Computer Room UPS

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Brian D. Nagy

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I'm adding circuits to a computer room UPS system. I noticed from the initial installation that each circuit whether 120v or 208v was ran in a seperate conduit. I would like to just add my circuits into existing conduits - I've talked with UPS manufacturer and they indicated it was not an issue. There are two panels - A & B. Of course I will comply with conduit fill guidelines.

My questions:

1. Can I add a second circuit to these conduit runs (they are EMT to LFMC).
2. I will not mix 120v with 208v, but should I plan on keeping A panel circuits within the same conduit run and B panel circuits in the same conduit run.
 
Why would you not be able to add conductors to the pipes?Are you concerned about chaffing the existing conductors?I would re-pull all the conductors through the pipe.
Are the 120V and 208V from separate systems?Why else could you not mix the circuits?
Maybe there is something I missed.
 
One circuit per conduit seems very bizarre. Maybe someone had stock in the conduit company.

Technically, the code says all wires should be pulled into the conduit at the same time. But you could still pull the other circuits back, and then pull them all back in.

I'm wondering how often electricians ignore this rule in cases like this??
 
Jesse7623 said:
Why would you not be able to add conductors to the pipes?Are you concerned about chaffing the existing conductors?I would re-pull all the conductors through the pipe.
Are the 120V and 208V from separate systems?Why else could you not mix the circuits?
Maybe there is something I missed.
Click to expand...
= These may be considered seperate systems? 647.5 Three Phase Systems specifies "shall be configured as three seperately derived 120-volt single phase systems".
 
Remember to derate the conductor ampacity when more than 3 current carrying conductors in single conduit, per NEC Table 310.15(B)(2)(a).
 
Brian D. Nagy said:
- Are there any concerns about isolated phase installations 300.5 that talks about only one phase per raceway or 300.20 induced currents in metal raceways?
Click to expand...

Induced current on a raceway is caused by several things.one easy way to induce current is run the phase conductors in separate pipes but that would mean the neutral would have to be in a separate pipe.
 
Brian D. Nagy said:
I'm adding circuits to a computer room UPS system. I noticed from the initial installation that each circuit whether 120v or 208v was ran in a seperate conduit. I would like to just add my circuits into existing conduits - I've talked with UPS manufacturer and they indicated it was not an issue. There are two panels - A & B. Of course I will comply with conduit fill guidelines.

My questions:

1. Can I add a second circuit to these conduit runs (they are EMT to LFMC).
2. I will not mix 120v with 208v, but should I plan on keeping A panel circuits within the same conduit run and B panel circuits in the same conduit run.
Click to expand...

Since they originally paid for separate conduits, they must had a reason. The reason may not be Code related and sound like this addition is not under the same engineering supervision and review as the original installation was.

It would be prudent to follow the original installation practice. A penny saved may cause a pound woth of trouble, ususally long after the installer is gone....:smile:
 
weressl said:
Since they originally paid for separate conduits, they must had a reason. The reason may not be Code related and sound like this addition is not under the same engineering supervision and review as the original installation was.

It would be prudent to follow the original installation practice. A penny saved may cause a pound woth of trouble, ususally long after the installer is gone....:smile:
Click to expand...


That's good advise IMO.
 
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