service disconnect location with emergency generator

[ggmclain]

I have a town goverment building that houses the 911 police dispatch area. Already existing is the 1600amp mdp, 1600 amp manual non fused disconnect, Asco 4 wire non service rated automatic transfer switch all located in the electrical room. the main service feed from the power company enters the building throught the slab and connects to the utility side of the transfer switch. The generator ties to the alternate power lugs of the transfer switch. From the load side of the tranfer switch the wires are tied to the line side of the service disconnect, the load side is a direct bar connection to the MDP. A third party has stated to the town that this wiring is incorrect to code and I was asked to check on it for them. I have not found any code that tells me it is wrong and would like a clearification on this. The third party stated that a disconnect must be between the meter and the transfer switch. This work was done in 1999. Thanks for the help

 

[charlie b]

I agree with the "third party." I think you have a violation of 230.70. The "service disconnecting means" is required to be able to disconnect all conductors in the building from the service entrance conductors. In your case, there is one set of conductors, namely the automatic transfer switch, that will not be disconnected by use of the non-fused disconnect downstream. Also, somewhere in the book (I don't have time to look right now) I believe there is a requirement that essentially says that whatever first comes into contact with the service entrance conductors, be it a disconnect switch, a switchboard, or a transfer switch, has to be "service entrance rated." Your transfer switch is not.

Welcome to the forum.

 

[skeshesh]

Welcome to forum. I agree with Charlie. The disconnect means is required to "disconnect all condcutors in a building or other structure from the service-entrance conductors" pretty much unconditionally. I should add that I am not familiar with the 1999 code, but I suggest you bring this install upto code since the correct placement of this disconnect means is actually a pretty good idea, as opposed to other parts of the code some may consider overly cautious. I'm looking in the 2005 handbook right now and art. 700 has a good illustration that clearly shows the disconnect upstream of the transfer switch, so you may want to take a look if you have a handbook around.

 

[SEO]

The basic content of section 230.70 has not changed from the 1999 NEC to the 2008 NEC. Per UL transfer switches intended for use as service equipment are marked SUITABLE FOR USE AS SERVICE EQUIPMENT.

 

[ceb58]

I have a town goverment building that houses the 911 police dispatch area. Already existing is the 1600amp mdp, 1600 amp manual non fused disconnect, Asco 4 wire non service rated automatic transfer switch all located in the electrical room. the main service feed from the power company enters the building throught the slab and connects to the utility side of the transfer switch. The generator ties to the alternate power lugs of the transfer switch. From the load side of the tranfer switch the wires are tied to the line side of the service disconnect, the load side is a direct bar connection to the MDP. A third party has stated to the town that this wiring is incorrect to code and I was asked to check on it for them. I have not found any code that tells me it is wrong and would like a clearification on this. The third party stated that a disconnect must be between the meter and the transfer switch. This work was done in 1999. Thanks for the help

Hopefully to expand on what Charlie and Steve have said your choices are to install a service rated disco w/ ocp between the utility feed and transfer switch. Or install a service rated ATS that has built in disco and ocp. You did not state it but you also must have a disco. between the ATS and gen. set

 

[RUWired]

Is there a service rated disconnect for the generator feed to the building?

 

[ggmclain]

no the transfer switch is not a service rated disconnect.