Grounding dilema ! ground wire required or not ?

[delta4u]

I have installed in dozens of mobile home parks, Distribution transformers primary 1ph 480 volt to 1ph 120/240 volt 167 kva in all instances except a few the inspecting body has been Ca HCD. A typical install is usually running a 2" sch 40 pvc pipe from the main panel underground to the unit substation using parallel 4/0 copper (no equipment ground wire) on a 350 amp breaker.
at the transformer we always drive a 10 ft solid copper ground rod and have never had any problems. Now we have installed one in a community thats under a cities jurisdiction and they are insisting it needs an equipment ground wire even though we have installed 50 or 60 of these exactly like this. I always figured this is a seperatly derived power source under article 250 and a ground rod is sufficient. Problem is i do not have room for a ground wire and have ran over 300 ft of underground pipe !!!

 

[jumper]

I have installed in dozens of mobile home parks, Distribution transformers primary 1ph 480 volt to 1ph 120/240 volt 167 kva in all instances except a few the inspecting body has been Ca HCD. A typical install is usually running a 2" sch 40 pvc pipe from the main panel underground to the unit substation using parallel 4/0 copper (no equipment ground wire) on a 350 amp breaker.
at the transformer we always drive a 10 ft solid copper ground rod and have never had any problems. Now we have installed one in a community thats under a cities jurisdiction and they are insisting it needs an equipment ground wire even though we have installed 50 or 60 of these exactly like this. I always figured this is a seperatly derived power source under article 250 and a ground rod is sufficient. Problem is i do not have room for a ground wire and have ran over 300 ft of underground pipe !!!

As usual I am confused.

1 ground rod; tested to 25 ohms or less?

I am seeing a feeder to a separate structure: are not not EGCs required?

2005 or 2008?

 

[tryinghard]

…A typical install is usually running a 2" sch 40 pvc pipe from the main panel underground to the unit substation using parallel 4/0 copper (no equipment ground wire) on a 350 amp breaker.

Equipment grounding is required to be separate from neutral bonding past the service disconnect 250.24(A)(5) & 250.142(B) unless you meet the exceptions and yours may under 250.30

…I always figured this is a seperatly derived power source under article 250 and a ground rod is sufficient. Problem is i do not have room for a ground wire and have ran over 300 ft of underground pipe !!!

If you are feeding a 480v 1ph circuit from your main to an induction type transformer in a substation it is a separately derived system and 250.30 applies for grounding and bonding, remember the earth is not an effective fault path. This means your 480v feed would include two phases and an EGC (of the type in 250.118 & sized per 250.122) - in other words you have a hot, hot, & EGC. Your XFMR’s secondary XO winding needs to bond either at the XFMR (most common) or at the first disconnect, where ever this bond takes place the GEC must terminate there as well.

 

[delta4u]

Is there a type of wire that is rated for more amperage ?

Is there a type of wire that is rated for more amperage ?

In order to supply an equipment ground in a 2" pipe that needs to handle 350 amps i would need a special 3/0 with high quality insulation that increases its current carrying capicity which would allow me to fit an equipment ground example 4-3/0 ____ + a #3 ground wire does anyone know of such a wire someone suggested MOR POLYRAD IEEE 1580 TYPE P HELP

 

[G._S._Ohm]

i would need a special 3/0 with high quality insulation that increases its current carrying capicity

does anyone know of such a wire someone suggested MOR POLYRAD IEEE 1580 TYPE P HELP

Try
http://www.hitechcontrols.com/cables/technical-information/55-heat-res-classes.html
Teflon can do 180 C.

 

[petersonra]

In order to supply an equipment ground in a 2" pipe that needs to handle 350 amps i would need a special 3/0 with high quality insulation that increases its current carrying capicity which would allow me to fit an equipment ground example 4-3/0 ____ + a #3 ground wire does anyone know of such a wire someone suggested MOR POLYRAD IEEE 1580 TYPE P HELP

what makes you think the code allows this?

 

[shepelec]

Probably would be cheaper and easier to run a bigger conduit and reuse the 4/0 than it would be to special order any other wire.

Got to give you credit though, 4-4/0 in a 300' 2" pvc run must have been a bear to pull. Even though it's to code, I would have run 3" or at least 2-1/2.