Fault Current and Fire Pump Controller

[Danielt]

A fire pump controller has a label on the exterior wit a 100k AIC rating, and a UL stamp. The main breaker inside, where the unfused lines connect, is only 35k. The secondary breaker, to the pump itself, is 65k. My fault current is 43k. I failed it, saying where the unfused conductors land must be good for the fault current. The manufacturer is saying it's good. Thoughts?

 

[electrofelon]

A fire pump controller has a label on the exterior wit a 100k AIC rating, and a UL stamp. The main breaker inside, where the unfused lines connect, is only 35k. The secondary breaker, to the pump itself, is 65k. My fault current is 43k. I failed it, saying where the unfused conductors land must be good for the fault current. The manufacturer is saying it's good. Thoughts?

That doesn't make any sense. Perhaps the manufacturer can explain how they are getting a rating higher than 35k for that MB? I am not aware of any procedure the manufacturer could use to get a higher AIC rating, other than series ratings which sounds like in your case would not apply since there is no upstream OCPD.

 

[tom baker]

It’s a UL listed controller, meaning it’s undergone testing to meet the standard. The two breakers are in series to give the required withstand rating.
See section 110.3

 

[electrofelon]

It’s a UL listed controller, meaning it’s undergone testing to meet the standard. The two breakers are in series to give the required withstand rating.
See section 110.3

But how can the FIRST breaker's rating be increased?

 

[Jraef]

Fire pump controller UL rules (UL-218) are different than what is used for regular control panels, mostly based on the “run to destruction” issue. Interrupt capacity on a breaker has to do with it attempting to interrupt a fault and surviving the attempt. You have to remember that any breakers used in fire pump controllers are selected to NOT trip under locked rotor conditions of the pump it is controlling, so the interrupt capacity printed on the breaker is basically irrelevant

I think if you look more closely at that label, it does not say “100kAIC”, I’ll bet it says it has a “100kA SCCR” (short Circuit Current Rating), which is a different thing from the “AIC” rating of the protective devices inside. 100kA SCCR just means that if there is a fault in the load side of the controller in a system with an available fault current of up to 100kA, it will not become a bomb. It may not survive either, but its failure mode is not going to present a new source of problems during your fire.

Mind you, it’s been over 25 years since I have had access to UL-218 while working for a fire pump controller mfr., so that was before the term “SCCR” was being used. But we would get this issue come up regarding what was then called the “withstand rating”, which generally is what has been replaced by SCCR.

 

[don_resqcapt19]

....
Mind you, it’s been over 25 years since I have had access to UL-218 while working for a fire pump controller mfr.,....

You can read all of the UL standards on line for free, using the same non-user friendly system that the NFPA uses to permit reading their standards online for free. Just like with the NFPA, you have to register with an email address.

 

[texie]

A fire pump controller has a label on the exterior wit a 100k AIC rating, and a UL stamp. The main breaker inside, where the unfused lines connect, is only 35k. The secondary breaker, to the pump itself, is 65k. My fault current is 43k. I failed it, saying where the unfused conductors land must be good for the fault current. The manufacturer is saying it's good. Thoughts?

While I agree with the others, I think I would get clarification from the manufacturer.

 

[brantmacga]

While I agree with the others, I think I would get clarification from the manufacturer.

I thought that was the purpose of the label and UL stamp.


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[Danielt]

It’s a UL listed controller, meaning it’s undergone testing to meet the standard. The two breakers are in series to give the required withstand rating.
See section 110.3

No where did I find that these breakers were series rated

The manufacturer's engineer says the controller was UL tested as a whole for the AIC rating, which doesn't make sense to me with a 35k main.
He is sending the UL information and a letter with his seal. At that point I'll have to approve it.

 

[jim dungar]

No where did I find that these breakers were series rated

The manufacturer's engineer says the controller was UL tested as a whole for the AIC rating, which doesn't make sense to me with a 35k main.
He is sending the UL information and a letter with his seal. At that point I'll have to approve it.

The ratings of individual components are all but irrelevant when those components are mounted into an assembly that is UL tested for a single overall rating.

The most common occurrence if this can be found in motor control center buckets.

 

[tom baker]

No where did I find that these breakers were series rated

The manufacturer's engineer says the controller was UL tested as a whole for the AIC rating, which doesn't make sense to me with a 35k main.
He is sending the UL information and a letter with his seal. At that point I'll have to approve it.

Not series rated but connected in series, by way of example;
The first fire pump controller (100 HP 480 V) I worked on dated from 1972. It had on single very large circuit breaker. I had to replace that controller with a newer one in about 20 years ago. The newer controller had two smaller circuit breakers in series to get the interrupting rating.
Both had the big red lever that manually overrode the circuit breaker if it tripped.

Fire pump controllers and fire pumps are very different from other motor/pump applications. The intent is to not have the controller trip and let the motor burn up in fire. If you get much more involved in fire pumps than a copy of NFPA 20 is a must

Since the controller had the UL listing, all the AHJ needs to do is look at the line and load wiring
In my first post I mentioned section 110.3 that was incorrect the correct section is 90.7 (I haven't been instructing classes recently so some sections are not readily available in my memory!)

 

[Jraef]

I don't know what brand you are looking at, but I just looked at a brochure for a Joslyn Clark Fire Pump Controller and see the kind of mistake that is likely behind the confusion here. Their brochure (page 3 of this pdf) says "Short-Circuit Current Withstand Rating Standard 100,000 AIC".

That is basically some ignorant technical writing work, likely by a marketing person and not properly vetted by an engineer for the correct use of terminology. That should have said "Short Circuit Current Withstand Rating 100,000A". Period, no "IC".

AIC stands for "Amps Interrupting Capacity" and that terminology ONLY applies to things that directly interrupt the flow of fault current, i.e. circuit breakers and fuses. A PANEL cannot have an "AIC", because the PANEL is not interrupting anything. A PANEL however has a "SCCR" as explained earlier, which is NOT the same as the AIC of the protective devices inside. If the panel manufacturer submitted their panel to UL under whatever UL's rules are for attaining an SCCR for a fire pump controller, and UL passed it for having an SCCR at 100kA (again, leave the "IC" out of this), then that is all that is necessary.

It does not always necessarily matter what the individual components used inside of the panel are listed at, so long as the assembly as a whole passes. One of the ways a mfr can attain an SCCR is by using components already tested and listed, but another way they can do it is to submit the entire assembly for testing as a unit. If they did that and it passed, there is no further need to question the listing value.