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Thread: Basic electrical questions

  1. #1
    DIY Member philp's Avatar
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    Default Basic electrical questions

    I'm looking at converting part of my basement into a home theatre. (This has led me to look at the whole electrical wiring in the house and I can see it needs an overhaul.)

    The area in question has a few electrical receptacles and a set of lights. I want to add three more receptacles and two more sets of lights. I have a few basic questions:
    1. Can I use the same circuit for the new lights and receptacles? Can I put in a new circuit from the breaker? Is there a rule on how many circuits you can have from a breaker (I have plenty of free slots but only 100A supply).
    2. I plan to use 14/3 and 14/2 NM cable for power and lighting but I've seen some cables with metal sheathing. When do I need metal sheathing?
    3. Most receptacle boxes are metal but I've seen PVC ones as well - which should I use?
    4. I've checked how to fish the new cables - in some areas it would be impossible to secure the cable (without ripping the walls/ceiling down). Is it OK to leave the cables loose?
    5. Can I run 3 or 4 power cables together? i.e. in the ceiling if I tape the cables together and fish them as one cable it would be much easier but it means leaving them all taped together and unsecured to joists.
    6. One of the junction boxes will have 6 or 7 cables - what is the best way to join these? Do I just marrette them all together or is there a limit? How big a junction box do I need?
    7. At present a junction box used for the lights has another circuit (i.e. on a different fuse), which seems dangerous to me (I was inspecting it with the fuse for the lights off only to find it had power). Is this safe or should I move it to another box?
    8. The same circuit provides power to other areas in the basement and ground floor. The wiring, done originally in the 1950's but obviously with several changes over the years, is very confusing (but clearly works). Are there any guidelines on how many receptacles and lights are on the same circuit and which rooms should be on the same circuit?
    9. On one other circuit some of the receptacles have no ground - should I replace these to provide a ground? (The receptacle has a ground socket but no ground wire - which sounds dangerous to me - if I can't replace the wire is there a way to make these safer?)
    10. I have been told that a few of the circuits are aluminum (most are copper) - is it easy to see an aluminum circuit and should I replace these?
    11. Is there any harm running speaker cable together with power cable?

    Sorry for so many questions - any suggestions much appreciated.

  2. #2

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    If you are going to do this much electrical you should invest in a copy of one of the home wiring books from one of the big blue or orange stores.

    Quote Originally Posted by philp View Post
    1. Can I use the same circuit for the new lights and receptacles?
    Yes.
    Quote Originally Posted by philp View Post
    Can I put in a new circuit from the breaker?
    You can put in a new cirucuit from a new breaker.

    Quote Originally Posted by philp View Post
    Is there a rule on how many circuits you can have from a breaker (I have plenty of free slots but only 100A supply).
    You are confusing your terminology. The load center houses your circuit breakers. Each circuit is derived from one circuit breaker. As long as there are available spaces you can add more breakers. A 100 amp main breaker is considered substandard these days. An average house has a 200 amp service. Don't go adding any new major appliances.

    Quote Originally Posted by philp View Post
    2. I plan to use 14/3 and 14/2 NM cable for power and lighting but I've seen some cables with metal sheathing. When do I need metal sheathing?
    Metallic cable was common in the 50's and 60's. Thats most likely what you are looking at. You don't need to use it UNLESS you town requires it, which is rare.

    Quote Originally Posted by philp View Post
    3. Most receptacle boxes are metal but I've seen PVC ones as well - which should I use?
    Either. You must be sure to ground the metal boxes though.

    Quote Originally Posted by philp View Post
    4. I've checked how to fish the new cables - in some areas it would be impossible to secure the cable (without ripping the walls/ceiling down). Is it OK to leave the cables loose?
    Yes, as long as they are not exposed. Secure everything you can though.

    Quote Originally Posted by philp View Post
    5. Can I run 3 or 4 power cables together? i.e. in the ceiling if I tape the cables together and fish them as one cable it would be much easier but it means leaving them all taped together and unsecured to joists.
    You can pull them together but don't tape them together. It limits their ability to dissipate heat.



    Quote Originally Posted by philp View Post
    6. One of the junction boxes will have 6 or 7 cables - what is the best way to join these? Do I just marrette them all together or is there a limit? How big a junction box do I need?
    There is a limit and there are very precise rules related to this. Read NEC section 314.16 - Number of Conductors in Outlet, Device, and Junction Boxes. Example: For 7 14/2 cables you would need a 4 11/16" X 2 1/8" deep square jbox. For 6 14/2 cables you would need 4" X 2 1/8" deep square jbox. If you have a mix of 12 and 14 gauge wire it gets even more fun:-) If this is new wiring your installing rethink your layout. You shouldn't have a need for that many wires in a jbox. If this is existing wiring, well, sometimes you got what you got.

