Running PC on 240V 60Hz

Actually, the power supplies will operate at slightly greater efficiency when run from 240V. (Only ~1%)

The only problem might be in getting the 20A branch circuits to the PC's the standard line cords supplied with PC's in the US fit 120V sockets with a ground pin and have parallel prongs for "hot" and neutral. The

240V sockets fit the same outlet boxes, but have "tandem" prongs. I haven't checked for the availability of PC line cords to this configuration, but they may be available. Otherwise it's simple to replace the present 120V plugs. (Any ham could do it.) :-)

I'd check the specs or have a look inside. I've never seen a 120V only ATX power supply. It has to have the doubler circuit to work on 120V, and to change to 240V requires only a SPST switch.

Virg Wall, K6EVE

>

Why, the PC is a line to line load. It should work fine on 240v if the PS has the 240v switch (some even autoswitch) Ground is still ground Tom's usual "fix your ground electrode system and install real surge protection" still applies) When you extend this 240v line, bond the ground from the box to your 120v boxes. You will need NEMA 6-15 cord sets but they should be pretty common in the used market from old computer equipment.

Phil, no computer shop that i have ever seen in the US has 220 (240) available on the test bench. consiquently you are setting the client up for some long term headaches. when the box comes back from service with the switch on 120 and gets pluged in to 240 ...

did you try Powerware?

Phil; Why not install a subpanel in place of the 240 VAC outlet. Install receptacles for two 20A 120 VAC branches, and obtain two 120 VAC UPS's. Divide your loads between the two UPS's. You will have a cheaper, off the shelf solution and some redundancy to boot.

The RFI-EMI-GUY

snipped-for-privacy@ipal.net wrote:

Just feed them with 277V and there won't be an issue with 120V between the neutral and ground. We all know that's what you really want. :-) )

From all such power supplies I've examined/dissected, the current carrying conductors go nowhere except for the circuitry for the switcher. The only possible thing I can imagine that would assume low voltage between neutral and ground would be built-in surge protectors, and I don't think any PC power supply has them. There is nothing else I've seen that would assume low/0 voltage between neutral and ground.

How old is the PC without the voltage switch? I believe newer PC power supplies are autoranging.

If your problem is not enough power, you want to take advantage of every circuit available. So put the PCs with switches on the 240V line and the other PC and wall warts on the 120V line.

Oh, is the "240V" outlet 240V or 208V (commercial building with 3 phase supply)? Check the voltage rating to see if the PCs can take 208V when switched in 240V mode.

I imagine this is what Tom was taking about. I bet he only has 2 hots and a ground in that outlet, No neutral for 120v loads.

On Sun, 23 Jan 2005 20:13:50 -0500 w_tom wrote: | Is it three prong 240 volts or four prong. Makes a | significant difference to the computer.

It's definitely a NEMA 6-20R. It looks like this, although it's really in a ROUND hole, not a square one (I'm not good at doing round in ASCII.

+---------+ | * | | | | -- |- | | | +---------+

Display in a fixed space font like courier if it shows bad.

| Phil, no computer shop that i have ever seen in the US has 220 (240) | available on the test bench. consiquently you are setting the client up for | some long term headaches. when the box comes back from service with the | switch on 120 and gets pluged in to 240 ...

Don't worry. These are MY OWN computers. And except for a couple of old Sun Sparc machines, I built them all. The location is an upper floor of a house I am considering renting to live and work in. The lady who owns it doesn't want any construction work done on it to add another outlet. Fortunately, it now has central A/C. I just hope it will be enough for the heat I'll be releasing. I have 6 computers now, and will be adding 4 more. I could run a couple in another room but the rest need to be together.

| did you try Powerware?

Yes, that was one of them. Also tried APC, Tripp-Lite, Sola, and a few others I've forgotten.

| Why not install a subpanel in place of the 240 VAC outlet. Install | receptacles for two 20A 120 VAC branches, and obtain two 120 VAC UPS's. | Divide your loads between the two UPS's. You will have a cheaper, off | the shelf solution and some redundancy to boot.

