Fire Pump Disconnects 3 part question.

[Sparky2791]

I am sure this has been asked before but....

First question

If one of my power supplies for a fire pump is a tap ahead of the main service disconnect with the service feed still over to the fire pump, following all the rules for that, outside underground or overhead if the rooms are next to each other.
Per 230.70 I require a service disconnecting means on the feed (service).

Can the circuit breaker in the fire pump transfer switch/controller be the service disconnect assuming it is rated as service entrance equipment?

If not;

Does the service disconnect require overcurrent protection? If it does not, can the disconnect itself be rated for locked rotor current? So lets say the FP motor FLA is 156A LRC is 907A without OCP in the switch a 200A switch would be sufficient but with OCP I would need a 1000A switch.

Second question

Second source of power is an emergency generator.

The gen set will have the main disconnect which protects the gen set. Than it will have a circuit breaker solely for the fire pump and one for life safety loads. Does the circuit breaker protecting the gen set itself need to comply with 695.4(B) (2) (2) (b)?

Third Question

695.4(B) (3) applies to all disconnect unique to the fire pump.

Item (1)
Not sure the the breaker on the gen set would not be listed as suitable for use as service equipment (?) Not wired as a separately derived system in my case - Solid Neutral transfer switch

Item (2) the breaker can be lockable so looks like no issue here

Item (3)

Would the breaker installed directly on the generator be in violation of this item. Technically not in the same enclosure, panelboard, switchboard, switchgear or MCC?


Item (4) no problem to comply

Let me know if there are any questions.

Thanks for looking.

 

[lkdiaZ]

It's been a while since we worked one so take this input into consideration and get second opinion.
First Question - 695.4 (A) actually requires the supply conductors to land directly on the FP Controller, FP Transfer Switch, combo FP Controller/ATS. Maybe this assumes that all the devices that they list have a main service disconnect to comply with 230.70 as you stated above. Otherwise this conflicts with 230.70. I have not seen a FP controller that does not come with 2 breakers. One for normal, one for emergency. We have run directly from the padmount service transformer to the FP controller.
Second Question - 695.4 (B) (1) (c) allows the generator to have this second disconnect/OCP as per your application. 695.4 (B) (2) (b) tells you how to size the breaker(s) for the generator. I think that's what you meant in your post above. I think you have an extra (2). I'm using NEC 2017 as reference. And I would say yes as the wording is that OCPD's between generator and fire pump controller shall.... In your case you have the main generator and the fire pump breaker at the generator so those 2 are between the generator and the FP controller.
Third question -
Item #1 - This has been an issue for us in the past. In a building where you have existing 3 pole ATS, the generator is wired as non separately derived for the purposes of the existing ATS'. However, the Fire Pump Controller/ATS is normally a 3 wire system (no neutral). From the service you have to run the grounded conductor but from the generator you don't. This technically requires the generator to be bonded as a separately derived. So now you have a situation where the house ATS's (3 Poles) need a non separately derived but the FP/ATS needs a separately derived. You could then argue that you'll run a a neutral to the FP/ATS from the generator to connect it with the grounded conductor from your normal source BUT, I can't remember that the FP/ATS has an isolated neutral that allows you to do this. In other words, the FP/ATS might be an only service equipment device. Not sure if this makes sense and would love others to provide feedback. What I'm proposing is that the FP/ATS by its mere nature of requiring only 3 phase conductors from the generator makes it the equivalent of a 4 pole ATS. There is no solid grounded connection between the 2 sources at the FP/ATS. In original design the solution is to specify all the ATS' as 4 pole and wire generator as separately derived.
Item #3 - That's a tough one. If you can have the FP breaker on the opposite side of the generator it solves the issue but I'm going to pass on this one. I would think that a call to a generator manufacturer would be able to assist in whether 2 breakers on same side and one of them being a fire pump application would be legal. I see it as not because of (c). I'm assuming this is the issue you are referring to.

 

[tom baker]

Thank you for your detailed reply. Fire pumps have different rules than normal motors. To the OP, you would benefit from having a copy of NFPA 20.

 

[Sparky2791]

Thank you for your detailed reply. Fire pumps have different rules than normal motors. To the OP, you would benefit from having a copy of NFPA 20

Thanks. I have one. Also available as part of the NFPA free viewer page. Use that often.

 

[Sparky2791]

