No secondary over current protection?

[iwire]

Thanks everyone, this has been very helpful. Please keep any thoughts coming.

My guy never did get the voltage measurements but I had already decided to just take ever ones word on it. If I am the only one thinking one way and ever one else is thinking the other way it is time to reconsider my opinion.

 

[erickench]

Fusing down below the rated primary current 36 Amps is not advisable. If you were to increase the size of the secondary conductors and add another receptacle there would'nt be a violation.

 

[augie47]

Fusing down below the rated primary current 36 Amps is not advisable. If you were to increase the size of the secondary conductors and add another receptacle there would'nt be a violation.

Being more stubborn than Bob , I'll politely and stubbornly disagree.
Addressing the transformer primary will satisfy the protection of CONDUCTORS on the secondary but not necessarily the receptacle or equipment plugged into it. To me, 210.19(C), 240.21(C) and the respective articles for utilization equipment require OCP for the equipment.

 

[iwire]

Fusing down below the rated primary current 36 Amps is not advisable. If you were to increase the size of the secondary conductors and add another receptacle there would'nt be a violation.

I do not believe I can supply a 60 amp receptacle(s) with more than 60 amps.

I believe that would be inadvisable.

Most likely I will recommend replacing the unfused disconnect on the secondary side with a fused disconnect equipped with 50 amp fuses.

 

[pfalcon]

Fusing down below the rated primary current 36 Amps is not advisable. If you were to increase the size of the secondary conductors and add another receptacle there would'nt be a violation.

Correct. Fusing primary below 45A dual element fuse will cause frequent trips. That's pretty much a guarantee. Bussmann recommends starting primary fuses at 125% of primary line current. If you have secondary fusing then you can work your way up to 250% to eliminate nuisance trips.

I insist on secondary fusing at our site. Secondary fusing is sized down to the required load current.

In iwire's application the 8awg conductor is too small to be protected by the primary OCPD by a bunch. 3awg is required (90A+ ampacity). 240.21(C)(1)
Nor does the primary OCPD protect the equipment.

 

[pfalcon]

Being more stubborn than Bob , I'll politely and stubbornly disagree.
Addressing the transformer primary will satisfy the protection of CONDUCTORS on the secondary but not necessarily the receptacle or equipment plugged into it. To me, 210.19(C), 240.21(C) and the respective articles for utilization equipment require OCP for the equipment.

The transformer primary OCPD cannot be addressed. I guarantee you won't make that transformer work fusing below 45A without a lot of trips on inrush.

I'm not sure what all the receptacle talk is about regarding 240.21(C). This section only refers to the secondary conductors. The primary OCPD never protects downstream equipment. 240.21(C)(6) requires downstream protection even for protected secondary conductors before 25'.

So, yes augie47. Fuse for the equipment. You're right.

 

[Pierre C Belarge]

From Bob
"Could I supply a 60 amp receptacle without OCP?"

Bob,
Yes, a ground fault alarm would be required. There is also a possible issue with 250.20(B)(1), but my take on that is since one of the ungrounded conductors will exceed 150 volts to ground if you bond X4, that this system is not a system that is required to be grounded as long as there are no line to neutral loads.

The secondary wire and receptacle would have to be rated for 90 amps if you keep the 45 amp primary OCPD.

You would be legal with 60 amp secondary conductors and the 60 amp receptacle if you changed the primary OCPD to 30 amps. If you do that there may be an issue with the transformer inrush tripping the primary OCPD.

Where in the NEC is there permission to supply equipment without OCPD and use a ground fault alarm?

 

[tryinghard]

Transformers are multi-use devices. With X4 not connected this is a single voltage transformer by usage. The tag covers all configurations that may be made. Circuit design determines whether 240.21(C)(1) applies.

I don?t know; does this also mean we can supply it backwards?

The misuse of an ungrounded system is dangerous. A grounded system that is not grounded is still a grounded system (i.e. 120v circuitry included yet not grounded/bonded at XFMR or 1st disconnect; this would be a system in violation). An intentional ungrounded system also includes alarming/annunciation for faults 250.21(B) it is also intended for critical machinery.

