Generator and Fire Pump

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barone

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I have read several threads to try and get an answer to my dilemma and have not had any success. Most of the threads deal with the obvious issues with providing an alternate source of power for a fire pump and how to make those connections. Here is where I get fuzzy and take issue with the way most installations have been done. Since the fire pump ATS/Controller is service entrance equip. we must provide a neutral conductor on the normal side and provide a main bonding jumper in the fire pump ATS controller. We do not however provide a neutral conductor from the generator, as there is nowhere to land it at the FP ATS or is it required because the load is delta. So what we have is an unbonded generator (not a SDS) and 3-pole transfer switches with solid neutrals, everywhere but at the fire pump ATS/controller. So my question is, how are we providing a low impedance path for fault current to actuate the emergency source overcurrent device (short circuit protection only) mounted on or near the generator? And if the path does exist (if we have an additional ATS with solid neutral anywhere else in the system, or if we are providing our normal source from a tap section in a service switchboard, which we are) then is that path not objectionable?

The way I see it if a phase to ground short occurs in the fire pump supply conductors or the fire pump itself for that matter, when the system is in emergency mode, current will flow through the equipment ground to the bond in the fire pump ATS, then through the normal neutral or the water pipe ground to the service switchgear, then back through the service neutral to the other ATS normal feeder neutral, across the neutral block in any other ATS and back to the generator alternator thorough that ATS's neutral conductor, or every ATS's neutral conductor should we have many, which we do (not to mention any stray currents that may flow in the equipment grounds). Thus being objectionable.

Code does not address this at all. Other than requiring that low impedance paths for fault current must not be objectionable.

Keep in mind that there is not a Fire Pump ATS/Controller manufacturer that will provide a connection for the neutral conductor from the emergency source or will they build a 4-pole transfer switch into them. They come one way only, grounded normal input and ungrounded emergency input. I have yet to see them any other way, and in talking to the manufacturers they just do not make them. With this in mind, providing a neutral conductor from the generator to the fire pump ATS is a waste of wire, as there is nowhere to land it, without violating its UL listing. And if I bond at the generator, they do not make a four pole fire pump ATS, so there is no way to switch the neutral. Again a waste of wire.

Sorry for the long post and lack of code sections, this was hard to describe.
 
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ohmhead

Senior Member
Location
ORLANDO FLA
fire pump neutral not needed

fire pump neutral not needed

Yes you dont need a neutral from genset just a grounding conductor run with feeds in a event of a fault they really dont care it will burn complete melt down the pump will run until its over .

Think if you really have a major fire no one cares about the electric connection of the neutral it doesnt matter at this point so dont run one we never do and ive done 30 installs since ive been a electrician over the years .

Yes you need neutral !one from the normal source for the return to transformer full size and a ground rod system at the fire pump or you can tie it into the main building ground rods which we always do anyway .

You take the neutral and attach it to the case of the fire pump controller just like a ground no jumper is needed its done .

Plus dont forget to use bonding bushings on the incoming service feed its a un protected incoming from transformer .

If you need more help ask iam hear for ya .
 
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ohmhead

Senior Member
Location
ORLANDO FLA
Typical fire pump controller install

Typical fire pump controller install

Heres a photo of one we did in a 35 story building in orlando it was a 200 hp 480 v 3 phase .
428.jpg
notice the neutral attached to the case with a lug section one and we also pulled one from the genset but you dont have to do it if you chose not to we just order wire in sets so we used it and attached it as you see in section two top left .
You can see the 6 wire pump feed reduced conductors wye /delta smaller wire .



There all the same not much to see but make sure if your doing it undeground you get the controller compartments piped in correct or you will have issues with the inspector meaning emergency and normal power and the pump feed must be in the correct section .
 
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barone

Member
Thanks but...

Thanks but...

Ohmhead: First off thank you for the excellent response. That being said it does not address my question. I see that in order to provide a nonobjectionable path for fault current, you decided to provide a neutral wire and a lug for the emergency feeder. The problem I have with your install is that I have been told that by adding your own lug for the neutral you have violated the ul listing of the controller. This was from the mouth of the manufacturer. I have looked at this further and have determined the correct solution thus answering my own question.

The generator must be provided with a main bonding jumper (making it a SDS) and there must be four pole ats's utilized everywhere but the fire pump ats/controller. This will ensure that personell is protected from objectionable fault currents should they occur during say a test of the fire pump.

If anyone disagrees I am all ears.
 
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barone

Member
Please check yout install

Please check yout install

Ohmhead,

Please check your install. There is still an objectionable path for fault current should a fault occur in the EM feeder to the fire pump ATS/controller as I describe above. The only way to remedy that is to provide the bonding jumper at the generator and use 4-pole switches.

I know the intent of a fire pump install is to let it burn should a fault occur, but that is only in a catastrophy. If someone goes to test that pump and there is a fault in the EM feeder, you will be sending current the the main service switchboard, which is objectionable and a NO NO.

