Genset

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hhsting

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Glen bunie, md, us
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I have genset that feeds service rated Fire Pump ATS/controller all in one. The drawing does not indicate the poles of the ATS. Their is no neutral run between the fire pump ATS/controller only equipment grounding conductor and phase conductors are run from genset to the fire pump controller/ATS.

The service rated Fire pump ATS/controller on normal side is fed from utility and has neutral to ground bond.

My questions are as follows:

1. If its 4 pole Fire pump ATS would the genset need to be grounded with grounding electrode conductor? I mean genset would be considered separately derived but no neutral is provided so how can their be neutral to ground bond and grounding electrode conductor from neutral at genset? Does equipment grounding conductor need to have grounding electrode conductor in that case?

2. If its 3 pole Fire Pump ATS then genset would be consider non separately derived I would run only equipment grounding conductor?
 
I maybe seeing this rather simplistically but, if the pump/controller is service rated and connected as a typical service disconnect your referring to the grounding conductor and not having a neutral is inaccurate. On service side what you're saying is the "grounding conductor" is your neutral (grounded conductor). Adding the ATS normally bonding is moved hthere and then creates need for 4 or 5 conductors from ATS to disconnect depending on how many pase system you have. Now if you are going to install genset as a SDS the ATS would need to be such that neutral is disconnected when switching services. Grounding and bonding of neutral at genset also would be their with it's own GEC to a GE. The pump/controller would keep its GEC to GE in tacked as is.
The fire pump is allowed to be on it's own service and thus between POCO connection and the pump/controller it would only require the phase conductors and the neutral with bonding N-G at the pump/controller. So if my interpretation of what you are saying about your drawing showing only phase conductors and a (correctly called) neutral is correct as long as the pump controller is supplied as a seperate service and acts as it's own service disconnect. Without details of the ATS type (does it switch the neutral) and genset (is the N/G bonded) useable for SDS, can't say for sure from your statements given.

hhsting said:
1. If its 4 pole Fire pump ATS would the genset need to be grounded with grounding electrode conductor? I mean genset would be considered separately derived but no neutral is provided so how can their be neutral to ground bond and grounding electrode conductor from neutral at genset? Does equipment grounding conductor need to have grounding electrode conductor in that case?
Click to expand...
Think about how a "neutral" is derived.
hhsting said:
2. If its 3 pole Fire Pump ATS then genset would be consider non separately derived I would run only equipment grounding conductor?
Click to expand...
Think about how a "neutral" is derived.
What is required under "normal" conditions (not a fire pump) what would happen to the bonding of the first disconnect when you introduce an ATS into the system? How many conductors would you run from ATS to the disconnect panelboard then?
 
Fred B said:
I maybe seeing this rather simplistically but, if the pump/controller is service rated and connected as a typical service disconnect your referring to the grounding conductor and not having a neutral is inaccurate. On service side what you're saying is the "grounding conductor" is your neutral (grounded conductor). Adding the ATS normally bonding is moved hthere and then creates need for 4 or 5 conductors from ATS to disconnect depending on how many pase system you have. Now if you are going to install genset as a SDS the ATS would need to be such that neutral is disconnected when switching services. Grounding and bonding of neutral at genset also would be their with it's own GEC to a GE. The pump/controller would keep its GEC to GE in tacked as is.
The fire pump is allowed to be on it's own service and thus between POCO connection and the pump/controller it would only require the phase conductors and the neutral with bonding N-G at the pump/controller. So if my interpretation of what you are saying about your drawing showing only phase conductors and a (correctly called) neutral is correct as long as the pump controller is supplied as a seperate service and acts as it's own service disconnect. Without details of the ATS type (does it switch the neutral) and genset (is the N/G bonded) useable for SDS, can't say for sure from your statements given.


Think about how a "neutral" is derived.

Think about how a "neutral" is derived.
What is required under "normal" conditions (not a fire pump) what would happen to the bonding of the first disconnect when you introduce an ATS into the system? How many conductors would you run from ATS to the disconnect panelboard then?
Click to expand...

Not sure what ur understanding.

I have generator used as back up that feeds only service rated fire pump all in one ATS/disconnect/controller . The generator side is Not brining any neutral to the Fire pump since is balance three phase load.

The two questions are about generator grounding and bonding. First if 4 pole is used and second is if 3 pole is used in all in one Fire pump ATS/controller/disconnect. In both cases Generator backup side no Neutral is brought.

I am not sure what you are saying.
 
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IMO, Step 1 would be to confirm if the generator has a neutral output or is simply 3 phase.
It appears it may just be 3 phase in which case you have no neutral to address.
 
hhsting said:
Not sure what ur understanding.

I have generator used as back up that feeds only service rated fire pump all in one ATS/disconnect/controller . The generator side is Not brining any neutral to the Fire pump since is balance three phase load.

The two questions are about generator grounding and bonding. First if 4 pole is used and second is if 3 pole is used in all in one Fire pump ATS/controller/disconnect. In both cases Generator backup side no Neutral is brought.

