Multiplier for 220v computer power supply

[jeepwx03]

I have been running two power supplies for a mining rig for some time now and converted them to 220v this weekend. I’ve been using emporia to monitor them on 110v since I installed emporia, but I noticed something odd that I cannot figure out. When it was running on 110v I was pulling 10 amps and about 2.5 kwh. After switching to 220v and changing the multiplier to 2 it shows 4.19 amps, which makes sense, but the kwh dropped to 1.0. Any idea why this would be? the mining rig is still operating at the same MH/s so it should be pulling the same amount of watts, I was thinking it would be a little more efficient and it would show lower watts, but not this drastic.

[djwakelee]

All PC power supplies should have a power factor corrector circuit, which means the power factor should be close to 1.0.  Given that, power is then just easily calculated to be Volts x Amps.  If you say your supply was drawing 10A at 120V, that is 1.2kW – not 2.5kW.  For your 240V conversion drawing 4.19A, that is indeed 1kW.  So you saw an efficiency improvement of 1.2kW (at 120V) to 1.0kW (at 240) – which makes sense.

 

[jeepwx03]

Thank you for the response, after reading it I believe I figured out what happened. When I updated the sensor on my emporia to a multiplier of 2 it changed everything in the past as well, so when I sent it back to check out the differences it was including the multiplier as well. I’m not sure I like this since my historical data will be incorrect, but at least it explains what was going on.

[djwakelee]

Good info about the historical data being impacted by the multiplier change.

The intent of your 120V to 240V input voltage change raises an interesting idea in general that I had never thought of.  At this stage, most home electronics work over a wide voltage range,  supporting either 240V / 120V (and 50Hz or 60Hz) like your PC power supply.  It seems that if we installed 240V outlets at these higher consuming devices (say TV’s, game consoles, performance PC’s), that would yield similar efficiency gain – and energy savings.  Perhaps of a similar order (10-20%).  Maybe not worth the hassle of changing outlets, rewiring, and dual pole breakers (given US split phase electrical system).  That is, except for heavy load 120/240V electronics – like your mining rig you mention.  But I suppose it could be done for most electronics, for people who are really looking for the most efficient electrical usage.

[jeepwx03]

I was actually considering something like this for my main desktop computer. I could run a 12/2 or 12/3 wire to my office. I did not consider the TV’s though. I know our 60inch is about 350w, so there could be some savings there, but I’m unsure of its voltage rating. I was able to verify our 40in is only 120v. While drafting this response I noticed my color laser printer out of the corner of my eye and recall the lights flickering when I print, checked this out and only 120v. There are some small potential gains if we start paying attention to it.

[djwakelee]

Yes, you’d have to definitely check that a given device can support 240V, before swapping it to a 240V line cord.

You don’t need to run 12/3 wiring for 15/20A 240V – can use 12/2.  The black is hot 1, the white is hot 2, and the ground is still ground.  If it is a dedicated circuit, you can switch it at both ends (outlets and breaker) without changing the wiring – still using 12/2.  If the circuit goes to other outlets, then they’d all need to switch to 240V – or make new runs for new outlets.  But you still only need to use 12/2.

• This reply was modified 2 years, 9 months ago by djwakelee.

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