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Wiring Receptacles, Recessed Cans and Using 12/2 Cable Instead of 14/2 Cable

June 27, 2007

Dave Brown Says:
I had a house built 2 years ago and I am trying to understand how it is wired. I want to add some outlets in the basement and have matched the wire with what is already in the house(12-2 nm-b 600v). I have 15 20A breakers, 2 20A AFCI(bedrooms), dbl 40A(range) dbl 30A(dryer), dbl 25A(AC). Without testing what amperage is going thru the 12-2 wire, should I assume because its a 20A breaker that is the current going thru that wire? If its 20amps do I need 20amp receptacles? I thought all you needed to power lights were 15A? Help! Thanks.

A: Your house was probably wired in all 12/2 because that was the specifications. 20 amps is the maximum current that can flow through # 12 AWG wire. In a residential application, you should not assume that the load on a 20 amp circuit is 20 amps. To determine the amperage draw on this circuit, turn on everything plugged into this circuit that will be used at the same time and measure the current flow at the circuit breaker.

You do not need to install 20 amp receptacles. You are correct, lighting and most receptacles circuits in a house only need to be on a 15 amp circuit.

Andy Says:
I have a a problem I’m hoping you can help me with.I am remodeling my basement and installed four can lights.its been a good week and I smell a slight burning smell when the lights are on and its only on one side of the room.I have checked the wires in the junction boxes just out side thte lights but the wires seem fine.any ideas would be great

A: Call an electrician immediately. Is there insulation in the floor joists? Are your recessed cans insulation or IC rated? Do your recessed cans have the proper clearances from combustible materials? Are there any open splices or uncovered junction boxes?

Anthony Says:
14/2 wire is connected to recessed light from 15 amp. I want to add 2 more recessed lights and bought 12/2 wire. Can I connect new 12/2 wire to existing 14/2 wire? Thanks!

A: In theory, yes you can. However, this is not the proper way to wire this. The problem is if someone else comes along and adds 1 more light after you have installed the 12/2 wire. If they connect to one of the lights with the 12/2, they may think the circuit is rated for 20 amps and change the breaker from 15 amps to 20 amps. This would overload the circuit and eventually cause a fire.

I recommend returning the 12/2 or hold onto it for a future project and get some 14/2 for this circuit.

Circuit Breaker Amperage Rating, Wiring a Sound System and 3-Way Switch Wiring Diagrams

June 26, 2007

Mark Bryan Says:
I have a question concerning the amperage rating on circuit breaker panels. If you buy a panel that is rated as a 100 amp panel the main breaker has two 100 amp breakers mechanically tied together. Theoretically couldn’t you draw 95 amps on each bus bar and not trip the main breaker, thus drawing 190 amps in a 100 amp rated panel? Also on a 220 circuit when using a 220 appliance does anything go to ground or since the polarity is reversed on each leg is the electricity just flowing between the two 110 lines? I have been trying to find the answers to these questions on my computer but haven’t had much luck.Thankyou,
Mark Bryan

A: You are only drawing 100 amps per phase. With a 2-pole breaker you will draw the maximum amperage rating per leg. So, with a 2-pole, 100 amp breaker you can draw up to 100 amps per leg before the breaker will trip.

Most 200 volt residential appliances require a neutral for control circuits within the appliance. The neutral is the grounded conductor. If there is no grounded conductor, the electricity will not flow to ground unless there is a fault. 

Tara Codner Says:
I am building a new house and would like to have a sound system installed so that music can play in most of the rooms in the house and the sound may be turned off in the individual rooms if desired. I am wondering:
1) What material I will need to accomplish this?
2) How do I install the sound system?
3) Any additional information that you can provide me.


A: You need to install speaker wires and possibly CAT5 cable from the stereo to a volume control in the room. Then you need speaker wire from the volume control to each speaker. The CAT5 cable would be used for an IPod. You need to do your research before installing your sound system to ensure proper installation and no humming on your speakers.

Carlos Says:
I need to draw a diagram of a 3-way switch with feed at 1 switch leg at the other?

A: I have some wiring diagrams on one of my other websites; Three way switch wiring diagrams are here:

Carlos Says:
if in a residential single phase circuit a 3 wire was employed to feed cut to 2 circuits, need to draw a diagram indication phasing of the 4 wires of the 3 wire:

A: I’m confused and I do not understand your question. 

Supplying Power to a Garage and Code Violations

June 20, 2007

Dante Says:
Hello. I am trying to run power from my detached garage to my home. The garage is already wired inside, and it just needs to be powered up. Several questions here. Can I use THHN wire the whole way as long as I run it in conduit? I mean buried in the ground in conduit to the house and then run along the attic rafters (without conduit) to the breaker box. The county inspector says its okay, but some local electricians tell me I have to run direct burial and then connect to SE once I am in the house. I would prefer one long wire instead of connecting two together. If I can use THHN, and I want a 50 amp circuit, do I need #8 or #6 copper wire? If I have a grounding rod at both the detached garage and the house, can I get away with running 3 wires and not 4 and what size conduit would I need? Thanx very much.

