I need a 100a circuit from a 600a panel. The DP feeds the Hotels air handlers and lights in office areas etc. We are getting the load summary from service provider to make sure we have the room in panel. The 100a will feed a xfmr for a 200a 120240 panel for misc circuits. Is there anything I should be looking out for when trying to add the new load. The hotel has 2 services believe it or not. One 277480 and other 120208 same building. The 120208 has NO breaker space but the 480v has 2 spaces but I was just concerned if any concern why the building would have 2 services and or if you see an issue with using the 480v for whatever reason.
600a 277/480v service 3 4w
- Thread starter MBLES
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
They are allowed to have two services. Even if they weren't that is what is there so what difference would it make.
Even if you have no spare slots on the 208 panel you can probably add a panel if needed. Might be able to just feed through, or move a few circuits to the new panel. Might be easier than adding a xfmr.
It is about how much capacity you have available. Did you get a load calculation on both services?
Even if you have no spare slots on the 208 panel you can probably add a panel if needed. Might be able to just feed through, or move a few circuits to the new panel. Might be easier than adding a xfmr.
It is about how much capacity you have available. Did you get a load calculation on both services?
There is a 600a sub panel on different floor feed from DP. We have the load summary for the 120208 service so we know its good for new 200a. The DP 1600a with 2 sub panels 1200 and 600. The 1600 and 1200a have no space but the 600a has plenty space. We dont know the load on this 600a. any suggestions on how to determine how to provide load summary without 220.87 or do we need to do 30dayload anaylsis?
JFletcher
Senior Member
- Location
- Williamsburg, VA
You may be able to calculate the load on the 480 / 277 service fairly easily... Chances are it is only feeding 265 volt PTAC units, maybe some other AC units and kitchen equipment if there is a kitchen. If it's just ptac units, figure out how many, what kW the heating (which will be larger than the AC compressor mode, unless they are all heat pumps with reversing valves and no electric heat strips) is, do a demand calculation (which may be 100℅), and go from there.
If there is sufficient amperage available on the 208 / 120 service from the transformer, it will probably be cheaper to remove one of the existing breakers, install a larger one and feed a new sub panel than to buy a 480-volt breaker and transformer... Unless you absolutely need 240 volts and not 208.
ETA.. wouldn't a 480 volt- 120 / 240 volt three phase transformer be a high leg secondary?
If there is sufficient amperage available on the 208 / 120 service from the transformer, it will probably be cheaper to remove one of the existing breakers, install a larger one and feed a new sub panel than to buy a 480-volt breaker and transformer... Unless you absolutely need 240 volts and not 208.
ETA.. wouldn't a 480 volt- 120 / 240 volt three phase transformer be a high leg secondary?
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
I seem to recall something about a 2P breaker so i assumed it was a single phase xfmr he was thinking of adding.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Voltages to ground all depend on which secondary conductor you choose to ground. If the center of one secondary, yes, you'll have a high leg. If you ground one line, you'll have a corner ground.
In my opinion, with 120v loads, the best option would be a 480v to 208/120v wye transformer, and ground the neutral. I have the feeling you already know this stuff. My apologies if I'm right.
JFletcher
Senior Member
- Location
- Williamsburg, VA
I agree with you that if no space can be made in the 208 / 120 volt panel, or there is no room for expansion, then the transformer you mentioned would be the best option if there are no loads that require either 240 volt single or three phase.
A single phase 480 to 120 / 240 transformer maybe all the op needs, however using that would induce a load imbalance on the 480-volt primary, acceptability of which would depend on the current loading on the transformer and if there is already an imbalance present, which could be lessened or corrected by the addition of a hundred amp single phase load.
From the hotels I have seen, they are extremely lacking in space in the electrical rooms, and few would accommodate a 45 or 50 KVA transformer.
If there is space, and both 208 and 480 Services could accommodate the intended load, then it is simply a design choice as to which one MBLES chooses. All other things being equal, I would not install a transformer when the desired voltage is present, though it may be cheaper in this situation to install a transformer than trying to make room in the 208 switchgear.
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