I'm putting in two dedicated circuits for my home theater. The wire needs to be purchased at a Home Depot, Mennard's, or Lowes. What kind of wire needs to be bought (gauge, grade, etc). I was told by someone that isn't into HT to be concerned with things resistance. Long story short, this is greek to me. Tell me what to buy.

Thanks in advance.

14/2 with ground if you are going to run 15A circuits, 12/2 with ground if you are going to run 20A circuits.

IMO, 12/2 and the 20A breakers is such minimal incremental cost over 14/2 and 15A breakers that it's a no-brainer to go with 20A circuits.

Might as well get decent receptacles too - none of those cheap-a$$ $0.99 ones. Get the commercial grade outlets, they'll run $5 each, give or take. No need for "hospital grade" or any of that nonsense.

In addition to what whoaru99 stated, you probably want to use 20A rated outlets which can accommodate 20a plugs (they are slightly different). And of course a 20A breaker at the panel. If this stuff is greek to you, you may want to contract a licensed electrician to do the wiring to ensure it meets code if you haven't already done so.

I would run 12/2 with ground, you can use this for a 15 or 20 amp circuit.

In addition to what whoaru99 stated, you probably want to use 20A rated outlets which can accommodate 20a plugs (they are slightly different). And of course a 20A breaker at the panel. If this stuff is greek to you, you may want to contract a licensed electrician to do the wiring to ensure it meets code if you haven't already done so.

Yeah, good point to clarify. Put in 20A receptacles since they will accept "normal" plugs in addition to 20A plugs if you ever need that option.

Never really did understand why one would put 15A receptacles on a 20A circuit - even though it's perfectly acceptable by NEC - as long as there is more than one receptacle on the circuit. I guess maybe to save a little $ since 20A appliances/devices are not all that common in residential use.

How far does this apply for? For example 12 gauge being run 50 ft might be fine for 20 amp, but what if it was run 150, or 250?

Reason I ask is I have a 12/3 romex dedicated line which is 15 amp and is 125-150ft and was wondering if I could get away with 20 amp. I also have a 10/3 of Carol stranded wire that is the same distance, and was wondering if I could get away with 30 amp.

Thanks.

Jared

Might as well get decent receptacles too - none of those cheap-a$$ $0.99 ones. Get the commercial grade outlets, they'll run $5 each, give or take. No need for "hospital grade" or any of that nonsense.

Do not bother buying anything higher then whatever matches the plugs you already have. Shouldn't cost more then $1.50 a piece. BTW, a hospital grade plug is only a little tighter fitting then a regular plug. Meaning it's a little tougher to plug/unplug things. It doesn't make a difference in terms of power transfer.

Here's exactly what you need to ask for, "12/2 romex" 12/2 is prounounced twelve-two.

Then all you need to know is the length you need. It comes in 25, 50, 75, 100, 125, 250ft spools. Just a recommendation, if you think you only need 50 feet get the 100ft spool. This will allow you plenty of room for error.

Also, are you doing this yourself? If so this will save you a few curse words when you trim the wires. Leave ~2 feet hanging out of the new outlet boxes. This will allow you plenty of room to screw up when stripping the wires.

-brien

How far does this apply for? For example 12 gauge being run 50 ft might be fine for 20 amp, but what if it was run 150, or 250?

Reason I ask is I have a 12/3 romex dedicated line which is 15 amp and is 125-150ft and was wondering if I could get away with 20 amp. I also have a 10/3 of Carol stranded wire that is the same distance, and was wondering if I could get away with 30 amp.

Thanks.

Jared

Afaik, it is a NEC violation to run a 30A circuit for residential lighting/general purpose circuit.

If you are 100% sure that the entire run is 12 ga wire, I don't see why a 20A circuit cannot be used. However, if the 15A circuit is not giving any problems, then upping the breaker to 20A will not make any difference in how things work.

It is acceptable to use a larger gauge of wire on a long run (i.e. 10ga wire on 20A circuit) to reduce the voltage drop.

whoaru99,

Thanks for the help. It is 12 gauge the entire run, I installed it myself along with the 10 gauge a couple of years back.

My power requirements have changed so I was going to change one or the other, up the 10 gauge to 30 amp or the 12 to 20 amp. I will up the 12/3 to 20 amp.

Thanks.

Jared

Do not bother buying anything higher then whatever matches the plugs you already have. Shouldn't cost more then $1.50 a piece. BTW, a hospital grade plug is only a little tighter fitting then a regular plug. Meaning it's a little tougher to plug/unplug things. It doesn't make a difference in terms of power transfer.

I like tight-fitting receptacles.... :D


But, really, the commercial grade outlets are better. Yes, they grip tighter and keep that tight grip for a long time. Those el-cheapo outlets start to loosen their grip after a relatively few insertions.

In the scope of things, I think $5 (give or take) for a name brand, commercial grade (P&S, Hubbell, Leviton, et. al) outlet isn't an extreme expenditure or waste of money. Also, for the extra dollar or two to use a 20A outlet, I think is a good plan.

