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Author Topic: Does running extension cords to your rigs screw up the power?  (Read 3214 times)
jjshabadoo
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February 22, 2012, 01:21:38 AM
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I have to run cords so i can have my rigs on different breakers for now(adding 3 20 amp outlets in my basement soon) I then of course have the cord plugged into a quality surge protector.

Could these cords be causing my inability to get 4 5970's running even though I'm using the same exact hardware and software as others who have pulled it off?

They are just regular extension cords, 25 feet, 50 and 100 feet long for three rigs.
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February 22, 2012, 02:20:04 AM
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I have to run cords so i can have my rigs on different breakers for now(adding 3 20 amp outlets in my basement soon) I then of course have the cord plugged into a quality surge protector.

Could these cords be causing my inability to get 4 5970's running even though I'm using the same exact hardware and software as others who have pulled it off?

They are just regular extension cords, 25 feet, 50 and 100 feet long for three rigs.
4 5970s is a lot of power. If you are using a 100 foot extension cable that is any less than 12 gauge, you will certainly be suffering from voltage sagging leading to instability. Most cords are 14 or even 16 gauge, so you should check that first.

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February 22, 2012, 05:00:41 AM
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There should be a ratings description on the cord showing you the available power draw it can support.  If it's a thick cord it should be rated for 15A but still, 4 5970s is going to be pulling a lot of power.

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February 22, 2012, 05:12:20 AM
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Running extensions cords for anything permanent is against fire code for a reason.

jjshabadoo
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February 22, 2012, 06:53:55 AM
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That's what i figured. I'm done with the whole 4x5970 fantasy, kudos to those who have pulled it off, but I'm done with that.

I'm looking toward rigs with 2 5970's and one or two 5870's I'll just stick with getting those running. I have two rigs running 2 5970's and 1 5870 and one rig running 1 5970 and 3 5870's and those are just fine. occasionally resets, but no big deal.

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February 22, 2012, 07:23:53 AM
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I have to run cords so i can have my rigs on different breakers for now(adding 3 20 amp outlets in my basement soon) I then of course have the cord plugged into a quality surge protector.

Could these cords be causing my inability to get 4 5970's running even though I'm using the same exact hardware and software as others who have pulled it off?

They are just regular extension cords, 25 feet, 50 and 100 feet long for three rigs.
4 5970s is a lot of power. If you are using a 100 foot extension cable that is any less than 12 gauge, you will certainly be suffering from voltage sagging leading to instability. Most cords are 14 or even 16 gauge, so you should check that first.

Yep, and even a 12 gauge cable at 100 ft will drop about 5 volts @ 15A.
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February 22, 2012, 07:56:49 AM
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I have to run cords so i can have my rigs on different breakers for now(adding 3 20 amp outlets in my basement soon) I then of course have the cord plugged into a quality surge protector.

Could these cords be causing my inability to get 4 5970's running even though I'm using the same exact hardware and software as others who have pulled it off?

They are just regular extension cords, 25 feet, 50 and 100 feet long for three rigs.

Even having fair bit of voltage sag from undersized extension cords should not result in instability of the system. Inside the power supply, all incoming power gets rectified to DC before being stepped down to the voltages the computer needs. These days power supplies also have power factor correction and sport universal input usually from 90-250vac or thereabouts. If your extension cords are dropping even 10-20 volts from 120v mains there is still plenty of room for the power supply to operate normally. If you have a low quality power supply or one that is being tested near its limits (which it probably will be running four 5970s) then it may be an issue.
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February 22, 2012, 10:52:21 PM
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I have seasonic gold 1250's single rail monsters, best of the best. It's the god damn extenders that screw everything up.

I got four running on the board for 24 hours and it only pulled 1060 watts peak on my kill-a-watt meter. That was with all extra mobo crap turned off and linuxcoin on flash drive.

Anyway, Jimm_64 has plenty of 4x5970's going and says he does it with $2 extenders, 2 seasonic 750 watt PSU's msi 890FXA-GD70, semprons, etc. with linuxcoin.

I followed his exact hardware list and failed, so something isn't right. he's doing something different, or it's a power issue for me. He even just shorts his second 750 watt psu with damn paper clip.
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February 22, 2012, 11:38:24 PM
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I have seasonic gold 1250's single rail monsters, best of the best. It's the god damn extenders that screw everything up.

