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Need 20 amp dedicated circuit advice


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14 replies to this topic

#1 of 15 stosh

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Posted June 24 2003 - 03:42 AM

hello,

I'm currently building a tv room, and I've had the electrician install a whole house surge protector, and a dedicated 20 amp circuit for the new room. He's wired the circuit and used 12 gauge wire, but is inquiring why i want a 20 amp circuit. Rather than say "because the folks over at the home theater forum said so". I'd like to know for myself also.

Questions:

- does a 20 amp circuit have to have a 20 amp receptacle? Is there a difference between a 15 amp receptacle and a 20 amp receptacle?

- does a 20 amp receptacle require any wiring changes from a 15? (I thought I read somewhere that a 20 amp dedicated circuit has to be the only receptacle on that circuit and that only one outlet can be used for each dedicated line, whereas a 15 can have multiple receptacles).


My equipment:
Pioneer Elite 47tx receiver
Sony 5 disc DVD player
Equitech T1500 Theater Power
Sony XBOX
Sony 50" XBR800 LCD HDTV
Paradigm Studio 40, Center, and Surrounds speakers (bi-wired)
Velodyne CHT-12 Subwoofer
SA Digital Cable TV converter


thanks for any advice...
Stosh

#2 of 15 Darren_T

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Posted June 24 2003 - 06:02 AM

Yes, there is a difference between a 20 amp and a 15 amp receptical. The 20 amp is built a tad beefier for the increased current. Also, a 20 amp circuit should use 12 gauge wire as it appears you will be. You can also gang up recepticals just as you can with 15 amp recepticals. I wired my garage with five 20 amp recepticals per circuit. I think you are confusing 20 amp circuits with 220 or 240 volt circuits which should have one receptical per circuit.

Tell the electrician you'd like the extra current the 20 amp circuit will give for the increased load your equipment's power supplies will place on the circuit.

Darren

#3 of 15 Wayne A. Pflughaupt

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Posted June 24 2003 - 06:59 AM

Stosh,

A 20A circuit requires a minimum wire size of 12ga. wire, whereas a 15A requires a 14ga minimum. However, 12ga wire can also be used with a 15A circuit.

A “dedicated” circuit merely infers that a circuit is “dedicated” for a specific application or equipment - not necessarily a single outlet. A circuit dedicated for say, home theater equipment or your computer equipment can have as many outlets as code allows.

However, if you have a dedicated circuit with a single outlet, the outlet must be rated for the full capacity of the circuit. This is why a 20A dedicated circuit with one outlet would require a 20A outlet (yes, they are different from 15A outlets). However, as Darren noted, it is fine for a 20A dedicated circuit with multiple outlets to use 15A outlets.

With the equipment in your system, there’s no real reason to use more than a 15A circuit. However, if you use 12ga. wire, “upgrading” to a 20A circuit is as simple as changing the breaker.

Regards,
Wayne A. Pflughaupt

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#4 of 15 ross ish

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Posted June 24 2003 - 01:54 PM

even with a dedicated circuit, you will still be tapped into the other circuits that happens to be on the same leg of the incoming line.

your eqpt does not demand the need for 20 amps. better to have the electrician install isolated ground outlets for your ht.

#5 of 15 stosh

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Posted June 25 2003 - 06:46 AM

Currently the way the electrican hooked it up was to wire two 15 amp receptacles on opposite sides of the room.(at the time he did that, I wasn't sure where my equipment was going to go).

so, can I have both 20 amp and 15 amp receptacles (a total of four outlets) on the same 20 amp dedicated circuit?

what exactly does an isolated ground do, and, is it difficult to install?

thanks for your responses, I appreciate the assistance.
Stosh

#6 of 15 Bill Kane

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Posted June 25 2003 - 07:08 AM

Yes, it's entirely adequate to use 15A duplex outlets on a 20A circuit. For upgrades, look for the beefier commercial/industrial specification grade. Your electrician may have used such already.

Generally, people use 20A circuits because they intend to use power-hungry components such as a 200wpc x5 audio amplifier. A 20A circuit can handle 1920 watts, applying a 20percent electrical code safety factor for continuous current draw.

I have never seen any HT components, other than specific surge/power conditioner transformers, that are rated for 20A plug-in service and thus come with the 20A plug (one brass bar is at right angle to fit corresponding duplex outlet). So you can install a 20A rated duplex if you want, it also takes regular 15A plugs, but it's not needed.

Consider: Nearly all surge protectors/power centers for the home market are rated 15A, so the circuit fuses/breaker here should operate well before hitting sustained 20A current draw.

Isolated ground initially was associated with hospital environment for equipment/patient safety from even miniscule elctrical zaps. Today's home electrical wiring uses 2 conductor/copper ground Romex and plastic gang boxes and not the metal conduit needed to create an isolated ground outside the main service panel. You will find Hospital Grade (orange) duplexes at the hardware center that are rated IG. But it's a waste of money without actually wiring for that IG.

bill

#7 of 15 ross ish

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Posted June 25 2003 - 01:41 PM

isolated ground you have to run a separate wire from the outlet back to the electrical box grounding screws. I have a cemented crawspace so it was fairly easy to do, about 10 minutes work.

used in conjunction with a monster hts5100, noticed a significant improvement in video quality.

