Operation of Manual Transfer Switche Under Load?

[KimoR]

Any thoughts Pro/Con of operating a 400V 3-Phase 1200A Manual Transfer switch and how to safely implement this?

Thanks!

 

[KimoR]

I should clarify that this is still in the design phase so please direct your comments/suggestions based on this info.
Thanks!

 

[augie47]

Does anyone manufacturer such a creature ? 600 amp is the largest I have ever seen.

 

[KimoR]

Yes, Lake Shore Electric Corporation has a 1200A Manual Transfer and Eaton a 1000A. Just not sure if implementing this into a design is the right thing to do for safety or is there something that I should be adding to make it safer.

Thanks

 

[ron]

Folks like ASCO, Eaton, GE and many more make transfer switches that can operate auto or manual and can transfer very safely under load.

Can you really predict? Better to specify a switch capable of load break.

 

[mayanees]

.. what Ron said, plus be sure to consider the arc flash rating at the switch. If it's rated over 40 calories there's no PPE level that would permit that operation.

 

[KimoR]

Here is more to help understand the application and thought process:
Not sure on how they actually plan on implementing. This is for a large dining facility, overseas, with refrigeration. There will be a 2000A main that will feed a 1000A DP for refrigeration and a 600A DP for general power/HVAC/lighting/etc. Each DP will have a transfer switch for a possible generator. If the facility is going to be down for an extended period they will bring in mobile generators. 1^st Priority is the 1000A DP for refrigeration so food does not spoil, 2^nd is the 600A DP if they decide to cook and serve. So, fast switching time is not an issue and hence why the do want/require an ATS. My understanding of how you would normally bring up a generator (as how it was normally done while I was in the Navy), start-up the generator (un-loaded), bring-on-line, and then apply loading. I would hope the procedure would be similar for this installation, but if someone does not turn off the refrigeration units prior to bringing the 1000 DP on-line, there is the potential of a large inrush of current as all the compressors are starting up simultaneously. My preference in this would be more inclined to have remote operation for this application, but I am not sure they even want to spend the money for this.

 

[texie]

Any thoughts Pro/Con of operating a 400V 3-Phase 1200A Manual Transfer switch and how to safely implement this?

Thanks!

Any MTS of this size is going to be electrically operated with pilot duty controls. Just put the controls outside the arc flash boundary.

 

[Oldbull]

We switch 800 amp ATS's

We switch 800 amp ATS's

Here is more to help understand the application and thought process:
Not sure on how they actually plan on implementing. This is for a large dining facility, overseas, with refrigeration. There will be a 2000A main that will feed a 1000A DP for refrigeration and a 600A DP for general power/HVAC/lighting/etc. Each DP will have a transfer switch for a possible generator. If the facility is going to be down for an extended period they will bring in mobile generators. 1^st Priority is the 1000A DP for refrigeration so food does not spoil, 2^nd is the 600A DP if they decide to cook and serve. So, fast switching time is not an issue and hence why the do want/require an ATS. My understanding of how you would normally bring up a generator (as how it was normally done while I was in the Navy), start-up the generator (un-loaded), bring-on-line, and then apply loading. I would hope the procedure would be similar for this installation, but if someone does not turn off the refrigeration units prior to bringing the 1000 DP on-line, there is the potential of a large inrush of current as all the compressors are starting up simultaneously. My preference in this would be more inclined to have remote operation for this application, but I am not sure they even want to spend the money for this.

We have 800 amp ATS's. They are switched every month. We found that transfering the Compressors of the ACs, Refigs and the like does not make the units happy. :happysad: So we have installed a delay timer in ATSs. Like you said the inrush causes the breakers to trip on some of the units. Delaying the ATSs about 10-20 seconds while it transfers from normal power to emergency power and back, gives the units time to come to a hault and restart again. Remote control the ATSs you have and build in a delay. Unless someone is really keeping an eye on the units they will never even notice it happening and most units will handle the change better.

 

[ron]

We have 800 amp ATS's. They are switched every month. We found that transfering the Compressors of the ACs, Refigs and the like does not make the units happy. :happysad: So we have installed a delay timer in ATSs. Like you said the inrush causes the breakers to trip on some of the units. Delaying the ATSs about 10-20 seconds while it transfers from normal power to emergency power and back, gives the units time to come to a hault and restart again. Remote control the ATSs you have and build in a delay. Unless someone is really keeping an eye on the units they will never even notice it happening and most units will handle the change better.

Be sure you specify a delayed transfer - transfer switch if you want a "middle" off position for a delay with neither source.

 

[meternerd]

We use lots of ATS units from ASCO. All are rated 1000A. But they are electronic with "synch check" for transferring. Make before break. Usually transfer to generator on loss of power, so there is no "load break". Pumps have already shut down. If manually transferred, they transfer when in synch. Not cheap, though. They have a manual operating handle inside the door, but it is not to be used when under load.