Fire Pump and Instantaneous CB's

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derekk

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Hello. This falls under 2011 NEC. We have a fire pump where the controller is fed directly from a utility meter/main. The inspector is telling us that we need to use an Instantaneous Trip CB (ITCB) in this application in order to comply with both 695.4(2)(a) AND table 430.52. I do not see any way to use an ITCB in this case as it's not listed in combination with the downstream fire pump controller. What I can't figure out and I'm hoping someone else can, is how to show that the 250% of FLA for an inverse time CB doesn't apply in the case of a fire pump, where the CB is sized based on locked rotor. Nothing that I can find in either section mentions an exception for the other. I see his point, he sees the 800% for an ITCB and the 250% for an inverse time CB and says, "well you can only meet the locked rotor requirement of 695.4 AND the FLA requirement of 430.52 with an ITCB. I do know that ITCB's have been rejected from previous code cycles and are now being included under a very limited exception for FP's under 2014. Any help here? Thanks.
 
Is your fire pump controller listed with your device in question already a part of the listing? If so that kind of takes some of the code interpretation out of it.

Otherwise 695.4(B)(2)(a)(1) says "protective device(s) shall be rated to carry indefinitely the sum of the locked-rotor current" As I read that it means if locked rotor current is more then 250% of full load current then you would not use 250% for sizing an inverse time breaker, you would use locked rotor current as minimum breaker size, whether it is inverse time or instantaneous trip.
 
derekk said:
Hello. This falls under 2011 NEC. We have a fire pump where the controller is fed directly from a utility meter/main. The inspector is telling us that we need to use an Instantaneous Trip CB (ITCB) in this application in order to comply with both 695.4(2)(a) AND table 430.52. I do not see any way to use an ITCB in this case as it's not listed in combination with the downstream fire pump controller. What I can't figure out and I'm hoping someone else can, is how to show that the 250% of FLA for an inverse time CB doesn't apply in the case of a fire pump, where the CB is sized based on locked rotor. Nothing that I can find in either section mentions an exception for the other. I see his point, he sees the 800% for an ITCB and the 250% for an inverse time CB and says, "well you can only meet the locked rotor requirement of 695.4 AND the FLA requirement of 430.52 with an ITCB. I do know that ITCB's have been rejected from previous code cycles and are now being included under a very limited exception for FP's under 2014. Any help here? Thanks.
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If I understand your install correctly you are feeding the fire pump controller with a feeder and he is questioning the size and type of the service disconnect that is supplying this feeder. He is clueless as you can't use an instantaneous trip breaker for this. You need an OCPD such as an inverse time CB rated to carry the locked rotor current indefinitely. The conductors only have to be rated for 125%. Article 695 rules here and Table 430.52 is irrelevant to this application. Art 430 only applies here as directed by Art. 695.
 
Texie, you understand me correctly. I know that table 430.52 doesn't apply to this application. I'm just trying to find something in the code to help me convince our AHJ of that. It's tough because, I'm explaining that using an ITCB in switchgear would violate 430.52(C)(3), so the response will be, if 430.52 table doesn't apply, then neither does the part of 430.52 that says an ITCB needs to be part of a listed assembly. Fortunately, the equipment manufacturers will back this up. What I was hoping for is that there is something similar to 690.3 (for solar photovoltaic) was starts with, "Wherever the requirements of other articles of this Code and Article 690 differ, the requirements of Article 690 shall apply."

I also have gotten the justification that says that the OCPD cannot have overload protection (hence the need for an ITCB). I've explained that the entire reason for sizing the OCPD to indefinitely carry the locked rotor current is because by doing this, you are taking the overload function of the breaker out of the equation (the CB will function only for short circuit protection since the overload portion of the curve lies above the locked rotor current of the Fire Pump). We've installed dozens of fire pump services (our utility requires an OCPD) and this is the first time I've ever had anything like this come up.

The best that I've found is under 430.31 that says, "these provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps." There is then an informational note referring to 695.6. I'll try that. If anyone thinks of something else, please let me know. Or if anyone disagrees with me and thinks that an Instantaneous Trip Circuit Breaker is required (or even permitted) in a meter/main which feeds a fire pump controller (and I've misinterpreted the code for the past 15 years), please let me know that too. Thanks.
 
derekk said:
Texie, you understand me correctly. I know that table 430.52 doesn't apply to this application. I'm just trying to find something in the code to help me convince our AHJ of that. It's tough because, I'm explaining that using an ITCB in switchgear would violate 430.52(C)(3), so the response will be, if 430.52 table doesn't apply, then neither does the part of 430.52 that says an ITCB needs to be part of a listed assembly. Fortunately, the equipment manufacturers will back this up. What I was hoping for is that there is something similar to 690.3 (for solar photovoltaic) was starts with, "Wherever the requirements of other articles of this Code and Article 690 differ, the requirements of Article 690 shall apply."

I also have gotten the justification that says that the OCPD cannot have overload protection (hence the need for an ITCB). I've explained that the entire reason for sizing the OCPD to indefinitely carry the locked rotor current is because by doing this, you are taking the overload function of the breaker out of the equation (the CB will function only for short circuit protection since the overload portion of the curve lies above the locked rotor current of the Fire Pump). We've installed dozens of fire pump services (our utility requires an OCPD) and this is the first time I've ever had anything like this come up.

The best that I've found is under 430.31 that says, "these provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps." There is then an informational note referring to 695.6. I'll try that. If anyone thinks of something else, please let me know. Or if anyone disagrees with me and thinks that an Instantaneous Trip Circuit Breaker is required (or even permitted) in a meter/main which feeds a fire pump controller (and I've misinterpreted the code for the past 15 years), please let me know that too. Thanks.
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You must be dealing with someone who has little, if any, fire pump experience. You might want to direct them to 430.5 and any number of trade articles such as this one: http://www.csemag.com/single-articl...bb72c20b0c8305.html?tx_ttnews[sViewPointer]=1

As you probably know, the preferred way for most installations is to not use a feeder at all for fire pumps, as all full service fire pump controllers are rated for use as service equipment. Then the issue you are having with the AHJ becomes moot as there is no disconnect to argue over. But if he is this clueless he may not understand this either. You just run service conductors directly to the controller using an "outside the building" method. This greatly simplifies the system and most would agree it is more reliable. But as you know, some POCOs won't cooperate with this arrangement or sometimes the job conditions won't allow this.

There are many who just say cave in and do what they want. But when what the AHJ wants is creating a larger hazard, I believe you have a greater responsibility to do what the code requires.
 
My fire pump experience is limited to the instales I've seen on jobs .
all the instales I have seen the disconnects that are located in the gear rooms have been lineside tapped .
 
I'm close to giving up on this. I've included articles from Square D and read everything I can find but I cannot prove to him that when we follow 695.4(B)(2)(a) the requirements of table 430.52 (250% max of FLA) do not apply. It doesn't say it anywhere. It clearly says that Article III of 430 doesn't apply to fire pumps, but nothing says anything about Article IV not applying. There is no way to satisfy both sections with an inverse time breaker.
 
OK, how about this logic? Article 430 Section IV is only for Motor Branch Circuits. Our application is a SERVICE, not a Branch Circuit, so it's covered under 230.90(A). Exception #1 allows us to use 430.52. but does not require it. Exception #4 is specific to fire pumps and directs us to 695.4(B)(2)(a). So, for a service directly supplying a fire pump controller, 430.52 does not apply. Comments on this logic?
 
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