TimK
Member
- Location
- Tacoma, WA
Can someone help me see how a permanently installed generator would be a nonseperately derived system? Do they install it and run it with normal power (POCO)?
Basically if you switch the neutral on a generator in the transfer switch then you have a SDS. If the neutral is not switched then it is not a SDSCan someone help me see how a permanently installed generator would be a nonseperately derived system? Do they install it and run it with normal power (POCO)?
Basically if you switch the neutral on a generator in the transfer switch then you have a SDS. If the neutral is not switched then it is not a SDS
You may be confusing a separately derived system with a paralleled system. As dennis said, separately derived system, as it relates to a generator, has to do with how the neutral is handled. In a paralleled system it could run in parallel with the utility and/or other generator set(s).
A generator can be either an SDS on not an SDS depending on the neutral being switched ( Check the definition of a SDS.).
Grounding is handled differently depending on the genny being a SDS or not.
A majority of the installs where the generator is "standby power" do not switch the neutral, therefore the generator is not wired as a SDS.
I do apologize, I am not trying to be stubborn. So if it is not a SDS than it is parallel or nonSDS?
As Augi said, it is SDS or not SDS. Parallel operation is whole different subject and a lot more complex. An SDS connected generator is not as common as a non-SDS, but is used (SDS) for example, on larger services where GF protection is involved. Just remember that SDS or non-SDS in most generator setups, they do not run in parallel with each other or the utility-the power source is utility OR generator to the load. In a parallel setup you could have utility and generator(s) supplying the load at the same time.
No need to apologize, you ask good questions.
I do completely understand the parallel, thats the one I can picture in my head, I guess that I don't see why switching nuetral makes it seprately derived or not?
Separately Derived System. A premises wiring system
whose power is derived from a source of electric energy or
equipment other than a service. Such systems have no direct
connection from circuit conductors of one system to
circuit conductors of another system, other than connections
through the earth, metal enclosures, metallic raceways,
or equipment grounding conductors.
So by definition, a generator that is an SDS has to have the neutral switched or it would have conductors in common and thus not be an SDS.
Money-- it cost more to switch the neutral but there may be other reasons- IDKOkay, we are narrowing the point a little at a time, I might be quick that way. I can understand why you would switch the neut, GF and all that, but why would you not? I always took separately derived as a second source of power.
That and the fact that in most cases there is no need to.Money-- it cost more to switch the neutral but there may be other reasons- IDK