NEC 110-34(A) Condition 1 or Condition 3?

Status
Not open for further replies.
S

stelthorst

Member
Hi All,

I am working on the design of a substation and there is a dispute about the working clearance requirement of our main switchgear. The line side switchgear (34.5kV) and the load side switchgear (13.8kV) are face to face in the electrical room.

Here are the two thoughts.
Camp 1 says this is a condition 1 clearance since the bus work can not be accessed from the front and when the circuit breaker is removed a barrier drops down to inhibit access to the buss. (See condition 1 statement after the or)

Camp 2 says that this is a condition 3 situation because you have live parts on both sides.

I've looked in the NEC handbook and while there is no explanation for NEC 110-34(A) there is an explanation for 110-26(A)(1). The problem is, the explanation for 110-26(A)(1) does not seem to address the exposed live parts on both sides that are effectively guarded by a barrier (Condition 1) scenario.

What does everyone think and can anyone direct me to a better explanation of which (and why) condition would apply.

Thanks in advance for your help,

Scott
 
is this installation subject to the constraints of the NEC ? if so, which code year version is in force ?
 
Condition 1 does not appear to apply to your installation...

Condition 1 does not appear to apply to your installation...

Steelhorst,

While over 600-volts is not where the bulk of my experience lies, I believe if you carefully read Condition 1 for Table 110.34(A), I believe you will find that Condition 1 does not appear to apply to your installation of facing switchgear with metallic (grounded) switchboard elclosures...


Condition 1 — Exposed live parts on one side of the working space
and no live or grounded parts on the other side of the working space,
or exposed live parts on both sides of the working space that are
effectively guarded by insulating materials.



...The "statement after the or" in Condition 1 does not appear to be helpful for you with metallic (grounded) enclosed switchboards on both sides of the working space...


I do hope this is helpful... (...I believe Camp 2 has nailed it... Are you in Camp 2 ??)

mweaver
 
Last edited:
mweaver said:
Steelhorst,

While over 600-volts is not where the bulk of my experience lies, I believe if you carefully read Condition 1 for Table 110.34(A), I believe you will find that Condition 1 does not appear to apply to your installation of facing switchgear with metallic (grounded) switchboard elclosures...


Condition 1 ? Exposed live parts on one side of the working space
and no live or grounded parts on the other side of the working space,
or exposed live parts on both sides of the working space that are
effectively guarded by insulating materials.

...The "statement after the or" in Condition 1 does not appear to be helpful for you with metallic (grounded) enclosed switchboards on both sides of the working space...


I do hope this is helpful... (...I believe Camp 2 has nailed it...)

mweaver
Click to expand...


Thanks mweaver,

Thanks for your input.

The condition 1 crowd are telling me it's the condition after the or "exposed live parts on both sides of the working space that are effectively guarded by insulating materials" that they feel applies.

I'm trying to stay neutral on this until I get further information, but their point is;

The "or" condition is specifically designed for this application otherwise why (or how) would it ever apply.

For that, I have no answer.

Any thoughts?
 
Scott,
Face to face equipment is condition 3. I base this on the rule in 110.26(A)(1)(c) that acts as an exception to the Table. Based on this wording, the code intends that face to face equipment be a condition 3 application. I know that this is in the under 600 volt section, but I think that the principle is the same for both voltages.
 
don_resqcapt19 said:
Scott,
Face to face equipment is condition 3. I base this on the rule in 110.26(A)(1)(c) that acts as an exception to the Table. Based on this wording, the code intends that face to face equipment be a condition 3 application. I know that this is in the under 600 volt section, but I think that the principle is the same for both voltages.
Click to expand...

Hi Don,

Another vote for condition 3. Not looking good for the camp 1 people.

Your code reference seems to indicate that condition 3 can be relaxed to condition 2 if a written procedure for maintenance is in place. Maybe this is a good compromise between the two camps?

Scott
 
Steelhorst,

As Don has noted, your installation falls under Condition 3.

Please Note:
The actual interpetation and enforcement of this requirement is subject to the AHJ.

.............................. ... After the fact, is not the time to be looking for that needed additional four feet of clearance...



In addition...
Excerpt from Section 110.34(A):
"... Distances shall be measured from the live parts, if such are
exposed, or from the enclosure front or opening if such
are enclosed...".

.............................. ...You in fact have exposed live parts on both sides of the working space...



I do hope this is helpful

mweaver
 
mweaver said:
Steelhorst,

As Don has noted, your installation falls under Condition 3.

Please Note:
The actual interpetation and enforcement of this requirement is subject to the AHJ.

.............................. ... After the fact, is not the time to be looking for that needed additional four feet of clearance...



In addition...
Excerpt from Section 110.34(A):
"... Distances shall be measured from the live parts, if such are
exposed, or from the enclosure front or opening if such
are enclosed...".

.............................. ...You in fact have exposed live parts on both sides of the working space...



I do hope this is helpful

mweaver
Click to expand...

Hi mweaver,

Thanks for the input.

The AHJ hasn't been much help in this situation.

Luckily we're still in the design phase so we're not in trouble yet. We have a budget bust, for our building of $750,000. We are trying to VE it to reduce the cost and one solution was making the building smaller by reducing clearances.

I haven't found a definitive answer as to when (or how) the condition one "or" statement applies but it sounds like we're going to need to find another way to cut costs.

If someone knows of paper or article that goes into more detail on this issue I would be interested in reading it.
 
I am in the "None of the Above" camp. :smile:

I submit, for your consideration, that the space between the two switchgears requires no working clearance at all! This is based only on your description, which may have left a relevant detail or two out. So I reserve the right to change my answer, without first having to change my mind. :roll:

If indeed there is no access to live parts from the front, then this is not a situation in which the first sentence of 110.34(A) applies. Working space is only required "in the direction of access to live parts."

That said, if you were to tell me that there are live parts accessible from the front of one of the switchgears, then I will reply that there are live parts accessible from the front of both. That brings us to Condition 3, and into Camp 2.

 
Thanks Charlie,

There are exposed live parts in the front BUT "they are effectively guarded by insulating material. I don't know how familiar you are with medium voltage switchgear but in this case it has a draw-out breaker. Live parts would be exposed IF the breaker was removed and the safety barriers have been tampered with to allow access.

I do like your suggestion of not putting any separation between them. It sure would reduce the footprint of our building. :) Of course I don't know how you'd ever turn things on or off.
 
Status
Not open for further replies.
Top