Bitcoin Forum
October 19, 2017, 11:12:23 AM
 News: Latest stable version of Bitcoin Core: 0.15.0.1  [Torrent]. (New!)
 Home Help Search Donate Login Register
 Pages: 1 [2]  All
 Author Topic: PSU Ampere Calculation (on the wall with 230V) ??  (Read 6181 times)
DeathAndTaxes
Donator
Legendary

Offline

Activity: 1218

Gerald Davis

 June 05, 2012, 02:13:48 PM

One thing that wasn't mentioned is power factor.
Volts * Amps is not Watts (well not on AC circuits).   It is VoltAmps.
VoltAmps * Powerfactor = Watts.

A power factor of exactly 1 (where voltamps = watts) only exists for resistive loads (like a old style light bulb).  For capacitive loads you will always have a PF of <1.  Modern Power supplies are pretty good and will tend to have a PF of 0.95 or higher (don't believe that 99.9% PF marketing crap).

The good news is that you only pay for Watts.  So if you are pulling 5A @ 230V = 1150 VA but the PF is 0.95 you are actually charged for 1150*0.95 = 1092W.

The bad news is the wire is rated on amperage so that "cost savings" doesn't make your wire handled more juice.  Yes if the circuit (outlet, wire, & breaker) is only rated for 16A and you are pulling 5.5A you can't fit more than 2 units.  Still with some modest power reduction (lower memclock, reduce cpu clock/voltage in bios, turn off unecessary functions in bios, use linux, use usb key, etc) you likely can get it under 5A and thus can fit 3 rigs per circuit.

To measure watts you need a more sophisticated meter.   You need a "wattmeter" which measures both amperage and voltage simultaneously and continually.  Your power meter installed by the power companies does this.  A handheld meter which can universally measure wattage on any circuit is expensive (usually \$500+) but dedicated meters you wire into a circuit or sub panel are much cheaper (say ~\$150).
1508411543
Hero Member

Offline

Posts: 1508411543

Ignore
 1508411543

1508411543
 Report to moderator
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
1508411543
Hero Member

Offline

Posts: 1508411543

Ignore
 1508411543

1508411543
 Report to moderator
1508411543
Hero Member

Offline

Posts: 1508411543

Ignore
 1508411543

1508411543
 Report to moderator
AzN1337c0d3r
Full Member

Offline

Activity: 238

★YoBit.Net★ 350+ Coins Exchange & Dice

 June 05, 2012, 07:56:15 PM

Modern Power supplies are pretty good and will tend to have a PF of 0.95 or higher (don't believe that 99.9% PF marketing crap).

That's why independent testing such as this shows that AX1200 as having 0.99PF above 600W right?

Quote
you likely can get it under 5A and thus can fit 3 rigs per circuit.

No, breakers for circuits are only rated for 80% continuous load, so you need to get below 4.26A, otherwise you'll get trips while mining.

Quote
To measure watts you need a more sophisticated meter. You need a "wattmeter" which measures both amperage and voltage simultaneously and continually.  Your power meter installed by the power companies does this.  A handheld meter which can universally measure wattage on any circuit is expensive (usually \$500+) but dedicated meters you wire into a circuit or sub panel are much cheaper (say ~\$150).

Kill-A-Watts can measure Power Factor (and thus VA and Watts). You dont need a super-expensive device to do so.

DeathAndTaxes
Donator
Legendary

Offline

Activity: 1218

Gerald Davis

 June 07, 2012, 12:25:00 AM

Kill-A-Watts can measure Power Factor (and thus VA and Watts). You dont need a super-expensive device to do so.
KAW doesn't work on 240V.  A portable wattmeter tends to be expensive.

[/quote]
 Pages: 1 [2]  All
 « previous topic next topic »