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Discussion Starter · #1 ·
I got asked to install three 240v/30a circuits for some computer equipment. Total distance will be 350ft from breaker to outlet. I'm thinking 8g stranded to be safe, so a total of 10 wires. My thought would be to use 1 1/2" EMT. Or should I break it up over two 3/4"? Been awhile for me on this so just need a little confirmation. Thanks
 

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Estwing magic
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Two sticks of 3/4 are half the price of one stick of 1 1/2.

Hang on, you’re pulling neutrals as well. That means six #8’s in a 3/4” conduit. Not good.
 

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Is it just computer equipment or could it be considered a DATA room?
 

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Discussion Starter · #5 ·
Two sticks of 3/4 are half the price of one stick of 1 1/2.

Hang on, you’re pulling neutrals as well. That means six #8’s in a 3/4” conduit. Not good.
I just got updated info, 120vlt not 240. So it'll be 7 total. That will fit in an 1".

Material cost is of no concern... This client supplies whatever I request without question. I just normally handle low voltage now days but they bugged me on this one and I figured it shouldn't be too bad.
 

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You will want to up your wire size. You say a 30A circuit so I am assuming a max 24A continuous load. I'm coming up with a #2 copper to maintain a 3% voltage drop. Will that be acceptable?
We are wrapping up a server project right now with maximum 1% voltage drop requirements. We had a similar situation to yours in needing to feed 3 120V 30A circuits at about the same distance.
We ended up setting a small panel there as it allowed us to calculate the VD as a 3 phase feeder and we used a smaller wire size than if we had done individual runs with separate nuetrals.

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Discussion Starter · #7 · (Edited)
You will want to up your wire size. You say a 30A circuit so I am assuming a max 24A continuous load. I'm coming up with a #2 copper to maintain a 3% voltage drop. Will that be acceptable?
We are wrapping up a server project right now with maximum 1% voltage drop requirements. We had a similar situation to yours in needing to feed 3 120V 30A circuits at about the same distance.
We ended up setting a small panel there as it allowed us to calculate the VD as a 3 phase feeder and we used a smaller wire size than if we had done individual runs with separate nuetrals.

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I'll have to look at my numbers again, 2g would be some serious wire. I couldn't do a sub panel as where there is and the environment won't allow it.

Edit: Ouch, you're right. Not sure what I was looking at for numbers. 7x2g it is...
 

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I ran the numbers on the #8s using the Southwire voltage drop app and got 10.2% drop. That was assuming a 24A load.

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Discussion Starter · #9 ·
I ran the numbers on the #8s using the Southwire voltage drop app and got 10.2% drop. That was assuming a 24A load.

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I sent a message to the client asking for device specifics. Maybe it'll run off 240v just fine. That would let me use 6g and 1 1/4" pipe. Cost isn't a factor but I rather bend 1 1/4 than 2".
 

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More than 3 current carrying conductors you will have to derate also!! Sell them on installing a sub panel
 

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Discussion Starter · #11 ·
More than 3 current carrying conductors you will have to derate also!! Sell them on installing a sub panel
I haven't done much with 3 phase though. Site is 3 phase with 208/120. Not sure how to size a 3 phase panel to be honest, last time I messed with it was when I was in the military running base power. They said no to running 208. So it'll probably be 2g and whole ton of pipe.
 

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If you run separate circuits use dedicated neutrals and not multi wire circuits. Does the equipment actually need 24/30 amps or does it draw 15 amps? Often times they are boiler plate specs that are over engineered. To illustrate, many people here use the 300 amp meter pans for 400 amp services.
 

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Discussion Starter · #13 ·
If you run separate circuits use dedicated neutrals and not multi wire circuits. Does the equipment actually need 24/30 amps or does it draw 15 amps? Often times they are boiler plate specs that are over engineered. To illustrate, many people here use the 300 amp meter pans for 400 amp services.
I can't say for sure but the spec sheet calls for 3x 120 volt 30 amp outlets. It's for some battery backups. This is a retail store and everything is decided on a corporate level. My job is to figure out how to make what they want work locally. I doubt corporate would allow a sub panel. All the panels have to be installed in the electric room, way way in the back. Outlets are going out front.
 

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I haven't done much with 3 phase though. Site is 3 phase with 208/120. Not sure how to size a 3 phase panel to be honest, last time I messed with it was when I was in the military running base power. They said no to running 208. So it'll probably be 2g and whole ton of pipe.
Regardless of phase, the code still requires derating for more than 3 current conductors in a conduit. If you opt to run branch circuits to the data room, you stated multiple circuits. Any wire carrying current including a Neutral on a 120v circuit will need to be derated if more than 3. If you run two single phase 208v circuits...that is four current carrying conductors and should be derated.
Technically it is not the electricians job to size a panel and feeders, it is the engineers job. Is this a job with drawings, or just a customer of your's requesting work?
 

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Discussion Starter · #15 ·
Regardless of phase, the code still requires derating for more than 3 current conductors in a conduit. If you opt to run branch circuits to the data room, you stated multiple circuits. Any wire carrying current including a Neutral on a 120v circuit will need to be derated if more than 3. If you run two single phase 208v circuits...that is four current carrying conductors and should be derated.
Technically it is not the electricians job to size a panel and feeders, it is the engineers job. Is this a job with drawings, or just a customer of your's requesting work?
Well if I go with 2g I don't think derating will mater. 2g is rated for something like 130amps, even if I had to derate to 50% I'd still be fine.

This is for a retail client. All we get is a blueprint and told where they need the outlets. It's about 350ft from panel to location. I might pass on this one, I think it might be way more involved than I thought.
 

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This is for a retail client. All we get is a blueprint and told where they need the outlets. It's about 350ft from panel to location. I might pass on this one, I think it might be way more involved than I thought.
If this is a good client, I would not pass on this job. It's not that involved, just bigger wire than usual. The client seems to trust you and if you send them elsewhere they may wind up liking the next guy a little better than you. Take care of your customers and they take care of you.
 

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If this is a good client, I would not pass on this job. It's not that involved, just bigger wire than usual. The client seems to trust you and if you send them elsewhere they may wind up liking the next guy a little better than you. Take care of your customers and they take care of you.
I completely agree. If it’s a good customer and they’re bugging him to do the job, why give the business to someone else? It’s only work, nothing complicated.
 

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I agree with oldsparky. Make them happy. Arm yourself with all of the info you need to sound professional to sell them on their best option. Show them your recommendations are not just about money for you...but the best option for them explaining the pros and cons of both, and mentioning that in the future they may need more circuits...so sub would be better option. Make sure they have sufficient AC in this data room. Often this is overlooked and can make yourself look better too by pointing out to them if they do not have it. Best of luck to you Sir!
 

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Discussion Starter · #19 ·
If this is a good client, I would not pass on this job. It's not that involved, just bigger wire than usual. The client seems to trust you and if you send them elsewhere they may wind up liking the next guy a little better than you. Take care of your customers and they take care of you.
Well I got an email from the project manager. He said they just want to use 8g and will be fine with 90-100v at the outlet. Personally I don't think that's a good idea. But guess how all their other stores have been done.
 
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