Products / Free Standing STS
Free-standing static transfer switches
When the load is a whole panel, a row, or one large machine, the switch moves to the floor. The free-standing DCC-4-S carries 100 to 600 A of three-phase or single-phase power between two sources as fast as a quarter cycle.
eight ratings
through one switch at 480 V
with maintenance bypass
How much load is that?
Choose a rating and a voltage to see the capacity of a single switch.
Where a large switch belongs
A free-standing STS feeds a distribution panel, a remote power panel, a mechanical switchboard or a single large load. One unit covers a great deal of equipment, which makes it the economical way to give two sources to loads that cannot take a switch of their own.
Be clear about what it covers. Protection extends upstream only. A breaker, feeder or panel downstream of the switch can still drop the load, and when a central switch is out of service everything behind it is affected together. That is why many sites pair one large switch for distribution with rack-mount or wall-mount switches at the most critical single-corded loads.
Engineering notes
- Choose 4-pole where the two sources are separately derived and the load uses the neutral. Choose 3-pole for three-wire loads.
- If a transformer sits downstream, tell us. An out-of-phase transfer can push it toward saturation, and the answer is in the settings and the sizing.
- Check the available fault current against the nameplate fault rating.
- Plan the maintenance bypass into the operating procedures from day one.
Sizing a distribution-level switch
Start from the connected load in kVA and convert to line current: kVA times 1000, divided by 1.732 times the line-to-line voltage. Add margin for growth, then choose the rating at or above the result. Because every TwinSource rating is 100% continuous, a 400 A switch carries 400 A without derating. Size the feeder breakers and conductors to your electrical code and the operating manual.
Inside the cabinet, each source has its own SCR assembly for every switched pole, with sensing on both sources and a maintenance bypass that carries the load around the electronics. The door carries the interface you choose, from a mimic panel to a touchscreen, and status is available remotely for the BMS or DCIM.
Models in this category
Where they are used
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Questions engineers ask
What is the largest TwinSource static transfer switch?
600 A three phase. At 480 V that is just under 500 kVA through one switch.
Do I still need rack-level switches if I have a large one?
For the single-corded loads that matter most, yes. The large switch cannot help with a failure between itself and the load.
Is there a smaller floor or wall option?
Yes. The same DCC-4 platform comes in wall-mount and rack-mount enclosures from 10 to 120 A three phase, or up to 200 A single phase.
Ready to specify?
Open the configurator with this category already selected, or send us your one-line diagram.