    Quote Originally Posted by philp View Post
    7. At present a junction box used for the lights has another circuit (i.e. on a different fuse), which seems dangerous to me (I was inspecting it with the fuse for the lights off only to find it had power). Is this safe or should I move it to another box?
    This isn't uncommon or unsafe - electrically anyway. It does offer the element of surprise when you think the power to the box is off though. Take a marker and write on the inside of the box cover where the wires go so you or the next guy will know where the wires go.

    Quote Originally Posted by philp View Post
    8. The same circuit provides power to other areas in the basement and ground floor. The wiring, done originally in the 1950's but obviously with several changes over the years, is very confusing (but clearly works). Are there any guidelines on how many receptacles and lights are on the same circuit and which rooms should be on the same circuit?
    There are guidelines, but more importantly you know what you will be plugging into those outlets and ideally you want to be at or under 80 percent of the breaker rating. That should be your guideline. I'd also consider keeping the lighting on a different circuit from the outlets.

    Quote Originally Posted by philp View Post
    9. On one other circuit some of the receptacles have no ground - should I replace these to provide a ground? (The receptacle has a ground socket but no ground wire - which sounds dangerous to me - if I can't replace the wire is there a way to make these safer?)
    Ungrounded boxes should not have a grounded outlet installed in them. This is a code violation. There is an exception to this: If you can locate the first outlet on that circuit and replace it with a GFCI outlet the downstream outlets can be of the grounded type. This is because the GFCI will detect any faults and cut power to the circuit. You can also replace the breaker withe a GFCI breaker, which is a bit more expensive, but would probably be easier than trying to locate the first outlet.
    Quote Originally Posted by philp View Post
    10. I have been told that a few of the circuits are aluminum (most are copper) - is it easy to see an aluminum circuit and should I replace these?
    I would replace any aluminum wiring you can get at. I can tell the difference, but that doesn't mean you are going to be able to. Aluminum wire is silver in color and the real giveaway is that is it more flexible than copper.
    Quote Originally Posted by philp View Post
    11. Is there any harm running speaker cable together with power cable?
    Its fine as long as you don't mind listening to the hum for 60Hz in you speakers:-) Otherwise keep it at least a foot away from your power wires. Same goes for phone, internet and CATV.

    -rick
    Last edited by drick; 08-30-2009 at 07:38 PM.

  3. #3
    Homeowner Thatguy's Avatar
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    Check what you have first.

    Turning off a 10A load (a hair dryer) should increase an outlet voltage by ~3 vac from the nominal 120 vac measured at the outlet.

    Turning off a ~20A, 240v load [e.g., elec. wall oven, central air] should increase the load center incoming voltage by ~0.4 vac from the nominal 240 vac measured at the load center. If you measure this voltage at an unused elec. dryer outlet you won't need to remove the panel cover.

    Use heavy speaker wire to maximize your damping factor
    http://en.wikipedia.org/wiki/Damping_factor
    and twist it to minimize hum pickup.

    Watch out for arc flash when working upstream of circuit breakers.
    Last edited by Thatguy; 08-30-2009 at 07:37 PM.

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    Electrician ActionDave's Avatar
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    Hoo Boy!! You're wading in deep. Let's try and simplify.
    How about running a new circut back to the panel and use it to power up your awesome home theatre.
    Have it inspected and get busy watching Gone With the Wind in surround sound.

  5. #5
    DIY Member philp's Avatar
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    Fantastic - many thanks for the answers.

    Quote Originally Posted by drick View Post
    If you are going to do this much electrical you should invest in a copy of one of the home wiring books from one of the big blue or orange stores.
    Thanks I'll check them out - any other recommendations on good resources (particularly websites)? Wiring a couple of switches and outlets sounded like a simple job when I started!


    Quote Originally Posted by drick View Post
    You are confusing your terminology. The load center houses your circuit breakers. Each circuit is derived from one circuit breaker. As long as there are available spaces you can add more breakers. A 100 amp main breaker is considered substandard these days. An average house has a 200 amp service. Don't go adding any new major appliances.
    Do you think we need 200A? It sounds a lot. We have a 1600 sq.ft. bungalow with gas furnace. Used to have electric water heater but just switched to gas tankless. Big draws will be stove, dryer and a/c. Also just changed dryer and a/c for higher efficiency (apparently there is no such thing as an energy efficient dryer or a/c!). One of the kitchen circuits does trip often - a 1250W microwave on 15A breaker being the culprit - I'm hoping to upgrade this circuit.