It's been a while since we worked one so take this input into consideration and get second opinion.
First Question - 695.4 (A) actually requires the supply conductors to land directly on the FP Controller, FP Transfer Switch, combo FP Controller/ATS. Maybe this assumes that all the devices that they list have a main service disconnect to comply with 230.70 as you stated above. Otherwise this conflicts with 230.70. I have not seen a FP controller that does not come with 2 breakers. One for normal, one for emergency. We have run directly from the padmount service transformer to the FP controller.
Second Question - 695.4 (B) (1) (c) allows the generator to have this second disconnect/OCP as per your application. 695.4 (B) (2) (b) tells you how to size the breaker(s) for the generator. I think that's what you meant in your post above. I think you have an extra (2). I'm using NEC 2017 as reference. And I would say yes as the wording is that OCPD's between generator and fire pump controller shall.... In your case you have the main generator and the fire pump breaker at the generator so those 2 are between the generator and the FP controller.
Third question -
Item #1 - This has been an issue for us in the past. In a building where you have existing 3 pole ATS, the generator is wired as non separately derived for the purposes of the existing ATS'. However, the Fire Pump Controller/ATS is normally a 3 wire system (no neutral). From the service you have to run the grounded conductor but from the generator you don't. This technically requires the generator to be bonded as a separately derived. So now you have a situation where the house ATS's (3 Poles) need a non separately derived but the FP/ATS needs a separately derived. You could then argue that you'll run a a neutral to the FP/ATS from the generator to connect it with the grounded conductor from your normal source BUT, I can't remember that the FP/ATS has an isolated neutral that allows you to do this. In other words, the FP/ATS might be an only service equipment device. Not sure if this makes sense and would love others to provide feedback. What I'm proposing is that the FP/ATS by its mere nature of requiring only 3 phase conductors from the generator makes it the equivalent of a 4 pole ATS. There is no solid grounded connection between the 2 sources at the FP/ATS. In original design the solution is to specify all the ATS' as 4 pole and wire generator as separately derived.
Item #3 - That's a tough one. If you can have the FP breaker on the opposite side of the generator it solves the issue but I'm going to pass on this one. I would think that a call to a generator manufacturer would be able to assist in whether 2 breakers on same side and one of them being a fire pump application would be legal. I see it as not because of (c). I'm assuming this is the issue you are referring to.

Thanks for the input! Article 695 ranks up there with Article 250 as the most read Articles of my 30 year career in electrical engineering and still do not know if I have it correct. I apologize for the beginning of my post as I rattled on and after I read it the next day I though what the heck was I saying. It was after a 14 hour day trying to make clients happy while the work piled up. like Appreciate the time you took to respond. God bless!

 

[lkdiaZ]

Thanks for the input! Article 695 ranks up there with Article 250 as the most read Articles of my 30 year career in electrical engineering and still do not know if I have it correct. I apologize for the beginning of my post as I rattled on and after I read it the next day I though what the heck was I saying. It was after a 14 hour day trying to make clients happy while the work piled up. like Appreciate the time you took to respond. God bless!

No problem.

But I'm still hoping someone can comment on the separately derived vs non separately derived issue I raised when it comes to Fire Pump Controllers. What I'm putting forth is that a combo FPC/ATS should be considered as requiring the generator to be bonded as separately derived. The reason being that only the phase conductors + EGC will be wired from generator to FPC. This essentially prevents the utility grounded conductor at the FPC from being solidly bonded to the generator grounded conductor. This makes the system separately derived. If to avoid this, we run a grounded conductor from generator to FPC for the sole purpose of avoiding this issue then we have the issue of where do we terminate the generator grounded conductor as there is no isolated neutral terminal to land the generator conductor and you can't terminate the generator EGC and the grounded conductor at same terminal location or we create parallel paths with generator EGC and generator grounded conductor. If this is accurate then the building needs to be wired with 4 pole ATS' in order to make the generator a separately derived system which satisfies ATS' + FPC.

The whole premise of my argument is based on FPC not having a grounded terminal location that is isolated from the cabinet that would allow the service grounded conductor, the generator grounded conductor and the main bonding jumper to equipment cabinet being terminated. If that's not accurate then my whole argument is incorrect.

 

[Sparky2791]

The whole premise of my argument is based on FPC not having a grounded terminal location that is isolated from the cabinet that would allow the service grounded conductor, the generator grounded conductor and the main bonding jumper to equipment cabinet being terminated. If that's not accurate then my whole argument is incorrect.

Is there a reason we need a grounded conductor (Neutral) at the fire pump at all. Then there is no bonding required only earth ground . This would be a 480V 3 phase 3 wire service. There are no line to neutral loads, only line to line. The EGC for the fire pump ties back to earth ground thru the transfer switch which ties back to the ground at the tap which should (?) connect to the same ground bar tied to earth through the GES connection at the main switchboard. This is interesting though because the gen set will essentially be servicing 2 different services. The main building service life safety loads and the fire pump service.

 

[Sparky2791]

The whole premise of my argument is based on FPC not having a grounded terminal location that is isolated from the cabinet that would allow the service grounded conductor, the generator grounded conductor and the main bonding jumper to equipment cabinet being terminated. If that's not accurate then my whole argument is incorrect.

Really need to draw it out as a diagram its how I absorb these things

 

[JoeStillman]

Is there a reason we need a grounded conductor (Neutral) at the fire pump at all. Then there is no bonding required only earth ground . This would be a 480V 3 phase 3 wire service. There are no line to neutral loads, only line to line. The EGC for the fire pump ties back to earth ground thru the transfer switch which ties back to the ground at the tap which should (?) connect to the same ground bar tied to earth through the GES connection at the main switchboard. This is interesting though because the gen set will essentially be servicing 2 different services. The main building service life safety loads and the fire pump service.

You need a grounded conductor or a supply side bonding jumper with the utility service so there is a path back to the transformer for ground fault current. If your generator is non-separately-derived, you have that path to the generator neutral point in an equipment grounding conductor. I don't see a need for a four-pole ATS. Even if you used a four pole ATS, there would still seem to be a path via the equipment grounding conductor for "objectionable neutral currents" if the fire pump and normal service are fed from the same transformer, but the currents will be negligible, and so not "objectionable".

The requirement that an overcurrent device carry locked-rotor current doesn't apply to the generator breaker. See 695.4(B)(2)(b). Most generator manufacturers can provide at least two breakers in separate compartments in the terminal box, as long as you order it that way.