A: Yes you may use THHN wire the whole way as long as it is in conduit all the way from the breaker box or a junction box in the garage to the breaker box or a junction box in the house. However, you may not run the THHN wire through the attic rafters, or anywhere else without conduit; the county inspector must have misunderstood your question.

I have the same recomendation as your local electricians. Copper prices are still high so, the THHN will cost considerably more than aluminum URD (direct burial) and changing over to aluminum SE cable at the house. This is how I would do it unless the ground is real rocky; then I would definately install conduit.

If you are going to use THHN copper wire installed in conduit, then #8 is rated for 50 amps maximum. However, if you are going to use aluminum URD (direct burial), USE (direct burial), SE or copper NM cable, then you need to use #6; which is rated for 50 amps maximum.

Use 3/4″ PVC minimum for #8 conductors or 1″ PVC minimum for #6 conductors. However, I recommend installing 1 1/4″ PVC minimum. This would allow you to increase the wire size to #2’s for 100 amps in the future. Fifty amps will work fine unless you are going to be welding and have a compressor running at the same time, then I recommend 100 amps.

If there is a gas line, phone cable, TV cable or data cable between the house and the garage, you need to install 2-hots, 1-neutral and 1-ground. If not, then you may install 2-hots and 1-neutral only. Then you need to establish a ground at the garage.

Robert Says:
I have a breaker box come from the meter with two 40 amps breaker in it one for my air condition i want to tap into one side of the 40 amps breaker a run a # 12 wire to a room i’m add to my house is this a safe way to do this? 

A: No this is very unsafe! Do not do this, you will cause a fire or electrocute someone. This is also a National Electrical Code (NEC) violation. You need to upgrade your breaker box from a 4-circuit to 6-circuit or larger. This will allow you to install a 20 amp circuit breaker maximum for your #12 wire. 

Answers to Electrical Questions about Wiring Photocells, Ceiling Fan Remote and Low Voltage Lighting

June 18, 2007

Tim Says:
I want to connect a photocell to existing outside front lights. there is a box on the side of the house with two pairs of wires two black and two white. This box is in same location of other houses with photocells installed. Photocell has a red wire but no red in box. Tried wireing red to one black and black to other black but photocell doesn’t control lights. ?????

A: The photocell needs to be wired properly to work. The red is the line side or power supply side of the photocell, this connects to the power supply wire. The black is the load side or light fixture side of the photocell, this connects to the wire that goes to the light. Depending on how this circuit is wired, you will probably need to leave the light switch on at all times to allow the photocell to work automatically. 

David Says:

Purchased a ceiling fan w/remote control and receiver. I have three switches tied to it. At the ceiling fixture, I have two whites, two blacks and two grounds. How do you suggest wiring from ceiling to receiver ((going in white, black) (going out to fan, white, black, blue, ground))
to fan (has white, black, blue and ground)

A: David, I am confused. I need more information. Is it possible to take a picture and email it to me? 

Todd Says:
Hi there.

I’ve installed low voltage lighting in the back yard. We have a bar area that I would like to light using the low voltage supply from the transformer. Is it possible to install a dimmer just for the lights in the bar? The only dimmer I can find is one that is supplied with power before the transformer (120v). Thanks for any information.


A: The only way to do this is to tap into the power before the existing switch and install a new transformer for your bar area lights. If you don’t do this, the existing switch that controls the lights now will also control the bar area lights.

Answers to Electrical Questions about Wiring LED lights, Sunshades and Switches

June 17, 2007

Jan asks:
Hello! i bought LED lights to replace my old lights under the kitchen cabinets. There are no hard wire install instructions. The wiring is coming out of a hole in the dry wall and it’s not close to a stud. The LED accent light is plastic, there isn’t any place for the ground wire and of course, I now have a hole that I don’t know what to do with. Any advice? I could just plug the LED light in but if I do that what do I do with the wire coming out of the wall? Thank you so much for this blog!

All electrical splices need to be terminated in a 2-hour, fire rated box. You need to cut-in a single gang, old work electrical box and make your splice in it. The blank cover can be painted the same color as your wall to help it blend in.

If your existing undercabinet lighting was an enclosed fluorescent, halogen or xenon fixture, you can leave the fixture in place and use this as a splice box. The fixture is low profile and not as easily seen under the cabnet.

If you plug in your lights and need to remove the wire coming out of the wall, either place it in a covered electrical box or disconnect it at the switch and remove the wire.


Keith Wilson asks:
I have bought an electric wind out sunshade, it has a reverser mech on one end and four wires, earth, blue, brown and black. unfortunately, no wiring instructions, could you give any suggestions?

The best solution is to contact the manufacturer for a wiring diagram. Try searching online using the manufacturer and model number of your sunshade. You may also trace the wires to determine which wire does what. The earth and 1 color will be the power supply. One of the other colors will be for the forward position and the final color will be for the reverse direction.


Apurva Muddappa asks:
Well this is how I have it wired, I am 99.9% sure it is not possible to tap into the swtich at then end of the run(the switch without power coming into it), but could you just confirm.

Great site by the way….

You are correct. You need to tap into the power at the first switch.