    Quote Originally Posted by drick View Post
    If this is new wiring your installing rethink your layout. You shouldn't have a need for that many wires in a jbox. If this is existing wiring, well, sometimes you got what you got.
    Yes - this will be an issue if I use the existing circuit - the box I will be tieing into already has 5 cables marretted together plus two cables that just join in the box (why do some boxes just have a pair of joined cables? is this a standard method of wiring? i.e. why didn't they run one cable in the first place?). I was planning to add an extension box - octagonal. What's the best way to join 7 14/2 cables together?

    Quote Originally Posted by drick View Post
    This isn't uncommon or unsafe - electrically anyway. It does offer the element of surprise when you think the power to the box is off though. Take a marker and write on the inside of the box cover where the wires go so you or the next guy will know where the wires go.
    Great tip! Why aren't all cables labelled? Even the breaker is poorly labelled - this should be an NEC requirement!

    Quote Originally Posted by drick View Post
    I'd also consider keeping the lighting on a different circuit from the outlets.
    Sadly I'd have to re-wire the whole house to do that. What's the advantage of having lighting separate to the outlets? I thought combining outlets and lighting spread the load better but I guess it would be good if each room had two circuits so that everything doesn't fail if there is a trip.

    Quote Originally Posted by drick View Post
    Ungrounded boxes should not have a grounded outlet installed in them. This is a code violation. There is an exception to this: If you can locate the first outlet on that circuit and replace it with a GFCI outlet the downstream outlets can be of the grounded type. This is because the GFCI will detect any faults and cut power to the circuit. You can also replace the breaker withe a GFCI breaker, which is a bit more expensive, but would probably be easier than trying to locate the first outlet.
    Thanks - this sounds like my first job to do - I thought it was unsafe. Most of the outlets are grounded so I don't know why they did this - hopefully it is just one circuit. There are also some exterior outlets and light switches - should all these be on GFCI circuits (there are no GFCIs in the house).

    Quote Originally Posted by drick View Post
    I would replace any aluminum wiring you can get at. I can tell the difference, but that doesn't mean you are going to be able to. Aluminum wire is silver in color and the real giveaway is that is it more flexible than copper.
    I was hoping it would be easy to tell from the breaker? I have heard that aluminum needs different receptacles/switches/etc. so thought it might also need different fuse/breaker?

    Quote Originally Posted by ActionDave
    How about running a new circut back to the panel and use it to power up your awesome home theatre.
    Have it inspected and get busy watching Gone With the Wind in surround sound.
    The breaker is in the garage with difficult access but I've planned the new layout so that I can switch to a new circuit when I renovate the room beside the garage (next year's job). When you say inspected - is this just by a licensed electrician or is this a permit requirement?

    I'm more a Blade Runner / LOTR kind-of-guy...

  6. #6
    DIY Senior Member Jeff1's Avatar
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    200A is a must - especially if you're adding a home theater. You'll need more power for a bigger TV and all the audio plus any lighting you will add. The last thing you want is to have the screen go out during a big play because someone is drying their hair.

    You might want to check with a licensed electrician to see about changing out your panel and looking at what type of wires you currently have. You could also have them look into a sub panel in the basement which could make adding circuits easier in the future.

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    DIY Member philp's Avatar
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    Quote Originally Posted by Jeff1 View Post
    200A is a must - especially if you're adding a home theater. You'll need more power for a bigger TV and all the audio plus any lighting you will add. The last thing you want is to have the screen go out during a big play because someone is drying their hair.

    You might want to check with a licensed electrician to see about changing out your panel and looking at what type of wires you currently have. You could also have them look into a sub panel in the basement which could make adding circuits easier in the future.
    Thanks - the home theatre equipment is already in operation so all I am adding to the total load is some LED accent lighting (I don't want high power lighting in my theater room - I want near total darkness most of the time).

    Removing my electric water heater took 30A (@ 240V) off my total load, my new a/c reduced the load by another 10A (at least I had to replace the breaker because it was rated 10A too high) so I should have tons of spare capacity. I guess if we turned on everything at exactly the same time the main 100A breaker could blow but this would probably happen with 200A as well. I've NEVER known a main breaker to trip, I'm more worried about individual circuits being undersized or the loads unevenly distributed or improperly wired. I guess it happens but would any of the pros here care to comment on how often they see the main breaker trip due to being undersized ?

    I'd prefer to add some solar or other green power before I looked at upgrading from my local hydro.

