300Amp Challenge

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curt swartz said:
What makes you say that? You might want to read 310.15(B)(6) again.
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Curt I would agree with you. 310.15(B)(6) applies also to some feeders, however T 310.15(B)(6) is based on the diversity of the load of a residence. When you change the diversity and only wire a few, many but not all circuits I think that 310.15(B)(6) should not apply.
 
Hi Dennis, I was under the impression that this generator was going to set up to supply all loads in the dwelling. If that is the case this would be a main feeder. If the generator is only going to connected to select loads then I agree that Table 310.15(B)(6) can not be used.
 
curt swartz said:
Hi Dennis, I was under the impression that this generator was going to set up to supply all loads in the dwelling. If that is the case this would be a main feeder. If the generator is only going to connected to select loads then I agree that Table 310.15(B)(6) can not be used.
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I thought just the opposite because there is a 600 amp service.... you may be correct in your assumption... I hadn't thought of that.
 
curt swartz said:
What makes you say that? You might want to read 310.15(B)(6) again.
Click to expand...

Curt, the main power feeder is between the main disconnect and the panelboard.The generator has a main and that could qualify, but the transfer switch is between the two.
Rick
 
would the generator not qualify as a seperatly derived system..

Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.

oh yea sure through in 250.20 FPN No. 1: An alternate ac power source such as an on-site generator is not a separately derived system if the grounded conductor is solidly interconnected to a service-supplied system grounded conductor. An example of such situations is where alternate source transfer equipment does not include a switching action in the grounded conductor and allows it to remain solidly connected to the service-supplied grounded conductor when the alternate source is operational and supplying the load served.

so if the tranfer switch opens the grounded conductor (nuetral) it is a seperately derived system correct...
 
wow now lets confuse the issue..:grin: not really

250.35 Permanently Installed Generators.
A conductor that provides an effective ground-fault current path shall be installed with the supply conductors from a permanently installed generator(s) to the first disconnecting mean(s) in accordance with (A) or (B).
(A) Separately Derived System. Where the generator is installed as a separately derived system, the requirements in 250.30 shall apply.
(B) Nonseparately Derived System. Where the generator is not installed as a separately derived system, an equipment bonding jumper shall be installed between the generator equipment grounding terminal and the equipment grounding terminal or bus of the enclosure of supplied disconnecting mean(s) in accordance with (B)(1) or (B)(2).
(1) Supply Side of Generator Overcurrent Device. The equipment bonding jumper on the supply side of each generator overcurrent device shall be sized in accordance with 250.102(C) based on the size of the conductors supplied by the generator.
(2) Load Side of Generator Overcurrent Device. The equipment grounding conductor on the load side of each generator overcurrent device shall be sized in accordance with 250.102(D) based on the rating of the overcurrent device supplied.
Creating a return path for ground-fault current is the objective of this section. Sizing a conductor to perform this function is dependent on which of the following the generator supplies:
1. A separately derived system; either interfaced with another power source through a transfer arrangement where the grounded conductor is also switched or used as a stand-alone power source. If this is the case, the sizing requirement for the equipment bonding jumper is specified in 250.30(A)(2).
2. A system that is not separately derived such as an installation in which the transfer equipment incorporates a solid neutral. In this arrangement, the method of sizing the conductor to return ground-fault current is based on the location of the first overcurrent protective device.
Application Example 1
A 100-kW generator operating at 480Y/277 volts, 3-phase, 4-wire is connected to the premises wiring via 200-ampere-rated transfer equipment. The transfer equipment has a solid neutral connection, and thus is not a separately derived system.
Installation A. There is a 125 ampere overcurrent protective device installed at the generator.
STEP 1.
Section 250.35(B)(2) refers to 250.102(D) for sizing load side equipment bonding jumpers. The minimum size is based on the rating of the overcurrent protective device installed at the generator using Table 250.122.
STEP 2.
Table 250.122: 125A OCPD 6 AWG copper or 4 AWG aluminum installed with the circuit conductors from the generator OCPD to the equipment grounding terminal of the transfer equipment.
Application Example 2
Installation B. There is no overcurrent protective device installed at the generator. The conductors terminate in a 125-ampere overcurrent protective device installed in the transfer equipment. The ungrounded conductors between the output terminals of the generator and the transfer equipment have been sized in accordance with 445.13 and are 1/0 AWG copper with THWN insulation.
STEP 1.
Section 250.35(B)(1) refers to 250.102(C) for sizing supply side equipment bonding jumpers. The minimum size is based on the size of the ungrounded conductors between the generator and the transfer equipment using Table 250.66.
STEP 2.
Table 250.66: 1/0 AWG ungrounded conductors 6 AWG copper or 4 AWG aluminum installed with the circuit conductors from the generator output terminals to the equipment grounding terminal of the transfer equipment.


dang it now forgot where I was going..
 
Table 310.15(B)(6) Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling
Services and Feeders. Conductor Types RHH, RHW, RHW-2, THHN, THHW, THW, THW-2,
THWN, THWN-2, XHHW, XHHW-2, SE, USE, USE-2

Conductor (AWG or kcmil) Service or Feeder
Rating (Amperes) Copper Aluminum or Copper-Clad Aluminum
100 4 2
110 3 1
125 2 1/0
150 1 2/0
175 1/0 3/0
200 2/0 4/0
225 3/0 250
250 4/0 300
300 250 350
350 350 500
400 400 600

I see 300 as 250 KCMIL copper

chp 9 says you can put 3 thhn 250 kcmil in a 2"schedule 80 pvc..
 
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