250.20(A)(1) ?Where the system can be grounded?? this XFMR is manufactured so it can be grounded because it includes the X4 term.

 

[tryinghard]

Where in the NEC is there permission to supply equipment without OCPD and use a ground fault alarm?

Only for an ungrounded type system - "08" 250.21(B) while 250.4(B) & 250.30(B) are met. An ungrounded system is not exempt of an effective fault path from/to source.

 

[augie47]

I don?t know; does this also mean we can supply it backwards?

The misuse of an ungrounded system is dangerous. A grounded system that is not grounded is still a grounded system (i.e. 120v circuitry included yet not grounded/bonded at XFMR or 1st disconnect; this would be a system in violation). An intentional ungrounded system also includes alarming/annunciation for faults 250.21(B) it is also intended for critical machinery.

250.20(A)(1) ?Where the system can be grounded?? this XFMR is manufactured so it can be grounded because it includes the X4 term.

No sure about your Code reference. In the '08 Code, 250.20(A)(1) references systems less than 50 volts.
But, in reference, to your comment, I entered this thread thinking the same since the transformer should be grounded under the rules of 250.21(B)(1), but Cold Fusion set me straight in post #27. In using X4, one of the leads would provide voltage in excess of 150 volts, therefore 250.20(B)(1) does not apply.

 

[erickench]

I believe the rule about receptacles is this. If you have two or more, each receptacle rating cannot be larger than the rating of the circuit. If you have only one receptacle, that single receptacle rating cannot be less than the rating of the circuit. So adding another 60 Amp receptacle should take care of that one violation.

 

[tryinghard]

...I entered this thread thinking the same since the transformer should be grounded under the rules of 250.21(B)(1), but Cold Fusion set me straight in post #27. In using X4, one of the leads would provide voltage in excess of 150 volts, therefore 250.20(B)(1) does not apply.

I saw that and still believe it as you stated. Two of the ungrounded conductors meet this criteria.

...maximum voltage to ground on the grounded conductors..." is interpetive to any as well; not just all. Because of this I would default to safety and ground it.

 

[Pierre C Belarge]

Only for an ungrounded type system - "08" 250.21(B) while 250.4(B) & 250.30(B) are met. An ungrounded system is not exempt of an effective fault path from/to source.

I understand an UNGRONDED SYSTEM is required to have a ground fault detector installed.

I do not understand where an ungrounded system permits the installation of a feeder or branch ckt without OCP.

 

[iwire]

I am glad this did not turn out to be easy. :grin:

 

[Pierre C Belarge]

I am glad this did not turn out to be easy. :grin:

When would you be asking a question with an easy answer?

 

[bob]

Edit: comment already covered

 

[tryinghard]

I understand an UNGRONDED SYSTEM is required to have a ground fault detector installed.

I do not understand where an ungrounded system permits the installation of a feeder or branch ckt without OCP.

Oops; :roll: I don't think it does.

 

[pfalcon]

I don?t know; does this also mean we can supply it backwards?

The misuse of an ungrounded system is dangerous. A grounded system that is not grounded is still a grounded system (i.e. 120v circuitry included yet not grounded/bonded at XFMR or 1st disconnect; this would be a system in violation). An intentional ungrounded system also includes alarming/annunciation for faults 250.21(B) it is also intended for critical machinery.

250.20(A)(1) ?Where the system can be grounded?? this XFMR is manufactured so it can be grounded because it includes the X4 term.

No, it means you can wire it in keeping with its listed usage. Most transformers of this type do not require X4.

 

[tryinghard]

No, it means you can wire it in keeping with its listed usage. Most transformers of this type do not require X4.

Thats my point as well, it is listed and manufactured as a grounded system transformer. Two of the ungrounded conductors can be 120v to ground therefore it requires grounding and would be in violation if ungrounded.

In my industrial circles most of our 240v delta's are grounded systems, our ungrounded systems are 480v.

 

[iwire]

Thats my point as well, it is listed and manufactured as a grounded system transformer.

I do not see that at all, any transfomer can be grounded or not.

I could use a delta wye transformer to supply an ungrouned delta simople by not using XO.