#8 of 15 Matt_Doug

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Posted June 25 2003 - 06:07 PM

regular self grounding outles ground off through their their mounting straps and thus have multiple paths to ground via metalic outlet boxes which either ground off directly to building steel or metalic conduit hopefully connected to the main panel or through a ground wire connected to usually a few metalic outlet boxes in series...etc Isolated ground outlets (they're always orange) can only be grounded via their ground terminals and require a dedicated ground wire connection to the panel box ground bus. the purpose being that sensitve medical equipment require the clean ground connection that a dedicated isolated ground provides. works well for sensitve a/v equipment too.

#9 of 15 Wayne A. Pflughaupt

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Posted June 26 2003 - 07:48 AM

To clarify some of what has been written here about isolated grounding:

If the electrical system is run in metal conduit, the conduit functions as the ground. Only hot and neutral wires are run to the outlets; grounding is automatic when the outlet is screwed into the metal electrical box, as the mounting tabs and the grounding terminal have continuity.

If the circuit is designated as isolated ground, then a third wire for grounding purposes is also run in the conduit. The orange outlets have the ground terminal isolated from the mounting tabs, which means that grounding is only accomplished when the third wire is connected to the outlet.

Conduit systems are commonly seen in commercial and industrial applications – not too often in residences. Technically “isolated ground” means the ground is isolated from the house ground (i.e., conduit system), which is also shared by air conditioners and any other heavy equipment that may be found at commercial locations.

However, many manufacturers of sensitive electronics (computers, copiers, hospital equipment, etc.) often require a further grounding safeguard – namely a separate, independent grounding stake. This insures that their equipment is separated from all the “hash” that may be generated by the commercial A/C equipment and such. Typically the two grounds are connected by a cable, to conform with code requirements.

As noted, conduit systems are rare in residential applications, so a ground is automatically established when the outlet is mounted in the electrical box (usually plastic in this case). Therefore the Romex cable that is typically used includes a ground wire. Since each outlet has a ground wire directly attached, and since each circuit has a direct path to ground at the breaker panel, expensive isolated ground outlets are not needed – unless you want a visual “flag” that a circuit is dedicated.

Generally there is little reason to do isolated ground in residential applications. However, if you want to it’s fairly easy. Just drive a new 8’ ground stake a few feet from your existing one and direct the ground from your dedicated circuit to the new the ground stake. Don’t forget to connect the two ground stakes with an 8 or 6 ga. cable.

Regards,
Wayne A. Pflughaupt

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#10 of 15 Matt_Doug

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Posted June 26 2003 - 08:36 AM

To clarify what was said about dedicated circuits and a new earth ground. IT'S NOT SIMPLE AT ALL!!!
To separately ground a dedicated circuit from building ground is only possible if the dedicated circuit is run from a branch panel that is electrically isolated from the main panel via an appropriately sized isolation transformer ($$$$$$)

#11 of 15 Gary Silverman

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Posted June 28 2003 - 01:33 AM

"Generally there is little reason to do isolated ground in residential applications. However, if you want to it’s fairly easy. Just drive a new 8’ ground stake a few feet from your existing one and direct the ground from your dedicated circuit to the new the ground stake. Don’t forget to connect the two ground stakes with an 8 or 6 ga. cable"

Except, that, once you connect the two ground rods together, they effectively become the same point electrically, negating any benefit of using a separate point.And, if you didn't, you have just created a ground loop.
Also, believe it or not, the main intent of the ground rod is for lightning protection. Overcurrent protection depends more on the bonding of the ground to the neutral at the main. The code isn't concerned with the noise in your home theater circuit, but it is concerned with that circuit breaker operating quickly.
The best you can hope for, with regards to an isolated ground, is to use a dedicated circuit back to the house main panel.If it's a dedicated circuit run all the way back, you can use romex, and you don't need an IG receptacle.It's still an isolated circuit.
The code is very vague on the term isolated, as applied to grounding, and in the field, it seems that a lot of electricians have different ways of interpreting and applying isolation to the circuits they run. At my company, we isolate the ground in an isolated circuit all the way back to the main service entrance. Some guys just isolate back to the sub-panel.
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#12 of 15 Darin Bess

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Posted October 27 2004 - 10:16 AM

Every reply I have read is partially correct. An isolated ground receptacle has it's yoke isolated from from the equipment grounding conductor. In installations where the conduit or other cable assemblies have a jacket that functions as an equipment grounding conductor the two are not bonded at the outlet box. In a truly isolated ground system a sub panel is set from the the main service and the equipment grounding conductors and grounded conductors are floated in the sub panel. The sub panel is bonded with the equipment grounding conductor from the service, however it isn't bonded to the floated equipment ground buss. The isolated grounds then are bonded to a seperate grounded electrode conductor system. This reduces the potential of noise on the equipment grounding conductor. This type of system is vary rare. The equipment grounding conductor in a properly wired system should never have current on its except under fault conditions. Current will flow to path of least resistence to ground. So if you have a "home run" circuit ran that has its own equipment grounding conductor. There is almost no poetenital for current to flow from the service up the equipment grounding conductor as the resistance under all circumstances should be higher than to ground at the service.

Just the humble opinion of a second generation Master Electrician.

#13 of 15 Wayne A. Pflughaupt

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Posted October 28 2004 - 05:30 AM

It’s always nice to hear from a qualified expert, Darin. Unfortunately you composed your post as if you were lecturing a room of master electricians. I expect most here will understand little of it.

Regards,
Wayne A. Pflughaupt

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#14 of 15 Gary Silverman

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Posted October 28 2004 - 07:06 AM

I got it.
(A first generation Master Electrician)
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#15 of 15 JimN

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Posted November 15 2004 - 07:49 AM

I got it also.
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