Deployable Shelter Bonding

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tsryan89

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Syracuse, NY
I have a question about the proper bonding of a shelter that can be connected to various power sources. This Shelter is used in a deployable radar system and therefore can be configured to operate off not only facility power, but also generator power. The system has a 3 pole transfer switch located externally to the shelter that allows for two power inputs. The possible configurations of the system are:
  1. Connected to Facility Power on Primary with Generator (DEG) on Secondary
  2. Connected to Facility Power on Primary with no Generator Connected
  3. Connected to Facility power on Primary and backup facility power on secondary
  4. Connected to Generator on Primary with no connection to secondary
  5. Connected to Generator on Primary and generator connected to secondary
Currently our configuration calls for bonding of the ground and neutral at the facility power source, which is completely acceptable and in my judgement in accordance with NEC Art. 250. This bonding location is acceptable for 3 out of 5 of our possible configurations, but is not adequate when our system is deployed and operating solely off generator power, as no bond exists within our shelter as the ground and neutral are isolated. This results in phase to neutral votlage mismatches and voltages being present between neutral and ground. A bond is only obtained when our 5 wire input is connected to a properly bonded facility. See figure below:

Drawing2.jpg

Given this configuration and desire to maintain a bond in all configurations, what is the correct way to bond this system? Is removal of the bond at the facility and installation of a bond at the shelter correct? Is a dual bond approach acceptable if the neutral is breakered at the facility? Should a kit be created to "bond" the system when deployed (undesireable as they will no doubt forget to do this)? Any insight would be well appreciated.

Regards,
Travis Ryan
 
This System does include a vehicle for transport, but in most instances the Shetler is seperated from this vehicle and there is never any electrical connection between the two. The shelter could be considered a portable building, with two seperate power sources possible. Their is a trailer but it is only used with the antena, the shelter mounts to the bed of the 5 ton truck but is removeable via jacks.

As for RF Exposure limits, that has already been taken into consideration.

Travis
 
but is not adequate when our system is deployed and operating solely off generator power, as no bond exists within our shelter as the ground and neutral are isolated.
Click to expand...

Looking at the diagram, the ATS does not open the ground - neutral bond at the facility.

When the genny is running, a hot to ground fault would go from the shelter to the facility and then back to the generator which should open an OCPD.

Granted, when the genny is running, the bond is not located at the first OCPD, which would be either in the genny or in the shelter, but it's still there, nonetheless.
 
K8MHZ

i appreciate the response, and agree that the bond is still present when operating off the generator as the ATS does not break the bond, i.e. not seperately derived. The concern is when there is no facility present (i.e radar deployed remotely), and therefore no bond exists. See figure below:

Drawing2.jpg

In this configuration there is no bond. I have flirted with the idea of adding a bond at the shelter, but then if the customer bonds at his facility then i have a ground loop, and isn't in accordance with Art. 250. I would like to make any solution permanent, and safe for all isntallations, but i am not sure that is the case. They may have to add/remove a jumper whenever the deploy the system remotely and its not connected to a facility installation with a bond. Is it possible to put an OCPD on the nuetral to prevent excessive currents from flowing, as long as it trips (linked) all the three phase breaker?
 
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