(I was not the one who signed the lease or reviewed the apartment)

My apartment has one 3prong/120v/15A outlet (NEMA 5-15, newer) and a 3prong/240v/20A outlet (NEMA 6-20T almost brand new and the breaker box says 1 phase), My air conditioner (7.2A/120v) runs on the first and all the other outlets are all ancient 2prong 1-15's painted over to the point where you can't even see the screws (why do people do this?)
My other electronics use too much power for me to happily use on the same circuit the ac is on.

I have 6 screens (incl TV) and 4 computers which are all auto 120-240V 50/60hz with the standard IEC power plug, my idea was to get something like this and use the 240v outlet. (one screen should be enough for everyone!)
Hammond Mfg. - International (IEC) - Industrial / Commercial Outlet Strips (1581 Series) (230V and not 240V? problem)
I'm smart enough to know that I know nothing at all, Is this acceptable/safe or am I going to electrocute myself?

 

Welcome to the forums! If your equipment is rated at 120 volts what do you think 240 volts will do to it? Why do you need multiple IEC cords? You may or may not electrocute yourself, but you will fry everything you own, so I would have the landlord upgrade the electrical to allow you to utilize three pronged equipment.

 

Since you are renting you are very limited to what work you can perform. You could run your computers on 240 volts, as the power supplies are many times duel voltage, but your displays will not.

Changing the 240 volt receptacle to a 120 volts is a rather simple task, but should be done by the building management (if qualified) or an electrician. The two prong receptacles may also be up graded to grounded devices, but this will depend on the wiring method that was used. A simpler fix might be to replace the devices with new ones and use a grounding adapter: Cheater plug - Wikipedia, the free encyclopedia but great care is required to make sure they are installed properly.

People paint over outlets and plates many cases because they are lazy, want them to be the same color as the wall, or are too scared to remove the cover plates.

 

How insulting.
In the OP I said that they are all (including the displays and TV) rated for 120-240V according to the back panels (I can take pictures/link datasheets if you think not)

The landlord will never, ever pay for socket upgrades and cheater plugs are pointless because there isn't anywhere to ground them to. (and would you want to pay lots of money to upgrade something you don't own?, a licensed electrician is $150+/hr here and running ground wires in a pre-war building will take many hours, the building staff have said cheater plugs without a ground are "fine" but renters insurance sure would never think of them as fine)

 

Insulting?? You apparently know more than we, since you have done your research on the power strip. Certainly it has a matching plug for the receptacle you plan on using. It is your only alternative since you rent. There are ways, but you can't do them due to the renting situation.

 

What you are suggesting is unusual in the home environment but workable and safe. It is what we do in commercial locations all the time so as to have fewer circuits. We put a rack together (including monitors) and then use an IEC power strip like you mentioned. Only issues for us are to get the right UPS to match if there is not a site UPS as the site determines if it is 120, 208, or 240v.

Also - if it says 230v it will work at 208v and 240v

To assuage the worry-warts please say that you will not make your own cords.

 

What exactly is a NEMA 6-20T? I am not familiar with that.

What makes you think there is only one circuit in the apartment (the one the A-C is on)? Has this been verified? You list your location as NY state, can you provide a little more specifics on that? There is a good possibility if you are in or anywhere near NYC that your apartment could have been wired with conduit. If so, you have a ground at each outlet. You may have close to what you need for your electronics, but the equipment you are expecting to use in the apartment is not exactly typical.

There are quite a few professionals on this forum who donate their time to assist people like yourself. If you don't like the comments or advice, you can ask for FREE advice anywhere else you'd like.

 

At work I have *occasionally* worked with some gear in the server room that's 120/240 capable that's plugged into a 240 circuit with no ill effects, including one tube monitor. The power cables for these devices had NEMA 6-20P ends on the supply end and the typical computer three-prong end on the device end, though if I remember right the device-end did have a keyway slot that was different than normal.

If you can afford to break your monitor or any other devices by trying it, then try it if they are indeed labelled for 120/240 service. I suggest you take a multimeter and confirm that you are getting 240V out of that receptacle, in case it's the wrong receptacle for the voltage. The only caution that I can think of is that most places that use 240V for standard consumer devices also use 50Hz timing rather than 60Hz timing, so if there's any association internal to the device between voltage and timing (like switching voltage automatically switches timing) then it's possible that things won't work right.

Like I said, in your shoes, if I were stuck I'd probably try it, or I'd shut off power to the 240V circuit, confirm that no other appliances are also now shut off (ie, one circuit for multiple receptacles) and then take the faceplate off to see if there's a neutral hanging out inside. If there is a neutral I'd rewire to use it, and if not I'd investigate what it might theoretically take to make it into a 120V circuit, if the breaker is sized appropriately, etc.

