Generator Sizing with Fire Pump

[gadfly56]

I see an informational note, yes. I also see code verbiage that specifically calls out the need for short circuit protection of a fire pump circuit.

(A) Power Loss Hazard. Conductor overload protection shall not be required where the interruption of the circuit would create a hazard, such as in a material-handling magnet circuit or fire pump circuit. Short-circuit protection shall be provided.
Informational Note:  See NFPA 20-2013, Standard for the Installation of Stationary Pumps for Fire Protection.

The short circuit protection is provided in the fire alarm controller.

 

[gadfly56]

700.2 Definitions.
Branch Circuit Emergency Lighting Transfer Switch. A device connected on the load side of a branch circuit overcurrent protective device that transfers only emergency lighting loads from the normal supply to an emergency supply.
Informational Note:  See ANSI/UL 1008, Transfer Switch Equipment, for information covering branch circuit emergency lighting transfer switches.
Emergency Systems. Those systems legally required and classed as emergency by municipal, state, federal, or other codes, or by any governmental agency having jurisdiction. These systems are intended to automatically supply illumination, power, or both, to designated areas and equipment in the event of failure of the normal supply or in the event of accident to elements of a system intended to supply, distribute, and control power and illumination essential for safety to human life.
Informational Note:  Emergency systems are generally installed in places of assembly where artificial illumination is required for safe exiting and for panic control in buildings subject to occupancy by large numbers of persons, such as hotels, theaters, sports arenas, health care facilities, and similar institutions. Emergency systems may also provide power for such functions as ventilation where essential to maintain life, fire detection and alarm systems, elevators, fire pumps, public safety communications systems, industrial processes where current interruption would produce serious life safety or health hazards, and similar functions.

I missed "fire pumps" when I scanned the list. Next time I use the "Find" feature in Adobe.

On the other hand, Informational Notes are not an enforceable part of the code unless the local jurisdiction has said otherwise. At my prior company I can't recall any AHJ insisting the generator meet the requirements for Article 700.

 

[publicgood]

I missed "fire pumps" when I scanned the list. Next time I use the "Find" feature in Adobe.

On the other hand, Informational Notes are not an enforceable part of the code unless the local jurisdiction has said otherwise. At my prior company I can't recall any AHJ insisting the generator meet the requirements for Article 700.

This was added in 2011. I agree - before this clarification a fire pump was typically considered 701...and still is in many cases, as this info note only says consider. Example WI DFD:

ftp://doaftp1380.wi.gov/master_spec/Electrical/Electrical Guidelines.pdf

 

[publicgood]

The short circuit protection is provided in the fire alarm controller.

The fire pump controller is downstream. How does it provide short circuit protection for the upstream feeder?

We should remind ourselves that instances you are describing and those which are ahead of the main on the normal side and/or at the transformer secondary are all taps. These may run a particular length without protection, as long as they follow conditions outline in 240.

 

[gadfly56]

The fire pump controller is downstream. How does it provide short circuit protection for the upstream feeder?

We should remind ourselves that instances you are describing and those which are ahead of the main on the normal side and/or at the transformer secondary are all taps. These may run a particular length without protection, as long as they follow conditions outline in 240.

In any structure, where is the short circuit protection for the service entrance conductors before they hit the main distribution panel? The feed to the controller is considered the equal of a service entrance.

 

[publicgood]

In any structure, where is the short circuit protection for the service entrance conductors before they hit the main distribution panel? The feed to the controller is considered the equal of a service entrance.

We are in agreement, the OCPD in the fire pump controller does not protect the feeder for the normal service entrance. For this reason, the service entrance is required to be disconnected at building entry.

This covers the condition of permitted, where service entrance is not required. I still fail to see how this gets one out of providing short circuit protection on the generator feeder, as it does not have exceptions that service conductors do.

 

[Sahib]

I still fail to see how this gets one out of providing short circuit protection on the generator feeder, as it does not have exceptions that service conductors do.

Overload protection to a fire pump-no
Short circuit protection to the fire pump-yes.

 

[publicgood]

Overload protection to a fire pump-no
Short circuit protection to the fire pump-yes.

Agree - thanks, Sahib.

 

[steve66]

In any structure, where is the short circuit protection for the service entrance conductors before they hit the main distribution panel? The feed to the controller is considered the equal of a service entrance.

I still fail to see how this gets one out of providing short circuit protection on the generator feeder, as it does not have exceptions that service conductors do.

If the fire pump generator feeder is installed with the same protection as service conductors, I suppose they can be considered to be "outside the building", and the "Outside Tap of Unlimited Length" rule would apply - 240.21 B 5. So in that regard, the short circuit protection could be provided at the fire pump ATS/Controller, instead of at the source.

But I'm still hung up on the need for a disconnect somewhere. And what about providing short circuit protection for the generator? The exception to 445.12 requires approval of the AHJ to omit the overload protection for the generator.

I suppose one could have the generator provided with a molded case switch that would work as a disconnect without any overcurrent protection. Or I suppose one could provide the generator with a magnetic trip only circuit breaker for short current protection only.

But I'm still on the fence regarding a direct tap to the generator.

 

[ChasMB]

But I'm still on the fence regarding a direct tap to the generator.


If you don't mind a bit of input from a fire sprinkler contractor that has also been involved in electrical work. We deal with many many fire pumps in the around here and all of them that have a transfer switch fed from a generator, There IS a breaker on the generator dedicated to the fire pump controller. Last new install startup was delayed as that was left off the genset build and we had to wait for it to be field installed. Fire pumps and their associated equipment is designed to run until it self destructs. No I can't quote NEC but I do know what I have dealt with 100s of times. Only thing about that that bothers me is if that breaker on the genset gets turned off there is no way to know until power fails to the FP controller, It starts the genset and does not get power. Maybe the last service tech working on the genset forgot and left it off, Who knows. (yes we have found them turned off, not tripped)

 

[publicgood]

Only thing about that that bothers me is if that breaker on the genset gets turned off there is no way to know until power fails to the FP controller, It starts the genset and does not get power. Maybe the last service tech working on the genset forgot and left it off, Who knows. (yes we have found them turned off, not tripped)

Good insight. Adding to this portion of the comment:

Code requires...

Supervision. The disconnecting means shall be supervised in the closed position by one of the following methods:
(1) Central station, proprietary, or remote station signal device
(2) Local signaling service that causes the sounding of an audible signal at a constantly attended point
(3) Locking the disconnecting means in the closed position