120/208V Y system

[Electron_Sam78]

Anyone come across a 120/208 system where the line voltage referenced to neutral or ground is 10 volts different (A phase 126 Volts, B phase 116)? Phase voltage is 213. Would this cause any problems for the loads attached?

 

[iwire]

It is not great for 3 phase motors, the voltage imbalance should stay under 1% you have about 5%.

http://www.engineeringtoolbox.com/electrical-motor-voltage-imbalance-d_648.html

 

[Electron_Sam78]

this is a single phase supply I'm working with

 

[480sparky]

this is a single phase supply I'm working with

Then it's not a 120/208 Y. It's 120/240.
Voltage difference could be explained by an imbalanced total load. Or a loose neutral.

 

[brian john]

Then it's not a 120/208 Y. It's 120/240.
Voltage difference could be explained by an imbalanced total load. Or a loose neutral.

Sure seems like it.

Check supply voltage.
Check taps on transformer.

 

[infinity]

Then it's not a 120/208 Y. It's 120/240.
Voltage difference could be explained by an imbalanced total load. Or a loose neutral.

Using his numbers how it that possible?

(A phase 126 Volts, B phase 116)? Phase voltage is 213.

 

[hardworkingstiff]

Anyone come across a 120/208 system......

this is a single phase supply I'm working with

Then it's not a 120/208 Y. It's 120/240.

It's single-phase, no it's 2 of 3 phases, no it's, no it's.

We really need a better terminology for single-phase loads served from 2-phases of a 3-phase wye.

 

[480sparky]

Using his numbers how it that possible?

Using his words.

this is a single phase supply I'm working with

 

[iwire]

His words also say 120/208Y

It is entirely possible to be working on a single phase feeder or circuit from a 3 phase supply

 

[Cold Fusion]

IEEE 141 lists 2 phases of 208 with a neutral as "120/208Y-volt service" for single-phase, three-wire, open-wye applications.

3phase 4W is designated as 208/120.

I figured 120/208 refered to open Y single phase applications and 208/120 refered to 3phase y applications.

cf

 

[hardworkingstiff]

I figured 120/208 refered to open Y single phase applications and 208/120 refered to 3phase y applications.

That makes the most sense, but everyone will have to understand/remember the correct way to list the voltage to maintain good communication.

 

[Cold Fusion]

That makes the most sense, but everyone will have to understand/remember the correct way to list the voltage to maintain good communication.

I suspect the only ones that will be bothered are the ones that are still working with 220 circuits or 440 motors :roll:

cf

 

[jim dungar]

I figured 120/208 refered to open Y single phase applications and 208/120 refered to 3phase y applications.

Yes,

Just like 120/240 is 1Ph 3W and 240/120 is 3Ph 4W.

 

[iwire]

A couple of points

1)I think it is clear the OP is not familiar with IEEE standards

2)No electrical class or training I have ever received even mentioned the IEEE standards.

Electricians seem to get as much IEEE training as engineers get NEC training

 

[hardworkingstiff]

Electricians seem to get as much IEEE training as engineers get NEC training

:grin:That's funny!:grin:






I don't care who you are.

 

[Electron_Sam78]

His words also say 120/208Y

It is entirely possible to be working on a single phase feeder or circuit from a 3 phase supply

Yep! The supply is a 3 phase Y system from the transformer but the subsystem I'm concerned with is fed with only two hot legs (single phase) and a neutral. I haven't had time to check the supply voltage at the 3 phase service panel yet to compare voltages, I'll do that next Monday. It was a call late on Friday that didn't justify overtime. Just thought I'd get some input from you guys before I continued with it.

 

[Cold Fusion]

A couple of points

1)I think it is clear the OP is not familiar with IEEE standards

2)No electrical class or training I have ever received even mentioned the IEEE standards.

Electricians seem to get as much IEEE training as engineers get NEC training

Bob -
I offered the IEEE reference to help with standard nomenclature. I figured a reference was better than pulling it out of my .... uh.. the air.

I really didn't have any interest is eliciting a demeaning response.

cf

 

[Cold Fusion]

...Electricians seem to get as much IEEE training as engineers get NEC training

That's good. Over the last 35 years I've had maybe 15 classes based on various aspects of the NEC. So, you should be right up there on the IEEE.:grin:

cf

 

[dicklaxt]

It has been my experience that when you see 208/120 as the secodary it is referencing a 3 phase system and when you see 120/208 as the secondary it is referencing a 1 phase system,,,,,,,,this is common place but could be the other way as well but would be the exception.

The primary could be just about about anything be it 1 or 3 phase but the best bet is to check with the manufacturer

dick

 

[jim dungar]

2)No electrical class or training I have ever received even mentioned the IEEE standards.

Actually it is not really an IEEE standard, although it can be found in the "Red Book". Voltages are per ANSI C84.1-2006 (see FPN for NEC definition of voltage system, nominal)