neutral ground bonding question

[wesley1]

new modular office building my company supplying underground sevice to is a double wide. 1 side has a 150 amp single phase 240 volt non fused disconnect and the other side has a 200 amp single phase 240 volt non fused disconnect. Directly thru wall on inside of each is a 150 amp panel and a 200 amp panel respectively. We are planning on installing 400 amp meter base in the center and feed off load side with double lugs to each disconnect. The wire length to disconnects are only 7' so tap rule should allow for less than 10 feet. As i try to design this though i have a question about where the neutral and grounds should be bonded togethor. The answer may simply be i will have to install a single 400 amp disconnect. I was trying to eliminate cost of this but might be unavoidable. The panels inside have a bonding strap that has each panels neutrals buss bonded. but im a wrong in saying that with 2 seperate panels they should not be bonded as you only want gec and egs bonded at 1 place? Also the supplied disconnects in picture does not have neutral lugs. Thus in the manufacturers design i dont think intended to be bonded there. Reading article 250 and 550 still. Any input would be appreciated.

 

[wesley1]

Just more on this!

Just more on this!

Even though the meter is not usually considered a disconnect, in this case the best install would be to bond at meter and isolate ground and neutrals at both disconnects and inside panels. Dont want to create a fault path if utility ground gets corroded, loose, cut etc.

 

[Smart $]

Even though the meter is not usually considered a disconnect, in this case the best install would be to bond at meter and isolate ground and neutrals at both disconnects and inside panels. Dont want to create a fault path if utility ground gets corroded, loose, cut etc.

Code requires the main bonding jumper to be located in the service disconnecting means.

To get this right, you're going to have to verify whether the "structure(s)" is/are mobile home, manufactured home (either used as other than dwelling*), or manufactured building. HUD pretty much regulates the distinction for the first two, while the last one varies from state to state. Appears as there is no permanent foundation, so I going to venture either of the first two...

If *mobile home, the service equipment or disconnecting means must be not greater than 30' from the exterior and cannot be attached to the structure.

If *manufactured home, the manufacturer's instructions have to be followed. Under the NEC the service equipment can be inside or outside and attached... but regardless of manufacturer's instructions, the non-fused disconnects cannot be considered the service disconnects.

 

[augie47]

Fist thing I would do, if you don't know for sure, check with your POCO. Some won;'t allow the meter/service disconnects to be mounted on a modular structure (often depending on wit/without foundation)
I doubt your AHJ will accept the two switches as the service disconnecting means.
Even if they are service rated you would still have to comply with 230.91 and 230.72
both of which would be a stretch, IMO.
AHJ call, but I see you adding a service disconnecting means with OCP.
(That may be the least of your problems depending on the units having a HUD sticker or acceptable pre-wired inspection certification)