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Old 05-08-2011, 03:14 AM   #1
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How To Determine 30A Outlet's Voltage?


Do I simply need to purchase a multi-thousand dollar voltmeter?

The ones at home depot only go up to 10-20A maximum. The ones on ebay are even worse

I am hoping to plug this HP E7681-63001 PDU into my 30A dryer receptacle and then plug some computers into that - a mini data-center so to speak. But first I need to determine the voltage, because it will determine whether or not I can plug in 7,200 Watts worth of computers (if 240V) or 3,600 Watts worth of computers into one outlet, correct?

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Old 05-08-2011, 03:50 AM   #2
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How To Determine 30A Outlet's Voltage?


I'm not gonna touch this one.

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Old 05-08-2011, 03:50 AM   #3
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How To Determine 30A Outlet's Voltage?


Typical North Américaine Dryer receptale are wired for 120/240 volts and there is two conferation of three wire and four wire verison and the power strip you set up in the link.,

That if have 4 wire then it is no issue with it due you can able run balnced load without issue.

Can you tell us if you have three or four wire receptale at the dryer location ?

Merci,
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Old 05-08-2011, 04:43 AM   #4
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How To Determine 30A Outlet's Voltage?


If your dryer circuit is 30 amps. You still can't draw 7200 watts continuous..
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Old 05-08-2011, 08:02 AM   #5
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by darkaspitch View Post
Do I simply need to purchase a multi-thousand dollar voltmeter?

The ones at home depot only go up to 10-20A maximum. The ones on ebay are even worse ?
The cheapest voltmeter will do. The 10 to 20 amp maximum is for measuring actual current usage or flow (in amperes) which you really do not need to do for this project.

The dryer receptacle has the same 120/240 volts as your breaker panel and the voltage won't change by more than two or three, unless there is a loose connection (a defect) which needs to be fixed before you use the circuit for anything no matter how small.

If the dryer circuit is wired with 10 gauge wire then you can draw two allotments of up to 24 amps (2900 watts) each on a continuous draw basis.

You need to make up a power load center (a kind of subpanel) with a cord and matching plug for the dryer receptacle, and a box with a number of breakers not exceeding 20 amps each, and 120 volt receptacles either in the same box or in additional boxes. Correction, the Power Distribution Unit linked to above is the load center; you don't need to make anything yourself. However, in the U.S. no one standard 15-20 amp receptacle may have access to more than 20 amps so if the PDU doesn't have built in breakers limiting each receptacle to 20 amps then the circuit into which you plug it has to have a 20 or fewer amp breaker.

If the dryer receptacle has only three prongs you will need to ground your load center. This may be done for a portable load center by adding a ground wire from the load center box strung to any known ground. (If you substitute a 4 prong dryer receptacle and the feed cable does not have a ground, then you need to replace the feed cable with one with a 4'th conductor for ground.)
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Last edited by AllanJ; 05-11-2011 at 08:34 AM.
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Old 05-08-2011, 08:16 AM   #6
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How To Determine 30A Outlet's Voltage?


hey everybody; the ebay site linked is a Canadian site and the PDU shown is apparently straight 240 volt (3 wire twist lock receptacle)



are you in Canada darkaspitch? The ebay site you used is the Canadian extension of eBay and I see some receptacles on that strip that look a bit odd compared to US styles.

Regardless, you will not be able to pull 7200 watts continuous. That is the max load available on a 30 amp 240 volt circuit and you will not be able to max it continuously, You need to reduce the load to 80% for a continuous use.
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Old 05-08-2011, 12:45 PM   #7
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How To Determine 30A Outlet's Voltage?


That looks like a 240V device, I don't see how you would get 120V out of it. Nap the two plugs by themselves look like they are 240V/15A plug, the other plugs look like regular 15A plugs but I don't see how that is possible.
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Old 05-08-2011, 01:40 PM   #8
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How To Determine 30A Outlet's Voltage?


