230.71(A)

[jaggedben]

...

Existing installations are just that, existing.

Seems like people keep missing the point.

Suppose I have an existing MLO meter main with one service disconnect, built to accommodate up to six. I want to add a second service disconnect. Does the 2020 code allow this? If not, seems pretty unfair. Now we have all the safety issues involved in replacing a service, when we didn't have that before. Especially for resi services, with non CT meters. Heck, just pull the meter if you need to de-energize. Heck of a lot safer than replacing the service panel, whether it is a trained lineman disconnecting the drop or a risk-taking EC cutting it, like they pretty much make you do in some places.

I will start a new thread in proposals forum about this, and post a link when I've done so.

 

[tortuga]

It is driven by 70E in an attempt to limit incident energy and exposure to line side energized parts.

Ahhh then there should be an exception for single phase equipment as there is not even an IEEE guide for that, or at least exempt 240 V and below unless it involves at least one 125 kVA or larger low transformer.

 

[jim dungar]

Ahhh then there should be an exception for single phase equipment as there is not even an IEEE guide for that, or at least exempt 240 V and below unless it involves at least one 125 kVA or larger low transformer.

NFPA70E does not exempt single phase systems from Arc Flash analysis. You just cannot simply use IEEE-1584 as you can with three phase systems.

The 125kVA and smaller 'exception' was removed from IEEE-1584 in the 2018. Effectively it was changed to 2,000A of fault current or less.

 

[tortuga]

NFPA70E does not exempt single phase systems from Arc Flash analysis. You just cannot simply use IEEE-1584 as you can with three phase systems.

The 125kVA and smaller 'exception' was removed from IEEE-1584 in the 2018. Effectively it was changed to 2,000A of fault current or less.

Thats interesting, again I wonder why and if there is an outbreak of single phase accidents or something?
I am not on the 1584-2018 yet. I wonder what the Basic Equation formula they published for 120/240V single phase is?

 

[kwired]

Thats interesting, again I wonder why and if there is an outbreak of single phase accidents or something?
I am not on the 1584-2018 yet. I wonder what the Basic Equation formula they published for 120/240V single phase is?

My guess is the majority of industrial single phase systems are rather low incident energy, more likely to be control circuit systems.

But there is a lot of light industrial/light commercial that are supplied with single phase and large enough sources that you may have higher incident energy at least at your service equipment.

 

[tortuga]

My guess is the majority of industrial single phase systems are rather low incident energy, more likely to be control circuit systems.

But there is a lot of light industrial/light commercial that are supplied with single phase and large enough sources that you may have higher incident energy at least at your service equipment.

Well I took a look at the new version of IEEE 1584-2018 today and section 4.11 states:

4.11 Single-phase systems
This model does not cover single-phase systems. Arc-flash incident energy testing for single-phase systems
has not been researched with enough detail to determine a method for estimating the incident energy.

I remain skeptical.

 

[kwired]

Well I took a look at the new version of IEEE 1584-2018 today and section 4.11 states:


I remain skeptical.

skeptical of what? It doesn't say there is no risk, just that it hasn't been investigated well enough that they chose not to publish any information on it.

 

[tortuga]

skeptical of what? It doesn't say there is no risk, just that it hasn't been investigated well enough that they chose not to publish any information on it.

I am skeptical that the requirement for a single main disconnecting means will enhance the safety of services.
No incident reports were mentioned, like with AFCI's there were tons of residential fires that started in bedrooms.
Huge costs will result to all services with substantiation of need only demonstrated for large 3 phase systems .
UL 891, defines a switchboard enclosure to include all of the vertical sections within the stack. Each stack is a complete electrical
enclosure. Changing 230.71 will add a huge cost switchgear installs.

From the Statement of Problem and Substantiation for Public Input

The six main rule for a single enclosure makes it impossible to work in service equipment when applying electrical safe work practices in accordance with NFPA 70E.

That statement is not true for 240V single phase systems less than 125kVA. I can model a typical farm 800A single phase service with 6 main disconnects in a Siemens P4 panel-board, 200' from the power pole and maintain NFPA-70E, easily.

 

[kwired]

I am skeptical that the requirement for a single main disconnecting means will enhance the safety of services.
No incident reports were mentioned, like with AFCI's there were tons of residential fires that started in bedrooms.
Huge costs will result to all services with substantiation of need only demonstrated for large 3 phase systems .
UL 891, defines a switchboard enclosure to include all of the vertical sections within the stack. Each stack is a complete electrical
enclosure. Changing 230.71 will add a huge cost switchgear installs.

From the Statement of Problem and Substantiation for Public Input

That statement is not true for 240V single phase systems less than 125kVA. I can model a typical farm 800A single phase service with 6 main disconnects in a Siemens P4 panel-board, 200' from the power pole and maintain NFPA-70E, easily.

It is not impossible to work in any six main equipment and comply with 70E. May be inconvenient but not impossible. If anything the supply can be killed.

Good design might mean designing it so you don't have to kill everything to work on it and may drive cost up anyway.