I am not sure what you are saying.
Click to expand...
Again think about how a neutral is derived. Unless you are using an ungrounded delta you have a neutral (grounded conductor) at some point. If these are your service conductors not a branch circuit, then the 4th should be at the neutral position at the source. The pump service panel would be bonded and have a GEC to a GE, and at that point between the panel and pump you have a branch circuit and the 4th would becomes or is your EGC. Also if service conductors, then ATS for a SDS would need to switch that grounded conductor, if you are counting the generator as a SDS.
 
augie47 said:
IMO, Step 1 would be to confirm if the generator has a neutral output or is simply 3 phase.
It appears it may just be 3 phase in which case you have no neutral to address.
Click to expand...

Generator has neutral output. Gen has 2 breakers one breaker fed Fire Pump the second breaker has neutral feed three ATS 3 poles for building life safety, optional, legally require.
 
Fred B said:
Again think about how a neutral is derived. Unless you are using an ungrounded delta you have a neutral (grounded conductor) at some point. If these are your service conductors not a branch circuit, then the 4th should be at the neutral position at the source. The pump service panel would be bonded and have a GEC to a GE, and at that point between the panel and pump you have a branch circuit and the 4th would becomes or is your EGC. Also if service conductors, then ATS for a SDS would need to switch that grounded conductor, if you are counting the generator as a SDS.
Click to expand...

I still don’t follow I have two sources. One utility (normal) and second backup the generator.

I have no questions or concern about utility side. On utility side Neutral is bought to the service rated Fire Pump disconnect/ATS/controller/all in one. Their is neutral to ground bond in Fire Pump disconnect/ATS/controller/all in one.

My questions are on generator side backup which is Not Service conductors. Their is no neutral brought to Fire Pump disconnect/ATS/controller/all in one and the 2 cases 3 pole Fire Pump disconnect/ATS/controller/all in one or 4 poles Fire Pump disconnect/ATS/controller/all in one generator grounding.
 
I agree that it is a separately derived system but I would say get rid of the IF’s in the question your controller needs a neutral or it doesn’t and that will define how things need to be set up, my controllers do not need a neutral.
 
david luchini said:
Article 100: Definitions.

See "Separately Derived System"
Click to expand...

Ok so my gen three phase conductors are not in direct contact with normal source three phase conductors and since their is no neutral its not direct contact with normal source neutral this is separately derived regardless of poles

So then about the grounding electrode part at the generator and system bonding jumper how? No neutral at the generator
 
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david luchini said:
Article 100: Definitions.

See "Separately Derived System"
Click to expand...

What makes it worse or complicated is that the generator has 2 breakers. One breaker feed Swbd which feeds three ATS, 3 poles one life safety, second legally req, third optional. Neutral is being brought. This would be non separately derived

The second breaker feeds Fire Pump disconnect/ATS/controller/all in one. This would be separately derived


So what is the generator?
 
From you post it appears the 2nd generator breaker feeds a 4 wire 3 pole ATS with no switched neutral so your generator is NOT an SDS (that determination is made by the T/S)
The circuit from the 1st generator breaker to the fire pump ATS is a feeder and would need the 3 phases and EGC.

(Neither of your T/Switches switch the neutral so SDS is not involved)
 
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hhsting said:
What makes it worse or complicated is that the generator has 2 breakers. One breaker feed Swbd which feeds three ATS, 3 poles one life safety, second legally req, third optional. Neutral is being brought. This would be non separately derived

The second breaker feeds Fire Pump disconnect/ATS/controller/all in one. This would be separately derived


So what is the generator?
Click to expand...
You have to look at the whole system when determining if it is separately derived or not; you can't just look at one branch and make that determination. You can have a hundred 4-pole transfer switches fed from a single generator, but the first 3-pole switch with an unswitched neutral that you add to the system turns the whole system into a non-separately derived system.

If there is GFP in your system, you may need to have the engineer revisit the design of a generator as a non-separately derived system. Multiple transfer switches on a non-separately derived system can cause the GFP to not operate properly.
 
d0nut said:
You have to look at the whole system when determining if it is separately derived or not; you can't just look at one branch and make that determination. You can have a hundred 4-pole transfer switches fed from a single generator, but the first 3-pole switch with an unswitched neutral that you add to the system turns the whole system into a non-separately derived system.

If there is GFP in your system, you may need to have the engineer revisit the design of a generator as a non-separately derived system. Multiple transfer switches on a non-separately derived system can cause the GFP to not operate properly.
Click to expand...

Well in my case if the fire pump ats/controller/disco all in one is 4 poles and all other ATS are 3 poles then the 4 poles branch would be ungrounded generstor while all the other is grounded no?
 
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Since you don't have a neutral run to the fire pump ATS from the generator the 4th pole is irrelevant.
As dOnut states above, you have one ATS which has a solid (unswitched) neutral so the gen is not a SDS.
You are simply dealing with feeders supplied by generator breakers.
Sounds like your plans are drawn correctly.
 
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