Tap with MCS panelboard.

[binwork91]

I have a project, tap conductor feeds a panelboard with MCS (molded case switch).

Is MCS a overcurrent protective device?

In my opinion, MCS is not a overcurrent protective device, it does not provide overcurrent protection, it only has a fixed instantaneous self-protecting trip element which may open the switch under high fault conditions, therefore, we can not use 10ft tap, 25ft tap rule to feeds a panelboard with MCS.

What is your opinion?

 

[electrofelon]

I have a project, tap conductor feeds a panelboard with MCS (molded case switch).

Is MCS a overcurrent protective device?

In my opinion, MCS is not a overcurrent protective device, it does not provide overcurrent protection, it only has a fixed instantaneous self-protecting trip element which may open the switch under high fault conditions, therefore, we can not use 10ft tap, 25ft tap rule to feeds a panelboard with MCS.

What is your opinion?

A molded case switch is just a switch. You need an OCPD at the termination of the tap conductors.

 

[charlie b]

Can you use conductors to feed the panelboard that are large enough to be protected by the upstream overcurrent device? In other words, can you make this not be a "tap"?

 

[binwork91]

Can you use conductors to feed the panelboard that are large enough to be protected by the upstream overcurrent device? In other words, can you make this not be a "tap"?

It is not my design, supply house provide the cutsheet for me to do the study, so I think change to MCB is easier.

Not sure which one is cheaper, "change 1set 3/0 cu to 1 set 500kcmil cu" vs "change MCS to MCB".

 

[petersonra]

A molded case switch is just a switch. You need an OCPD at the termination of the tap conductors.

It is not just a switch. It also has a magnetic trip, but no thermal trip. And I think the magnetic trip is a lot more than you would want.

I wonder why the supply house quoted such an odd beast. I don't think I have ever seen a mcs as a main for a panelboard

 

[binwork91]

I wonder why the supply house quoted such an odd beast. I don't think I have ever seen a mcs as a main for a panelboard

I think supply house follow the equipment schedule, and equipment schedule might have a typo. It shows as MCB panel, but with a note "MCB shall be Molded case switch".

 

[jim dungar]

It is not just a switch. It also has a magnetic trip, but no thermal trip. And I think the magnetic trip is a lot more than you would want.

I wonder why the supply house quoted such an odd beast. I don't think I have ever seen a mcs as a main for a panelboard

The magnetic trip setting is often at a self-protection level to provide a higher short circuit rating than a plain switch. I think UL introduced this about 10 or more years ago.

If have seen these used where someone wants a local disconnect, but they do not want the issues with having two OCPD in series.