I was wondering whether ya'll think I would trip a breaker / create an unsafe situation with the following items plugged into one wall socket. The building is about 30 years old, but I don't know about the electrical system.

In approximate order:

Computer with 550 watt power supply
Computer with 250 watt power supply
100 watt speaker system
21" monitor
17" monitor
75 watt bulb
50 wat bulb
Inkjet printer
5 other devices totaling about 100 watts

Should I be concerned?

John

How many amps is the circuit breaker/fuse on that outlet? You need to compute how many amps you draw at peak power usage. If it's over the rating you'll be venturing to the breaker box a lot or buying fuses by the case.
I may be wrong but I think you would use the formula Watts = volts x amps (this is used for single phase motors) I'm sure others will know if it's correct or not...

edit Actually that won't work because it's a DC equation. Easiest thing is to add up the amperage ratings on all the devices and see if it's close to the breaker/fuse max rating...

My knowledge of US electrical systems comes from cable DIY shows (which for someone familiar with UK electrical practice is scary viewing), but I believe that each circuit is typically 20amps. I think an average house has about four or five circuits, so what you have hooked up doesn't sound too much.

In the UK, each socket is rated to a maximum of 13amps, with a total of about 30amps for the circuit and each plug has a 3-13amp fuse.

You can do a few things to make sure that it doesn't end in smoke and tears.
- Make sure you have a ground leak isolator in the house's switch board. If things fuse up this will trip like a normal circuit breaker preventing greater tragedies.
- Use a switched power board with a circuit breaker built in. If the load it too great it will shut off first. A board with individually switched outlets would be ideal.
- You could also try a UPS on some of the equipment too. If there is too much load for the main circuit, the UPS would soak it up for a short time. you want to be careful with this as too great a load on the UPS will burn the batteries

when you turn the equipment on, do it in stages so that you don't have a huge initial current draw. Most devices draw close to their current rating at start up, eg hard drives spinning up, monitors warming up.

Most American wall sockets are rated for 15 amps (they're NEMA 5-15 sockets), even if the wiring and breaker are capable of more.

Why are American DIY shows scary to British electricians?

Why are American DIY shows scary to British electricians?

Wire nuts.

Those things are hideous. Mains wiring should (a) use a real colour code (IEEE standard for example), and (b) be fastened VERY securely. Something like choc-block (a sort of screw-terminal in plastic strip thing, for americans who may never have come across it), not a naff little bit of plastic and metal that screws onto the twisted together wires and holds it in place more by the grace of god than anything else.

I've done quite a bit of wiring in North America, and a hell of a lot in England, and I know which I think is safer. Wire nuts, cables stapled in place with nasty, very sharp metal things you hammer in across the wire with only a little bit of cardboard to insulate it, and predominantly wooden houses is a situation begging for a disaster.

Several electrical-type engineers I know across the pond say I'm being prejudiced, but do admit they seem to see a lot more house fires caused by electrical faults than we get over here.

I remember servicing an imported coke machine a few years ago at a job I had at the time, and after taking the cover off just staring in disbelief, afraid to touch it. I have no idea how it was inported, but I can guarantee it wouldn't pass european safety directives. The health and safety people would have had a nervous breakdown if they'd ever inspected it internally.

Nasty, nasty, nasty wire nuts.

pca

As a Brit living on this side of the pond, here's my take:

The biggest problem IMO with the US electrical code is the part that the average user is most exposed to: plugs and sockets.

1) The sockets are not protected against insertion of [insert whatever a 2 year old can find around the house here]. UK sockets have protective flaps on the live and neutral, that are released when the earth pin is inserted. This makes it near impossible to stick anything but a proper plug into the live connection. The earth pin on a UK plug is longer than the other 2, and this also has the benefit of ensuring that the earth connection is made before the other 2.

2) UK plugs have shrouded pins. The shrouds are such that if the plug is partially pulled out of the wall then the connections are broken before any of the pin's metal becomes exposed.

These 2 measures are so easy to take for granted in the UK, but when you have a toddler in the US you soon learn to miss them.

Other bug-bears:

1) Those little 3pin -> 2pin adapters that are so easy to get and seem to exist in every house. The ones that allow you to plug an earthed plug into an older unearthed socket. They have a little metal earth tab that is supposed to be connected to a water pipe or similar, but I have never seen anyone doing this. Arrgh.

2) Those flimsy extension cords. They need to die now.

3) The screw-on wire-nuts used in junction boxes. Twist the wires together and then twist on a wire-nut. Although they seem to work quite well if you use the right size for the number and gauge of wires, they still scare me - I'd much rather have a block of screw terminals. Combined with (4) below especially.

