300Amp Challenge

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How much work would it be to bust the slab and add another conduit? What are the distances involved here? Couple feet, 50ft, 75ft?? What I'm getting at is, is it cheaper for you to do that or have another pipe bored underground so you can run parallel or just bore in a bigger pipe?
 
Chris it is way more profitable to set a sub panel..You need to be a salesman here..you need to go to the HO and explain the math and the dollars involved with the math..You do not need to do a whole house generator set..You can go and create a punch list and set a sub panel and use a manual genset system you could still supply all of the critical circuits and some of the non critical circuits..in the mean time you sell some extra equipment and get a good job out of it..So you can give him all of his options I would assume if he contacted you with some PR work you could land a nice job here..

edited to add: you do not need to run the generator at 100% load if you size the load to less than what the generator can produce you are oaky..size the conductors to a 250 and use appropriate over current protection..
 
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Ok I know I'm stretching it here but how about this.

Use the 90 deg column and drop down to 300kcmil. You would have 320 amps. You would need to check your lugs for temp rating. You may even have to junction up to 350kcmil after leaving the 2" in order to land on a 75 deg lug or device.

If your going to a disco you may not have to drop to 300kcmil.
 
We did a 1200 amp service and installed an energy management system in. The generator guys installed a 100kw generator that wired the entire estate (all 1200 amps).

An energy management system may cost about $2000.00 or a bit more (around here) but it would be cheaper than tearing up the concrete.
 
Chris, Did you check out the compact conductors table C10A. It shows 3- 350kcmil in a 2" and 7-2/0 in a 2".

Rick
 
RUWired said:
Chris, Did you check out the compact conductors table C10A. It shows 3- 350kcmil in a 2" and 7-2/0 in a 2".

Rick
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I did not. I will. Some good stuff here kids, thank you all. For those that have posted cost effective type post, thanks again but this was posted in the NEC Forum. This is not my job and I have not nor will I be likely to ever see this install.

This thread was posted as a NEC challenge, like Challenge X. The winning entry will receive the $2 the DA is sending me.(don't hold your breath):grin:
 
Okay, a really unorthodox idea:

Run only 240v with no neutral and install a 240v-to-120/240v transformer to derive a new neutral at the load end.
 
LarryFine said:
Okay, a really unorthodox idea:

Run only 240v with no neutral and install a 240v-to-120/240v transformer to derive a new neutral at the load end.
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That's called "thinking outside the box" in modern parlance. :cool:
 
I have just skimmed this thread but if this generator is supplying the entire dwelling why not use Table 310.15(B)(6)?

It would not be a fun pull but you could get 3 ? 250 THWN and 1 - #3 in the 2? SCH 40 PVC. XHHW would be even slightly smaller.
 
curt swartz said:
I have just skimmed this thread but if this generator is supplying the entire dwelling why not use Table 310.15(B)(6)?

It would not be a fun pull but you could get 3 ? 250 THWN and 1 - #3 in the 2? SCH 40 PVC. XHHW would be even slightly smaller.
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It is a 600 amp service with a 300 amp trany. The trany is only doing part of the load.
 
If the transfer is interrupting the entire utility feed to the house then the generator would be supplying the entire load. When the transfer switch is in the ?generator position? the service would now be 300 amps.
 
What size generator is it? (kW/kVA)
Is the 300A rounded up from 125% the full kVA of the genny at .8pf?
(300A genny doesn't tell us much(enough))
 
If the conduits stub up not to far from the edge of the pad, I would try to core a hole for a new conduit and dig out from the side and try to get a new elbow under the pad. This way you dont have to bust up the pad and there is no patching needed.
The only problem might be with compaction under the pad.
 
wasasparky said:
What size generator is it? (kW/kVA)
Is the 300A rounded up from 125% the full kVA of the genny at .8pf?
(300A genny doesn't tell us much(enough))
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I just called this guy for more info. It's a 65kw (271A) and the conduit run is 20' under the slab the whole way.
 
curt swartz said:
I have just skimmed this thread but if this generator is supplying the entire dwelling why not use Table 310.15(B)(6)?
.
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Table 310.15(B)(6) is for service conductors only.
 
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