sercvice conductor size
- Thread starter tim
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Minuteman
Senior Member
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- The Sooner Nation
Re: sercvice conductor size
Tim
Table 310-16 in the 90* Column it
says that 500kcmil THHN is rated for 430 amps (Here we have to use the 75* column unless we have 90* lugs, and we (rarely have them).
Then Table C8, using the 500's, for single or 3 phase, you would need 3" GRC
Tim
Table 310-16 in the 90* Column it
says that 500kcmil THHN is rated for 430 amps (Here we have to use the 75* column unless we have 90* lugs, and we (rarely have them).
Then Table C8, using the 500's, for single or 3 phase, you would need 3" GRC
- Location
- Massachusetts
Re: sercvice conductor size
The service voltage is pretty much irrelevant.
We do need to know if it is single or 3 phase.
Assuming it is single phase you could fit six 4/0s in each conduit. I did not verify if you could still fit an EGC, I doubt it.
With derating you would end up with a total capacity of 832 amps.
If it is three phase I don't see it as a possible with only two 2.5" RMCs.
The service voltage is pretty much irrelevant.
We do need to know if it is single or 3 phase.
Assuming it is single phase you could fit six 4/0s in each conduit. I did not verify if you could still fit an EGC, I doubt it.
With derating you would end up with a total capacity of 832 amps.
If it is three phase I don't see it as a possible with only two 2.5" RMCs.
Minuteman
Senior Member
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- The Sooner Nation
Re: sercvice conductor size
I did not even think using the 4/0 since some people get all freaked out about harmonics. However, you shouldn't need a EGC in a service riser.
I did not even think using the 4/0 since some people get all freaked out about harmonics. However, you shouldn't need a EGC in a service riser.
- Location
- Massachusetts
Re: sercvice conductor size
Good point.
Minuteman
Senior Member
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- The Sooner Nation
Re: sercvice conductor size
So since I missed it on the 4/0's, that makes my average on this thread .500
So since I missed it on the 4/0's, that makes my average on this thread .500
- Location
- Massachusetts
Re: sercvice conductor size
Tim we are pretty good at helping here so if you want some more suggestions we need more info.
1)The Calculated load
2)Single or three phase
3)A general overview of what the job is.
There are a few 'tricks' that can be used in order to use smaller service conductors. But the calculated load must be know before they can be used.
In a nutshell the service conduits only need to be large enough for the calculated load not the total of the service disconnects if you use more than one.
As an example if you used two 400 amp service disconnects for this service and each was loaded to 300 amps the service conductors would only need to be rated 600 amps total.
Tim we are pretty good at helping here so if you want some more suggestions we need more info.
1)The Calculated load
2)Single or three phase
3)A general overview of what the job is.
There are a few 'tricks' that can be used in order to use smaller service conductors. But the calculated load must be know before they can be used.
In a nutshell the service conduits only need to be large enough for the calculated load not the total of the service disconnects if you use more than one.
As an example if you used two 400 amp service disconnects for this service and each was loaded to 300 amps the service conductors would only need to be rated 600 amps total.
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: sercvice conductor size
What would the size of the conductor have to do with harmonics, or with the price of Tea in Bulgaria, anyway?
Minuteman
Senior Member
- Location
- The Sooner Nation
Re: sercvice conductor size
Not just in this forum, but every time I have been in a conversation with PE's about parallel SERVICE conductors in the same conduit, the next thing that is said is, "Harmonics". So, I thought I would play it safe this time and not bring it up.
Re: sercvice conductor size
Minuteman, are you thinking about a 200% neutral (parallel wires for this conductor) which at times is used for installations where additive harmonics may be a concern on the grounded conductor?
Roger
Minuteman, are you thinking about a 200% neutral (parallel wires for this conductor) which at times is used for installations where additive harmonics may be a concern on the grounded conductor?
Roger
Minuteman
Senior Member
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- The Sooner Nation
- Location
- Massachusetts
Re: sercvice conductor size
Minuteman I think Roger nailed it.
Harmonics are not caused by running conductors in parallel.
However many times parallel neutrals are run as a way to prevent the effects of harmonics from overloading the neutral.
I followed your link and I see this.
What Pierre is talking about is this rule.
Read it slowly and carefully there is a lot of info in a short paragraph.
Feel free to ask more questions as we are talking about at least 5 separate issues here.
Harmonic Currents
Non-linear loads
Parallel conductors
'Super Neutrals'
Derating
[ January 04, 2006, 04:40 AM: Message edited by: iwire ]
Minuteman I think Roger nailed it.
Harmonics are not caused by running conductors in parallel.
However many times parallel neutrals are run as a way to prevent the effects of harmonics from overloading the neutral.
I followed your link and I see this.
Pierre probably did not notice that your installation was a single phase.
What Pierre is talking about is this rule.
Read it slowly and carefully there is a lot of info in a short paragraph.
What this is saying is if you had a 208Y/120 service or feeder that supplied a lot of nonlinear loads (think computers and other electronics) the neutral would have to be counted as a current carrying conductor for purposes of derating.
Feel free to ask more questions as we are talking about at least 5 separate issues here.
Harmonic Currents
Non-linear loads
Parallel conductors
'Super Neutrals'
Derating
[ January 04, 2006, 04:40 AM: Message edited by: iwire ]
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
- Location
- Massachusetts
Re: sercvice conductor size
If the load is above 760 you will need 600 Kcmil.
That will do it if the calculated load is less than 760 amps.
If the load is above 760 you will need 600 Kcmil.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: sercvice conductor size
Dang, you're quick. I barely had a chance to look at the book and you'd answered it.
(Tim, we're assuming you're using copper, correct?)
I'm kinda surprised that a load calc would come in for 760 amps for a 12-plex. Feasible, but I would like to hear what the calculated load is.
Dang, you're quick. I barely had a chance to look at the book and you'd answered it.
(Tim, we're assuming you're using copper, correct?)
I'm kinda surprised that a load calc would come in for 760 amps for a 12-plex. Feasible, but I would like to hear what the calculated load is.
Minuteman
Senior Member
- Location
- The Sooner Nation
Re: sercvice conductor size
Re-read my original post. The service I refer to was single phase. I upgraded it to 3 phase DELTA... Not wye.
My point has been over labored. But, all I was saying was... The Inspector, the City Engineer, the PE that I was referred to, and Pierre all brought up the question about harmonics. Not me.
True, there are still some single phase loads in my application. However, the topic in discussion is harmonics. We don't know enough about Tim's situation, whether he has single phase or 3 phase wye or delta. My suggestion was that if he had a 3" GRC he could have up to four 500 kcmil per riser to handle his service.
Thanks
Re-read my original post. The service I refer to was single phase. I upgraded it to 3 phase DELTA... Not wye.
My point has been over labored. But, all I was saying was... The Inspector, the City Engineer, the PE that I was referred to, and Pierre all brought up the question about harmonics. Not me.
True, there are still some single phase loads in my application. However, the topic in discussion is harmonics. We don't know enough about Tim's situation, whether he has single phase or 3 phase wye or delta. My suggestion was that if he had a 3" GRC he could have up to four 500 kcmil per riser to handle his service.
Thanks
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