4 pole ATS

[mbrooke]

What do others think about them? I've heard that they should be avoided, but unsure why or its justified. Also has anyone heard of line to neutral loads being damaged from a 4 pole ATS?

 

[dkidd]

There is a good article at

https://www.ecmweb.com/content/switching-neutral-whats-controversy

If both sources have the neutral bonded to ground, you generally need to switch the neutral.
A switched neutral is also needed if there is ground fault sensing.

 

[mbrooke]

There is a good article at

https://www.ecmweb.com/content/switching-neutral-whats-controversy

If both sources have the neutral bonded to ground, you generally need to switch the neutral.
A switched neutral is also needed if there is ground fault sensing.

In other words avoid a 4 pole if you can.

 

[texie]

In other words avoid a 4 pole if you can.

There are some applications where switching the neutral is required. Cummins has some really good white papers on switched VS solid neutral switches.

 

[texie]

Here are the Cummins white papers on this:

Part 1: [FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://mart.cummins.com/imagelibrary/data/assetfiles/0056629.pdf
Part 2: [FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://mart.cummins.com/imagelibrary/data/assetfiles/0056582.pdf[/FONT]
[/FONT]

 

[mbrooke]

Here are the Cummins white papers on this:

Part 1: https://mart.cummins.com/imagelibrary/data/assetfiles/0056629.pdf
Part 2: https://mart.cummins.com/imagelibrary/data/assetfiles/0056582.pdf

Links don't work

 

[texie]

Links don't work

Copy and paste?

 

[mbrooke]

Copy and paste?

Didn't work the first time, works now.

Anyway, reading them now. Good stuff.

 

[ActionDave]

I can't think of any reason to switch the neutral unless there is ground fault equipment involved.

 

[romex jockey]

Dibs afci's tripping would be a major complaint ~RJ~

 

[ActionDave]

Dibs afci's tripping would be a major complaint ~RJ~

Whatever. :roll:

 

[mbrooke]

Whatever. :roll:

Give it a few more cycles and they will be in commercial.

 

[mbrooke]

I can't think of any reason to switch the neutral unless there is ground fault equipment involved.

Honestly, same here. Unless you have dismantle/replace the main gear while on generator power.

 

[ron]

We do anything possible to leave the generator with 3W only to an ATS so we don't have to deal with the issue. We bond N-G at the gen and leave the neutral there.

Honestly, same here. Unless you have dismantle/replace the main gear while on generator power.

Imagine you were the unsuspecting guy that had to work on that gear, bummer.

 

[mbrooke]

Assuming you had no GFP, what 4 pole type would you use given the option?


Looks to me like a 3 wire system would be ideal stepping down to 120/208 or 230 volts after the ATS.

 

[dkidd]

We do anything possible to leave the generator with 3W only to an ATS so we don't have to deal with the issue. We bond N-G at the gen and leave the neutral there.

From

Part 2: https://mart.cummins.com/imagelibrary/data/assetfiles/0056582.pdf


Power topic #6006 | Part 2 of 2 | Technical information from Cummins Power Generation

Grounding of AC generators and
switching the neutral in emergency
and standby power systems

If, and only if, 4-pole transfer switches are used the
generator must be grounded as a separately derived
system. The generator neutral should not be bonded to
its equipment grounding electrode where the generator
neutral is solidly interconnected with the grounded
neutral of the normal supply, except where switched
neutral transfer equipment is required.

 

[mbrooke]

From

Part 2: https://mart.cummins.com/imagelibrary/data/assetfiles/0056582.pdf


Power topic #6006 | Part 2 of 2 | Technical information from Cummins Power Generation

Grounding of AC generators and
switching the neutral in emergency
and standby power systems

If, and only if, 4-pole transfer switches are used the
generator must be grounded as a separately derived
system. The generator neutral should not be bonded to
its equipment grounding electrode where the generator
neutral is solidly interconnected with the grounded
neutral of the normal supply, except where switched
neutral transfer equipment is required.

View attachment 23248

I know


I guess my question primarily is: what is the advantage of a separately derived system vs no having one.

A lot of my questions are around the design of building power systems from scratch, wondering what I should consider vs not doing so.

 

[kwired]

I can't think of any reason to switch the neutral unless there is ground fault equipment involved.

+1

I know


I guess my question primarily is: what is the advantage of a separately derived system vs no having one.

A lot of my questions are around the design of building power systems from scratch, wondering what I should consider vs not doing so.

Unless GFP is necessary, I don't see any need or advantage for SDS.

 

[dkidd]

I can't think of any reason to switch the neutral unless there is ground fault equipment involved.

If both sources have the neutral bonded to ground, you generally need to switch the neutral.

That will be likely if there are two utility sources.

 

[mbrooke]

If both sources have the neutral bonded to ground, you generally need to switch the neutral.

That will be likely if there are two utility sources.

Perhaps...