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Kevin, Licensed Electrician
Category: Electrical
Satisfied Customers: 3202
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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Can I use the power connecting an outlet to power a small panel

Customer Question

Can I use the power connecting an outlet to power a small panel box to add two lights and and attic fan?
Submitted: 1 year ago.
Category: Electrical
Expert:  Kevin replied 1 year ago. name is ***** ***** I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!
1) Can you please provide some additional details on the application?
2) You want to install a sub-panel (small panel box) off of an existing receptacle and then extend the lights and fan from the sub-panel?
3) Does your main electrical panel contain 2 empty circuit breaker slots or is the main panel maxed out and no more available slots left?
Customer: replied 1 year ago.
1. Yes
2. Yes - it is in an attic. I have currently have two bulbs and an attic fan on the circuit. I just want to add an exterior light in a blind spot on my house.
3. Main panel is maxed out and is also a long way from where I want to put small panel box. And when I say long way the main panel box is in the garage and the outlet I am thinking of using is in the center of the house in attic
Expert:  Kevin replied 1 year ago.
Thanks for the replies and confirmation.
1) Do the 2 existing lights and the attic fan all reside on the same circuit breaker? Or will the lights and fan all be a new installation?
2) How many watts are the existing light bulbs and new exterior light?
3) No you can't extend a sub-panel feeder circuit off of an existing wall receptacle. Sub-panel feeder circuits must always extend from the main electrical panel. The smallest size sub-panel is a 30 amp and the feeder circuit needs to be a 4 wire circuit that provides both 120 and 240 volts. A wall receptacle box is only 120 volts and resides on either a 15 or 20 amp circuit breaker.
4) Is the home a single story ranch or a 2 story? Does the electrical panel share the same exterior wall as the attic? Will it present a problem to extend a new circuit into the attic area or a difficult install? Any chance you have EMT metal conduit in the home or all Romex cable?
5) Even though the panel is maxed out, you may be able to add some twin (tandem type) breakers to it. Take a look at the panel label and see if it allows tandem type breakers. The other way to determine if the panel can accept tandem breakers is to remove one of the bottom breakers and perform a visual inspection on the hot bus bar stab. If the hot bus bar stab contains a notch in it, then the panel will accept tandem breakers. If no notch on the stabs, then tandem breakers won't fit in the panel.
Customer: replied 1 year ago.
1. All are currently on the same circuit
2. 100 watt x 2, Attic Fan + new exterior light with 2 - 60 watt bulbs + 100 watt interior. I plan on using LED Bulbs in the fixtures with 100 watt equivalent
3. Ok
4. Single Story - built in '93 I can probably feed cable up with wiring going from current panel box to attic. Some wiring already in attic going to ceiling lights all over house. No conduit or Romex that I have found.
5. Hot bus bar does not have a notch
6. I have been quoted $1,600 to put a new main panel in and add subpanel but he wanted to do it unpermitted which made me cautious.
Expert:  Kevin replied 1 year ago.
Thanks again for the replies.
1) If the lights and the fan are the only loads that are connected to the circuit, I recommend to tap into the existing circuit and extend the new light from there.
2) This really depends upon the total amps or wattage on the existing circuit. For example, the average attic fan is a 3 amp motor and will "in-rush" to 6 or 7 amps upon initial start-up and then go back down to 3 amps or so. If the total light bulb wattage is around 420 watts, that gives you approximately a total amperage of 3.5 amps for the lights and another 7 amps for the fan (upon initial fan motor start-up). Therefore, the total amps required for these loads are well under a 15 or a 20 amp circuit breaker. All depends on whether all of the connected loads will ever be run simultaneously or not.
Whenever tap'ing into an existing circuit, electricians will typically use a clamp-on amp meter at the circuit breaker and then turn all connected loads to the ON position and obtain an amp measurement. Once the existing amps are known, then the determination can be made to tap into that circuit or install a new circuit. If no clamp-on amp meter available, then all of the wattage and/or amps on all of the connected loads must be calculated to make sure the breaker won't overload and trip.
Watts Law is used to calculate the total wattage or amps on a circuit as shown below:
P = I x E, where P = Watts, I = Amps and E = volts
or I = P/E. Once the total wattage is known, then the total amps can be calculated.
3) $1,600 is a reasonable price to perform a panel upgrade as well as installing a new sub-panel. However, I always recommend when hiring a local electrician to perform such work, that they be licensed, bonded and insured. All major electrical work should also be inspected by a local electrical inspector. Yes, I would also be cautious. Any major electrical work such as panel upgrades, etc. require that the electrician pulls an electrical permit and not the homeowner. Once the electrician pulls the permit, any liability is on the electrician.
4) Even though the main panel is maxed out, a sub-panel can still be installed. A sub-panel requires a double pole breaker to act as the feeder circuit. Two of the existing single pole breakers can be relocated and swung over to a sub-panel. The main panel will still be maxed out, but due to the feeder circuit, you now have the capability for future circuits inside the new sub-panel.
Hope this helps………If you have any additional questions, let me know and I’ll be glad to answer them for you.
Otherwise, don’t forget to rate me before you log Off.
The next time you have an electrical question, you can also request for me at: ……….Thanks…………..Kevin!
Expert:  Kevin replied 1 year ago.
If you have any additional questions, let me know and I’ll be glad to answer them for you.
Otherwise, don’t forget to rate me before you log Off.