Working in a live Motor Control Center 480V 200 Amp

[Jraef]

Ok....maybe I have had experience with the ONLY non-removable buckets in existence. Several of our older pump stations have the main breaker hard-wired to the vertical bus behind the bucket. No way to remove it except de-energizing the MCC. Many are not in buckets at all, but are control cabinets with a fused disconnect in the same enclosure as the controls. Built in the 50's and 60's. As I stated before, troubleshooting a control circuit is often impossible unless the control is energized. Most are located in the same bucket as the 480 starters. Working in the now required PPE while doing so is EXTREMELY difficult, especially when using small tools or test leads. We do the best we can, but sometimes reality gets in the way. No more arguments from me, though. We all should know the rules and follow them. Nuff said.

I think he meant that comment about all MCC units being removable as a joke (good one by the way, I'll have to use that). What you are describing would fall just outside of his "some are easier than others" category.

Side story related to "some are easier than others".
I once did a project with an MCC lineup of 5kV 1000HP soft starters in 3 different pump stations. The specs called for providing two empty bays in the lineup for the "future addition of new soft starters". I put them on the end of the lineup, knowing full well what when the time came in the future, new starters would come in new structures, there is no such thing as an "open style" MV soft starter that can be mounted in the field into an existing box, because the main bus had to be removed and there would be too much liability for cable routing etc. on listed MV gear. The consultant, in his infinite wisdom, decided that he wanted the feeder switches on the end, so he made me change the "future unit" locations to the middle of the lineup. I warned him of the problem, he didn't seem to care. Flash forward 6 years, they finally released a contract to add those two new starters in each station. I work for a different company now and ours would not fit in that box, but I bid it anyway, figuring on adding them to the end with a transition section and moving the feeders in to the middle, re-pulling new conductors, running new conduits etc., the only way it COULD be done. I was way too high of course, but the poor guy that got the contract found out AFTER the fact that he could not do it the way the consultant had described it. They would NOT give him a change order, they said it was his responsibility to have understood the details. I hear he lost his ass on that contract.

 

[kwired]

My experience is primarily with units that are easy to remove - but if it can be assembled why can't it be disassembled? Now back to the fact that some are easier then others

 

[meternerd]

My experience is primarily with units that are easy to remove - but if it can be assembled why can't it be disassembled? Now back to the fact that some are easier then others

It can....but only by killing the entire MCC, which means no water to the beloved customers until you get the work done. Funny how people don't notice water until it isn't there!

 

[kwired]

It can....but only by killing the entire MCC, which means no water to the beloved customers until you get the work done. Funny how people don't notice water until it isn't there!

When you have a private well as your main water supply you get to experience that much more often then those on municipal water - and when there isn't any it usually also means a repair bill is coming where if you are on municipal water you are still paying for repairs - but you are doing it a little at a time, every month, and for the entire system, not just your individual tap onto the system.

 

[meternerd]

When you have a private well as your main water supply you get to experience that much more often then those on municipal water - and when there isn't any it usually also means a repair bill is coming where if you are on municipal water you are still paying for repairs - but you are doing it a little at a time, every month, and for the entire system, not just your individual tap onto the system.

Yup...was on a well in Alaska. Good water, though....no chlorine! I live in a mountain area where we have several subdivisions that are fed by deep wells and then the water is pumped uphill to tanks and booster pumps all the way to the top. 2000 ft climb. But....they only have one path. Water starts at the first booster station, then up to the next, then begins to split up. If either of the two lower stations is down, ALL of the upper tanks go dry. That's why they consider it a dire emergency if we kill the entire station for repairs. Bad design!

 

[kwired]

Yup...was on a well in Alaska. Good water, though....no chlorine! I live in a mountain area where we have several subdivisions that are fed by deep wells and then the water is pumped uphill to tanks and booster pumps all the way to the top. 2000 ft climb. But....they only have one path. Water starts at the first booster station, then up to the next, then begins to split up. If either of the two lower stations is down, ALL of the upper tanks go dry. That's why they consider it a dire emergency if we kill the entire station for repairs. Bad design!

How much reserve is in the tanks and how long can one afford a minor shut down? That is somewhat the concept behind any municipal system is that you at least have enough reserve for either short term power loss or temporary surges in consumption.

 

[meternerd]

How much reserve is in the tanks and how long can one afford a minor shut down? That is somewhat the concept behind any municipal system is that you at least have enough reserve for either short term power loss or temporary surges in consumption.

This is a resort area, so lots of second homeowners. Winter ski season is pretty busy, but water usage is lower. In summer such as 4th of July, reserve may be only a few hours. What we have done in the past if we have to kill the station is shut off the pumps for the lower tanks so they fill all the way up, then we have the shutdown long enough to rip out the bad MCC section and get it safe enough to run the other motors (3 per station). But that's a major deal, so fixing it without a shutdown makes us electricians way more popular.