SDS Generator setup - why SDS vs non-SDS?

[sw_ross]

Discussion at work about setting up generators and switching the neutral (SDS).
The conclusion was that “if” you set up a generator as a SDS then the neutral has to be switched (and neutral is bonded at each source). There appears to not be a code reference that specifically says to switch the neutral but that it’s inferred from 250.30.

Under what circumstances would you choose (or be required) to set up an SDS generator format?

 

[tom baker]

A service with ground fault protection requires SDS, otherwise the GFP will not work.
Otherwise it’s a design choice.
For small home plug in generators, a SDS is required when the generator has a bonded neutral, but I would say very few home generators setups transfer the neutral.

 

[d0nut]

Configuring your generator as a SDS would also permit you to remove the neutral-ground bond on the normal side if you had to replace the service or something similar without affecting the rest of the distribution. Not that this scenario would happen often or couldn't be worked around, but choosing to provide the generator as an SDS allows the normal service and the generator to function as independent systems.

 

[texie]

Discussion at work about setting up generators and switching the neutral (SDS).
The conclusion was that “if” you set up a generator as a SDS then the neutral has to be switched (and neutral is bonded at each source). There appears to not be a code reference that specifically says to switch the neutral but that it’s inferred from 250.30.

Under what circumstances would you choose (or be required) to set up an SDS generator format?

Cummins has some excellent info on SDS VS Non SDS:

https://mart.cummins.com/imagelibrary/data/assetfiles/0056629.pdf

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

Cummins has a lot of excellent white papers on all facets of emergency and standby power: https://www.cummins.com/generators/white-papers

 

[LarryFine]

Under what circumstances would you choose (or be required) to set up an SDS generator format?

Basically, the goal is to not have multiple bonds, so the choices are:

1. Each source is bonded, the load is not bonded, and you switch the neutral.

2. Each source is not bonded, the load is bonded, and you do not switch the neutral.

Which method is chosen usually depends on the difficulty of making both sources match.