kirk key interlock on power distribution unit

[New EE]

Could someone please explain to me what a kirk key interlock does on a power distribution unit (PDU)? The PDU has a dual input from two seperate distribution panels along with the kirk key interlock. I'm a bit confused on what this does. The PDU has dual input, isolation transformer, and two panelboards with main breakers on each panelboard. Does it mean that one panelboard can be live at a time or can both panelboards be live at the same time? Please clarify for me. Thanks. Attached is a wiring diagram.

 

[New EE]

Sorry. I forgot to mention the wiring diagram does not show the kirk key interlock only the PDU configuration.

 

[augie47]

"Kirk Key" is a mechanical means to allow you to select between the two inputs but prevents both from being "on" at the same time. It prevents overloading the buss and backfeeding while allowing you some selection of sources

 

[New EE]

Thanks for the reply. In my case I have a PDU feeder some IT server racks. So please correct me if I'm wrong, only one panelboard within the PDU can be live so if I have for instance two receptacles (there will be more than two receptacles) feeding a server rack, one receptacle is connected to panel "1A" and the other receptacle is connected to panel "1B", only panel "1A" or "1B" receptacle can be energized at one time. Does this setup basically act as a redundant sytem should one of the dual input feeders fail? Thanks.

 

[augie47]

You may have some other arrangement. I am assuming your kirk-key
locks are on CB-1 and CB-2 ahead of your transformer.

 

[zog]

You may have some other arrangement. I am assuming your kirk-key
locks are on CB-1 and CB-2 ahead of your transformer.

Ditto, however there are hundreds of diferent possible configurations for using kirk locks, I have seen some crazy complex systems.

 

[SG-1]

If the Kirk Key Interlock is on CB1 & CB2 as Augie has surmised then both panelboards downstream of the transformer can be energized from either Source 1 or Source 2. The locks most likely prevent the sources from being paralleled.

 

[brian john]

Typically there should be an electric key release the works in conjunction with the key interlocks. The two sources have to be in sync in order to release the key of the source that is not on line. You release the key unlock the open CB, closes this CB, then open the closed CB, re-insert the key in the captive key electric interlock.

This assumes you are not talking about a PDU with static transfer and the interlocks are for the bypass.

 

[Jraef]

If your drawing is accurate to the internal wiring, BOTH of the 42 circuit panels are being fed from the same transformer. The only place I see two breakers that might be interlocked is ahead of the transformer primary, so I don't see how you would have one OR the other but not both panelboards being live. So in this case if the KK interlocks are on CB-1 and CB-2, then they serve only to prevent both sources from being hot at the same time and thereby preventing back feeding. It's also going to possibly serve to ensure that only someone with that key can change the power source, depending on how the KK is set up with regards to key removal.