3 phase y 100 amp subpanel.

[mdshunk]

Computer rooms often feature Liebert type cooling systems. If that happens to be the case, you're certainly need 3-phase.

 

[iwire]

Just won't be able to power any 3-phase loads.

And all circuit conductors leaving the panel will be current carrying conductors.

This may or may not be an issue depending how you feel about multi-wire branch circuits.

 

[Pierre C Belarge]

100 amp, 3 phase panel for a school computer room...quite the panel for such a load. Maybe you can run a smaller feeder size to the panel, thus the pull will not be as difficult.
I would find out from the school if SER is permitted by the school.
Without really knowing what the load is, I am going to guess that a 4 AWG CU may be large enough or 2 AWG Al supplying a 3 phase panel protected by a 70 amp Circuit breaker.

Set up some racks in the ceiling to pull thru and away you go. I hope you have some help for all of this, it sounds like you have a child in the school and may be helping out, Good Luck!

 

[ram11379]

I see so I will just be missing one leg of the power. Do I have to worry about unbalancing the 3 phase panel if I do this(going single phase)? By the way there will be about 30 computers and monitors and maybe a pribnter or two on this panel if that helps.

 

[bob]

Ram
You need to do a little calculation and determine what load you are expecting.
Are you only going to power only computers or is there other load?
I did a quick VD calculation using 50 amps per phase, 18 kva, an came up with the following:

Using 3 #3 AL VD = 3 volts drop line to neutral. 2 volts using #1 Cu
Using 3 # 1 AL VD = 2 volts drop line to neutral. 1 volts using #1 Cu.
Check the voltage at the existing panel. You don't want to start with Low
voltage at the source.
50 amps would seen more that enough load to estimate the VD if the load is
only computers. Your EGC conductor is based on the breaker size. I don't have my NEC book at this time.

Yes you need to balance the load.

 

[mdshunk]

Your EGC conductor is based on the breaker size.

Except for the fact that you've upsized due to voltage drop. Need to upsize that EGC too, which is where MC sometimes bites you.

 

[LarryFine]

What is the difference between se and ser?

SE is the typical bare strands wrapped around the insulated conductors, while SER has a bare conductor paralleled with the insulated conductors, because there is an insulated neutral separate from the bare conductor. This is why MD called it "subfeed cable".

Is #1 AL ok considering it is over 100' away?

That depends on (a) the current load and (b) the acceptable voltage drop.

And no the existing wiring is in pipe and armored cable.

That's for a reason, as MD also said.

I would bid based on FMC and THHN.

I can't imagine pulling aluminum anything through 160' of FMC.

He needs 5 conductors. Does they make SER with 5 conductors?

Absolutely. I have a partial roll I found abandoned at a jobsite. Three blacks, one black with a white stripe, and a bare, all #2 al. It's perfect for 3-phase use.

Ok as all the different options are coming in here... what wire size can we agree on considering the 160" run?

Again, depends on load and acceptable VD.

And am I correct in assuming I need 3 hots 1 neutral and 1 ground?

Yes, for 3-phase and beyond the main disconnect. The only way to eliminate the GEC is to use a wiring method that provides one.

For my buck I would install a 3 phase feeder and panel. For 1 extra conductor you'll get a 50% increase in 120 volt circuit capacity.

Absoloopy!

I honestly wasn't sure if I was going to run a 3 phase or single phase panel. I guess that is why I am here . If I go 3 wire w/g(single phase) I am limiting this panel to only 120 volt usage correct?

You mentoned only line-to-neutral loads anyway, but keep in mind that, for each phase wire you eliminate, the larger the remaining one(s) must be to provide the same amount of power.

Also still waiting on the opinions of WIRE SIZE.[/]

What will be your total load?

By the way thanks everyone for all the help.

You're welcome. :smile:

 

[iwire]

I have a partial roll I found abandoned at a jobsite. Three blacks, one black with a white stripe, and a bare, all #2 al. It's perfect for 3-phase use.

If you look close you will find a red stripe and a blue stripe as well as the white.

 

[chris kennedy]

I can't imagine pulling aluminum anything through 160' of FMC.

I never said AL. I use CU thhn and a man to shake the FMC while the fish tape goes through. Pull boxes? Yes!

 

[mdshunk]

I mostly use AL SE and SER. From time to time, when I get copper SE and SER, the phase conductors are sometimes black, solid red, and solid blue. Pretty nice stuff. Looks really neat hanging out of a weatherhead. Probably something only an electrician would appreciate. Just depends on what company that master spool of cable came from the day the supply house bought it, I suppose.

 

[LarryFine]

If you look close you will find a red stripe and a blue stripe as well as the white.

"Captain Kirk! I shall consider it!" ~ Bearded Spock in original Star Trek episode Mirror. Mirror

 

[iwire]

Evil Spock?

 

[kbsparky]

"Captain Kirk! I shall consider it!" ~ Bearded Spock in original Star Trek episode Mirror. Mirror

Since you mentioned "Mirror, Mirror," you should be aware that next week, on Monday, June 19 SciFi channel will be showing the Enterprise episodes that take place in the "alternate" universe -- complete with references to several eposides from the original series:

Mirror, Mirror
The Tholian Web
Arena

A must see for any original Trek fan!

 

[LarryFine]

Evil Spock?

You tell me:

 

[LarryFine]

. . . next week, on Monday, June 19 SciFi channel will be showing the Enterprise episodes that take place in the "alternate" universe -- complete with references to several eposides from the original series:

Mirror, Mirror
The Tholian Web
Arena

A must see for any original Trek fan!

Thanx!

Live long and prosper!

 

[nysprkdude]

This is a school?

Place of Assembly over 100 persons.

2005 Code could be OK with this if it met the criteria for type III, IV, or V construction.(NYS hasn't adopted 2005 code yet)

However, romex(non-mc) above a drop ceiling should be a no go as it would be considered "exposed to physical damage."

Pipe and THHN are the only proper way to do this install.

And if it can't be done right....walk away.