Confusing UPS wiring - 208 Single Phase


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Old 09-25-08, 07:35 AM
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Confusing UPS wiring - 208 Single Phase

I have a wiring question that can probably be answered easily...

We are wiring in a large UPS system that requires input voltages of 208V, Single phase and outputs the same.

The input lugs are labeled like this:

G ----- L1 ---- L2(N)

the outputs are the exact same.

Now, normally when dealing with 208/220 voltage, I expect to see two hots, a ground and a neutral. So, is L2 actually the Second Load lug or the Neutral Lug? I don't get it.\

Any help would be appreciated.
 
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Old 09-25-08, 07:48 AM
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Okay, I actually think I've answered my own question here... there answer is acutally IN the question, LOL...

SINGLE phase 208/220 - referring to one path in, one path out. This means that the second load HAS to be HOT... so we have one ground, and the two cables coming from the double-breaker in the main panel feeding the UPS.

On the output side, we have a single ground again, and the two cables feeding the two sides of main lug in the sub-panel, thus breaking it down to 110 on each side (2 110's in, 2 110's out)

Correct me if I'm wrong.
 
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Old 09-25-08, 08:09 AM
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There is no neutral in a 208V or 240V circuit (in North America). L1 and L2 are where the hots land and G is the bare ground. The unit is probably intended for worldwide use where a neutral could be used and still get the required voltage.

In North America 208V circuits are derived from a three-phase system which has 208V hot-to-hot and 120V hot-to-neutral. The single-phase operation of this UPS means that you will supply it with only two hots from a three-phase 208V panel.

Usually this type of hookup would be done by a licensed electrician. I do not mean to be insulting, but there are many more complications with a three-phase panel than with what most people's experience encompasses from doing home wiring. It may be a good idea to hire one to check it out.
 
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Old 09-25-08, 08:22 AM
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Thanks for the reply, and you're right, it can be complicated. I actually did have a licensed electrician come in and look it all over for me. This is being used to replace an existing (but dead) UPS system.

The electrician essentially told me that, since all the wiring was already there and the circuits were correct, all I had to do was "swap the wires between the UPS boxes, and you're done!"

I just wanted to ensure that I was, indeed reading the back of this UPS right. Turns out, I was.

Once I get it all hooked up, I'll double check my voltages one last time.
 
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Old 11-07-08, 03:04 PM
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Okay, now what?

Okay, I know this is an older post, but I am having an additional issue here.

I have the UPS hooked up, and it shows a load when powered on, but when the SOURCE A/C power drops, all the equipment goes dead.

I've done some voltage checking and here's what I've found:

A/C SOURCE power on

L1 -> G = 110V
L2 -> G = 110V
L1 -> L2 = 208V

L1 -> source G = 110V
L2 -> source G = 110V

A/C SOURCE power off

L1 -> G = 0V
L2 -> G = 0V
L1 -> L2 = 208V

L1 -> Source G = 0V
L2 -> Source G = 0V

So what the heck is going on? I'm stumped and, frankly, so is my electrician.

BTW, this is a tripp-lite UPS.
 
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Old 11-07-08, 03:41 PM
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Is the UPS perhaps in battery maintenance bypass mode? Or are the battery packs not connected? UPS are usually shipped with the batteries unhooked because of transportation cargo laws. You often need to plug in a cord inside the battery compartment, pull out a tab or something like that. Another option is that the batteries aren't charged enough -- does the UPS have a battery charge level indicator or some type of management interface that reports battery stats?
 
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Old 11-07-08, 03:47 PM
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Re-reading your post, I think I might have misunderstood you. Are you talking about voltages on the line power feeding into the UPS from the building panel or the line power coming from the UPS feeding the computers?

Also what kind of meter are you using?
 
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Old 11-07-08, 10:11 PM
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Originally Posted by vshortt View Post
Okay, I know this is an older post, but I am having an additional issue here.

I have the UPS hooked up, and it shows a load when powered on, but when the SOURCE A/C power drops, all the equipment goes dead.

I've done some voltage checking and here's what I've found:

A/C SOURCE power on

L1 -> G = 110V
L2 -> G = 110V
L1 -> L2 = 208V

L1 -> source G = 110V
L2 -> source G = 110V


Is any chance are you reading line or load side of the UPS ? and which Ground you are refering to ( line side or load side ) ??


A/C SOURCE power off

L1 -> G = 0V
L2 -> G = 0V
L1 -> L2 = 208V

L1 -> Source G = 0V
L2 -> Source G = 0V

So what the heck is going on? I'm stumped and, frankly, so is my electrician.

BTW, this is a tripp-lite UPS.
One of my question above is printed in bold so you can see where is my first question is.

Is this UPS is plug in type or Hardwire type ?

The L1 - L2 line supply when it is off all the legs should be reading 0 volts no matter which legs you are reading from


Let us know what your answer we will go from there

Merci,Marc
 
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Old 11-08-08, 10:42 AM
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this is an image of the back of the UPS. the connections are as follows:

1. Output power to equipment single phase 208/220 (outside lug is earth ground, inside 2 lugs
are Loads)
2. Source power from building single phase, 208/220 (outside lug is earch ground, inside 2 lugs
are loads)
3. (acutally unlabled on pic, it's the three round-holed connector to the bottom left of the
power block) - Battery plug for attaching backup batterys
4. Input power breaker
5. output power breaker

I will reference these numbers in my post.

Notice that the earth ground symbol on the SOURCE side (2) is circled, where the earth ground symbol on the Output side is no (?)

The battery backup will NOT function if there are no batteries attached. I currently have two batteries in series attached to this unit, per the specs from the company. I have tried using a single battery, think I had a back pack, but it made no difference.

This is a direct wire unit. The instructions simply say "attach cable between the UPS block 1 and your equipment, attach cables between the building power and your UPS at block 2" - thats it.

The UPS does show a load (60%or so) - and shows the battery are 100% charged and are putting out 216 volts, as they should. When the input breaker is tripped (4) all equipment goes dead, the UPS beeps, load goes to 0% and the ups shows it is on battery power.

The unit it not is maintenance or battery bypass, it can be PUT into bypass, but is currently NOT in bypass. (there is a large green light on the front to shows when the system is in bypass)

Voltages from the building panel, leading to block2 are correct. (110 from each load to gnd, 220 from load to load) When the input breaker (4) is tripped (output breaker (5) is NOT tripped), the unit should go to battery. The unit DOES beep, and the LCD display does show the unit on battery power, but the out voltages are

OUTPUT L1 -> OUTPUT G = 0V
OUTPUT L2 -> OUTPUT G = 0V
OUTPUT L1 -> OUTPUT L2 = 208V

OUTPUT L1 -> Source G = 0V
OUTPUT L2 -> Source G = 0V

the same scenario happend when the double pole building breaker that supplies the ups at (2) is tripped. When the breakers are ALL ON and building power is being supplied to the UPS at the source block (2), the voltages at the output (1) block are as follows:

OUTPUT L1 -> OUTPUT G = 110V
OUTPUT L2 -> OUTPUT G = 110V
OUTPUT L1 -> OUTPUT L2 = 208V

OUTPUT L1 -> Source G = 110V
OUTPUT L2 -> Source G = 110V

Additionally, I originally thought that perhaps I had a bad power module (which is what they call this box) so I had them ship me a replacement - but the new power module is doing the same thing the old one was doing. I'm really stumped here. This isn't my first UPS to hardwire, but it IS the first one to act like this.


Does that make more sense? Thanks for taking your time on this post, I really appreciate it.
 

Last edited by vshortt; 11-08-08 at 10:54 AM. Reason: formatting
 

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