I will try to draw something up when I get time later and post a picture of it here.
 
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ohmhead

Senior Member
Location
ORLANDO FLA
Article 250 grounding

Article 250 grounding

Well lets see thanks for you help .

But i must disagree with you findings this is why an alternate ac power source as a on-site generator is not a separately derived system if the neutral is solidly interconnected to a service supplied system neutral .

In our case the fire pump controller transfer switch located in the controller is inside the FP service it is totally by itself it does not or is not supplied by our main switchboard .

The generator feeds the Fire pump controller only and the fire pump controller has the 3 pole ATS installer per factory .

Funny but we also have few contacts with the factory of that controller like when the lugs dont match they write a letter to us giving us approval we show that to inspector and engineer plus document and its done .


A solid neutral in ATS is ok in my code book if its a 3 pole ATS read 250 D you dont bond the generator you bond the service which is the fire pump controller in my case .



Now if you have a 4 pole in that FP controller of yours id like a photo because they dont make one that ive ever seen .

Were normally fed out of the power companys transformer not any switchboard and we have a onsite generator for fire pump .

If we had all 3 pole ATS ,s in building it would still be the same .

Let me know what you think but read the code book first .
 
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barone

Member
Apples and Oranges

Apples and Oranges

Ohmhead: What we have here is apples and oranges. I should not have commented on your install without knowing more info. I apologize for that. I assumed that you responded with the picture and your comments because they had some similarity to my design, but they are far from similar. I am not doing an install I am preparing a design for a project. The details of the system are far too complex and I have drawn up everything to help trace the fault current paths, but the attachment manager will not allow me to upload the pdf's I have. Oh well.

Basically we have a situation that is becoming more common that the code does not address. We are utilizing a new switchboard product that was introduced a few years back, that is a fire pump tap section for switchboard lineups that allows you to make a tap of the board in it's own section just after the CT section. So you end up with a fire pump service lateral that is not really a service lateral as it is tapped from a service switchboard which is already making the ground to neutral bond. When we re-bond at the fire pump controller, we create the same problem you have when you bond at a sub-panel. You get an objectionable path for fault current. Art. 695 does not address this, as Art 695 only addresses the fire pump service as a separate service from the source and does not yet take into account this new switchboard section setup, although it does allow you to use it. Adding the generator only makes the situation much worse. The answer in my case is bond at the generator and provide 4-pole switches everywhere but the fire pump ATS. This does not totally eliminate the objectionable paths, but it limits them the best we can with the current codes is place. If we were allowed to remove the bond at the fire pump ATS it would eliminate our problem, but code does not allow that, as we are forced to treat that ATS as service entrance equipment, even though it technically is not in our case, as we are tapped from a switchboard and service lateral that is already provided with a MBJ.

I understand that the common feeling is that it is OK to let the fire pump burn, but if it or someone working on it were to burn during a test and thus burn the building and the people in it, would that not be ironic?

Maybe I am way off here, but every time I come back to this the problem is the same, and when speaking with the code panel member, he agreed that code does not address it and asked that I submit a formal letter with a request for a code review in this area. He would like them to review the use of these new switchboard tap sections and if any code modifications are needed to address their use. I hope to prepare that by years end, but we'll see, work is busy, thankfully.

Have you ever run into an install with my situation? The use of the tap section, I mean?
 

ohmhead

Senior Member
Location
ORLANDO FLA
Double bonding two paths

Double bonding two paths

Well yes if you come out of the main switchboard thats a different issue then when you bond at both genset and fp controller you now have two paths from which current can flow or take in a event .

This can effect the trip time of a breaker i think it might even effect the gfi operation of anything up stream cordination by that extra bonding jumper or connection .

Interesting we would like to see what others think about this maybe they will chime in ?

Your ok no hard feelings good post good point made .

I think if the manufacture would install a 4 pole ats in FP controller we would not be here .
 
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barone

Member
Thanks

Thanks

Ohmhead: Thanks for your time and input. I appreciate any angle or any input that someone would offer, and just having a dialogue can produce results, so I thank you again for that.

I wonder if anyone else has done any installs with the fire pump tap section of a switchboard, as is my case. I would love to hear how they handled their install, and how they eliminated objectionable paths for fault current. The issue I see is that local inspectors demand that the bond be made at the fire pump controller because Art. 695 & Art. 230 requires it. For now there is no way to legally get around it, so the answer is to bring this up to the code panel and let them make a determination and possibly revise the code to take this situation into account. Another solution may be to make a rule that outlaws the tap sections, and force everyone to provide their fire pump service as a completely separate lateral. This will not eliminate problems that arise when you introduce a generator with several ATS's and in some cases where a single generator backs up three separate systems fed from three separate POCO xfrmrs, not to mention the GFI's that will give you problems, but there must be a way to do this safely and without the objectionable paths.
 
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