: Is a 15 amp circuit enough for all these HT toys?
2007-01-10, 09:51 AM
I only have access to one 15 amp circuit in the basement where I'd like to plug in my plasma, receiver, subwoofer, computer, dvd player, and digital cable receiver. That would total about 1700 watts of power consumption! Should I run a new 20 amp circuit to this location? And how many watts can a 20 amp circuit handle? Thanks.
I've moved this to the Construction and Setup forum.
2007-01-10, 10:20 AM
This is a tough question to answer definitively because there are a lot of variables involved. I 'think' the max load on a 15 amp AC circuit is 120 x 15 x .707 = 1272 watts (because voltage and current are 90 degrees out of phase in alternating current). I assume that you calculated 1700 based on the wattage of the individual components. I think this is more of a max load rather than an actual load number, because devices draw based on the what they are doing or what is currently on. For example, if your computer has a 300 watt power supply, its not really drawing 300 watts, it draws what it needs to power the motherboard, hard drive, DVD drive and whatever else is connected. 300 is just the max.
The rule of thumb as I understand it is for a maximum of 12 'items' per 15 amp circuit. So in your case (provided there are no other items like lights or other outlets in other rooms sharing the circuit), it should be ok for the items you've listed.
Of course the safe route is to just install another 15 amp circuit if thats an option. You don't necessarily need to upgrade to a 20 amp circuit. Also, if you do decide to put in a 20 amp circuit, be aware that you need to install new wire as 15 amp circuits typically use 14 guage wire and 20 amp circuits need 12 guage wiring. So you cannot just replace the circuit breaker/fuse.
Wow, the things I learn on this forum. Thanks GQueue!
2007-01-10, 10:50 AM
Thanks. Yes, I was aware that I would need to run 12 gauge wire for the 20 amp circuit. But I didn't realize that power consumption was variable like that. That's interesting. Maybe the existing 15 amp circuit is enough then. Can you give some idea of what the average power consumption would be of these components? (450 watt computer, 500 watt plasma, 500 watt receiver, 200 watt subwoofer).
2007-01-10, 11:04 AM
FWIW, I have the following on a single 15A circuit without any issues.
61" plasma, HTPC, Xbox 360, HDPVR, receiver, subwoofer, printer, lava lamp, wireless router, DSL modem.
There are devices that will allow you to measure power consumption. 57 had a thread where he discussed using one. I think you can get them at Canadian Tire.
2007-01-10, 11:27 AM
The rule of thumb that GQUEUE refers to is not a rule of thumb rather it is an electrical code.
Code states that there can only be 12 devices per circuit. What they are referring to here are light and electrical outlet combinations. i.e. You can have 4 lights and 8 outlets on one circuit or any combination thereof. The only limit to the number of devices that you can plug into your outlets is the circuit breaker. It is designed to protect the wiring in your home when you've exceeded the current limitations of the circuit breaker.
I have all of the same components plugged into a power bar that you require on a 15 amp circuit. I also have lights on that circuit as well and have never had a problem with the C.B. popping.
I 'think' the max load on a 15 amp AC circuit is 120 x 15 x .707 = 1272 watts (because voltage and current are 90 degrees out of phase in alternating current).
I've never once seen voltage and current at a phase displacement of 90°, ever.
even when supplying a purely capacitive or inductive load, there will always be a resistive component that will offset the phase angle to something other than 90°
15A x 120 v = 1800 watts, and the CEC requires us to derate the cct to 80 percent (1500 watts) for continuous use.
2007-01-10, 02:17 PM
I've never once seen voltage and current at a phase displacement of 90°, ever. Hmmm... I guess I'm talking theorectical here. I'm not an electrician or an electrical engineer so I can't say with any certaintly. I just recall from school that when discussing alternating current, something about voltage and current not being in phase which is why you cannot do a straight power calculation of volts x amps to determine wattage (you see this with UPS's where they use VA ratings rather than watts to avoid confusion). I see what you are saying though about the resistive component causing the current to be more in phase with voltage. And if the CEC says to use 80%, that's fine with me.
Merritt64 is correct about the 12 'items' being a code thing with the number of outlets and lights on a circuit. But while there's no 'limit' to the number of things you can plug in, I think its a valid way of thinking about it for at least what the OP was asking about.
2007-01-10, 02:26 PM
Can you give some idea of what the average power consumption would be of these components? (450 watt computer, 500 watt plasma, 500 watt receiver, 200 watt subwoofer).
That's the thing, I don't think you can estimate an average draw. For example, your 500 watt receiver is going to vary based on how loud the sound is and whether you're listening to an action movie or a classical sonata. Your plasma will vary whether you're watching a daytime HD movie or a dark SD picture. The computer will vary whether its in idle mode or doing a DVD burn from a hard disk. So I don't think you can do any type of guess.
But as others have mentioned, many have the same number of device plugged in with no problems. I wouldn't worry about it too much and just make sure you have a quality surge protector on the circuit. I also understand that its pretty easily to have a whole house surge protector installed for even added protection.
