20amp Circuit How many computers

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Can anybody tell me if 3 computers are too much for a 20 amp circuit? Actually it is 3 monitors a printer "not laser" and 3 thin clients if anybody knows what a thin client is. it is about the size of a book and is not a full tower so I assume it consumes alot less power then a full computer tower.
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You'll be just fine

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On Tue, 30 Jan 2007 21:14:14 -0500, "RBM" <rbm2(remove

Every bit of electrical equipment with a UL rating should have somewhere on it a plate that tell you what sort of power it draws.
Add them up.
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Not that tough to compute if you really are a computer geek.
500 W power supply at 120 volts AC = 5 Amps approximately if you want to use conservative figures.
So factor in the peripherals - which really don't draw much at all, and you're getting pretty damn close to 20A at full draw startup.
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Has no disks, and is booted from the network?

Shouldn't be a problem.
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Mark Lloyd
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True thin client workstations are far less power hungry than their larger PC cousins. Also, keep in mind that even though a desktop PC may have a 400-watt power supply, its maximum power draw is likely to be less than half that.
Here's the scoop according to eWeek:
"While a PC can consume as much as 220 watts of power, a thin client such as Sun's Sun Ray 2FS consumes less than 8 watts. Even a thin client with a processor and DDR (double data rate) RAM such as HP's HP Compaq t5720 consumes about 30 watts or less."
Source: http://www.eweek.com/article2/0,1895,1958315,00.asp
If the accompanying monitors are LCD flat screens, add an additional 30 to 60-watts per workstation; if, however, they are of the CRT variety, you might bump that number up to 100 or 120-watts.
One other thing to note: if these thin clients are, in fact, older generation or "obsolete" PCs that have been "reborn" as thin clients, 150-watts per workstation may be a more reasonable estimate.
So with that in mind, total wattage could fall anywhere from as little as 150 to 200-watts (< 2.0 amps) at the low end, to perhaps as high as 800 or 900-watts (< 8.0 amps), with the monitor type accounting for much of this spread. Even at 900-watts, this load would represent less than half the circuit's rated capacity; a 20-amp circuit would seem more than sufficient.
Cheers, Paul

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wrote:

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On Tue, 30 Jan 2007 20:54:55 -0800, "Eigenvector"

Electricians will thank you for the extra work but it is not necessary.
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According to the EPA, a typical desktop computer uses between 25 and 60-watts and a CRT monitor between 55 and 90-watts (they peg LCD monitors at 30-watts). At the upper end, that suggests the combined wattage of a computer and monitor would be in the order of 150-watts.
Source: http://www.microtech.doe.gov/energystar/
According to an article published in this week's Economist, "a typical desktop and monitor together use perhaps 150 watts."
Source: http://www.economist.com/daily/columns/greenview/displaystory.cfm?story_id 15835
Tufts University tells us "the average desktop computer uses about 120 Watts (the monitor uses 75 Watts, and the CPU uses 45 Watts.)"
Source: http://www.tufts.edu/tie/tci/Computers.html
A 20-inch iMac "with both of Core Duo's cores cranked to 100 percent utilization," is reported to consume just 95-watts.
Source: http://weblog.infoworld.com/enterprisemac/archives/2006/02/imac_keeps_its.html
So, if you wanted to be a bit more cautious, you might budget a combined total of 200-watts per workstation. Again, we're told these are thin clients and not high-end servers, so you wouldn't expect them to be decked out with multiple hard drives nor power guzzling multi-chip processors.
Cheers, Paul
On Tue, 30 Jan 2007 20:54:55 -0800, "Eigenvector"

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On Tue, 30 Jan 2007 20:54:55 -0800, "Eigenvector"

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On Wed, 31 Jan 2007 04:10:04 GMT, Paul M. Eldridge

There should be very little startup surge, since there's no disks.

And power consumption will be higher than THAT. These things (power supplies) aren't 100% efficient.

A large CRT monitor can easily use more power than the computer itself. A good reason for turning the monitor off when you're not using it.

