120/260V 3ph

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  #1  
Old 04-05-11, 06:02 PM
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120/260V 3ph

How does it work? The panel feeds machines at my school's woodshop. There is also a 120/208 wye panel. Single and three phase machines.
 
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Old 04-05-11, 08:44 PM
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Originally Posted by Justin Smith View Post
How does it work? The panel feeds machines at my school's woodshop. There is also a 120/208 wye panel. Single and three phase machines.
The 120D240 volt is a delta system which you have combation of three phase and single phases however this delta system do have a wild leg which it result 208 volts if you read from netural to B phase { typical some are will use C phase as well }

But most place I know and deal with it most are start to get rid of delta system for safety issue.

The delta system is the best for strictally motour loads nothing else the lightling loads or mixed bag loads the wye system work better this way.

You can able look up more about delta system when you do the goggle search it will show up a bit.

Merci.
Marc
 
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Old 04-06-11, 02:48 PM
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So it is a delta system? The contactor is under the wye panel, so there is probably an xfrmr somewhere. All conduits from the delta go into the floor, and there are receptacles coming out of the floor. some 3ph hubbelock and some 6-20.
 
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Old 04-06-11, 03:08 PM
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A 120Δ240 delta system is really best for serving mostly 3ɸ loads. If the A-C winding is center-tapped you can support 120V loads, but it places unbalanced load on the service so it is not ideal unless you have a relatively small 120V load compared to the service size. You also need to be careful because the B leg is the high leg at 208V to ground and will smoke your 120V loads if accidentally wired to a 120V circuit. The delta system can also be wired as an open delta which reduces total power but is cheaper to install. You can also have center-tap grounded, corner grounded or ungrounded.

Basically there is a lot to check out when dealing with a delta service that makes it more complicated to work on and less flexible, making it move more and more toward obsolete compared to the wye service.
 
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Old 04-06-11, 06:11 PM
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If I recall GE has a limit of 5% of total load on their delta transformers for 120v "IF" they have a tap, so you are very limited. A pain in the arse to order panels too...LOL. A contractor who has dealt with these many times ordered a 42 circuit 120/240 delta panel but he insists on only ordering a few single poles and no two or three pole breakers...He was going to add later on...until he saw that GE blanks off ALL of the B phase not having breakers factory installed in it. Our guy should have reminded him too, but bottom line is I had to fly in B phase connectors and disasemble and reassemble his panel to help out.
 
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Old 04-06-11, 06:38 PM
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Note I said 120/260V, not 120/240v. I think it is fed off wye, and everything is squareD, alot of QO. Alot of 480, too.
 
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Old 04-07-11, 05:07 AM
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There's no such thing as 120/260. It's either 120Δ240 or 120Y208. Then you have 277Y480.

120Δ240 is 240v phase to phase, 120v phase A or C to neutral, and 208v phase B to neutral (B-N is never used for loads, it is just a "side effect")
120Y208 is 208v phase to phase, 120v any phase to neutral
277Y480 is 480v phase to phase, 277v any phase to neutral
480Δ is 480 phase to phase only. There is no neutral.
 
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Old 04-07-11, 05:56 AM
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I was wondering if perhaps it was 120/240 delta with taps adjusted up slightly.
 
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Old 04-07-11, 06:23 AM
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I can't imagine why that would ever be done purposely. Technically it's within the tolerance, but just barely. If anyone in the US tested their mains L-L voltage and came up with 260 we'd all be telling them to call their poco immediately.
 
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Old 04-07-11, 07:19 AM
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For better or worse, if the 120/240 volt system had the taps adjusted up to 260 volts phase to phase then the "120" volt connections will also be high, like 130 volts.
 
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Old 04-07-11, 02:33 PM
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It could be labeled wrong. All of the conduits go into the floor, while the wye panel seems to go everywhere. There is no point in asking to take the deadfront off, or even test anything with a multimeter because I know I will be told no.
 
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Old 04-07-11, 09:40 PM
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Very rare but I do know it did happend to one place when someone hook up the buck et boost transfomer and got the connection hook up wrong which it result 260 volts as Justin mention.

To make sure if you are reading the voltage correct get a diffrent type of voltmeter to verify it some case the voltmeter can get funky espcally with DVM which I know it can happend when the battery get weak.

Merci,
Marc
 
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Old 04-08-11, 01:53 PM
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All that I know is that it is labled 120/260V three phase. All conduits go into the floor.
 
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Old 04-08-11, 02:09 PM
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I suspect it's probably a typo on the panel label. I've never heard of a 260V service nor could I think of a practical reason to have one.
 