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    Homeowner Thatguy's Avatar
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    http://www.wholesalesolar.com/pdf.fo...ower-table.pdf

    A 2 kw [sine-wave power] sound system at 80% efficient would pull 2.5 kw, but nobody listens to sine waves for very long.
    Last edited by Thatguy; 08-31-2009 at 11:06 AM.

  9. #9
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Quote Originally Posted by Jeff1 View Post
    200A is a must - especially if you're adding a home theater. You'll need more power for a bigger TV and all the audio plus any lighting you will add. The last thing you want is to have the screen go out during a big play because someone is drying their hair.
    Are you kidding me?

    A hair dryer is what--1500W? That's 12.5A. I know that the largest connsumer big-screen TV these days doesn't even draw that much.

    Your size of service and number of breakers, etc is governed by calculations per the NEC (plus some margin for good measure isn't bad).

    FYI, unless you're adding a new range or electric heat or a new A/C or something similiar, if 100A (i.e. 100 amps on each of the two legs) is good for you now it's probably going to be for some time.



    Jason

  10. #10

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    I'm not going to try to discourage you from doing this, but please get it inspected and permitted. No offense but it sounds to me that you know just enough to be dangerous. Also read up on which year NEC your town uses and also any local additions to it. For example my town requires metal boxes. Its not rare for a town to require metal sheathing or rigid conduit. Find out what your town requires.

    Drick has good advice
    I consider myself an accomplished DIY'er. I don't know everything but help where I can. I'm not a pro, but like to think I'm professional.

  11. #11
    DIY Senior Member Jeff1's Avatar
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    Quote Originally Posted by Lakee911 View Post
    Are you kidding me?

    A hair dryer is what--1500W? That's 12.5A. I know that the largest connsumer big-screen TV these days doesn't even draw that much.

    Your size of service and number of breakers, etc is governed by calculations per the NEC (plus some margin for good measure isn't bad).

    FYI, unless you're adding a new range or electric heat or a new A/C or something similiar, if 100A (i.e. 100 amps on each of the two legs) is good for you now it's probably going to be for some time.



    Jason

    Perhaps I didn't specify my comment clearly enough. If you put too many appliances on one circuit it will cause problems. I was not implying that a hair dryer will cause the main to break. With some home theater's a larger service is necessary. If all you are running is a TV and cable box you won't have a problem. There are some systems that have amplifiers, projectors, lights, curtains, music servers, computers and more devices. It really depends on what you are looking to do. As you said, there is a formula to determine how many circuits and size service you need.

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    Quote Originally Posted by philp View Post
    Do you think we need 200A? It sounds a lot. We have a 1600 sq.ft. bungalow with gas furnace. Used to have electric water heater but just switched to gas tankless. Big draws will be stove, dryer and a/c. Also just changed dryer and a/c for higher efficiency (apparently there is no such thing as an energy efficient dryer or a/c!). One of the kitchen circuits does trip often - a 1250W microwave on 15A breaker being the culprit - I'm hoping to upgrade this circuit.
    Like I said 100 amps is considered substandard. You can get by with it, especially if you already have been, and your house is on the smaller side which helps, but 100 amps is still not great.

    A/C efficiency is rated in SEERs 10 being low and 17+ being great. Electric clothes dryers use resistance heating which is considered 100% efficient, so basically one dryer is about as efficient as the next.

    Quote Originally Posted by philp View Post
    Yes - this will be an issue if I use the existing circuit - the box I will be tieing into already has 5 cables marretted together plus two cables that just join in the box (why do some boxes just have a pair of joined cables? is this a standard method of wiring? i.e. why didn't they run one cable in the first place?). I was planning to add an extension box - octagonal. What's the best way to join 7 14/2 cables together?
    The best way to join 7 cables is not to do it in the first place. You are going to be trying to twist too many wires together. You may end up with a loose connection and loose connections = heat and heat = fire! There is no reason you can't use two boxes and divide up the connections. Whatever you do be sure your connections are tight.

    Quote Originally Posted by philp View Post
    Great tip! Why aren't all cables labelled? Even the breaker is poorly labelled - this should be an NEC requirement!
    Labeling the panel is a NEC requirement. It hasn't always been though.

    Quote Originally Posted by philp View Post
    Sadly I'd have to re-wire the whole house to do that. What's the advantage of having lighting separate to the outlets? I thought combining outlets and lighting spread the load better but I guess it would be good if each room had two circuits so that everything doesn't fail if there is a trip.
    The advantage is if you overload the circuit by plugging in one too many things you won't end up in the dark. Combining lighting and outlets on one circuit is fine, but what you do is combine the outlets from one room with the lights from another. This is not always practical and I'm not suggesting you rewire to accomplish this.