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Hi Mark,
I'm sure some of the larger CRTs could consume in excess of 100-watts but more typical office-type CRTs are likely to come in below this. For example, the University of Waterloo tells us their 17" SONY CRTs draw 75-watts when in use.
Source: http://windows.uwaterloo.ca/Hardware/PC_Power_Consumption.asp
The maximum power draw of my 17" NEC MultiSync LCD 1700V (the one I'm using now to type this) is 40-watts and in standby mode it comes in at under 4-watts.
Unless we're looking at some unusual setup, budgeting 30 to 60-watts for a 17 to 19-inch LCD panel and 75 to 125-watts for the equivalent CRT doesn't strike me as unreasonable.
As a sidebar to this, with the low cost of LCD panels, I can't imagine why anyone would want to buy a CRT monitor, unless they had a pretty compelling reason to do so. I can purchase a name brand 22-inch LCD monitor for under $400.00 Canadian (less than $340 US) and a 17-inch LCD monitor for half that. The energy savings and, in particular, the resulting space savings make this a no-brainer.
The other thing we shouldn't forget is that OP has told us these are thin clients about the size of a large book, so it's safe to assume their power consumption is quite low. We know, in fact, the Compaq t5720 has a maximum power draw of just 30-watts and that Sun's Sun Ray thin client is under 8-watts, or about the same amount of power as would be consumed by a night light.
So if we were to allocate 60-watts for an LCD monitor and 40-watts for a thin client PC, our total combined wattage for these three work stations is 300-watts (~ 2.5 amps) and that's being rather generous. And if CRT monitors are used in lieu of LCD panels, total wattage might then jump to between 350 and 450-watts (< 4 amps).
Cheers, Paul
On Wed, 31 Jan 2007 14:19:53 -0600, Mark Lloyd

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T.J. wrote:

Typical computer power supply is ~400W rated. I can see any problem. CRT monitors consume quite a bit more than LCD panels.
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Two desktop PCs. One Compaq Proliant 2500 server Two 21" CRTs One Laptop PC 5-10 60W bulbs
... is too much for a 15 amp circuit. I guess people didn't use equipment like that back when wiring four rooms per circuit was okay.
I almost picked up a 5-node RS6000 on Ebay but I'd have had to rewire the house to power it!
-rev

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Check the power ratings of the devices and add up the amperage.

If you are talking about something like the Sun Ray devices ( http://www.sun.com/sunray/sunray2/ ) then the power draw is probably quite low. The monitors and printer will be the major consumers.
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wrote:

The printer should be a major consumer only when printing.
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Hi Mark,
OK, I realize I'm being a F-N PITA this evening, but I wanted to note the OP has indicated the printer is "not laser", so I'm taking that to mean it's an ink jet. And if that's the case, the difference between operating and standby consumption should be fairly modest.
We now return you to your regular programme, already in progress....
Cheers, Paul
On Wed, 31 Jan 2007 20:36:06 -0600, Mark Lloyd

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On Thu, 01 Feb 2007 04:32:40 GMT, Paul M. Eldridge

I remember some ratings that were very different, but haven't actually measured it. Yet.
I checked my inkjet printer (Epson Stylus Photo R220). Measured current consumption during standby was 20mA. During initialization or printing, it varied with a maximum of 90mA. This printer doesn't use much power, and that isn't a very big change compared to the information I had (probably for a very old printer, maybe it was laser).
I do remember something about not putting a laser printer on a UPS because of the power surges.
So, I'm saying you're right. I don't have a problem admitting mistakes I actually made.

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Hi Mark,
I hadn't set out to prove anyone right or wrong, but I did want to assure the OP that the varying power demands of an ink jet printer are really very modest compared to those of a laser, and that the printer wouldn't have any material impact on circuit capacity compared to these other loads (which I think we're all agree are fairly modest in themselves).
Cheers, Paul
On Thu, 01 Feb 2007 13:03:26 -0600, Mark Lloyd

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Simplest way to find out without guesstimating is to use a Kill-S- Watt, and _measure_ the actual va, watts, amps, whatever drawn by the combination of devices connected downstream from it. Clue: watts are not the limiting factor, since power-factor can vary widely; count amps.
Sure bet: nowhere near 20a draw.
HTH, J
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