My power requirements have changed so I was going to change one or the other, up the 10 gauge to 30 amp or the 12 to 20 amp. I will up the 12/3 to 20 amp.

Thanks.

Jared

12/3 is used for three way switches. Do not get that. You need 12/2. That means 2 conductors plus a ground.

"But, really, the commercial grade outlets are better. Yes, they grip tighter and keep that tight grip for a long time. Those el-cheapo outlets start to loosen their grip after a relatively few insertions."

I guess. I've never had a problem. Just don't buy the $0.25 ones. LOL

I guess I wouldn't be pissed at someone for spending $5 per outlet. That's not too much. Just more then needed :)

Didn't realize that, I thought the 2nd number was the # of conductors. I already have it wired I was just going the change the breaker. It is a run of 12/2 15a breaker and a run of 10/2 20a breaker.

Thanks.

Jared

A run of 125 to 150 feet (one way?) is long enough for you to consider voltage drop.

Voltage drop involves considering wire guage, length of the run, and the current drawn by the load. The greater the load the more greater the voltage drop. For example assuming 120v, 125' one way run, 12 AWG and a 15 amp load the voltage drop will be 10 volts. Ten amps --7 volts, 5 amps -- 3.5 volts. Note there are many voltage drop calculators on the net you can use.

Although your equipment is designed to work with a range of voltages, 110 is a bit low. It is too low if you ever add something with an AC motor.

Even though HT hardware does not draw its rated power continuously, powerful experiential arguments based on circuit breaker performance have been made on this forum for treating them as continuous loads. If you do that then your total load should not be more than 80% of the circuit capacity. I am not convinced that one has to go that far, but should you at some point add a refrigerator or some other heavy drawing motorized load both capacity and voltage drop will be issues.

As you have already wired with 12 AWG, changing the breakers to 20 amps does nothing for the voltage drop. When everything is turned on, measure the voltage at outlets on both branches. If it is within about 2% of the voltage at the panel you are OK; if not try splitting the load.

Didn't realize that, I thought the 2nd number was the # of conductors. I already have it wired I was just going the change the breaker. It is a run of 12/2 15a breaker and a run of 10/2 20a breaker.

Thanks.

Jared

The second number is the number of conductors - but does not include the grounding wire.

12/3 is used for three way switches.

Yes, and also for 120/240 circuits. Or, it can also be used for two 120V circuits in a single run of cable by sharing the neutral wire - as long as you use a dual pole breaker with a common trip.

Yes, and also for 120/240 circuits. Or, it can also be used for two 120V circuits in a single run of cable by sharing the neutral wire - as long as you use a dual pole breaker with a common trip.

Great way to overload the ground wire

Just hope a full 120V 40A load isn't dumped onto that single ground wire

Great way to overload the ground wire

Just hope a full 120V 40A load isn't dumped onto that single ground wire

This is a commonly used method, approved by the code and many jurisdictions. The assumption is that the load will be more or less balanced in the two legs. The phase or polarity it opposite in each leg so a 20 amp draw in each leg produces no current in the ground wire. :cool:

This is a commonly used method, approved by the code and many jurisdictions. The assumption is that the load will be more or less balanced in the two legs. The phase or polarity it opposite in each leg so a 20 amp draw in each leg produces no current in the ground wire. :cool:

That's there theory.

Measure the current on the ground wire though. You'll quickly see that theory isn't always right.

I'd rather be safe then sorry. Two full 12/2 runs for me :)

That's there theory.


"their" theory is correct.

Measure the current on the ground wire though. You'll quickly see that theory isn't always right.

If there is any current flowing through ground, then there is a fault condition, that should be repaired.
In a balanced circuit, the shared neutral will have no current flowing through it. If the load is unbalanced (most likely) then you can have up to 20 Amps flowing through the neutral, there will NEVER be 40 amps flowing through the neutral. You're not considering the phase of the supply voltages.

That's there theory.

Measure the current on the ground wire though. You'll quickly see that theory isn't always right.

I'd rather be safe then sorry. Two full 12/2 runs for me :)

How many amps did you find when you measured? ;)

If you already have the 12/3 run, you could consider running 240 V, and then stepping down to 120 using a rather large transformer (you'd need something rated 5000 VA or so). I believe the voltage drop will be proportionately less with a higher voltage (which is the theory behind high-voltage transmission lines).

How many amps did you find when you measured? ;)

None :)

Except when either the Compressor in the fridge or the AC turned on. Then I measured 1amp on the ground. That went away as soon as the inital draw stopped. So it wasn't more then a second.

I'm just giving a worst case scenario. All current drops to ground. That's the worst that can happen. Technically a 12awg wire in a normal house run can handle 40amps with only a bit of heat loss, but NEC only rates 12awg up to 20amps.

Then I measured 1amp on the ground.

Do you actually mean neutral when you say ground, or do you really have a dangerous situation there?

Technically a 12awg wire in a normal house run can handle 40amps with only a bit of heat loss, but NEC only rates 12awg up to 20amps.

You still don't get it. There will never be 40 Amps flowing through the shared neutral on a split phase circuit. There will never be more then 20 Amps flowing through this neutral.

