Really still would like answers based on 05 NEC......

How do you all interpret 200.2?

Say a warehouse had a 3 phase panel in each unit. The panels were 120/240 delta with a high leg. A single phase "sub panel" was installed off of this unit's main panel and no grounded conductor was ran with the feeder, just a grounding conductor.(2 hots and ground) Furthermore the 208v to ground high-leg was one of the ungrounded conductors. The "sub-panel" is only used for 1phase loads, compressor, welder and auto lift but there are 2 spare spaces left in the panel.

Should I require a neutral be pulled into "sub-panel"?

2005 NEC. Assuming that the building service main disconnect(s)comply with NEC Sect. 250.24(C) the neutral is not required to be run with feeders if not needed. The phase to phase voltage would still be 240v. and the high leg would still be required to be marked orange. I wouldn't advise adding a neutral since a midpoint grounded delta in this specific panel would have one leg at 120v. to ground and the second at 208v. to ground.

Don't miss NEC Section 240.85 which would require straight voltage 240v. rated two pole breakers for this system, feeder and subpanel.

I tend to agree with Ron. As well as the caveat of adding a ungrounded conductor. To easy to add a 120v circuit thinking that a neutral is present. And could use it on either of the two spare poles. One of them is going to cause some grief when connected.
If the neutral is not present then maybe it will cause the electrician to investigate why and see they have a high leg.

If this is the typical center tapped delta with 2 transformers you will have trouble putting L/L loads on the "high" leg.
It tends to unbalance relationship to the other phase.
If they have 3 transformers, it usually won't make a difference.

It is fairly common for data center panels not to have a neutral brought to them simply because they don't want any 120v loads.

Well if you want to really get into this issue. Then you need to consider the utility point of view. Typically this is a system that has a smaller transformer for the high leg. Dedicated for lighting loads only. They are not engineered for adding increased loads to a existing building. And they should of used the two phases that are not the hi-leg.
This is probably the case in this issue and before adding the sub panel the contractor should have contacted the utility company first.

WHOE!
Couple of questions.
What will be the loads on the subpanel that you intend to feed a High Leg and Regular Phase conductor?
I have (in my ignorate youth) tried to load up the High leg to "balance the load" on the panel of a small business served with a three phase service. BUT you cannot use the "high leg" as if it were any other phase conductor.

1

(I hit the wrong button! sorry)

You cannot use the "High Leg" as though it was any other phase conductor.

You must use a breaker rated for 240 volts, not one rated 12/240 volts. The voltage to ground is in excess of 120 (or 150 ) volts

You cannot use it to feed a typical furnace of A/C unit- they are rated for 12/240. NOT voltage to ground in excess of 150

Feeding an air-handler with a control transformer (as most small units have) with voltage in excess of 150 V. to ground requires you to provide a grounding electrode, connection to the secondary of transformer, etc. etc. Not likely to happen in a typical installation. And would require rewiring the Air Handler- in violation of the listing.

In our (North West Florida) area, the "High Leg" is designated fby the utility for use on three phase loads ONLY. That transformer is only capable of 87 1/2 % of its capacity due to the (mysterious) way t generates the third phase. It is under rated, AND undersized. The utility will tell you NOT to use it for single phase loads.

The NEC will limit the way you use this 208 volts to ground.

The bigger question is why take the High Leg and a phase to a sub-panel. WHEN THEY CANNOT BE USED??

Lynn Adams

In the computer rooms I have seen with center tapped delta they only serve 3 phase panels with the high leg. The other 2 legs will serve a single phase 120/240 panel for the office loads.
Even with that, we got in trouble with some equipment that had single phase L/L loads.