120/240 three phase (high leg) load centers and panelboards

[electrofelon]

Just a brief update here on a topic that comes up frequently. I didnt try to dig up the threads I am thinking about, but one was discussing whether three phase loadcenters were ok on a high leg delta system. The other was about using a true panelboard factory marked as 120/208Y on a high leg delta system. Regarding the loadcenter, I did some digging and everyone I could find was marked as suitable for either system. There is no update to that, just recapping. The second case however is a bit more curious. I had said that for siemens panelboards, the part number system does have a different letter code in the part number scheme for 208Y/120 and 120/240 delta, i.e. P1C42ML250ABST VS P1B42ML250ABST where the C is a 208Y/120 system and the B is a high leg delta system with the B phase the high leg. I had also said that I doubted there was any actual difference other than the factory marking (and presumably for the B version strategic factory placement of two pole breakers or use of straight rated breakers in the appropriate locations). I have used C coded panelboards on high leg systems several times and just relabeled the system type. Recently I went to order a factory B panelboard and discovered that they no longer offer the B system type for a P1, you have to go up to a P2 series to get that voltage (they go from P1 to P5 in increasing size and capabilities). So I asked why that was and this is the response I got:

"When Siemens redesigned the P1 the B voltage was removed as there was ‘low volume’ of panels requiring the voltage."

Which doesnt really answer the question. I still stand by being nearly certain there is no actual difference in the construction of a P1C and a P1B. I wonder if it is just an administrative reason, like perhaps UL charges $20,000 for every voltage system evaluated as part of the testing and listing process and siemens decided to skip it for the P1? IT doesnt make a lot of sense to me that I can get a rinky dink loadcenter that can be used on either, but a nice rugged true panelboard cant be used on both? Any ideas?

 

[Knightryder12]

I would think that in either case that it would not be cost effective to build two different load centers or panelboards for 120/208 or 120/240v systems. I would think it would be like disconnects that are rated for 240v and 600v. That bus in that panel will handle 240v.

 

[kwired]

I can mostly only tell you what I know about Square D panels.

There is only one NQ series panelboard in their catalogs, it is rated for 240 volts. Whenever I have purchased these I almost always specified the components and assembled what I needed from stocked items from my supplier, occasionally maybe had to wait for some component they did not have to come from the manufacturer.

Only time I know of getting a panelboard that is marked 208/120 would be if you ordered a factory assembled unit, then they would custom mark it that way though it is still assembled with the same components as a 240 volt panel is assembled with. Factory assembled has always had longer lead times and why I have always ordered the components and field assembled them. The past couple years or so those lead times got even longer and did impact getting components for field assembly as well.