I have three motors that need to be fed/stopped/started from and adjacent building.

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Rsteenson

Member
My customer has a grain elevator about thirty feet away from a large bagging warehouse (he owns both buildings). When he first put up the building the previous electrician fed the 200x100 building with 100 amps of 480v 3 phase. This summer we did a sizely expansion on the grain elevator side of things and i installed a new service and MCC. The adjacent bagging warehouse is fed underground (under concrete) and the pipe was stubbed up convieniently where i placed the new 1200 amp CT can. I decided to feed the old 100 amp panel straight from my ct can instead of feeding it from the new 800 amp mcc. My problem is that my customer has now added 3 motors in the bagging warehouse that are actually part of the milling process for the elevator building thirty feet away. (in a nutshell, its a dust system) Problems- #1. The 100 amp service to this building will not serve the needs of these new motors- furthermore i am going to run into classification issues if i have to change anything related to this service. #2. The equipment needs to be stopped and started from the elevator building anyways.
What nec issues will i run into with this application? I have read 225 and 230 and have a good guess what is going to have to happen but i would like some other opinions. Any insight would be great!
 

Rsteenson

Member
i think i could pull bigger wires if i absolutely had too but that would be a last resort. Im trying to stay away from altering the existing service in that building because there would need to be some major changes to bring it up to code (the last guy made some major screwups on his "classification" of equipment) Even if i were to install three motor buckets in the bagging warehouse i would still have to have the control wires from one building to the other which is the same problem as runnning the motor feeder from one building to the other. My concern isnt running the conduits and wires to the building....its that theres technically power from "two" different services in the building. Im kind of confused about the exceptions listed in 225 and 230 regarding doing this...Im kinda wondering if i just should call the AHJ and ask what he wants me to do? what do you think?
 

kwired

Electron manager
Location
NE Nebraska
How many meters? 1 or 2?
Sounds like 1 so only one service.

One service from utility, but he has service entrance conductors at each of the two buildings as each building is fed straight from the CT cabinet. Even if building two were supplied by a feeder from building one there is some problems though, first one is it can only be supplied by one feeder (225.30), so how do we interconnect control circuits between the two? The second paragraph of 225.30 may allow us to do this but the second circuit or feeder would need to be supplying power back to the first building. A person could also use wireless, ethernet, power line carrier communications devices, etc. to control equipment from another building and not have to worry about whether or not there is more than one feed to a second building, or find a way to tie the buildings together and call them a single building, but then you must eliminate the second service entrance location.
 

Smart $

Esteemed Member
Location
Ohio
... so how do we interconnect control circuits between the two? ...
IMO, control circuits aren't subject to 225.30. When run to a second building or structure, they do not supply that building or structure. To circumvent any doubt, simply implement 225.30(E) Documented Switching Procedures and include signage at remote control station(s) as to location of power source.

Another option is to use low voltage control (e.g. 24 or 48V)
 

kwired

Electron manager
Location
NE Nebraska
IMO, control circuits aren't subject to 225.30. When run to a second building or structure, they do not supply that building or structure. To circumvent any doubt, simply implement 225.30(E) Documented Switching Procedures and include signage at remote control station(s) as to location of power source.

Another option is to use low voltage control (e.g. 24 or 48V)

I don't think they should be either, but we have issues with simple three way switches between two buildings discussed here all the time. True the typical three way switch discussed is not normally a 725 control circuit, but is still another voltage source and can create a potential hazard when you thought all the power to the building was off - then you discover there is still a live circuit.

I think this is one reason you see more 24 volt controls today than you maybe used to, more relaxed requirements for the 24 volt circuit, ability to turn of parts of a system and not kill all the controls in the process - effectively killing the entire process.
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
Nec2002
225.3, he is on the line side, so 225.3 is about the load side of the main. One meter, one service, many laterals.
I too think controls are not "supplying" power.
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
225.30 b2
225.30d
225.30e
You should be able to do it one way or the other; your on the line side so 225.30 is not part of the problem. If you were on the load side then one of the above should work.
See 225.37 and 230.2
 
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kwired

Electron manager
Location
NE Nebraska
Nec2002
225.3, he is on the line side, so 225.3 is about the load side of the main. One meter, one service, many laterals.
I too think controls are not "supplying" power.

Controls are not "supplying power" I totally agree with. They are supplying voltage and any hazards that go with it to the second building.

225.31 does require disconnecting all ungrounded conductors that supply or pass through the building or structure, this would include control circuits IMO and help prevent exactly what I was concerned with, turning off the main power and finding out it does not kill everything. Is multiple disconnects acceptable to open any ungrounded control circuits that originate from another building? If so do they count toward the six allowed by 225.22. Is auxilary contacts on power disconnecting means acceptable to disconnect these conductors and not count toward 225.22 number of allowed disconnects?
 

Smart $

Esteemed Member
Location
Ohio
...

225.31 does require disconnecting all ungrounded conductors that supply or pass through the building or structure...
Well we've already established that the control circuits do not supply the building. I think I can also assume correctly that they do not pass through the building.

...this would include control circuits IMO and help prevent exactly what I was concerned with, turning off the main power and finding out it does not kill everything.
It is a concern, and that's why I recommended the document switching procedure and signage.

Is multiple disconnects acceptable to open any ungrounded control circuits that originate from another building? If so do they count toward the six allowed by 225.22. Is auxilary contacts on power disconnecting means acceptable to disconnect these conductors and not count toward 225.22 number of allowed disconnects?
See 225.32 Exception No. 1
 

kwired

Electron manager
Location
NE Nebraska
Well we've already established that the control circuits do not supply the building. I think I can also assume correctly that they do not pass through the building.


It is a concern, and that's why I recommended the document switching procedure and signage.


See 225.32 Exception No. 1
I like that but have yet to see anyplace that will meet all the requirements for the exception. Larger industries are more likely to at least even be aware of things like "documented safe switching procedures" but larger industries for work I do are not all that large, and maintenance people they do have are not that well educated about electrical - even if they think they are.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I like that but have yet to see anyplace that will meet all the requirements for the exception. Larger industries are more likely to at least even be aware of things like "documented safe switching procedures" but larger industries for work I do are not all that large, and maintenance people they do have are not that well educated about electrical - even if they think they are.
All that would be required is some signage to provide the "documented safe switching procedures". The EC could provide that.
 

Rsteenson

Member
Hey guys, Met with my inspector today and it went better than expected. He wants signage at both service disconnects....works out great!
 
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