277 VOLT NUETRAL CONNECTION
277 VOLT NUETRAL CONNECTION
(OP)
I design 3 phase 3 wire motor controls. I must admit I rarely get away from my desk anymore and into the field. Could anyone tell me what is done in the real world with these 277 volt branch circuits?
My concern is I never see 3 pH 4 wire specs because most of my circuits are so far from the panel boards that the 4th wire is not run. I know I never supply an insulated terminal for the contractor to land it on but yet I am told from customers that a 277 volt heater or lighting circuit was added to the motor controller.
My guess is they land the 277 volt heater nuetral on the equipment ground terminal and get the 277 volts.
If someone would be kind enough to tell me what happens in the real world and what problems occur by not running the nuetral back to the panelboard I would really appreciate it.
In my younger years I did work in maintenance on lighting circuits and am familiar how lighting is connected to 480 and nuetral to acheive 277. Just want to know more about other applications.
My concern is I never see 3 pH 4 wire specs because most of my circuits are so far from the panel boards that the 4th wire is not run. I know I never supply an insulated terminal for the contractor to land it on but yet I am told from customers that a 277 volt heater or lighting circuit was added to the motor controller.
My guess is they land the 277 volt heater nuetral on the equipment ground terminal and get the 277 volts.
If someone would be kind enough to tell me what happens in the real world and what problems occur by not running the nuetral back to the panelboard I would really appreciate it.
In my younger years I did work in maintenance on lighting circuits and am familiar how lighting is connected to 480 and nuetral to acheive 277. Just want to know more about other applications.






RE: 277 VOLT NUETRAL CONNECTION
Here's a link to a quick and dirty summary that may help clarify. http://www.sea.siemens.com/step/default.html
RE: 277 VOLT NUETRAL CONNECTION
I have heard a lot of people say 277 is 480 volt to ground.
RE: 277 VOLT NUETRAL CONNECTION
RE: 277 VOLT NUETRAL CONNECTION
Are you sure the contractors aren't just installing 480 / 277 volt transformers between two of your phases? That's what we do if we don't have a neutral running to the motor control centre. (But I'm in the UK, so it's 415V / 240V (or 400V / 230V these days, as we've recently become Europeans...)).
Brian
RE: 277 VOLT NUETRAL CONNECTION
Thanks
RE: 277 VOLT NUETRAL CONNECTION
You may want to ask the customer the clarification as to how that 277V is acheived.
RE: 277 VOLT NUETRAL CONNECTION
1. Customer install an extra neutral insulator and supply the panel with 3ph 4 wire sytem,
or
2. Customer install an transformer in the panel to obtain 277V,
or
3. Customer use the earth as a neutral conductor. Code and safety violation, could end in a fatal.
or
4. Customer use two 277V bulbs, or two heaters in series. (Connected in series between two phases) Not a very good way of doing, but there will be 240V across each element.
RE: 277 VOLT NUETRAL CONNECTION
RE: 277 VOLT NUETRAL CONNECTION
I think most of us have seen it, or at least heard of something similar that happened. There can be a lot of reasons for such violations: inexperience, trying to save money, shortcuts, not enough time, etc, etc, but as if this are not enough, a lot of this are qualified artisans. Maybe due to decreasing standards? Lack of pride in their work? I do not know what the reasons are, but it is totally unacceptable.