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Old 04-15-11, 06:57 PM
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I looked very closely and it actually said 120/280, some of it didn't ingrave to the white part.
 
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Old 04-15-11, 09:13 PM
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Originally Posted by Justin Smith View Post
I looked very closely and it actually said 120/280, some of it didn't ingrave to the white part.
Justin., 120/280 ?? I don't really buy that one if that the case someone may have both 120 and 277 in the same enclosure and by our rules we never mix both single and triphase supply source like that.

And just leave that panel alone unless you have qualifed electrician to help you to verify it.

Merci,
Marc
 
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Old 04-15-11, 09:14 PM
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That makes a bit more sense.. But there still is no such thing as 120/280 service. What it means it that it is rated as a single phase panel for EITHER 120 or 280 volts. It does not have both voltages available. You would normally see it used as a lighting panel (marked HA, HB, etc) in a commercial building with 277Y480, where the lighting runs on 277, but I suppose there are 277/480v single phase motors in the shop.
 
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Old 04-16-11, 08:05 AM
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Originally Posted by Justin Smith View Post
I looked very closely and it actually said 120/280, some of it didn't ingrave to the white part.
Is this the panel manufacturer's label or a label applied by the contractor? Who is the panel manufacturer? I would rather believe someone made a typo and the correct voltage designation is 120/208. Identifying the breakers might help to clear up the confusion without removing the panel cover. Most 120 and 277 volt breakers can be distinguished without removing the cover unless they are very old.
 
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Old 04-16-11, 10:03 AM
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I'm guessing ti is a typo and the voltage is either 120y208 or 120D240. Marking applied by EC, squareD panel, think qo. The contactor is under the 208Y panel, so I doubt it is 480. There is 480 in other places in the building. I will look for 480 receptacles in the shop.
 
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Old 04-16-11, 08:07 PM
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Originally Posted by Justin Smith View Post
I'm guessing ti is a typo and the voltage is either 120y208 or 120D240. Marking applied by EC, squareD panel, think qo. The contactor is under the 208Y panel, so I doubt it is 480. There is 480 in other places in the building. I will look for 480 receptacles in the shop.
You are saying Square D "QO". A "QO" loadcenter cannot be used for 480 volts. Later NQOD panelboards generally accept either "QO" or "QOB" breakers. "QO" series breakers cannot be used for voltages over 240 volts. I don't think older Square D panelboards accepted the plug-on style breakers at all. Are the breakers in the panelboard 1 pole, 2 pole, 3 pole or a combination of these?
 
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Old 04-16-11, 08:40 PM
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I know the 208y panel is qo, but I'm not so sure of the one in question. The door is locked so I cannot just open it up and look. All of the service equipment in the school is sqd, except one panel that I know of in the computer room is ge. I would like to go down in the basement to look, but the school is too paranoid. You can get more stuff on a plane legally than at school.
 
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Old 04-17-11, 03:17 AM
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I know SqD EH or ED series breaker are rated for 480Y277 { they can not use on Delta supply for safety reason realted to corner grounded and ungrounded system I will save that for other time }

They look little bigger almost the same size as you see the HOM line series breaker but couple milmeter longer than the HOMs and they are NOT interchangebale and majorty of the EH or ED are bolt on few are clip on I still get those verison in European side but they are not cheap btw.

Merci,
Marc
 
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Old 04-29-11, 05:37 PM
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I just checked the panel I said was a wye panel and it actually also said 120/280V. All of the receptacles say 250V 3o/
Also, how do you get the O with the line through it?
 
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Old 04-29-11, 10:54 PM
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Do you mean like 208Y/120 3?

On a Win XP machine, go to:

Start> All programs> Accessories> System Tools> Character Map

Find the character you want to use, double click on it, the click "copy". Now you can paste this character into the text you are writing.

Too much trouble for me to bother.
 
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Old 04-30-11, 12:12 AM
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On a regular keyboard, it's ALT+0216 (hold down ALT and type 0216 on the number pad). ALT characters don't work on a laptop keyboard though unless you have a "Fn pad" where you can turn the right side of the keyboard into a number pad by holding "Fn". It doesn't work using the regular number row.
 
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Old 04-30-11, 12:20 AM
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  #27  
Old 04-30-11, 06:36 PM
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I just checked the panel I said was a wye panel and it actually also said 120/280V. All of the receptacles say 250V 3. For now, I will just assume a typo.

Thanks, guys. fn>f11>alt>0216.
 
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