I will doing my first residentical transfer switch hook-up. Do I tie the neutrals together at the transfer switch enclosure.

[This message has been edited by guschash (edited 01-30-2007).]

Yes. There needs to be exactly one ground/neutral connection in the entire system, and the ATS is generally the place to do it. (250.30(A)(1) Exception 1 permits this.

NEC 250.30 will tell you what you need to know. Well, if you can decipher it at least- it's one of the most confusing codes to try to read. Why can't the NEC just use plain english?

[This message has been edited by SteveFehr (edited 01-30-2007).]

I haven't done many of these but the ones I have done have NOT been seperately dervied systems since the grounded conductor was NOT switched.

It was my understanding that generators and UPSs are are always a seperately derived source, regardless of how the neutral is handled.

Quoth NEC 2005:


[This message has been edited by SteveFehr (edited 01-30-2007).]

It is up to the installer to decide if it will be a separately derived system or not.

If you switch the neutral and put a bonding jumper at the generator it will be an SDS.

If you do not switch the neutral and do not install a bonding jumper at the generator than it will not be an SDS.

Both ways have advantages and disadvantages.

Primarily non-SDS is cheaper, SDS works better with GFP mains.

You also need to check the generator. Some come with the neutral bonded, others, particularly Honda, don't.

Interesting that you mention Honda, with this being a foreign make. By far the majority of generators on the U.K. market are sold with an unbonded neutral, as I believe are most in Europe. Perhaps this accounts for it?

That's odd, now that you mention it- I'd think it would be the other way around, as PME & shared earth/neutral is illegal in the US but more prevalent in Europe.

Boy that THAT throw me for a loop the first time I saw it! 3W WYE bus duct? Not very common in the US

[This message has been edited by SteveFehr (edited 01-31-2007).]

This is a Honda, so if I don't tie neutrals together, how do the loads that will be running now on the generator get there neutal. From the generator?

Guschash, here is a diagram from Ed MacLaren that shows a proper hook up for an unswitched neutral transfer switch.

Notice the generator neutral is not bonded to the generator housing.



Roger

And here's a much more complete explanation: http://www.schneider-electric.ca/www/en/products/stab-lok/Gen_Panels_Appl_Note_EN.pdf
All the usual ways to do it incorrectly and some that are correct - plus you'll understand the pros and cons of each method

Thank you Ms. Ann I needed that clarification for a project coming up.

Thanks everybody.

Do you mean PME as in the British sense (Protective Multiple Earthing) ?

It would still be against our "code" to have a shared neutral/earth at any point on the customer's side of the main service equipment (including any multiple bonding on a generator which would result in neutral current being shared on a protective grounding conductor).

The multiple-earthing aspect of PME applies only to the distribution side of the network here, the last point at which at parallel earth can be applied being at the service entrance to the premises.

Continental Europe is another story.

Paulak, are you saying that USA we can't share the neutral? How do I get a neutral for the loads that will be on the generator? Is the neutral coming from the generator? I don't know if that is the correct way of puting that. Do I seperate the neutrals in the subpanel?

Ok, I think I got it. Took me awhile but I understand it now. Thanks again the web page was every helpful.