L21-30 to single phase

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ppokorny

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I've got a 19" rack full of single phase equipment and the facilities have provided an L21-30R to power it.

The equipment has APFC power supplies and will run off of 208 or 120V.

Can I wire three L6-30R in a delta config to the X-Y-Z phases of the L21-30R and power the equipment from 208V power strips?

Can I draw 24Amps (derated) at 208V from all three phases?

I've gotten confusing explainations from companies like Pulizzi Engineering (www.pulizzi.com) about why they don't offer L21-30 to L6-30 PDU's.

Thanks,
:v)
 
Re: L21-30 to single phase

Bit confused. You have a L21-30 receptacle on the wall. Pulizzi PDU's- how many and what model? APC(?) UPS's- how many and what model?

-Hal
 
Re: L21-30 to single phase

There is an L21-30 on the wall.

I have Qty 35 of 1U computers that each have active power factor correcting power supplies (APFC) so they appear as a 99%+ resistive load.

Each computer draws about 275W, so the total power needed by the rack is 9.6kW

I want to use three power strips like either the APC AP9566 or AP9561. These are both 208V PDU's with IEC 320 C13 connectors. They have L6-20 and L6-30 input plugs respectively.

At first glance, it would seem to be possible to create a "cable" with L21-30P on one end, three L6-30R recepticals (HBL2623), and a wiring box in the middle to make the connections. Alternatively, I could cut the connectors off the PDU's and run them directly into the wiring box.

The question is, how do the currents in the 208V "phases" add with regard to a given 120V leg of the L21-30, 3phase power?

Put another way, if I draw 10 Amps from the XY and ZX phases, how much current is drawn from the X phase? Is it 10 Amps (because the XY and ZX legs are 120 deg out of phase?) or is it more or less?

Since posting the original question, I've done some analysis and it seems like the answer is: the 120V current is 1.73 times the 208V current.

So you can't pull 30A @ 208V from a 30A @ 120V 3-phase system. But you might be able to pull 20A @ 208V.

But then why do PDU's like the Pulizzi TPC4000-B exist which offer a L21-20 in and 6-15R out with a 16A main breaker? Wouldn't two 15A loads at 208V blow the 16A main breaker?

Or the VPC2864-1 which appears to claim that I can draw "16 Amps de-rated full load ... per phase" at 208V from an L21-20 plug.

Why couldn't you just upgrade the wiring from 12/5 to 10/5 w/L21-30 and make the VPC2864-1 a 30Amp device with 24Amps derated per phase?

Thanks!
:v)
 
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