I got four running on the board for 24 hours and it only pulled 1060 watts peak on my kill-a-watt meter. That was with all extra mobo crap turned off and linuxcoin on flash drive.

Anyway, Jimm_64 has plenty of 4x5970's going and says he does it with $2 extenders, 2 seasonic 750 watt PSU's msi 890FXA-GD70, semprons, etc. with linuxcoin.

I followed his exact hardware list and failed, so something isn't right. he's doing something different, or it's a power issue for me. He even just shorts his second 750 watt psu with damn paper clip.

The difference between 110v and 220v?

jjshabadoo
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February 23, 2012, 12:23:58 AM
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might be, jimm did say he had a bunch of 220v installed.

I'm getting 3 new 20 amp outlets all on separate breakers installed tomorrow to see if that helps.

I still don't give a shit about 4 5970's, but i'm hoping to run 2 5970's under water and 2 5870's on air per rig.

Under water only because I got a bunch of water cooling stuff for super cheap. About 1200 worth for 500 bucks.
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February 23, 2012, 12:26:15 AM
 #11

I have to run cords so i can have my rigs on different breakers for now(adding 3 20 amp outlets in my basement soon) I then of course have the cord plugged into a quality surge protector.

Could these cords be causing my inability to get 4 5970's running even though I'm using the same exact hardware and software as others who have pulled it off?

They are just regular extension cords, 25 feet, 50 and 100 feet long for three rigs.

Even having fair bit of voltage sag from undersized extension cords should not result in instability of the system. Inside the power supply, all incoming power gets rectified to DC before being stepped down to the voltages the computer needs. These days power supplies also have power factor correction and sport universal input usually from 90-250vac or thereabouts. If your extension cords are dropping even 10-20 volts from 120v mains there is still plenty of room for the power supply to operate normally. If you have a low quality power supply or one that is being tested near its limits (which it probably will be running four 5970s) then it may be an issue.

On the other hand, if you're dropping 10 volts on a 120V circuit, you're pissing away 8% of your power consumed. You're basically paying to heat the air around the cord and effectively increasing your electricity costs by 9% (as measured at the computer). That would also mean you're drawing about 19 A and that cord should be feeling pretty toasty.

Get a volt meter and measure as close as possible to the computer (a Kill-a-watt meter will do). If you're measuring anything below 115V (~10A draw over 100ft on 14 gauge copper will do this), I'd consider using a shorter or lower gauge (thicker) cord.

And if you do manage to get a 20 volt drop on a 100 ft 14 gauge cord, you're drawing about 39 amps and can soon expect a fire. :-)

My advice is to run as short of circuit as possible, including the house wiring. If you're going to be drawing serious power 24/7 it certainly make sense to wire some plugs right off the breaker box or run 12 or 10 gauge (for 20A circuits).

If the circuit is 100 ft long and 14 gauge, and you're running 15 A off the end, you're losing about 8% of your power. If power is 10¢/kWh, that's costing you about 19.2¢/day, or $70/year.

Switch to 12 gauge, lose 5%, and spend $44/year in heating the air.

Switch to 50ft and 14 gauge, lose 4%, and spend $35/year.

Switch to 50ft and 12 gauge, lose 2.5% and spend $22/year.

And as a worse case, running 100ft cord + 50ft house wiring at 15A, you're wasting about $102 in electricity per year.

Play with the numbers.

TLDR: Wire some plugs off your circuit panel and save a ton of money.
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February 23, 2012, 02:58:04 AM
 #12

Something else to think about in terms of saving money. If you are plugging in an extension cord near your panel and running 100ft to your rig, you will have decent voltage drop across it. However, if you plug it into a duplex outlet right by your rig, it's also likely running through at least as much 14 gauge wire for a 15A circuit (12 for 20A), probably more for the runs up and down walls and since all angles are usually 90 degrees. Running a dedicated line is still preferable, but you probably won't save a ton of money from doing it.
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February 23, 2012, 05:19:17 AM
 #13

I use 10/3 extension cords.  It's basically like you are plugged into the wall at 100ft.

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