power .
The issue I have is this, I would like to monitor L1 and L2 directly however since I cannot double tap the wire feeding the breaker I need a way to legally and safely tap into L1 and L2 with the 18-awg wire. I could pigtail off the breakers for a branch circuit but would rather not since turning off that breaker will not allow me to monitor that particular leg of the main.
Any suggestions would be greatly appreciated.
Submitted: 1 year ago.
Category: Electrical
Expert:  Mike G. replied 1 year ago.

Hi, I'm Mike G and I'll be assisting you. Simple solution - install a junction box ahead of the entry into the panel. You can make up your taps there.

Customer: replied 1 year ago.
Unfortunately it is a manufactured home and the walls are finished so that isn’t an option. I have to stay within the confines of the box.
Expert:  Mike G. replied 1 year ago.

The junction can be anywhere. Either use the power inlet box or add a junction box there. Another way would be to use a quad breaker for the gen power and the connections for the 18 wire.

Customer: replied 1 year ago.
The power inlet box is not in close proximity to the breaker panel so running wires to it are not practical. With respect to running a quad breaker, my panel is full and I do not have the space available to use a quad.
Expert:  Mike G. replied 1 year ago.

If you are using a 2 pole 30A for the interlock, replace it with a 3030/1515 quad.

Customer: replied 1 year ago.
already using a quad in that location
Expert:  Mike G. replied 1 year ago.

Can you use another quad to free up the terminations?

Customer: replied 1 year ago.
Unfortunately not, I'm pretty much maxed out, which is why I was looking for an alternative solution
Expert:  Mike G. replied 1 year ago.

Sorry but I've run out of ideas for you. I'll it out and possibly another expert can think of something to help. Please stand by. Good luck.

Expert:  Kevin replied 1 year ago.

Hello and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.

1) Show below is a partial solution to the problem, but this will only provide you with amp measurements. In order to monitor the wattage, you would need to monitor the current on each leg connected to an amp and L2 and then multiply each current leg by 120 volts to convert to watts. Not sure if this is an acceptable solution for your application or not?

A) At the 30 amp double pole Interlok generator breaker, install a 30 amp rated solid core current transformer (CT) toroid on each of the breaker hot legs. Then extend the current transformer wires and connect them to a panel amp meter. Solid core CT's take up less panel space than split core CT's.

The solid core current transformer does not require any physical wire termination to a circuit breaker. When the toroid is placed around the hot conductor, it senses the amount of current via inductance. This will solve your problem since it sounds like your panel is maxed out and you cannot use any tandem or quad breakers to free up breaker space. If a solid core current transformer with a panel amp meter is not acceptable as a partial solution, then a sub-panel would need to be added in order to free up circuit breaker slots.

B) Refer to the 2 links shown below for an example of a CT application:

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.