MCC location

[Mila15]

I have a situation where LV-MCCs are installed in a structure with a skid/pumps. I couldn't tell for sure in the NEC what LV-MCC location requirements are. Even thought MCCs are located indoors, a possible leak from the skid could occur. My questions are:
1- Is there a minimum distance requirement that applies to the situation I described above?
2- Does the possibility of leak require that MCCs shall be rated for outdoor installation (NEMA-4 for example)?

The section in NEC that is most applicable is: 110.26.

Thanks!

 

[jraef]

As far as the NEC goes, if you follow the guidelines in 110.26 for working space etc., no problem. The onl;y place needing attention to leak possibility is the area 6ft above the MCC (or the celing, whichever is lower). But that does not excuse one from prudent consideration of the facts. If the potential volume of water that could build up in the room runs the risk of making contact with the bus bars (6-8" off the floor), then certainly that should be taken into consideration. But NEMA 4 would NOT protect you from that, it is not "submersible". NEMA 4 is for "hose down" installations where someone will be aiming a fire hose at it and you do not want to allow water inside around the gaskets. NEMA 3R would address falling / splashing water (wind driven rain), but only means that water that enters not be allowed to build up to the live electrical parts, so you have the same situation.

What is typically done is that the ME determines the maximum flood capacity of the piping system and requires a floor drain capable of allowing that flow to leave the space without building up in the time it takes for safety backup systems to stop the flood. In other words, this is not usually something the EE worries about, unless for some reason the ME cannot solve the problem.

I have run into that by the way. I had to put an MCC in a basement mechanical room at an old flour mill (outside of the hazardous area) but the mill had been built in a flood plain, so it was expected that it would occasionally flood to a maximum of 2 feet off the floor. I had them build a catwalk 2 feet off the floor, then used short (71") MCCs because the ceiling height was too low. I have also seen people specify MCCs where there is no vertical bus bar below a certain height off the floor, but I have never done that one. Makes no sense to me.


"Will work for salami"

 

[Padlock01]

Hi MichaelUSA
Not knowing the full application, what we do here in SA mining is for surface pumping of excess water in a Pit we have two Skids/Trailers one for the pumps
and the other for the MCC ( because of vibration), pump drives are coupled to the MCC via rubber cable and power plugs - Underground with moving skid pumps out on strike we use 11kV/550volt Minisubs feeding wall mounted starters all electrical equipment is rated IP65 with intrigal earth leakage cct breakers / core balance. Hope this is of interest.

 

[Mila15]

Thanks guys! That was helpful.