It is my first time working with residential buildings especially of this magnitude. I'm looking into what options I have to achieve this. I am trying to run 120/208 single phase power from the meter bank (from basement) to each apartment in a high rise. There are around 140+ apartments in this building. Is it permissible to use a long vertical wire trough going from the basement to each floor in a high rise building? I know we would have to derate if there's more than 30 current carrying conductors so I'm planning on adding more long vertical wire troughs to accommodate that. Another issue I have with this is supporting the conductors. How is what I'm trying to achieve typically done? Are there better ways to achieve this? What really are my options? Thanks for your input!
Running raceways from meter bank to apartments in high rise building
- Thread starter Tainted
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Are all of the meter banks in one location? How are you planning to transition from the wireway to each apartment location? Personally I would not run these risers in a wireway.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
What sizes are we talking about? I am assuming there will be some upsizing of the farthest ones for voltage drop? Have you been provided with a Chase or conduits through the floors?
I have never done anything like this so I fully admit I do not have any first-hand experience but AL MC cable jumps out at me.
I have never done anything like this so I fully admit I do not have any first-hand experience but AL MC cable jumps out at me.
I am working with a building architect and he just wanted to know what size my vertical raceway should be. Perhaps he will make me some kind of wall to put all my wires in. The services for the apartments are like 100-125A each. I would still have to derate with Al MC cable? I am trying to minimize derating and the amount of vertical wire troughs
It goes from EMT conduits from meter bank to wire trough riser. I personally wouldn’t too but the architect was asking me what size raceway riser I would need to achieve this, basically I told him I would need some time to figure that out.
Last edited:
I'm actually curious about another aspect of the job.
Most of the multi-apartment meter banks I see have (1) breaker supplying loadcenters in/at each unit.
What size are thee new circuits and how are you supplying them from the meter bank ??
Most of the multi-apartment meter banks I see have (1) breaker supplying loadcenters in/at each unit.
What size are thee new circuits and how are you supplying them from the meter bank ??
This is correct, all the meter bank are in a single room, each unit has a dedicated breaker at the meter bank. The sizes range from 100A to 125A. 100A would be #4 wires minimum and 125A is #2 wires minimum. If voltage drop occurs they would be 1 size larger
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
You would only have to derate if the multiple MC cables are installed "without maintaining spacing for continuous length longer than 24 inches". Because this is 120/208, you would have 3 CCC in each cable and you would have to do the math to figure out the specifics of the derating and how many you could bundle together. If some of these cables are going to be upsized for voltage drop, then the derating may not be an issue but you would have to run the numbers.
perhaps you could fasten them in bundles with something to maintain spacing between the cables so the derating wouldn't apply. maybe someone else who does these types of buildings has some tips on this, I would think this would be a common thing in such buildings.
Your solution seems interesting. I read somewhere that if you have 20 CCC bundled with MC cable you would need to derate to 60%? This means I can put up to 6 circuits bundled up together without derating?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
You are likely referring to exception 5 to 310.15(B)(2) which only applies to cables with 12 AWG copper.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
If you used 1/0 AL, you could bundle 3 cables together and still end up with a 125A feeder (depending what the calculated load is). Not sure how much real estate you have to work with but maybe put up some strut and zip tie bundles of 3 to the strut. If you had say 36 in wide, I imagine you could get 12 bundles of 3....then stack another layer of strut over that and repeat. If you end up getting into 4/0 for voltage drop reasons on the longer runs (no idea, just a WAG) then the flood gates open on those and you can bundle 20 cables together without issue.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Since you're leaving the meter with EMT then I would run the entire riser in EMT. IMO a wireway for this type of application is a poor choice.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I am not really clear on the "It goes from EMT conduits from meter bank to wire trough riser" part - whether that is existing or proposed. I agree though I am no t really seeing the wireway as being economical. You only get 10 units per wireway and that is a lot of labor and materials to install all that wireway.
MC cable is probably the most cost effective and its just a matter of figuring out the securing and supporting detail without getting into severe derating. I ran AL feeder MC exposed on strut with strut clamps throughout a mill building once, but for the number of cables the OP is talking about, I'm sure individual strapping of each cable to strut isnt going to be practical which is why I proposed groups of 3.
Everything is proposed. I think the architect is planning on making me some kind of wall riser to run all the feeds. So the architect wants to know how much space I would need depending on all my feed requirements. Supporting feeds in enclosed wall riser is a tricky one too. By the way how did you determine 1/0 MC cable cable can bundle up to 3 at 120/208?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Neutral counts as a CCC for single phase 120/208 so in this case 3 cables is CCC if we bundle 3 cables together, which requires a derating of .7. We can derate from the 90 degree column which is 135 X .7 = 94.5. Now we get to use the 83% rule so using that and next size up you can get it up to a 125A OCPD.
I see, I usually spec for 90 degrees C but use the 75 degree column if it's more than 100A.
Last edited:
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
In practice, these days all conductors will be rated 90 degrees, and all terminations will be rated 75. Although we are limited to the 75 degree ampacity for terminations, we can derate from the 90 degree value.
I see, also, instead of MC cable could I just use EMT and stack multiple struts and have architect enclose them with a wall riser?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Can 240.4(B) be combined with 310.15(B)(7)? That's not clear to me from the wordings.
Cheers, Wayne
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Ya know Wayne I did have the same concern. They use the term "feeder rated....." So it's not really clear if you have to start with a standard size OCPD and work back from there. Or is the "feeder rating" the "normal" ampacity?
- Status