Control Panel

Status
Not open for further replies.

Byrd

New User
Location
Ohio
I have a 500A CB feeding a 300A contactor and from the contactor to the 250A softstart. Can the tap rule be applied to the conductors on the load side of the 500A breaker to the contactor and from the contactor to the softstart? The distance from the breaker to the contactor is less than 10ft and from the contactor to the softstart is less than 10ft. Or do I have to use the OCPD rating to size the conductors? I will be using a DLO conductor.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I don't find a clear cut answer as 240.21(B)(1)(b) states the conductors must not be less than the rating of the "device" at termination, however, 240.21(B)(2) does prohibit the tap conductors from extending beyond that device so, IMO, it is a violation.

Also note that DLO cable with that marking alone is not an Approved Art 310 wiring method. Be sure your cable is also rated as prescribed in 310.13

You entitled your thread "Control Panel". Keep in mind that actual "Control Panels" are often built to specifications other than the NEC and are often, and sometimes required, to be NRTL rated.
 
Last edited:

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have a 500A CB feeding a 300A contactor and from the contactor to the 250A softstart. Can the tap rule be applied to the conductors on the load side of the 500A breaker to the contactor and from the contactor to the softstart? The distance from the breaker to the contactor is less than 10ft and from the contactor to the softstart is less than 10ft. Or do I have to use the OCPD rating to size the conductors? I will be using a DLO conductor.

I do not think this is a tap. They are motor circuit conductors and there are rules for that found in article 430.

Taps have to terminate at an OCPD so it cannot be a tap.
 
Last edited:

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I have a 500A CB feeding a 300A contactor and from the contactor to the 250A softstart. Can the tap rule be applied to the conductors on the load side of the 500A breaker to the contactor and from the contactor to the softstart? The distance from the breaker to the contactor is less than 10ft and from the contactor to the softstart is less than 10ft. Or do I have to use the OCPD rating to size the conductors? I will be using a DLO conductor.
If this is your ENTIRE circuit (other than maybe a CPT), then it is a motor branch circuit. In that capacity, the CB is only providing the Short Circuit protection, over current is handled by the Over Load Relay, or in the case of a digital soft starter, the OL protection built-in to the soft starter. So your conductor rules are determined by the applicable parts of article 430.

But 2 other issues:

1) You say "soft start", not "soft starter" and there is a significant difference. A soft starter will have OL protection included, either internal digital OL protection, or an external OLR as part of the starter. There are, however, soft starts (no "er") that are intended for use BEHIND another electro-mechanical starter. They do NOT always have OL protection and it is sometimes not clear. Be careful.

2) DLO cable, while nice for being extra flexible, has a major flaw for something like this. The ONLY approved termination method is crimp lugs as far as I am aware. The standard mechanical lugs that will come on your breaker, contactor and soft starter will NOT be rated for use in terminating DLO cable.
 
Status
Not open for further replies.
Top