Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Can MCC section be either bus or cable tied together or usually bus tied? Thanks.
MCC's
- Thread starter Alwayslearningelec
- Start date
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Could an MCC actually come in 21 separate sections?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
To your first question: no, unless you specify that you want lugs at the ends of each section. You cannot just slap some wires on the ends of the bus bars. Those lugs will then take up unit spaces.
To your second question: technically yes, and I’ve done it, but it’s a really bad idea. MCCs are typically split up into “shipping splits” of 3-4 sections max., that come with bus splice kits to join the main horizontal bus bars together in the field. Most manufacturers will say there is a finite limit to the number of bus splices in a lineup without requiring engineering review, which means someone will try to talk you out of it. The problem is that each bus splice is a field connection and therefore a possible point out failure door to installation errors, plus even if done perfectly, there is still a small amount of resistance. That is a low probability of failure, but the more splices you have, the higher that probability becomes.
On one of my projects, we had to lower the MCC sections down into an underground vault, one section at a time due to the size of the access hatch. There were 23 sections total so 22 splice kits. Allen Bradley had a limit of 8 bus splices max, do they went into cardiac arrest and I had to convince a factory engineer that I knew what we were doing, they eventually allowed it. That was a nightmare of a project and I would never do it again, but it all eventually worked out and has been running for about 12 years now without issues.
To your second question: technically yes, and I’ve done it, but it’s a really bad idea. MCCs are typically split up into “shipping splits” of 3-4 sections max., that come with bus splice kits to join the main horizontal bus bars together in the field. Most manufacturers will say there is a finite limit to the number of bus splices in a lineup without requiring engineering review, which means someone will try to talk you out of it. The problem is that each bus splice is a field connection and therefore a possible point out failure door to installation errors, plus even if done perfectly, there is still a small amount of resistance. That is a low probability of failure, but the more splices you have, the higher that probability becomes.
On one of my projects, we had to lower the MCC sections down into an underground vault, one section at a time due to the size of the access hatch. There were 23 sections total so 22 splice kits. Allen Bradley had a limit of 8 bus splices max, do they went into cardiac arrest and I had to convince a factory engineer that I knew what we were doing, they eventually allowed it. That was a nightmare of a project and I would never do it again, but it all eventually worked out and has been running for about 12 years now without issues.