ATS shedding controls

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lowans

Member
Location
Cayman islands
Hi I have a 400kva generator that supplies emergency power to 5 ATS's three are on the north side transformer for normal power and two on the south side for normal power. 1st ats is for the laundry 2nd is for the office 3rd for the fire pump 4th for condos north side and 5th for condos on south side. In the event that normal power fails the back up generator powers the whole complex, now if during this time the fire pump kicks in due to a fire I have to shed all the other 4 ATS's leaving only back up power to the fire pump ats. How do I go about doing this as do I need specific controls in the transfere switches.
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
ATS Load Shedding

ATS Load Shedding

To answer your question, you need to provide more detailed info on the ATSs.
Manufacturer and model # to start or complete nameplate info found some where on ATS or on the inside of enclosure)
If they are older relay logic (15 to 20yrs) types then they may or may not have the load shed feature. All newer ASCO, GE-Zenith, Russelectric, Kohler, Cummins/ Onan, etc that employ solid state controllers have this feature and provide dry, output contacts to disconnect these loads via the motor starter contactor in the MCC or by a shunt trip in the feeder breaker feeding the load.
If they are relay logic then the control circuits can be modified by a good controls guy to provide these contacts.
 

Fordean

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
To answer your question, you need to provide more detailed info on the ATSs.
Manufacturer and model # to start or complete nameplate info found some where on ATS or on the inside of enclosure)
If they are older relay logic (15 to 20yrs) types then they may or may not have the load shed feature. All newer ASCO, GE-Zenith, Russelectric, Kohler, Cummins/ Onan, etc that employ solid state controllers have this feature and provide dry, output contacts to disconnect these loads via the motor starter contactor in the MCC or by a shunt trip in the feeder breaker feeding the load.
If they are relay logic then the control circuits can be modified by a good controls guy to provide these contacts.

I would say some type of SHunt breaker system.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I would say some type of SHunt breaker system.
A shunt trip can keep the active load below the generator output, but it will not allow any disconnected load to be reconnected automatically when the other load drops. In fact, you would have to manually reset those breakers once POCO comes back.

You might as well just use an MTS instead and manually manage the load.
 
To answer your question, you need to provide more detailed info on the ATSs.
Manufacturer and model # to start or complete nameplate info found some where on ATS or on the inside of enclosure)
If they are older relay logic (15 to 20yrs) types then they may or may not have the load shed feature. All newer ASCO, GE-Zenith, Russelectric, Kohler, Cummins/ Onan, etc that employ solid state controllers have this feature and provide dry, output contacts to disconnect these loads via the motor starter contactor in the MCC or by a shunt trip in the feeder breaker feeding the load.
If they are relay logic then the control circuits can be modified by a good controls guy to provide these contacts.

This is the correct answer. Sometimes ATS can be ordered from the factory without the proper switching terminals pre-installed. Usually this can be fixed with an add-on kit, but not always.
 
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