The PDU has IEC 60320 output connectors - C13 and C19 - commonly used for computer servers, network equipment, battery backup units, etc. Input is a L6-30p 240v,

ftp://ftp.compaq.com/pub/products/se.../ds_e7681a.pdf

Last edited by vsheetz; 05-08-2011 at 01:47 PM.
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Old 05-08-2011, 02:32 PM   #9
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by vsheetz View Post
The PDU has IEC 60320 output connectors - C13 and C19 - commonly used for computer servers, network equipment, battery backup units, etc. Input is a L6-30p 240v,

ftp://ftp.compaq.com/pub/products/se.../ds_e7681a.pdf
great. I couldn't find that the other night.

so, unless the OP has the proper plugs on his equipment, that is not going to do him any good.
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Old 05-08-2011, 03:59 PM   #10
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How To Determine 30A Outlet's Voltage?


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Originally Posted by nap View Post
great. I couldn't find that the other night.

so, unless the OP has the proper plugs on his equipment, that is not going to do him any good.
My impression is he knows the computer side of he project, else he would not even know such devices exist - the power input side is primarily where help is needed.
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Old 05-08-2011, 05:42 PM   #11
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How To Determine 30A Outlet's Voltage?


Why dont you use a clamp on amp meter ?
such as this -
If you search around you could find a plug in version,
Not too expensive, and the safest way to do it.


Quote:
Originally Posted by darkaspitch View Post
Do I simply need to purchase a multi-thousand dollar voltmeter?

The ones at home depot only go up to 10-20A maximum. The ones on ebay are even worse

I am hoping to plug this HP E7681-63001 PDU into my 30A dryer receptacle and then plug some computers into that - a mini data-center so to speak. But first I need to determine the voltage, because it will determine whether or not I can plug in 7,200 Watts worth of computers (if 240V) or 3,600 Watts worth of computers into one outlet, correct?
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Old 05-08-2011, 06:08 PM   #12
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by beenthere View Post
If your dryer circuit is 30 amps. You still can't draw 7200 watts continuous..
I don't plan on it... I was just mentioning that is the total amount available.

I was going to plug a voltmeter into the outlets to determine if it was 120 or 240V (or 3,600 or 7,200 watts maximum...)

I plan on only using ~75% continuous load.
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Old 05-08-2011, 06:11 PM   #13
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by AllanJ View Post
The cheapest voltmeter will do. The 10 to 20 amp maximum is for measuring actual current usage or flow (in amperes) which you really do not need to do for this project.

The dryer receptacle has the same 120/240 volts as your breaker panel and the voltage won't change by more than two or three, unless there is a loose connection (a defect) which needs to be fixed before you use the circuit for anything no matter how small.

If the dryer circuit is wired with 10 gauge wire then you can draw two allotments of up to 24 amps (2900 watts) each on a continuous draw basis.

You need to make up a power load center (a kind of subpanel) with a cord and matching plug for the dryer receptacle, and a box with a number of breakers not exceeding 20 amps each, and 120 volt receptacles either in the same box or in additional boxes.

If the dryer receptacle has only three prongs you will need to ground your load center. This may be done for a portable load center by adding a ground wire from the load center box strung to any known ground. (If you substitute a 4 prong dryer receptacle and the feed cable does not have a ground, then you need to replace the feed cable with one with a 4'th conductor for ground.)
...swooooooosh.... (way over my head) but thanks!

Edit: after re-reading, I think I may have got some of it!?

So I can plug a 10A voltmeter into any wall receptacle and it will give me a proper reading?

And basically what you are saying is... that if my entire apartment is 120 volts, then the dryer receptacle is most likely 120 volts as well..?

There are two dryer plugs actually, so I assume it is 120 volts coming out of there... darn.

Last edited by darkaspitch; 05-08-2011 at 06:16 PM.
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Old 05-08-2011, 06:12 PM   #14
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by nap View Post
great. I couldn't find that the other night.

so, unless the OP has the proper plugs on his equipment, that is not going to do him any good.
Most all computer power supplies take c13 females connections. I simply need a few c13 male/female cords to plug in my computer power supplies.
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Old 05-08-2011, 06:14 PM   #15
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How To Determine 30A Outlet's Voltage?


Quote:
Originally Posted by darren View Post
That looks like a 240V device, I don't see how you would get 120V out of it. Nap the two plugs by themselves look like they are 240V/15A plug, the other plugs look like regular 15A plugs but I don't see how that is possible.
It is indeed a 240V device.

Which is why I need to know if my dryer receptacle is spitting out 120 or 240 volts before I purchase it.

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