120/240V Delta Question

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Make sure to get a nice engraved label made for the panel.
Siemens plug on straight (240V) rated breakers are commonly available the plug on breakers use a different part number that ends in R, like Q220R
Eaton BR straight rated breakers end in H, like BR220H
 
ptonsparky said:
How would you size the transformer?
You would still be using a phase that was not intended for L-N loads.
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On top of that commonly available buck boost transformers don't have ability to configure a buck coil of up to 88 volts.

It would need to be higher VA rating since it is making that large of a voltage change than what is needed for 208 to/from 240 buck boost situations as well. This likely makes it more practical to just use a full isolation transformer for this situation if it weren't for the problems it might cause for the source transformer.

Of course that also means another panel for 120 volt loads you want to supply from the high leg or a transformer for every branch circuit you run off of it. I guess it would be the same for a buck boost as well though. If you bucked the incoming high leg before the main panel to have 120 to neutral on that line you wouldn't have 240 for phase to phase loads anymore, I think it should be about 152 phase to phase if you did that. Plus the buck transformer again would need to have high VA rating to carry all the load it would be handling.
 
I'm a little confused about the 277/480V panel comment. @kwired Are you saying if we use a 277V/480V panel we would not have to use fully rated 240V breakers, and we could use 120/240V breakers instead?

@ptonsparky correct, I'm just wanting to make sure it's not a code violation, I did not think about the shared neutral situation, but just for some more information. These aren't typical tenants. It's more of a telecomm room, that is shared by multiple providers (i called them tenants), but once their equipment is installed, it's left alone for 5+ years until new upgraded equipment that provides better coverage is going to be installed.

@winnie there are some 120V convenience outlets and single pole lighting for the room where the equipment will go in, but that wont be fed from this providers/tenant's panel. I'm thinking worst case if they ever did need to add a 120v circuit, we could potentially feed off the 120/240V panel and still be able to run that circuit through the sub meter since most of the emon meters can handle multiple circuits.

@xformer I'm not really sure how this would work if the B phase is the hi-leg? but i'm also not an expert on buck boost transformers:)

Thanks for all the help guys!
 
i missed the last two comments

@tortuga yes, I'll definitely be sure to get a big engraved label for the panel. I'm also thinking about placing labels next to each 2 spaces stating 240V breakers/loads only.

@kwired thanks for the explanation on that
 
Kidd said:
I'm a little confused about the 277/480V panel comment. @kwired Are you saying if we use a 277V/480V panel we would not have to use fully rated 240V breakers, and we could use 120/240V breakers instead?
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No. You need breakers that are rated for 240V to ground. The 'trick' is that the breakers in a 277/480V panel are 'slash' rated for 277V to ground, and you can use them for lower voltage.

Kidd said:
@ptonsparky correct, I'm just wanting to make sure it's not a code violation, I did not think about the shared neutral situation, but just for some more information. These aren't typical tenants. It's more of a telecomm room, that is shared by multiple providers (i called them tenants), but once their equipment is installed, it's left alone for 5+ years until new upgraded equipment that provides better coverage is going to be installed.

@winnie there are some 120V convenience outlets and single pole lighting for the room where the equipment will go in, but that wont be fed from this providers/tenant's panel. I'm thinking worst case if they ever did need to add a 120v circuit, we could potentially feed off the 120/240V panel and still be able to run that circuit through the sub meter since most of the emon meters can handle multiple circuits.
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Sound like a lights out facility that just needs 240V. Meaning 120V loads will be small.

Good luck. Sounds like you have your head around it.

After the installation is completed, please post back with an update.

Jon
 
Kidd said:
I'm a little confused about the 277/480V panel comment. @kwired Are you saying if we use a 277V/480V panel we would not have to use fully rated 240V breakers, and we could use 120/240V breakers instead?
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Winnie basically answered the question, I will add a little to it though.

You basically won't find a single pole breaker in the commonly available 120/240 types that is rated for 208 or more to ground. You can find two and three pole breakers for these panels that have a straight 240 rating and those can be used on the high leg, but that burns additional spaces if you are intending to use a single pole only.

A 277/480 rated single pole breaker is already rated for more than 208 to ground so no problem using that in such a situation as we are talking about here other than whether it is a good idea for transformer loading reasons. For that matter you could also use 600 volt rated breakers (could get this in something like I-Line panels and breakers) and they would be compliant as well.

A single pole 120 volt rated breaker will work, but is not designed and tested to be used for this.
 
tortuga said:
He can run the lights off the 240 L-L but would need 2 pole contactors / switches and or occupancy sensors per article 410.
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Or could run them on 208 volt high leg to neutral with single pole switches, have to be 277 rated switches though, but then comes the other problems mentioned with availability of proper rated breakers and transformer loading issues.
 
Thanks guys for your help! @winnie , @kwired , @tortuga

Also thanks for the explanation on the 277/480V breaker trick. I'll let you all know how this one turns out, but for now I'm designing it as a straight 240V, single phase panel.
 
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