Automatic Transfer Switch Location

[hbendillo]

I am wondering if there is ever a condition where the load side of an automatic transfer switch (ATS) would require overcurrent protection if both the normal and emergency feeders both have overcurrent protection. This is not an service rated ATS question but typical condition. I.E. feeder with OCP from building normal power switchboard feeds normal side of ATS and Generator with main feeder breaker feeds emergency side of ATS . The load side of ATS feeds a panelboard adjacent to the ATS. I always show a main breaker in the emergency panelboard.

The design issue I am considering: Feeding an existing emergency section of a switchboard from a new ATS. New ATS fed from generator with integral circuit breaker for the emergency feed, new ATS fed from breaker in normal power switchboard on normal side, load side of ATS feeds the emergency section that has no main circuit breaker. The new ATS is in same room as the load but not right next to it Probably 10 feet away on an adjacent wall. Is any additional overcurrent protection required on the load side of the ATS?

Next issue: Owner is worried about space to install the ATS the same room as the load. Wants us to locate the ATS in an adjacent room not in sight of the load. Does this present any issues?

 

[HackElectric]

The ATS is your service disconnect and you have to follow the same rules as if it was a normal main breaker panel acting as your service disconnect. Remember things such as limiting the amount of service entrance conductors inside the building.

The panel you put on the load side of the service rate ATS doesn't need a main breaker, I will often use an MLO panel if I find it cheaper. This is nothing more than a typical sub-panel and can be located anywhere that a sub-panel can go. Remember that the grounds and neutrals have to be separated in this panel.

 

[mopowr steve]

I see where you would want a main in the emergency panel because if you were to work in it you would not be able to turn the power off to the bussing by just turning off the main in the ATS which would trigger the generator to come on and transfer.

 

[HackElectric]

I see where you would want a main in the emergency panel because if you were to work in it you would not be able to turn the power off to the bussing by just turning off the main in the ATS which would trigger the generator to come on and transfer.

From a code standpoint, that doesn't apply.
From an OSHA standpoint, that still doesn't apply. You'd still have the hot feeders entering the cabinet.

From a realistic standpoint, well that doesn't apply either. The generator can be shut off with the push of a button before the main disconnect is thrown, making the panel completely dead, if you are so inclined.

 

[hbendillo]

The ATS is your service disconnect and you have to follow the same rules as if it was a normal main breaker panel acting as your service disconnect. Remember things such as limiting the amount of service entrance conductors inside the building.

The panel you put on the load side of the service rate ATS doesn't need a main breaker, I will often use an MLO panel if I find it cheaper. This is nothing more than a typical sub-panel and can be located anywhere that a sub-panel can go. Remember that the grounds and neutrals have to be separated in this panel.

In my situation the ATS is not service rated. The normal feed comes from a branch feeder in the main switchboard downstream of the service disconnect. So the neutrals and ground will be separated.

 

[hbendillo]

From a code standpoint, that doesn't apply.
From an OSHA standpoint, that still doesn't apply. You'd still have the hot feeders entering the cabinet.

From a realistic standpoint, well that doesn't apply either. The generator can be shut off with the push of a button before the main disconnect is thrown, making the panel completely dead, if you are so inclined.

Yes, one would have to disable the generator, I would disconnect the emergency feeder with the generator circuit breaker and set the generator so it would not run, and then turn off the normal breaker in the switchboard to completely remove power from the emergency switchgear. I haven't found anything in the NEC or any other code that tells me that is not acceptable.

If I designed this from scratch, I would have put a main in the emergency switchboard section, but this is an existing installation and the design-build contractor doesn't want to add a load circuit breaker in the ATS or the load side feeder. I just wanted to make sure the arrangement complied with all applicable codes.

 

[HackElectric]

In my situation the ATS is not service rated. The normal feed comes from a branch feeder in the main switchboard downstream of the service disconnect. So the neutrals and ground will be separated.

Unless it's in the specs, you don't need that panel to have a main.