 

It should work.
A 240v/20A outlet should run a C13 power strip with six outlets.
It's actually a novel idea, I never realized that standard computer cords were rated to 240v 10A.



That being said, here's what could mess things up...

First, it this a large multi-unit apartment building or a single house converted to multiple apartments? Larger apartments built AS apartments should be wired correctly; single homes converted to apartments are more likely to have "creative wiring" which could kill your equipment. Either way, check voltages (and ground!) with a multi-meter.

Second, I'd inquire with the landlord/manager why that outlet is there in the first place.

A 240v/20A circuit sounds about right for an old fashioned efficiency apt. dual burner cook top.
That would be good news, it would suggest that outlet only powers your apartment.

If your apartment building was converted from office space over the years, a 240v/20A circuit also sounds about right for commercial vacuums or big rotary floor polishers, which suggests that single circuit may be shared throughout the entire floor. Bad news for your computer equipment if somebody decides THEY want to plug in a 2 burner 240v cook top...

If you have access to the breaker box, double check the assumption that the 6-20T plug is actually set up for 240v. Also whether it's hooked up for 15 or 20 (or more) amps.
Check that it's a double breaker (2 wires) which provides 240v and that it says 20 amps.
(That's in contrast to, something bad like, one leg wired to 15A breaker, the other leg wired to a 20A breaker.)



Looking at prior comments -

So, sounds like they may be pre-WWII unpolarized outlets?

 

Ya gotta have that neutral, and a regular 240 circuit won't have one, especially one that old.

 

Ok, I give up.

Why would a straight 240v setup need a neutral?

A 240v computer power supply simply converts A/C into three flavors of D/C (12v, 5v 3.3v (+/-).

What does a neutral do?

 

Chandler, you DON'T need the neutral IF the equipment is rated as 120-240 volts. Most of the items that have such a rating also allow a frequency range of 50 to 60 Hz. This is to make them as close to universal as possible.

I agree with Hal, this should work okay IF everything connected IS rated for the higher voltage.

One more thing. IF this is inside NYC boundaries it IS possible that the voltage available is 208 volts as a single phase offshoot from a three phase service to the building. Even if this is so it should not be a problem.

 

I would be very careful about pin outs of the cables you're thinking of using. The reason your electronics are rated for such a wide range of voltages is so that the same equipment can be shipped internationally. Countries that run 240 VAC run one line at 240 VAC, a neutral and a ground, like in the US neutral and ground are tied together at the panel ("0 volt reference"). The 220 you want to plug into is 110+, 110-, and a neutral... To recreate the equivalent international voltage you need an isolation transformer to create a ground reference that sits on the negative waveform ("international equivalent 0 volt reference").

That said, good switching power supplies can take nearly any filth and turn it into nice clean DC, so you might get away with it...

If i were you I would flip the 220 breaker off, make sure that is the only outlet powered by it, and swap it to a single 110 rather than risk your electronics

The reason it works for the industrial guys is because they likely have an isolation transformer generating a true 240, 0 reference wave.

 

That is incorrect. Its 240 on both legs if single phase or 208 on both legs if from a three phase, four wire wye feed. In single phase supplies the 120 is derived from one leg of the 240v and a center tap from the supplying transformer called the grounded conductor (neutral). Three phase systems providing single phase 120 volts are more complex depending on the wiring of the three phase.

Single phase residential:


Four wire wye connection:

 

You're right on the 240 volt thing. I was still thinking he wanted to run the power strips at 120 volts from that receptacle. Pardon the oversight, please.

Ray, is your drawing on the single phase transformer accurate? With 12000 primary and a 100:1 winding, the secondary would be 120 each, combined to make the 240 for residential use. Just curious.

 

Allow me to restate, 110+\110- mean peak voltages of 110 Vrms, 180 degrees out of phase. In reference to ground or neutral your peak voltage is 110 Vrms. In reference to each other, peak voltage is 220Vrms.

European power is ~240Vrms in reference to ground (as best as I remember).

Meaning there is probably not a line cord available to do the power conversion correctly (without an isolation transformer, or a 1:2 transformer on a single phase).

5 out of 6 of your monitors may let you get away with it, but for the replacement cost of your 6th monitor it may be cheaper to hire an electrician to set you up with a standard 110 receptacle.

 

Yes and so is your first one but you are reading it wrong. There is only one secondary and that secondary from one end of the winding to the other is 240 volts. It is not two windings connected together. It is one with a center tap. I'm not sure what your second drawing represents. It appears to be drawn wrong because it shows two sets of winding on the primary and two sets on the secondary..

