200 Amp Service

[1793]

I have been asked to construct a 200 amp underground service.
Just wanted to run this by some of you. This is the first time I've been asked to submit a plan.

I'm thinking that I would trench 18" and run 2" Schedule 80 with 3 4/0AL runs. The distance is about 250 ft. from transformer to meter base. There could be as many as two 90's and one 45.

Any other thoughts or considerations that have forgotten would be greatly appreciated.

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[wirenut1980]

Re: 200 Amp Service

See Table 300.5 for coverage in your particular situation. Also check for any other local codes to adhere to, etc. I might be a little worried about fitting 3-4/0 conductors in 2" conduit with the bends and depending on the type of insulation of the wire (I am assuming you are running 3 parallel conduit runs). It looks like you are over-sizing the conductors maybe to comensate for voltage drop, but 3-4/0 runs for a 200 Amp service seems excessive. But to do a voltage drop calc, we need to know the service voltage. That is what I am thinking, but I am sure there is more...

I'm surprised the utility is not installing from the transformer to the meter??

[ November 05, 2004, 03:25 PM: Message edited by: wirenut1980 ]

 

[1793]

Re: 200 Amp Service

According to Table 310.15(B)(6) Al or CU Clad has a Service or Feeder rating of 200. I also used Table 310.16 4/0 THWN is rated @ 205. Have I missed something here?

I could run 21/2" for the conduit.
This is a detached garage.
240 Volt service

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[ November 05, 2004, 03:58 PM: Message edited by: 1793 ]

 

[wirenut1980]

Re: 200 Amp Service

Sorry, I thought you were planning on running three parallel 4/0 runs.

Wire size should be good for voltage drop, although it is pushing 5% if my calculations are correct. In using table 310.16, you quoted the Ampacity of 4/0 conductors from the 90 deg column. You can do that as long as all of terminations, connectors, etc are rated for that temperature, and the insulation of the wire you are actually using is 90 deg. You may also use that column if you are de-rating for any reason (which it looks like you are not), and then that de-rated ampacity cannot be greater than the ampacity of the temperature rating of the conductor you are actually using.

So unless you meet the requirements listed above, you may need to use the 75 deg or the 60 deg column ampacity for 4/0 Al which is 180 Amps or 150 Amps respectively. If your OCPD protecting that feeder is 200 Amps, then it might be a violation.

If I understand you, you are running feeder from a main panel to a sub-panel in a garage?

 

[luke warmwater]

Re: 200 Amp Service

18" is to the top of the conduit, so your trench will actually have to be deeper.

 

[kiloamp7]

Re: 200 Amp Service

I am not a contractor, but I like good old copper wire.

 

[1793]

Re: 200 Amp Service

luke warmwater:

Thanks I forgot to figure the diameter of the conduit.

I have had another thought, I have not yet looked into the material cost difference, I doubt it would take much longer trenching a little deeper and I thought I would use 3/0al USE direct burial at 24". This should be quicker to install. If anyone has done this before I would like to know how it worked for you. $$$$

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[hurk27]

Re: 200 Amp Service

By 1793: I thought I would use 3/0al USE

3/0 alu. can not be used for a 200 amp service.
Table 310.16 rates 3/0 USE ALU.@ 155 amps@75c. But table 310.15(B)(6) allows 175 amps rating for the same wire if this is a dwelling. so ether way you have to run at least 2/0 copper or 4/0 alu. Then go from there for voltage drop.

 

[1793]

Re: 200 Amp Service

I appreciate the input I've received. I thought the 3/0 alu was small for this application.

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[goldstar]

Re: 200 Amp Service

Most of the POCO's in my area allow you to use 2 wide sweep 90's and 1 45 degree fitting for an underground service. In addition, they require a concrete junction pull box for any runs over 150' between transformer and residence.

One final note - take a look at the KO's in your underground meter pan - I'm sure it can take up to a 3" conduit. If you have the $$$ in the job I would install a larger conduit than 2". Why kill yourself with the pull ???

 

[cclmcvay]

Re: 200 Amp Service

you might want to check with power company to see what max distance is that they will pull without setting pedestal.

 

[cclmcvay]

Re: 200 Amp Service

might also want to check with power company for pipe size. Ive learned different companys want different sizes. Some will call for 2in, some 2.5, and some even 3in. All for 200Amps