Does Automatic Transfer switch considered to be disconnecting means?

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faresos

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Hello everyone:

I have an existing situation where I need to evaluate. There is a feeder (350Kcmil) coming from a secondary transformer (208/120V) to 200A meter socket then to automatic transfer switch then to 400A service entrance rated fused disconnect switch with 225A fuse. The second power source to the ATS is the generator. My question, does the ATS considered to be the first disconnecting mean and needs to be service entrance rated? if the ATS didn't have any kind of overcurrent protection device will this still need to be a service entrance rated or just considered to be just a switching device and it doesn't have to have an overcurrent protection device?

Thanks,
 
IMO no. We have never installed a disconnect for an ATS and all of the feeders to the ATS are remote so they're not within sight.
 
I believe this section requires a disconnect between the meter and ATS or a service rated ATS.

230.82 Equipment Connected to the Supply Side of Service
Disconnect. Only the following equipment shall be
permitted to be connected to the supply side of the service
disconnecting means...


 
Coppersmith said:
I believe this section requires a disconnect between the meter and ATS or a service rated ATS.

230.82 Equipment Connected to the Supply Side of Service
Disconnect. Only the following equipment shall be
permitted to be connected to the supply side of the service
disconnecting means...
Click to expand...

Good point, is this a feeder or service entrance conductors? The OP mentions feeder first.
 
infinity said:
Good point, is this a feeder or service entrance conductors? The OP mentions feeder first.
Click to expand...

The existing situation is a feeder. This ATS currently fed from a feeder originated from near by building, however, this configuration will be modified as the feeder will be demolished and we will need to tap from the secondary of the transformer. These conductors now are considered to be service entrance conductors. My thought on it since now it's a service entrance conductors it needs to terminate in a service entrance fused disconnect then will need to go to the ATS. Basically, I believe the new configuration should be: service conductors will go through the meter then fused disconnect (service entrance rated) then ATS then main distribution panel. Do you see any wrong with this installation?
 
I could be way off base here but IMHO, the first disconnect means on the load side of the meter should be service rated and should have OCP. That’s MHO and not based on any NEC article or POCO requirement. That said, I have some questions :
  • If you turn off the ATS doesn’t the generator start?
  • Wouldn’t you then also need a shut-off or disconnect for the generator?
  • Are you able to protect the load side with 225A fuses if the meter socket is rated for 200A?
  • After the disconnect, is there a MLP or a MB panel?
I’m not trying to come across as an authority here, just looking to be educated.:cool:
 
faresos said:
The existing situation is a feeder. This ATS currently fed from a feeder originated from near by building, however, this configuration will be modified as the feeder will be demolished and we will need to tap from the secondary of the transformer. These conductors now are considered to be service entrance conductors. My thought on it since now it's a service entrance conductors it needs to terminate in a service entrance fused disconnect then will need to go to the ATS. Basically, I believe the new configuration should be: service conductors will go through the meter then fused disconnect (service entrance rated) then ATS then main distribution panel. Do you see any wrong with this installation?
Click to expand...

Look at 230.82. A transfer switch is not on that list so either your transfer switch is service rated and the service disconnect, or there is a service disconnect before it. Either way is fine. Just keep in mind that Your service OCPD is required too, so you could have a situation where you have a transfer switch but it doesnt have any overcurrent protection in it so you would need to provide that separately.

So to answer your specific question, that would be fine, unless your transfer switch is marked "suitable ONLY as service equipment" (probably academic). If it is service rated, you could save on some equipment and make it your service disconnect.
 
faresos said:
..... My thought on it since now it's a service entrance conductors it needs to terminate in a service entrance fused disconnect then will need to go to the ATS. Basically, I believe the new configuration should be: service conductors will go through the meter then fused disconnect (service entrance rated) then ATS then main distribution panel. Do you see any wrong with this installation?
Click to expand...
That is the way I would do it.
 
faresos said:
The existing situation is a feeder. This ATS currently fed from a feeder originated from near by building, however, this configuration will be modified as the feeder will be demolished and we will need to tap from the secondary of the transformer. These conductors now are considered to be service entrance conductors. My thought on it since now it's a service entrance conductors it needs to terminate in a service entrance fused disconnect then will need to go to the ATS. Basically, I believe the new configuration should be: service conductors will go through the meter then fused disconnect (service entrance rated) then ATS then main distribution panel. Do you see any wrong with this installation?
Click to expand...

Many ATS units have a service rated breaker ahead of the actual switching unit; if your ATS is one of those you do not need a disco ahead of it.
 
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