Hospital Operating Room

[erickench]

Okay!!! The $64 million dollar question from the PassBook.

A 480/120 volt isolating transformer in a closet is used to supply ungrounded 2-wire circuits for a hospital operating room. The design error involved in this arrangement is that

A. all operating room circuits must be grounded
B. only 3 wire circuits may be used
C. maximum permitted primary voltage is 300 volts
D. all of the above

What is your answer? Tick Tock Tick Tock Tick Tock

 

[Little Bill]

Okay!!! The $64 million dollar question from the PassBook.

A 480/120 volt isolating transformer in a closet is used to supply ungrounded 2-wire circuits for a hospital operating room. The design error involved in this arrangement is that

A. all operating room circuits must be grounded
B. only 3 wire circuits may be used
C. maximum permitted primary voltage is 300 volts
D. all of the above





What is your answer? Tick Tock Tick Tock Tick Tock

At the risk of not agreeing with this text book going by some of the other posts you have, I would say A.

 

[erickench]

At the risk of not agreeing with this text book going by some of the other posts you have, I would say A.

The answer key give's 'D' as the answer.

 

[Little Bill]

The answer key give's 'D' as the answer.

I didn't figure I would get it right according to your "brilliant" book!:roll:

 

[erickench]

Well according to NEC 250.20(B)(1) the system is required to be grounded. But there are no requirements for three wire systems in operating rooms or transformers permitted a maximum 300 volt primary.

 

[Little Bill]

Well according to NEC 250.20(B)(1) the system is required to be grounded. But there are no requirements for three wire systems in operating rooms or transformers permitted a maximum 300 volt primary.

That's why I chose A

 

[Electric-Light]

This makes no sense. What hospital receives power at <300v? I'm pretty sure they receive at 4,160, 13,200 or something, complete with its own on-premise transformers.
What's the definition of primary? If you put a wall inside the closet and add a 480 to 240 transformer and step it down to 120 with another transformer, does that satisfy the "primary <300" requirements?

 

[roger]

"D" is the correct answer.

Isolated Power Systems are ungrounded systems that are monitored by a Line Isolation Monitor set to alarm at 5 ma, so this throws "A" out.

The circuits are 2 wire circuits even though there is a bond wire tied to all the ground prongs and conductive surfaces for equipotential purposes, so "B" is gone

See 517.160(A)(2) to get rid of "C"

Roger

 

[DetroitEE]

"D" is the correct answer.

Isolated Power Systems are ungrounded systems that are monitored by a Line Isolation Monitor set to alarm at 5 ma, so this throws "A" out.

The circuits are 2 wire circuits even though there is a bond wire tied to all the ground prongs and conductive surfaces for equipotential purposes, so "B" is gone

See 517.160(A)(2) to get rid of "C"

Roger

Huh? Isn't D saying that all of those things are design errors?

 

[roger]

Huh? Isn't D saying that all of those things are design errors?

Yes it is because they are.
The question was

The design error involved in this arrangement is that

and they are all in error.

Roger

 

[erickench]

If A, B, and C are incorrect then perhaps 'D' should be 'none of the above' and there is nothing wrong with the design. 'All of the above' implies that A, B, and C
are rules that should apply to the design. We know that this is not the case.

 

[DetroitEE]

Yes it is because they are.
The question was and they are all in error.

Roger

The arrangement the are referring to is the one stated in the question, not the arrangement listed in A, B, C. There are no design errors in the arrangement.

I agree with Eric, if D were "none of the above", that would be the correct answer.

 

[roger]

The arrangement the are referring to is the one stated in the question, not the arrangement listed in A, B, C. There are no design errors in the arrangement.

I agree with Eric, if D were "none of the above", that would be the correct answer.

I gotcha, the question itself has nothing wrong in it but answers A,B, and C are incorrect as well as D

Roger

 

[charlie b]

If A, B, and C are incorrect then perhaps 'D' should be 'none of the above' and there is nothing wrong with the design.

There can be something wrong with the design, and that something might not be contained in either A or B or C. Chalk up another score for the DIY test question writers. :roll:

 

[LeeB]

But are ISO systems required by NEC?

But are ISO systems required by NEC?

Good answer Roger! And the wires are required to be orange and brown, both of which now require a distinctive continuos stripe other than white, grey or green.

My question is - Are iso systems required in operating rooms that do not have explosive anesthetics?

I think NFPA 99 has the last word on this, but I don't have a current copy of it.
Last time I read it, they recommend iso systems but do not require them.

Am I correct?

 

[roger]

Good answer Roger! And the wires are required to be orange and brown, both of which now require a distinctive continuos stripe other than white, grey or green.

My question is - Are iso systems required in operating rooms that do not have explosive anesthetics?

I think NFPA 99 has the last word on this, but I don't have a current copy of it.
Last time I read it, they recommend iso systems but do not require them.

Am I correct?

You are correct, ISO systems are an option in both NFPA 70 and 99, they are not required however, depending on where you are they may be, in NC they are.

Roger