The existing circuit is a 2-wire 240 volt circuit. That means there are two hots and a ground. NO NEUTRAL! Further construction is not an option.

| Just feed them with 277V and there won't be an issue with 120V between the | neutral and ground. We all know that's what you really want. :-) )

Might be fun :-)

But there is no 277 there.

| From all such power supplies I've examined/dissected, the current carrying | conductors go nowhere except for the circuitry for the switcher. The only | possible thing I can imagine that would assume low voltage between neutral | and ground would be built-in surge protectors, and I don't think any PC | power supply has them. There is nothing else I've seen that would assume | low/0 voltage between neutral and ground.

Good.

|>I want to avoid the added expense of a transformer. | |>One of my PCs (I forgot where I got the case for this one ... I built them |>all myself) has no voltage switch. Any chance it is an autoranging model? |>I guess I should play it safe and leave that one on the 120 volt circuit. | | How old is the PC without the voltage switch? I believe newer PC power | supplies are autoranging.

I think I got it around 1998. It's about 170 watts for uATX form factor.

| If your problem is not enough power, you want to take advantage of every | circuit available. So put the PCs with switches on the 240V line and the | other PC and wall warts on the 120V line.

That seems the thing to do. There's at least one 120 volt circuit in the room.

| Oh, is the "240V" outlet 240V or 208V (commercial building with 3 phase | supply)? Check the voltage rating to see if the PCs can take 208V when | switched in 240V mode.

I have no voltage rating info other than the 115/230 switch and what little is on the P/S itself (virtually nothing). But I am looking at replacing some of the P/S's (some have fans that are making abnormal noises at times). It's a 2-floor house in a residential area; I doubt it has 3-phase. I hope it's all single phase (I don't want to worry about 208 volts and triplens). The only houses I've ever seen with 3-phase are really big ones, and the one my grandfather used to have where it run a nice woodshop out back.

The computer could care less, if it gets 240 volts across the PS input and has its case grounded properly. Conforming to electrical code is another thing entirely!

A solution which would probably meet code would be to attach a standard dual duplex box to the existing 240V outlet box, ensuring that the two metal boxes are electrically connected. Then use two 240V, (tandem blade), duplex outlets in the new box. You would need extension cords to the individual computers. A second box could be attached, giving an additional four outlets. Your local code may not allow additional outlets on 240V circuits, but at least this meet safety standards.

Using the existing 120V, (parallel blade, U ground) at 240V will work electrically, but is definitely not in accordance with code, otherwise you could just build a junction box with 120V duplex sockets and wire it to the present 240V outlet with a cord with the correct plug for the existing outlet. I *DO NOT* recommend this!

In any case make sure the existing ground in the present circuit is preserved. This will be a green or bare wire, or in many cases, the metal box and the flex or EMT feeding it will be the ground. This must be electrically connected to the ground pin in all sockets.

Virg Wall, P.E.

On Tue, 25 Jan 2005 18:05:35 GMT VWWall wrote: | snipped-for-privacy@ipal.net wrote: |> On Sun, 23 Jan 2005 20:13:50 -0500 w_tom wrote: |> | Is it three prong 240 volts or four prong. Makes a |> | significant difference to the computer. | | The computer could care less, if it gets 240 volts across the PS input | and has its case grounded properly. Conforming to electrical code is | another thing entirely!

I just wanted to make sure it didn't assume a grounding polarity since both 120 volt countries and 220-240 volt countries supply their standard voltage as hot+neutral.

|> It's definitely a NEMA 6-20R. It looks like this, although |> it's really in a ROUND hole, not a square one (I'm not good |> at doing round in ASCII. |> |> +---------+ |> | * | |> | | |> | -- |- | |> | | |> +---------+ |> |> Display in a fixed space font like courier if it shows bad. | | A solution which would probably meet code would be to attach a standard | dual duplex box to the existing 240V outlet box, ensuring that the two | metal boxes are electrically connected. Then use two 240V, (tandem | blade), duplex outlets in the new box. You would need extension cords | to the individual computers. A second box could be attached, giving an | additional four outlets. Your local code may not allow additional | outlets on 240V circuits, but at least this meet safety standards.