4) The mandated use of solid-core wire in circuits. Combined with the 8" length of free wire at the junction box. Trying to get three 12-gauge wires twisted neatly together in a wire-nut is the first excercise in manual dexterity anbd frustration. Then repeat for neutral and earth. And then trying to get all 3 bundles of 3 x 8" wires to sit neatly in the junction box without one of the wire-nuts coming off really takes the piss. It is equally frustrating when something to be connected is multi-stranded. Getting one of those wire-nuts to hold multi-strand and solid-core wires together is a PITA. And working with 10 gauge solid-core wire is a PITA period.

5) The fact that the NEC requires a crazy number of "convenience" circuits in a dining room, but not in the living room. The only thing that gets plugged in in my dining room is the vacuum cleaner. My living room OTOH has a list similar to that in the first post of this thread. Go figure.

Aside from all that, most of the other stuff is ok. The separation of circuits in the panel is far better than that in the UK, which makes working on them easier. No need to plunge the house into complete darkness in order to change a light switch. Just find the appropiate breaker. The nearly-exclusive use of breakers instead of fuses (which are still common in the UK). No fumbling around during a thunder-storm looking for fuse wire. No possibility that a non-technical person can accidentally use incorrectly rated fuse wire etc.


But anyway, just what is scary about Martha Stewart turning an ornamental fountain into a desktop lamp? Waaaaaaaaaargh.


To get back on topic though:
The circuit breaker is matched to the wire used in the circuit. (I'm assuming that this is to code). There will be a safety factor included in this matching so that the circuit breaker will trip before the wire is at risk. You still need to take into account the 15A limit on a socket though (IIRC this applies to the socket as a whole, ie both outlets combined = 15A, not each outlet =15A) You also want to check the amp capacity of any surge protector strips that you use - don't assume that they can handle 15A.
This gives you a maximum of 1800W on a socket, and 2400W on the circuit if you have access to multiple sockets (assuming 20A circuit??). You might want to consider getting an additional circuit added anyway specifically for this bunch of equipment. The existing circuit probably services other outlets too.


Edit:
Looks like Patrick posted whilst I was typing and shares my hatred of wire-nuts.

Further analysis of requirements:
Computer with 550 watt power supply.
Computer with 250 watt power supply

These are maximum PSU ratings, and you are not likely to be hitting them. But lets play safe and take them at 800W combined.

100 watt speaker system
21" monitor
17" monitor

My Dell 21" monitor is rated on the back as drawing 2A, ie about 500W.
Lets assume 300W for the 17"

75 watt bulb
50 wat bulb
Inkjet printer
5 other devices totaling about 100 watts

My inkjet printer is rated at 0.4A, ie about 50W.

So, That's 1975W, lets say 2000W. too much for a single socket.

thanks

I remember a while ago, when we were going around the office unplugging everything so that the electricians could test the wiring, one of the directors from the US office was visiting and had a look at our server rack. He was quite concerned that the 12 or so computers, three printers, two monitors and numerous other comms kit were plugged into just four sockets and that none of us were at all concerned that we might be overloading them.

... I forgot one of my other gripes with US plugs. They aren't individually fused - which means that if one piece of equipment goes down it could take the whole circuit with it. Granted, the use of many circuits reduces the impact that has, and a lot of equipment has it's own fusing, but still...

They aren't individually fused - which means that if one piece of equipment goes down it could take the whole circuit with it

This is a very common occurance in my house, considering it's age. The electrical system is a mess, and I still have no clue what outlets are on what circuit. The rule though right now is no cleaning at night, since usually whatever circuit so many of the plugs are on can't take the lights, and a vaccum cleaner. The best was when I took out the trash, turning on the back porch light, and left two friends in the basement in pitch blackness.

In reply to:

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I may be wrong but I think you would use the formula Watts = volts x amps (this is used for single phase motors) I'm sure others will know if it's correct or not...

edit Actually that won't work because it's a DC equation.

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The correct power formula for AC is watts= volts x amps x PF with PF being the power factor of less than or equal to 1. Resistive loads approach 1.0, whereas inductive loads such as electric motors develop peak current consumption out of phase, reducing overall power consumption.

Stu

All the wire nuts I've ever put on could pretty much support my whole body weight as well as the wire itself. Given, this takes some practice, but it's certainly doable. I also almost always cover the entire thing with electrical tape, in case there's some exposed wire there I can't quite see.

And wire staples aren't that big a problem, as there's much more danger from a homeowner accidentally putting a picture frame nail through a cable than an electrician putting a staple through one.

And don't forget that mains wiring in the US is almost always required by law to be done by a licensed electrician, and usually government-inspected after the fact.

government-inspected after the fact

As if that implies good workmanship....this is the government we're talking about here...

In the state of North Carolina (where I see you reside), I've seen a room addition plan scrawled on the back of a napkin get approved with a response of, "Looks like you know what you're doing."