 

Circuit-wise the two diagrams are identical, one secondary with a center tap in each case, what am I missing? Is it improper to model series inductors as a single transformer winding? If they use the same core it's all the same to the electrons.

 

The above does bring up an interesting discussion-

When the computers are marked 120-240v, does that refer to American 240v, or European 240v?


Do the manuals specify what TYPE of 240v power - (50hz or 60hz).

European 240v has: first wire 240v (hot), second wire 0v (return), and 3rd wire + 0v (ground).
So, the voltage between 1st and 2nd wires is 240V

US 240v has first wire +120v (hot), second wire -120v (hot), and 3rd wire + 0v (ground).
The voltage between 1st and 2nd wires is also 240v, but in a different way.

The concern is that if the computer is "sensing" 240v, it may assume it's a European system,
worst case scenario is the power supply treats a hot wire with 120 volts as a neutral that should have 0 volts. Some bad outcomes I can imagine would be something like the computer cases "grounded" to a live hot wire; or you somehow get 12v DC, 5.5v DC, 3v DC, but for 0v DC, one rail is at 0v DC but the other rail is at 120v AC.

Just double check the manuals for what TYPE of 240v power it can recognize.

 

Hal_S, you have the right idea, the two main differences between the power types available are the frequency and the 0v reference.

The frequency doesn't matter that much, especially in AC to DC conversion (AC circuits that count on polarity switching might be affected, like AC motors or clocks that count AC periods to keep track of time--a US clock in the UK will run 17% slower because it takes 1.2 seconds to count the 60 pulses it needs to tick off one second).

The main issue is the cable that these power supplies accept are expecting 1 line (either 120 or 240 or whatever voltage range is specified), 1 neutral (at 0 volts), and 1 ground (also at 0 volts). The receptacle provides 1 0deg line (+120 VAC), 1 180 deg line (-120 VAC), and one neutral (0 volts). To my knowledge a cable doesn't exist that will fit the 240 US receptacle and power the devices correctly.

There are many ways that it is possible to do it, but none that would be endorsed by the folks in this forum (hence no one is giving any specifics on how to do it)

I think the best option is to remove the 240 receptacle, cap one of the hot wires, and replace it with a 20A 120 receptacle (GFCI if no ground is available). I don't like leaving live unused circuits capped in a box so I would replace the double breaker with a single and cap the other end of the unused circuit at the panel.

 

Here is the NEMA 6-20P to IEC power cord that will work with computer equipment. The OP can try one device at a time. Some older PCs do have a switch on the back to select between 120 and 240.

Lynn Electronics C13620P15A-10F NEMA 6-20P to IEC 60320-C13 15A/250V 14AWG/3C SJT 10-Feet Power Cord, Black - Amazon.com

 

Nice summary.
Guess we all need to see the power supply spec sheets before passing further judgment.

Eh, there is a simpler (but in-elegant) solution -

The OP finds a 240v air conditioner on craigslist, uses THAT on the 240v outlet, then plugs all the computer equipment into the available grounded outlet.

Problem solved. Likely net cost (after selling an ac unit during a heatwave) will probably be lower than the cost of the C13 power strip.

 

Apologies, i had the NEMA 6-20T wiring wrong, the receptacle is not wired with a neutral, it's actually a ground.

The ground is still at +/- 120 VAC relative to L1 and L2, but power supplies are not allowed to dump any current into the ground, and therefore will be safe to use with the line cord that Astuff found!

The one remaining caution being that C13/C14 adapters are limited to 15A max.

Also I'd follow Astuff's advice to make sure to flip the 110/240 switch to 240 on any ATS power supplies you have

 

Actually, IIWY, I'd just go computer by computer,
1) open the computer case and un-hook the power supply mains from the board.
2) plug it in see if it smokes,
3) check DC voltages on the cables.
4) If they're good, power down, re-connect the power cables and boot up.

repeat as necessary.

 

Thanks everyone.
Right on, I suppose this is a moot topic until blue smoke or a successful powerup.

Maybe slightly cheaper if you want to spend all day messing around with large objects (and if you don't get a broken unit) and have a day or two without an AC in 95F + humidity.

Most 240V AC's are 14K+ BTU's and significantly more expensive than my 8K anyway.
C13 to 6-20 Power Cords (cheaper alternative, although still expensive compared with monoprice type stuff) and all of my electronics are autosensing so no switch.

50-60hz, dell claims my screens can run US240V (two hots and a ground, i asked and got a screenshot) and so do my computers PSU OEM's although the first test won't be with anything that expensive.

It's a large pre war apartment building, never any offices (afaik) and all the non lighting breakers are 20A
They said it's for an air conditioner and it's right next to the 5-15 (and a window).

Never, for electricity quality stuff is a must.