Where does the UPS fit into that?

| Using the existing 120V, (parallel blade, U ground) at 240V will work | electrically, but is definitely not in accordance with code, otherwise | you could just build a junction box with 120V duplex sockets and wire it | to the present 240V outlet with a cord with the correct plug for the | existing outlet. I *DO NOT* recommend this!

I have no intention of using NEMA 5-XX at anything more than 140 volts.

| In any case make sure the existing ground in the present circuit is | preserved. This will be a green or bare wire, or in many cases, the | metal box and the flex or EMT feeding it will be the ground. This must | be electrically connected to the ground pin in all sockets.

If I can find smaller 240 volt UPSes, I might go with two of them. But I have found a 240-in 240-out at the size that would let me use the full capacity of the 20 amp 240 volt circuit. I can _build_ a 240 volt PDU if I need to. I already have half the parts for that, now. Cord that have IEC-320 female and NEMA 6-15P male would be cool. I found ONE at a shopping site, but it's a $20 thingy from Cisco. I'll decide later if I waste money on that or just cut plugs off the excess 5-15P cords I do have and stick hardware store 6-15P's on there. Premise wiring will be to code, and the PDU will at least be right, if not UL-listed.

Probably better if he makes his own 'extension cord/power strip', so that only one 'device' (it) is plugged into the outlet, and there is absolutely no modification to the house. A 6-20P cord feeding a metal dual duplex box with 2 duplex 6-20R or 6-15R outlets. Maybe a second segment of wire from this box to a similar second box. (in our computer room we have daisy chains of 3 or 4 of these boxes with each box containing 2 duplex

120V outlets and a 3 phase 20A plug feeding it)

I'd forgotten about the 240V ups! :-(

the UPS. The output of the UPS to

Good idea!

Virg Wall

snipped-for-privacy@ipal.net schrieb:

Hello,

use a transformer from 240 V to 120 V.

Bye

snipped-for-privacy@ipal.net schrieb:

Hello,

the plugs used in germany (Schuko) may be inserted in two positions, this will swap hot and neutral. The computer therefore should not expect the hot line to be really the hot one. Computers build for export to Germany too should not assume a grounding polarity. But you should check that with your computers.

Bye

| snipped-for-privacy@ipal.net schrieb: |> |> I just wanted to make sure it didn't assume a grounding polarity since |> both 120 volt countries and 220-240 volt countries supply their standard |> voltage as hot+neutral. | | Hello, | | the plugs used in germany (Schuko) may be inserted in two positions, | this will swap hot and neutral. The computer therefore should not expect | the hot line to be really the hot one. Computers build for export to | Germany too should not assume a grounding polarity. But you should check | that with your computers.

So how would you ensure that the metal base of a screw in light bulb has the grounded, rather than the hot, wire connecting to it? Or is that just not done in Germany?

| snipped-for-privacy@ipal.net schrieb: |> |> The reason I'm looking is that I have a situation where I need to run many |> computers in a room where I cannot add new wiring, but a 20 amp 240 volt |> outlet is available and live (formerly used for a window air condition I |> suspect, due to it's location about a foot to the left of under a window). |> 20 amps at 120 volts would not provide the capacity I need, but 20 amps |> at 240 volts I believe will. | | Hello, | | use a transformer from 240 V to 120 V.

While transformers would be a slight bit cheaper in 60 Hz land, they are still quite expensive when you're talking about units in the 3600 watt 4500 VA range. The reason I am looking at doing it this way in the first place is to avoid the transformer. It would have to be a full isolation transformer since an autotransformer wouldn't be easily grounded in this situation.