Generator Choosing SDS or not

[Twoskinsoneman]

I understand when a gen is an SDS or not.
My question is if your installing an optional gen that can be installed either way. Is there ANY reason to choose one or the other.
The only thing I can think of is the cost saving of one less pole for the transfer equipment. Is there ANY thing else?

 

[steve66]

I understand when a gen is an SDS or not.
My question is if your installing an optional gen that can be installed either way. Is there ANY reason to choose one or the other.
The only thing I can think of is the cost saving of one less pole for the transfer equipment. Is there ANY thing else?

Unless I had a compelling reason, I would use a 3 pole non-SDS. Its simpler.

Reasons to consider a SDS with a 4 pole ATS include ground fault sensing on some larger services, and places where there are multiple generators, transfer switches, and services.

 

[tom baker]

" above post. SDS is a design decision, 95% are not SDS, but there are some cases where it has to be an SDS, example 1200 amp service with GFP.

 

[iwire]

When there are GFP breakers involved it is a better plan to switch the neutral at the ATS.

 

[charlie b]

I know that I have designed far fewer backup power systems than you guys and gals have installed. But I have always preferred making the generator an SDS. I like the power systems upstream of the ATS to be completely separate from each other. For example, with a 3-pole transfer switch, the fault path from a load that is served by the generator will include the N-G bond point at the (normal source) main service panel. I can't think of many scenarios in which that would limit future maintenance or operational evolutions, but I still don't care for it.

 

[renosteinke]

"Simpler" is relative. All manner of strange power quality issues seem to pop up whenever you mix things up.

That's why I like to go SDS with every power source- whether it be a generator, ups, or even a Mr. Fusion.