FYI, upgrading a circuit to feed a 20-amp outlet requires more than just a breaker and re-wiring the outlet. The outlet also needs to be changed to a 5-20R. The standard 5-15R is the three-prong plug you're all used to seeing in any home or office.
A 5-20R receptacle has one of the "legs" in the shape of a T. This way any load that is 15 amps or less, which will have the standard 5-15P plug configuration, can be plugged into the outlet. Any load that is 15-20 amps uses a 5-20P plug. This plug has one blade rotated 90 degrees so you can't physically plug it into a 15 amp receptacle. These larger loads will also have heavier gauge wire in the cord.
Have a look here
to see what the different receptacles look like.
2007-01-10, 03:53 PM
The outlet also needs to be changed to a 5-20R.Ken, do you have to use the 20 amp outlet on a 20 amp circuit? If his intention is to never plug a 20 amp device into the circuit is it ok to use a normal 15 amp outlet? Is there a safety concern?
Can. Electrical Code would say yes, you need to use the 20R receptacle on a 20 amp circuit. Real world situation, if you change your breaker to 20-amp probably no one would know until the next time an electrical inspector visits. However, for safety I personally would change the receptacle and all wiring.
The CEC doesn't allow for your intended use but looks at worst case. If you put a 20-amp breaker in today, then move out of the house, someone else could load up the circuit to 15+ amps, not knowing or even thinking that they're no longer properly protected. Wiring in the wall could heat up more than heat rise calcs have allowed for and start a fire. Or if you're running an extension cord from the wall and plugging 3 6-amp loads into the cord then the cord could overheat, insulation could break down etc, etc.
2007-01-10, 04:47 PM
I used these receptacles, 12 guage wire and 20A circuit breaker when I wired my workshop. I seem to recall concluding that the thicker guage wire (12AWG) would be easier on the motors in power tools. These receptacles were not a stock item at Home Depot or the local hardware stores.
P.S. Ken, its a small geeky world. Dave (ABR, mtb)
Yo dave, long time! Last time was VPS fest at Whizler I think?
Still working for the City?
2007-01-11, 08:48 AM
I've decided to run a new 15A circuit to the area where most of the A/V equipment will be. The computer, monitor, and subwoofer are a few feet to the side and can be plugged into the original 15A circuit. So the entire load will be split between two circuits.
Thanks for sharing your knowledge. This is a great website.
2007-01-12, 06:25 PM
Just plug it all in. The listed power is a maximum. I bought a Canadian Tire watt meter just to see what's going on. My PC (Athlon 2500, 450W power supply, 2 hard drives) uses 160W. The 19" CRT monitor -- 100W. My "Home Theater" (27" CRT, HK AVR, Velodyne sub, DVD, VCR) 160W. Even though the sub-woofer is rated at 150W output the supply side is 75W max and is normally closer to zero.
Because of the stupid wiring, two PCs, home theatre, room lights, hall light entrance light (600W) and a 1200W heater all sit on one circuit. I can turn on everything except the entrance light.
2007-01-12, 09:56 PM
There are a lot of factors in deciding what is necessary. General rules of thumb:
1. 15 amp circuits are the norm and most consumer products are rated for 15 amp circuits. A 20 amp circuit is rarely necessary or advised.
2. If the breaker/fuse breaks with a 15 amp circuit, add another circuit for the high amperage devices.
3. If high amperage or special need devices are identified upon installation, add a separate circuit for those devices.
A/V fall under special need devices. Most A/V setups can be fed with a single 15 amp circuit. An existing circuit is often sufficient but some situations can make it necessary to install a separate circuit. These are: 1. High surge or high load devices on the same circuit. These include heaters, refrigerators and air conditioners. 2. Noise generators on the same circuit. These include motors, fluorescent lights, refrigerators and air conditioners.
The most variable load in a HT system is the A/V amp. Most draw about 200 watts (~2 amps) at low volume. Some can draw 10,000-20,000 watts (~10-20 amps) at full volume. Unless you are trying to simulate the sound levels of a Def Leopard concert, most will rarely exceed 500 watts (~5 amps.) If you have an unusually high powered A/V amp, run a separate 15 amp circuit just for the A/V amp (rarely necessary.)
In the case that it is difficult to install a separate circuit at the A/V center, install an outlet in an accessible location and run a 12 AWG extension cord to a high quality power bar at the A/V center. This works just as well.
My A/V amp is rated at 11 amps. I monitored it at normal listening levels and it draws about 2-4 amps. I have that, a HDTV, several other A/V devices, a computer and an aquarium on one circuit with no problems.
2007-01-16, 09:55 AM
Some can draw 10,000-20,000 watts (~10-20 amps)
I think you mean 1000-2000 watts ;)
2007-01-16, 09:58 AM
Also, it would be advisable to hook up a UPS to your system, this will reduce wear on your system in case of brownouts or power surges. (Very good for new LCD/DLP/PLASMA tv's, in case of a power outage the cooling fans will keep running) It will also help filter out the power going into your precious HT equipment. ;)