transformer & 1st disconnect grounding

[boptrop]

250.30 (1) states that basicaly that a Main bonding Jumper (MBJ) will be located at 1 point between the trans. and the 1st disconnect, inclusive. the transformer and the 1st disconnect (usually a pannel)with a netural and ground conductor installed between. People in my company and the inspector seems to think that this is normal pratice and is acceptable. I think its disastourous. My question is about exception 1. It seems what this means is that bonding is allowed at both points but there will be only 1 grounded conductor and no grounding conductor installed and if a conducting raceway is used the continuity of this raceway must be broken as to not create a parallell path for grounded condutor current. Is this correct thinking??

 

[boptrop]

Re: transformer & 1st disconnect grounding

sorry, what i ment to say is that most people in my company (as well as the inspector) think its normal pratice to install a MBJ at the x-former and the 1st disconnect as well as install a grounded conductor and a grounding conductor between. Furthermore they try to justify it with the above cited 1st exception. As well as go on to say that this set up is is ok cause its just redundant grounding. I feel this is completely wrong, violating the parallell rule as well as the objectionable current rule as Mike H. cites.
It seems to me that this is a extremely careless use of the code.

 

[hurk27]

Re: transformer & 1st disconnect grounding

Boptrop
You are correct!

250.30 Only allows the neutral to be Bonded at both the transformer and the main disconect where doing so does not establish a parallel path for the neutral conductor. If this cannot be avoided then it is only allowed to be bonded at one location. which can be anywhere from the transformer to the disconnect. Like if these conductors was ran in RMC, IMC, EMT. then they could not be bonded at both locations. But if they are ran in PVC then this allows us to not have to run a equipment grounding conductor and allows the grounded circuit conductor to be both the EGC and the GCC as allowed in 250.142(A)(3)

Just remember where ever the bonding jumper is located so has to be the GEC connection point.