been blocked by every electrician as far as article 250 is concerned

[drknexus02]

ok i currently have a system consisting of a 10kva single phase 3 wire 0/0/N-G bonded generator connected to a 16KVA 2 wire 0/0/G connected to a multi-tap isometric transformer to convert 2 wire 240 (0/0/G) to 230 (O/N/G). Now this system is mobile (trailerized) and the generator does not carry a neutral wire (so it is directly connected to ground) and the transformer is also Neutral/Ground Bonded. this system is hooked up to energize a communications antenna with a small computer network system. any thoughts on this??? any critism or suggestions would be great. if you want to quote the NFPA 70 then please add the article and paragraph please. i have an idea on what i need to do but i would like to know what should have been done from a more removed/unbiased perspective.
thanks
drknexus02

 

[dpc]

What's the question? You certainly can't rely on a grounding conductor or metal frame or trailer or earth as a current-carrying neutral conductor if that is what you are asking.



David Castor

http://www.cvoes.com

 

[drknexus02]

well that answers one part of the question. pretty much i need to evaluate exactly what is wrong with the system and what we need to do to rectify the problems it currently has. unfortunately, everyone has this idea that your neutral is pretty much earth ground so you can bond it at anytime and any point. i have been doing research on high impedence loads and varistors. so i need to see what people think as far as what i currently have and know of the system and what they find to be wrong.

cleverson

 

[alehman]

There should be only one connection from neutral to ground for each separately derived system. We would need to see a diagram of your system to provide any more definitive advice.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[drknexus02]

btw the 16kva is a UPS with a O/O/G input and output... i need to scan it when i get home to white out the manufacturers name and contact info.

 

[waross]

Some of the things that confuse me with your post;
Isometric transformer
single phase 3 wire 0/0/N-G bonded generator ................. the generator does not carry a neutral wire (so it is directly connected to ground)
0/0/N-G bonded generator
0/0/G
240 (0/0/G) to 230 (O/N/G).
Why 230 Volts?
Where in the world are you? Are you working to a British or European standard?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[drknexus02]

funny you ask that. yes the neutral conductor is directly connected to ground and it ends there. and the transformer converts from US O/O/G to O/N/G 230V 60HZ. dont ask i didnt design anything here and yes we are in the US. i cant change the load requirements and i have an idea for the fix if my theories are correct.

 

[waross]

It would be strange for a single phase generator with three leads to not have a neutral. Normally equipment in North America is rated for either 120:240 Volts or, in the case of motors, 115:230 Volts. All is designed to work on a nominal system volyage of 120:240 Volts.
It may be more informative if you gave yopur requirements in a different format.
Try something like 120/N/120, or the British standard, 240/120/N
Converting betwqeen the standards requires defining a different wire as the neutral and moving the ground connection to the newly defined wire. I encountered this issue with a number of single phase gensts from GB. The first one threw me, but after knowing the issue the alterations were quick and simple. I contacted the supplier and future sets were supplied with the appropriate connections.
If you are powering standard North American equipment, reconfigure your generator, loose the transformer, and carry the neutral to your panel.
The generator neutral should be grounded to the generator and trailer frame with one connection only between the neutral and ground.
THE TRAILER MUST BE PROTECTED BY AUXILLIARY GROUND RODS OR A GROUND GRID. Often there will be an existing ground grid to which the trailer frame may be connected.
If your equipment is other than 115V, 120V, 115:230V, 120:240V, 230V or 240V. Let us know and we will take it from there.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[drknexus02]

well the equipnemt that this trailer is energizing requires 240V 60HZ 0/N/G. the problem with converting the who system to only that configuration and not have the transformer is that it has to have the capacity to utilize commercial power as a primary power source and the generator is the backup. the UPS is more of a filter and the transformer is what converts everything in the end to create the necessary requirements in the end of the day. the system has to be mobile and rapidly deployable. i see where you are going Waross but that avenue cannot be utilized only because of the neccesity of utililzing commercial power.

 

[drknexus02]

the requirement at the load side is 230/N 60HZ

 

[LionelHutz]

I'm confused and still don't understand the question.

Your incoming power system (UPS and transformer primary) doesn't seem to require a neutral so you don't need to feed one from the genset or from utility.

You have a transformer that takes 240V input and produces 240V output with one leg being called the neutral and grounded? This isn't a typical North American power source but if that is what your equipment requires then that's what you need. This neutral is seperate from the primary side neutral (or no neutral) and would not get connected back to the genset or the utility. Seems to me you would bond this neutral to ground at the service panel in the trailer and ground the trailer.

 

[jghrist]

well the equipnemt that this trailer is energizing requires 240V 60HZ 0/N/G. the problem with converting the who system to only that configuration and not have the transformer is that it has to have the capacity to utilize commercial power as a primary power source and the generator is the backup.

I'm unfamiliar with the 0/N/G nomenclature, but I'll assume like LionelHutz that you mean 240 volts to neutral. You will not find commercial power in this configuration in the USA. You'll get 120 volts to neutral, 240 volts between hot wires, or 208 volts to neutral.

 

[waross]

Let's start over. Are you saying that you have a number of installations that each and all have a non-standard supply configuration?
What utility is supplying your grid power?
Your nomenclature is confusing some of us who probably have a combineed total of a few hundred years experience.
LOSE THE 0/N/G. It is nonstandard and ambiguous.
Tell us your voltages from
Line to line. L1 to L2 if aplicable.
Line to neutral. L1 to N, L2 to N if applicable.
Tell us which conductor, L1, L2, or N is grounded.
Buy (North) American

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Waross - As of right now, we have a vague system description and a "please comment". We need a specific question that can actually be addressed.

jghrist - I think you meant 277V line to neutral (from a 480V/277V system). 208V is typically the phase to phase voltage of a 3-phase 208V/120V system.

 

[jghrist]

jghrist - I think you meant 277V line to neutral (from a 480V/277V system). 208V is typically the phase to phase voltage of a 3-phase 208V/120V system.

Right you are.