Portable generator

[hhsting]

I have MTS that has generator tap box for portable generator for building small bank.

I am not sure what the poles of MTS should be.
My question is portable generator manufacturer do they come as separately derived system or no separately derived system?

 

[infinity]

What size is the generator?

 

[hhsting]

What size is the generator?

Its portable generator that is to be brought whenever needed so not sire about size. However it feeds 200A 208V three phase panelboard so from that at least 73kVA

 

[zbang]

I am not sure what the poles of MTS should be.

Sounds like it should be three hots (switched), a neutral (not switched), and a EGC (also not switched). If there's a bond in the bank's panel/switchboard, then none on the generator.

 

[hhsting]

Sounds like it should be three hots (switched), a neutral (not switched), and a EGC (also not switched). If there's a bond in the bank's panel/switchboard, then none on the generator.

I dont follow bond in bank’s panel/switchboard? You mean main service switchboard?

 

[zbang]

Wherever is the proper place for that installation (bank’s panel/switchboard could be the same as main service switchboard, but we don't know since we don't have a diagram.... the 200 amp panel could be the entire electrical system for a small bank).

 

[hhsting]

Wherever is the proper place for that installation (bank’s panel/switchboard could be the same as main service switchboard, but we don't know since we don't have a diagram.... the 200 amp panel could be the entire electrical system for a small bank).

See above the hexagonal note #1 is MTS. The engineer grounded it but that is not the main service disconnect. Not sure why it is grounded.

The incoming service is at existing main distribution panel.

I am not sure but something is not correct about grounding the MTS which is for temp portable generator.

What would be scenario if MTS was 3 poles and 4 poles both cases? Where to ground and does portable generator require 4 poles or 3 poles MTS generally?


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[dkidd]

Have a look at the thread

generator question SDS or Non-SDS

I have been reading up on generators and their connections to transfer switches (and looking at some of Ed Maclaren's fabulous drawings) and was wondering if it is preferrable to have the generator set up and connected as an SDS or a non-SDS, and then thus whether or not the neutral is switched...

forums.mikeholt.com

 

[hhsting]

Have a look at the thread

generator question SDS or Non-SDS

I have been reading up on generators and their connections to transfer switches (and looking at some of Ed Maclaren's fabulous drawings) and was wondering if it is preferrable to have the generator set up and connected as an SDS or a non-SDS, and then thus whether or not the neutral is switched...

forums.mikeholt.com

I know what SDS and non SDS is. Confusion is if its portable generator then does manufacturer provide neutral to ground bond or they dont in the portable generator? If the MTS is 4 poles then where should ground be since generator is temp portable it is not onsite until it is needed? If its 3 poles MTS then ground is not needed?

 

[wwhitney]

Confusion is if its portable generator then does manufacturer provide neutral to ground bond or they dont in the portable generator?

Both are possible, so the building side has to be designed for one choice, and then you have to stick to only used portable generators that match that choice. [And maybe there's an NEC section requiring placarding documenting that choice, not sure.] The final result needs to be that whether the generator is connected or not, and regardless of the state of the MTS, the supply side of the MTS needs to have exactly one neutral-ground bond.

The choice of floating neutral at the generator is simpler for the building side, as then your MTS doesn't need to switch the neutral.

Cheers, Wayne

 

[dkidd]

WARNING:
FOR CONNECTION OF A SEPARATELY DERIVED
(BONDED NEUTRAL) SYSTEM ONLY
or
WARNING:
FOR CONNECTION OF A NONSEPARATELY
DERIVED (FLOATING NEUTRAL) SYSTEM ONLY

 

[hhsting]

Both are possible, so the building side has to be designed for one choice, and then you have to stick to only used portable generators that match that choice. [And maybe there's an NEC section requiring placarding documenting that choice, not sure.] The final result needs to be that whether the generator is connected or not, and regardless of the state of the MTS, the supply side of the MTS needs to have exactly one neutral-ground bond.

The choice of floating neutral at the generator is simpler for the building side, as then your MTS doesn't need to switch the neutral.

Cheers, Wayne

Ok but lets say MTS is 4 poles then where should the grounding electrode conductor connection be? The engineer in post #7 attachment is showing it at MTS. I dont think that would be correct am I wrong?


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[dkidd]

Ok but lets say MTS is 4 poles then where should the grounding electrode conductor connection be? The engineer in post #7 attachment is showing it at MTS. I dont think that would be correct am I wrong?


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It isn't clear he is showing a bond. What does Note 1 say?

 

[dkidd]

There should be a neutral to ground bond at the existing distribution panel, and one at the generator (there should be a bonding screw or jumper).
The neutral switched in the MTS. No additional bonds.

 

[Seven-Delta-FortyOne]

I wire all my MTS/portables as non-SDS.

We are required to post a sign stating which type of generator the system is designed for.

How it comes from the factory will depend on the manufacturer. I regularly un-bond portables so they will work on my MTS.

The fact that he shows bonding at the MTS is just that, bonding. It’s not a N-G bond.

 

[jap]

All these portable generator discussions are exhausting.

So what terrible things happen if a MTS is wired with an unswitched neutral, and, the generator shows up with a bonded neutral and hooked up?

JAP>

 

[wwhitney]

So what terrible things happen if a MTS is wired with an unswitched neutral, and, the generator shows up with a bonded neutral and hooked up?

As soon as you hook up the generator, regardless of the state of the MTS, you will have a second neutral-ground bond in the system, and some part of the EGC system will be carrying neutral current.

Cheers, Wayne

 

[jap]

As soon as you hook up the generator, regardless of the state of the MTS, you will have a second neutral-ground bond in the system, and some part of the EGC system will be carrying neutral current.

Cheers, Wayne

Correct,

So, if we lift the neutral to ground bond at the portable generator when using a tranfer switch that doesn't have a switched neutral isn't the frame of the generator carrying neutral current also?

Or, is an EGC not pulled from the generator to the XFR switch in that scenario?

JAP>

 

[wwhitney]

So, if we lift the neutral to ground bond at the portable generator when using a tranfer switch that doesn't have a switched neutral isn't the frame of the generator carrying neutral current also?

No, as with only one neutral-ground bond in the entire system (at the service), there's no path for neutral current to move onto the EGC system and then back off of it elsewhere. The EGC and associated bonded metal (including the generator case) is a "dead-end" and not part of a circuit.

Cheers, Wayne

 

[dkidd]