Basic electrical questions

Discussion in 'Electrical Forum discussion & Blog' started by philp, Aug 30, 2009.

  1. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    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. drick

    drick In the Trades

    Messages:
    392
    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.

    Yes.
    You can put in a new cirucuit from a new breaker.

    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.

    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.

    Either. You must be sure to ground the metal boxes though.

    Yes, as long as they are not exposed. Secure everything you can though.

    You can pull them together but don't tape them together. It limits their ability to dissipate heat.



    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.

    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.

    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.

    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.
    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.
    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: Aug 30, 2009
  3. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    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: Aug 30, 2009
  4. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    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. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    Fantastic - many thanks for the answers.

    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!


    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.

    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?

    Great tip! Why aren't all cables labelled? Even the breaker is poorly labelled - this should be an NEC requirement!

    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.

    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).

    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?

    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. Jeff1

    Jeff1 New Member

    Messages:
    102
    Location:
    So Cal
    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.
  7. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    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.:D
  8. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Last edited: Aug 31, 2009
  9. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    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. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    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
  11. Jeff1

    Jeff1 New Member

    Messages:
    102
    Location:
    So Cal

    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.
  12. drick

    drick In the Trades

    Messages:
    392
    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.

    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.

    Labeling the panel is a NEC requirement. It hasn't always been though.

    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.

    Lighting does not matter, but all outside outlets, kitchen counter, bath, garage, and unfinished basement outlets should be GFCIs.

    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
  13. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    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.
  14. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    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).:eek:

    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?!:mad:
  15. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    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.

    Thanks. I presume it's ok to use a pigtail in an extension box instead of two boxes?


    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.


    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).

    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.:)
  16. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    I wasn't calling you dangerous really. I was just inferring that you didn't seem to know enough to catch little things like box fill, and derating. I'm sorry if you took offense to that. All I was saying that was you should get your work inspected to be sure you're not doing anything wrong. People here can advise you how to do things, but how you actually do them at your house may be different. Without being there, there may be something that is missed. Getting into junction boxes and adding breakers can certainly be a DIY job, but IT IS more than just "adding a couple outlets and lights"


    Now, pigtailing is fine in a junction box so long as the box is sized correctly for all the wires (box fill).

    Some lighting circuits do need to be GFCI protected, like shower lights for instance.

    Do you have an attic fan? That may be your missing dead circuit.
  17. philp

    philp New Member

    Messages:
    41
    Location:
    Ontario
    Of course I don't know enough - that's why I'm here! (and I've no clue what derating means or why I need to know this?!) All I want to do is add a couple of outlets and lights - all the rest is trying to put right all the presumably licensed electrician installed and inspected wiring I acquired. (I am assuming it was all done by a professional - and there is lots of evidence for that - but I can't rule out some DIY changes over the years).

    How about outside light switches? They are underneath a patio awning so rain doesn't get to them but they are just normal indoor switches (and outlets) - not even weatherproof.

    No attic fan - it does worry me that there was a live aluminum cable leaving the MCB and as far as I can tell it is unused. Would a licensed electrician or inspector have noticed that if all they were asked to do is install a couple of outlets and lights or check the new wiring? This is why I took offence - how many times do contractors or inspectors go to do a specific job and spend the time and effort to check everything? I'm checking everything because I want to remove the danger.
  18. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    I ran my last house off a 100a service for 7 years, ~1600 sq ft by the time I was done
    I had a 50a hot tub that I used all the time, plus 24k AC & a 12k AC
    Big old 35" CRT & sound system, never kicked a breaker during that time

    Key is making making sure the high load items aren't on the same circuit

    I had (2) live 240v lines at the bottom of the stairs that were curled up & not protected w/wire nuts - missed by Home Inspector
    Also stated that no evidence of recent water intrusion
    The gravel on the upper cement wall by the rim joist must have magically passed thru the wood

    Derating is when too many wires are bunched together for more then 2'
    Like every old house that was wired & they tucked ALL the wires back against the rim joist ;)
    That means the wires can carry LESS power & will heat up faster
    So a 12g wire normally fed by a 20a breaker can (might) only be fed with a 15a breaker

    The only electrican I hired (Service feed) could not understand why I pulled them all out & spread them out. #1 for easier access, #2 to prevent any derating

    Box fill is the Max number of wires/cables/devices that can enter/be installed in a box per code
    7 cables is way too many for a single box
    You would need a quad box or better

    I'd verify that Alum cable & get rid of it

    The only switch I've had outside was rated for outdoor use
    -one of those grey switch boxes

    Code is Min required, you can do better then what is required by code
    IE GFCI a light in the bathroom/shower
    Last edited: Sep 1, 2009
  19. drick

    drick In the Trades

    Messages:
    392
  20. drick

    drick In the Trades

    Messages:
    392
    Outdoor switches are required to be installed in a weatherproof enclosure and the mechanism used to activate the switch is either plastic or is grounded. The switch would be safe to use wet or dry. If you want to add GFCI protection to these switches it would not hurt anything, its just not required.

    This is a code violation. An awning is not sufficient shelter. You should still treat this as a wet location. The switches must have a weatherproof cover.

    -rick
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