You still don't get it. There will never be 40 Amps flowing through the shared neutral on a split phase circuit. There will never be more then 20 Amps flowing through this neutral.

Exactly.

The neutral in this circuit will only see the difference of the load of each leg. So, if one leg had 5A load and the other leg had 15A load, the current in the neutral would be 10A. If the legs were 10A and 10A, then current would be 0A in the neutral wire.

It's the dual-pole breaker tapping both legs of the split phase power that's the key to this type of circuit working out.

OTOH, if someone used this circuit methodology with (typically single pole) breakers, both on the same leg, then yes, a shared neutral wire would see the SUM of the currents, not the DIFFERENCE of the currents.

Do you actually mean neutral when you say ground, or do you really have a dangerous situation there?

SOrry, You're right. I was measuring the neutral.

The problem is that you guys keep saying the full 40amps won't end up on the neutral or ground.

What happens when and idiot connects the two? Via lets say a faulty cord.

There's going to be full power on the neutral or ground until the breaker trips. Hopefully tthat's fast enough to prevent fire

The problem is that you guys keep saying the full 40amps won't end up on the neutral or ground.

It's not a problem, because there will never be more then 20 Amps flowing through the neutral.

What happens when and idiot connects the two? Via lets say a faulty cord.


If you connect a hot to neutral, a short circuit condition exists, and hopefully, the 20 Amp breaker protecting the circuit will open. No more then 20 Amps will flow continuously.

If both, opposing phase, hots are shorted to neutral, then the opposite phase short circuit currents will add together, and since the polarity of one of them is negative, they will cancel out, nullify each other, resulting in zero current through the neutral.

There's going to be full power on the neutral or ground until the breaker trips. Hopefully tthat's fast enough to prevent fire

Wires are fairly conservatively rated, to prevent events such as you describe.

I'm putting in two dedicated circuits for my home theater. The wire needs to be purchased at a Home Depot, Mennard's, or Lowes. What kind of wire needs to be bought (gauge, grade, etc). I was told by someone that isn't into HT to be concerned with things resistance. Long story short, this is greek to me. Tell me what to buy.
Don't buy any wire. Either buy a book and read until you know enough to answer your own question, or hire an electrician. (Hire one to do the panel hookup and review your work in any case.)

There's more to this wiring stuff than you know to ask questions about.

12/2 + 20 amp receptical (I personally use Leviton 5800-(color) If it is over 100ft run then consider 10/2 instead with a 20 amp breaker.

Anything higher than 20amp is considered a dedicated or special purpose outlet such as a dryer or a range and cannot be used for general purpose outlets.

Also take in consideration when figuring out your load, that a 20amp breaker will trip at 16amps and a 15amp breaker will trip at 12amps. (this is only for breakers, fuses OTOH are good up to 100% of their rating)

Quote:
Originally Posted by poormanq45
Great way to overload the ground wire

Just hope a full 120V 40A load isn't dumped onto that single ground wire



This is a commonly used method, approved by the code and many jurisdictions. The assumption is that the load will be more or less balanced in the two legs. The phase or polarity it opposite in each leg so a 20 amp draw in each leg produces no current in the ground wire.

This was fairly common in the 70s and 80's I was under the impression that this was no longer acceptable by NEC sometime in the mid 90s

If you put in a 30 or 40A circuit I believe the way to get around the general purpose outlet rule is to put a four prong outlet on it.

This will prevent anything randon from being plugged into that circuit. Then If your amps or whatever have IEC cords you can make a new one with a four prong male connector on one end

12/2 + 20 amp receptical (I personally use Leviton 5800-(color) If it is over 100ft run then consider 10/2 instead with a 20 amp breaker.

Not a bad idea.

Anything higher than 20amp is considered a dedicated or special purpose outlet such as a dryer or a range and cannot be used for general purpose outlets.

That's my understanding too, yet I see people claiming to put in 30A and even in one case, a 40A circuit using regular 15A or 20A receptacles. Uff da.....


Also take in consideration when figuring out your load, that a 20amp breaker will trip at 16amps and a 15amp breaker will trip at 12amps. (this is only for breakers, fuses OTOH are good up to 100% of their rating)

This I disagree with.

It may be good practice, or maybe even code in some situations, to load a circuit to only 80%, but I think that depends on the nature and type of load. Regardless of that, I believe breakers will carry 100% of their rating indefinitely based on the trip curves I've examined for Square D products. The trip curves also indicate breakers will carry two or three times their current rating for several seconds.


This was fairly common in the 70s and 80's I was under the impression that this was no longer acceptable by NEC sometime in the mid 90s

Afaik, a two circuit shared neutral setup is perfectly acceptable by the NEC - as long as it is done properly, of course. I've seen it used mostly in kitchens to comply with the two 20A small appliance circuit rule.

Afaik, a two circuit shared neutral setup is perfectly acceptable by the NEC - as long as it is done properly, of course. I've seen it used mostly in kitchens to comply with the two 20A small appliance circuit rule.
Yes, although I think the provision is that the two circuits must be out of phase, netting zero at the neutral.