    Quote Originally Posted by philp View Post
    Thanks - this sounds like my first job to do - I thought it was unsafe. Most of the outlets are grounded so I don't know why they did this - hopefully it is just one circuit. There are also some exterior outlets and light switches - should all these be on GFCI circuits (there are no GFCIs in the house).
    Lighting does not matter, but all outside outlets, kitchen counter, bath, garage, and unfinished basement outlets should be GFCIs.

    Quote Originally Posted by philp View Post
    I was hoping it would be easy to tell from the breaker? I have heard that aluminum needs different receptacles/switches/etc. so thought it might also need different fuse/breaker?
    Most breakers are rated AL/CU meaning they accept aluminum or copper wire so it is unlikely you will have different breakers for the aluminum wire.
    Aluminum doesn't necessarily need different devices, the devices just have to be rated for aluminum wire.

    -rick

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    Electrician ActionDave's Avatar
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    Quote Originally Posted by philp View Post
    The breaker is in the garage with difficult access but I've planned the new layout so that I can switch to a new circuit when I renovate the room beside the garage (next year's job). When you say inspected - is this just by a licensed electrician or is this a permit requirement?
    Ok. So get it ready for a dedicated circut and tie it in later. I get it.
    Get some qualified help. By that I mean a good electrician. That doesn't mean the biggest shop in town. drick gave some solid advice, find someone that talks like he does.
    By inspected I mean an Electrical Inspector. They are nothing to be afraid of and are most often a good resource.

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    DIY Member philp's Avatar
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    Quote Originally Posted by iminaquagmire View Post
    No offense but it sounds to me that you know just enough to be dangerous.
    Why the scaremongering? This is true for every DIYer (and probably a few pros!). The important point is not what I know now but what I know when I do the job.

    My "dangerous knowledge" has so far found out that at least one circuit is undersized, at least one circuit is ungrounded (but with ground pin on the outlet), that exterior, bath and garage outlets are not GFCI protected and nothing is labelled. And this set up has been in use for upto 50 years presumably installed by a qualified electrician following legislation in force at the time (and perhaps taking some short cuts).

    None of this was picked up by the home inspector when I bought this house and how many DIYers who want to add a couple of outlets and lights do a full electrcial inspection? And you call me dangerous?!

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    DIY Member philp's Avatar
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    Quote Originally Posted by drick View Post
    A/C efficiency is rated in SEERs 10 being low and 17+ being great. Electric clothes dryers use resistance heating which is considered 100% efficient, so basically one dryer is about as efficient as the next.
    Sorry, what I meant was the "energy star" qualification. As far as I am aware there are no electric clothes dryers that get the energy star. When I was buying a new a/c all the suppliers said they were energy star partners but very few models were actually energy star qualified and nothing under 14 SEER/11 EER.

    Quote Originally Posted by drick View Post
    The best way to join 7 cables is not to do it in the first place. You are going to be trying to twist too many wires together. You may end up with a loose connection and loose connections = heat and heat = fire! There is no reason you can't use two boxes and divide up the connections. Whatever you do be sure your connections are tight.
    Thanks. I presume it's ok to use a pigtail in an extension box instead of two boxes?


    Quote Originally Posted by drick View Post
    Labeling the panel is a NEC requirement. It hasn't always been though.
    What would be good to see is a sticker in the receptacle saying which number breaker or better an electrical plan showing every circuit. Getting a land survey is standard - getting HVAC, electrical, plumbing plans would probably be more useful to most home owners.


    Quote Originally Posted by drick View Post
    Lighting does not matter, but all outside outlets, kitchen counter, bath, garage, and unfinished basement outlets should be GFCIs.
    Why doesn't lighting matter? Isn't it just as dangerous (and more likely) to touch a wet light switch? Wouldn't you get just as bad a shock? (In any case all the outside outlets and lights are on the same circuit - so I'll put a GFCI at the MCB).

    Quote Originally Posted by drick View Post
    Most breakers are rated AL/CU meaning they accept aluminum or copper wire so it is unlikely you will have different breakers for the aluminum wire.
    Aluminum doesn't necessarily need different devices, the devices just have to be rated for aluminum wire.
    So far it is obvious that the wiring for my old eletric water heater was aluminum and one other circuit which I can't trace but turning off the breaker has not disabled anything I use - I expect one day I'll find an outlet or light that won't come on! Otherwise I think I can safely ignore the aluminum aspect - all other circuits are clearly copper.

    Thanks once again Rick - your answers are hugely helpful - much appreciated.

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