Service rated fire pump controller ATS all in one

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hhsting

Senior Member
I have service rated fire pump ATS controller all in one that feeds 125HP 208V three phase fire pump only. Please see attached sketch.

Internal breaker utility side is 2200A trip and generator side is 450A trip.

Questions:

1. Does anyone know how many poles does the internal ATS have typically?

2. Does anyone know what amps is the service rated all in one equipment internal ATS typically?

3. If the internal ATS is lets say 450A rated then how does the 2200A trip breaker protect the internal ATS?

41a1d76fd17ea22da048844108243b90.jpg
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Probably a three pole switch, since most fire pumps do not use a neutral, though an equipment ground is still required.
 

d0nut

Senior Member
Location
Omaha, NE
Fire pumps follow different rules than other equipment. They are designed to run to failure. The controller and the fire pump are listed equipment from the manufacturer and will function as the manufacturer intended.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Fire pumps follow different rules than other equipment. They are designed to run to failure. The controller and the fire pump are listed equipment from the manufacturer and will function as the manufacturer intended.
Agree. If it's a listed controller and the HP matches the controller. Smile & walk away. It's all been taken care of for you.
 
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don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
There is no intent to protect the fire pump equipment ....the intent it that the fire pump be able to run to failure.
 

ramsy

Owner/Operator
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
how does it protect the ATS
Maybe ATS control is isolated sufficiently to only monitor utility failures, regardless of 2200A pump loading, making the switchover to generator only after utility is monitored to have droped out.
 

hhsting

Senior Member
Maybe ATS control is isolated sufficiently to only monitor utility failures, regardless of 2200A pump loading, making the switchover to generator only after utility is monitored to have droped out.

Thats is not the question.

Lets say current of 1000A suddenly appears utility side. The breaker wont trip since it is trip 2200A. The current would fry the ATS since it is rated at 450A. What is protecting that ATS?
 

NTesla76

Senior Member
Location
IA
Occupation
Electrics
Thats is not the question.

Lets say current of 1000A suddenly appears utility side. The breaker wont trip since it is trip 2200A. The current would fry the ATS since it is rated at 450A. What is protecting that ATS?
What protects the line side of any service?
 

ramsy

Owner/Operator
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
Thats is not the question.

Lets say current of 1000A suddenly appears utility side. The breaker wont trip since it is trip 2200A. The current would fry the ATS since it is rated at 450A. What is protecting that ATS?
I see, if ATS utility-side switch smokes in open position, then the whole system is only good for 450A, or weekest link in the chain.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Thats is not the question.

Lets say current of 1000A suddenly appears utility side. The breaker wont trip since it is trip 2200A. The current would fry the ATS since it is rated at 450A. What is protecting that ATS?
If 1000 amps appears, there is a problem with the fire pump equipment. It is designed not to trip even if the pump is locked up or near locked up. They want the pump to try and run at all costs.
 

ramsy

Owner/Operator
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
The validity of the listing may be questionable, if 450A rating is below the UL standard, or out of line with other properly-sized equipment.

Confirming listing integrity has become more of a challenge, with all the counterfeit or missing listings in the internet marketplace and from salvage brokers.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
They want the pump to try and run at all costs.
Actually they want the pump to perform in any running overcurrent condition, including locked rotor. There is no requirement that the pump be able to run during a short circuit event (during a short circuit the voltage to the motor will be approaching zero).
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
I see, if ATS utility-side switch smokes in open position, then the whole system is only good for 450A, or weekest link in the chain.
Only if it’s on generator, and the generator would most likely shut down.
Actually they want the pump to perform in any running overcurrent condition, including locked rotor. There is no requirement that the pump be able to run during a short circuit event (during a short circuit the voltage to the motor will be approaching zero).
Which 1000 amps would probably be a ground fault, not an actual short circuit, where a bolted fault should trip the breaker if the current is available.
 

hhsting

Senior Member
If 1000 amps appears, there is a problem with the fire pump equipment. It is designed not to trip even if the pump is locked up or near locked up. They want the pump to try and run at all costs.

How can pump run at all if ATS and controller rated for 450A frame starts to melt at currents greater than 450A? I mean at 500A the equipment would melt and pump not be able to run?

Whats the logic behind service rated ATS, controller all in one have amps frames rating that is lower than the internal upstream breaker trip rating for fire pump?
 
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d0nut

Senior Member
Location
Omaha, NE
You are still thinking about the controller and transfer switch the wrong way. The controller and transfer switch are rated for the locked rotor amps of the motor. The transfer switch is rated for not less than 115% of the motor full load current and is suitable for switching the locked rotor amps of the motor. All of the requirements for the controller and transfer switch are in NFPA 20, Chapter 10. Section 10.8.2 covers the fire pump controller and transfer switch arrangements and section 10.8.3 covers the power transfer switch requirements.

The breaker on the generator side is smaller because the generator system is not required to carry the locked rotor amps of the fire pump indefinitely. Regular motor rules apply to that side of the switch.

If it helps in your specific example, think of the ATS as a 2200A ATS that is protected on the generator side at 450A.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Generally, but not required, most engineers will call for the generator feed to the ATS to be ahead of any ocp on the generator output, but as others have said, the generator is not held to the same standard as the utility.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
The generator only has to be sized large enough to start and run the fire pump along with all other loads on the generator. Some engineers will specify a shunt trip breaker controlled by the fire pump to dump the optional loads. This allows for a smaller generator.
 
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