Disconnect

[ohmhead]

Have a question does a 3 phase 480 volt fused disconnect mounted on a wall 8ft high need the 30 inch working space like a panel per the NEC ?

This is a elect rolling door in a commercial building it has a motor control box mounted below the disconnect on the wall.

These would both be accessed using a ladder .

 

[kingpb]

You need the 3 to 3.5ft clearance in front (Condition 1 or 2) and you need the 90 deg open with 30 inches wide. You also need the clear space from the floor to equipment, except where other electrical equipment mounted below does not extend more than 6 inches farther out than the front of the disconnect.

110.26

 

[ohmhead]

You need the 3 to 3.5ft clearance in front (Condition 1 or 2) and you need the 90 deg open with 30 inches wide. You also need the clear space from the floor to equipment, except where other electrical equipment mounted below does not extend more than 6 inches farther out than the front of the disconnect.

110.26

What if it was just a non fused switch with out the need to service it ?

 

[jrannis]

What if it was just a non fused switch with out the need to service it ?

Would you be able to open the door of that 480 volt fused disconnect while it was energized?

 

[Smart $]

Would you be able to open the door of that 480 volt fused disconnect while it was energized?

I think the point of his question is that it would never be necessary to open the door while energized.

IMO, for a non-fused disconnect, the working space requirements of 110.26(A) are moot as long the location permits "ready and safe operation" under 110.26 general statement.

 

[infinity]

Why would the presence of fuses matter? Couldn't they be tested when the fuse disconnect was de-energized?

 

[Smart $]

Why would the presence of fuses matter? Couldn't they be tested when the fuse disconnect was de-energized?

Yes, they could. :happyyes:

JMO they would NOT be "likely to require examination, adjustment, servicing, or maintenance while energized". Of course that will be subject to the mentality of whomever is doing the "examination, adjustment, servicing, or maintenance". Not everyone thinks de-energize before proceeding... though they very well should.

Also JMO, the working space requirement is mostly applicable only to equipment with multiple circuits or load management schema which intensifies the likelihood to examine, adjust, service, or maintain while energized. Physically isolated, one-circuit supply switching and fusing does not fit that description (other than a service disconnect, which is not so easily de-energized).

 

[don_resqcapt19]

... Not everyone thinks de-energize before proceeding... though they very well should. ...

That is exactly why my opinion is that all electrical equipment will be worked on while energized and that 110.26 applies to all electrical equipment. (yes, I am well aware that it is impossible to apply the 110.26 work spaces to all electrical equipment)

 

[infinity]

This section is so ambiguous that you would literally need to get AHJ approval before you could install anything otherwise you run the risk of having someone who uses Don's interpretation and have to deal with that after the fact. This enter concept of working space and testing needs to be clarified and then re-written. This notion of an overly broad, one size fits all statement is problematic.

 

[iwire]

It is my opinion that the word 'requires' is in that section for a reason and little electrical equipment requires servicing while energized.

 

[iwire]

That is exactly why my opinion is that all electrical equipment will be worked on while energized and that 110.26 applies to all electrical equipment. (yes, I am well aware that it is impossible to apply the 110.26 work spaces to all electrical equipment)

Is a disconnect likely to require servicing while live or is that simply a lazy choice by the person testing?

 

[Dennis Alwon]

This came up last week and the member that answered it was adamant that the disconnects need to have the clearance. They even stated above a hung ceiling the clearances were required because most contractors would not shut the power off. It is true-- when I test the equipment the first thing I do is open the disconnect and check that there is power going to the unit. I would not change the fuses with the power on unless the disconnect killed the line side of the fuses as well.

 

[kwired]

Is a disconnect likely to require servicing while live or is that simply a lazy choice by the person testing?

Probably the lazy choice .... but we still need the AHJ to approve the location based on his interpretation of the rule.

This came up last week and the member that answered it was adamant that the disconnects need to have the clearance. They even stated above a hung ceiling the clearances were required because most contractors would not shut the power off. It is true-- when I test the equipment the first thing I do is open the disconnect and check that there is power going to the unit. I would not change the fuses with the power on unless the disconnect killed the line side of the fuses as well.

But isn't that voltage check you do first thing considered "examination", and according to most safety procedures isn't it considered to be live until the voltage test has been completed and it has been determined there is no voltage?

Then comes the fact that if you don't turn off the upstream supply there is still voltage in there on the line side terminals.

Many people will test for proper voltage at such a disconnect as one of their first steps of troubleshooting to determine if they need to be looking at the supplied equipment or upstream in the distribution when there is a problem.

 

[iwire]

This came up last week and the member that answered it was adamant that the disconnects need to have the clearance. They even stated above a hung ceiling the clearances were required because most contractors would not shut the power off.

That member is not thinking it through.

It is impossible to provide all the clearances required by 100.26 to equipment above suspended ceilings.

 

[kwired]

That member is not thinking it through.

It is impossible to provide all the clearances required by 100.26 to equipment above suspended ceilings.

Well at least most of the time it isn't possible, I can think of at least one place I have been where it may be possible, the height may still be a little low but was a place where you actually walked around in the ceiling space instead of using a ladder/lift from below.

 

[don_resqcapt19]

Is a disconnect likely to require servicing while live or is that simply a lazy choice by the person testing?

If it is simply a choice issue, then we can completely get rid of 110.26(A) as there are always ways to do the work, even if the work is troubleshooting, with the circuit de-energized.

 

[don_resqcapt19]

That member is not thinking it through.

It is impossible to provide all the clearances required by 100.26 to equipment above suspended ceilings.

That is correct, that for the most part, providing the required work space is impossible in an area like that, but where is the exception that says we don't need the required work space?
As I have said many times this section is unworkable as currently written and needs major changes, but the CMP refuses to accept changes.

 

[iwire]

That is correct, that for the most part, providing the required work space is impossible in an area like that, but where is the exception that says we don't need the required work space?
As I have said many times this section is unworkable as currently written and needs major changes, but the CMP refuses to accept changes.

I really don't think we disagree here.

The same question applies to counter receptacles.