Neutral bring to disconnect

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hhsting

Senior Member
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Glen bunie, md, us
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Junior plan reviewer
I have customer owned delta to wye 13.8kv to 480/277V system and its located outside. The transformer does not system bonding jumper i.e no neutral to ground at the transformer. However the transformer has grounding electrode conductor going to ground ring around its perimeter pad. It has 2 sets of secondary conductors provided and owned by customer. The first set of secondary conductor feeds SWBD inside Building #1. The SWBD has main bonding jumper i.e neutral to ground bond. The second sets secondary conductor feeds fire pump controller inside Building #2. Should neutral be brought from customer owned transformer to the fire pump controller? If yes then which NEC 2017 Article?
 
hhsting said:
The second sets secondary conductor feeds fire pump controller inside Building #2. Should neutral be brought from customer owned transformer to the fire pump controller?
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Yes, if there is no neutral at the fire pump service disconnect then there is nothing to connect the MBJ to. This is no different than any other service disconnect.
 
infinity said:
Yes, if there is no neutral at the fire pump service disconnect then there is nothing to connect the MBJ to. This is no different than any other service disconnect.
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Please read carefully their is no service conductors brought from the transformer. The transformer is customer owned. So those are secondary feeders brought to the fire pump controller. Does it still require neutral being brought? I dont see anything in NEC 2017 about feeders must bring neutral.
 
hhsting said:
Please read carefully their is no service conductors brought from the transformer. The transformer is customer owned. So those are secondary feeders brought to the fire pump controller. Does it still require neutral being brought? I dont see anything in NEC 2017 about feeders must bring neutral.
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I missed the customer owned part. So this a 480 volts ungrounded system?
 
infinity said:
I missed the customer owned part. So this a 480 volts ungrounded system?
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Well the customer owned transformer has grounding electrode conductor to ground ring around its pad. It has no system bonding jumper. The transformer feeds two feeders. One is going to SWBD and they put main bonding jumper in the SWBD because transformer is separately derived.

The second feeder goes to fire pump controller.

I dont know what to call that 480V ungrounded system or not?
 
infinity said:
Since it's not a service disconnect a 3Ø, 3W fire pump controller does not require a neutral.
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Sorry for light attachment but drawings has this part lighted as existing and new part bolded. Cant do much better might have to zoom in.

Just to make sure in the attached Transformer T3 is the customer owned transformer. The yellow highlighted conductor is one set of secondary feeder 3 phase plus ground goes to fire pump controller. The ECC3 is the swbd that the second set of secondary feeder feed.

The transformer is separately derived. The fire pump is powered from secondary 3 phase wye windings. Right now the fault currents goes from fire pump controller to 2 awg ground to the ground bus but has no way going back to wye windings.

If you dont bring neutral to the fire pump controller from center of wye and do neutral to ground bond in fire pump controller then I dont see how fault currents would get back to wye windings where it originated?

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Tell me if this is correct.
Customer owned transformer after the service disconnect?
Transformer Delta/Wye secondary is 480Y/277 3 phase, neutral bonded?
Fire pump controller 3 phase, 3 wire fed by a feeder with EGC and no neutral?
 
infinity said:
Tell me if this is correct.
Customer owned transformer after the service disconnect?
Transformer Delta/Wye secondary is 480Y/277 3 phase, neutral bonded?
Fire pump controller 3 phase, 3 wire fed by a feeder with EGC and no neutral?
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Customer owned transformer after the service disconnect?

YES

Transformer Delta/Wye secondary is 480Y/277 3 phase, neutral bonded?

NO neutral bonded in the transformer. However the transformer is delta/wye and the secondary is 480Y/277 3 phase.

Fire pump controller 3 phase, 3 wire fed by a feeder with EGC and no neutral?

YES fire pump controller 3 phase, 3 wire fed by the transformer secondary feeder with EGC and no neutral.
 
Since this is specified as a 480/277 volt system, I am going to require a neutral be run to the fire pump controller, a system bonding jumper be installed and a connection to a GEC.

In addition, since there is no system bonding jumper at the transformer, supply side bonding jumpers will be required from from the system bonding jumper in the switchboard and one from the system bonding jumper at the fire pump controller.
 
don_resqcapt19 said:
Since this is specified as a 480/277 volt system, I am going to require a neutral be run to the fire pump controller, a system bonding jumper be installed and a connection to a GEC.

In addition, since there is no system bonding jumper at the transformer, supply side bonding jumpers will be required from from the system bonding jumper in the switchboard and one from the system bonding jumper at the fire pump controller.
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If they run neutral to fire pump controller disconnect can I put neutral to ground bond in it fire pump controller? I would now have two secondary disconnects and one of them SWBD has neutral to ground bond.

Please see attached what I have. NEC 2017 Article 250.30(A)(1) says system bonding jumper can be at any single point on the separately derived system from the source to the first system disconnecting means.

Do I have first system disconnecting means in the attachment this post?

IMG_8985.jpg


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hhsting said:
NEC 2017 Article 250.30(A)(1) says system bonding jumper can be at any single point on the separately derived system from the source to the first system disconnecting means.
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If only a single point is permitted then there would need to be a SBJ at the transformer and not at each disconnect. Which leads to the question why not just install the SBJ at the transformer?
 
infinity said:
If only a single point is permitted then there would need to be a SBJ at the transformer and not at each disconnect. Which leads to the question why not just install the SBJ at the transformer?
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Swbd is existing that has system bonding jumper. When the existing customer owned transformer was installed they had single point of connection and they selected swbd. Not sure why they did that.

Now should they chose to have secondary disconnects for the fire pump then they would need to remove existing swbd system bonding jumper and then put one in the transformer.

I am not sure what the problem is with doing this because I haven’t gotten back to the designer about this. I needed to research a bit more as to what would be code complaint system bonding jumper at the transformer or multiple system bonding jumpers one at each secondary disconnects before I open my mouth.
 
IMO, iF the SDS is outdoor the exceptions to 250.30(A)(1) and A(2) can apply but you would need a grounded conducto9r or a SSBJ to assure a return path,
 
augie47 said:
IMO, iF the SDS is outdoor the exceptions to 250.30(A)(1) and A(2) can apply but you would need a grounded conducto9r or a SSBJ to assure a return path,
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Ah yes that can be option but plans shows they are bringing both neutral and supply side bonding jumper from existing transformer to swbd but in the grounding detail they only show neutral from the existing transformer to the existing swbd.

If they bring both neutral and supply side bonding jumper from existing transformer to the existing swbd then putting system bonding jumper in transformer and at swbd will create parallel path so cant use NEC 2017 Article 250.30(A)(1) exception 2.

If they bring only the neutral from the existing transformer to the existing swbd then it parallel path is not issue given only one side of the conduit from the existing transformer to the existing swbd is bonded otherwise would create parallel path but somewhere I read in NEC 2017 that for 480/277V system both side of the conduit would need to be bonded. So I dont see how the exceptions would apply unless the conduit is non metalllic
 
infinity said:
If only a single point is permitted then there would need to be a SBJ at the transformer and not at each disconnect. Which leads to the question why not just install the SBJ at the transformer?
Click to expand...
infinity said:
If only a single point is permitted then there would need to be a SBJ at the transformer and not at each disconnect. Which leads to the question why not just install the SBJ at the transformer?
Click to expand...
If you have two first means of disconnects, then you can have two bonding points, just like a service.
 
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