Need Help Journeymens exam

[Joseph Wojcik]

I have 2 questions i AM STUMPED ON. Any help would be greatly appreciated.

A 2 phase 460 volt wye pump service with no neutral load requires a) a grounded service conductor be run to and isolated from the service disconnecting means. b) a grounding electrode conductor connected to the service disconnecting means c) a grounded service conductor be run to and bonded to the service disconnecting means d) no Adittional grounding or bonding.


Next is 4/0 AWG 75 Degree C aluminum transformer secondary conductors shall be protected at not more than a) 175 amperes b) 200 amperes c) the calculated load connected to transformer d) not required for multiphase delta-wye transformer secondary conductors

I dont know where to even look.

 

[George Stolz]

Joseph, I'm headed out, here's 30 seconds worth.

A 2 phase 460 volt wye pump service with no neutral load requires...

Start looking around 250.24-ish.

Next is 4/0 AWG 75 Degree C aluminum transformer secondary conductors shall be protected at not more than a) 175 amperes b) 200 amperes c) the calculated load connected to transformer d) not required for multiphase delta-wye transformer secondary conductors

I dont know where to even look.

Start looking around the beginning of 450, that should get you close.

(Hey, it was 45 second's worth, and you said any would help.

 

[Smart $]

...

A 2 phase 460 volt wye pump service...

Is this an actual test question?

TTBOMK, there never has been, and likely never will be such a service. Remove the "wye" and perhaps it would be a legitimate question. Remove the "2 phase", and it's good to go. But as it is, it requires at least one assumption to determine the correct answer. Assume wrong and...

I often wonder about the knowledge of the person(s) writing these questions :roll:

 

[don_resqcapt19]

George,

Start looking around the beginning of 450, that should get you close.

Not really...450 is only for transformer protection. The question is about protection of the secondary conductors and that answer will be found in 240.21(C).
Don

 

[rcarroll]

Is this an actual test question?

TTBOMK, there never has been, and likely never will be such a service. Remove the "wye" and perhaps it would be a legitimate question. Remove the "2 phase", and it's good to go. But as it is, it requires at least one assumption to determine the correct answer. Assume wrong and...

I often wonder about the knowledge of the person(s) writing these questions :roll:

It is an actual test question. Here in Colorado, we are required to pass a little test every 2 years to keep our licenses. The people who write them toss in something extra to try to trip us up. My advice to those who take the tests, KISS!

 

[bstorey2]

It is a 3 phase, 460-volt wye.

 

[Smart $]

It is a 3 phase, 460-volt wye.

Yeah, that's another possibility for a more legit' question. Is 460Y/266, 3?, 4W a standard service anywhere?

 

[bstorey2]

My guess to the first part is A, but I can not find the NEC section that would cover "A 3-Phase, 460-volt wye pump service with no neutral load."

My guess to the second part is C because 240.21 (C) 1 excludes delta-wye transformers from having the secondary protected by the primary protection device.

I can not find definitive sections to answer these questions with total confidence.

Anyone else?

 

[George Stolz]

Here is someone else with the same question.

Not really...450 is only for transformer protection. The question is about protection of the secondary conductors and that answer will be found in 240.21(C).

Well, I guess I'll have to open the book next time.