Ok once again I need help. I am down in Texas doing emergency power assesments in support of FEMA operations. However i have had a serious brain lapse in the last few hours and cant for the life of me figure this out. I have to size generators for a few E.O.C.s running out of office buildings. What generator voltage do i need to request in order to go straight into the panel box and heat up lighting and a/c's. i need 110/208 but i cant get a 3 phase generator that produces 110/208 and hook it up to the panel can i? So i guess what i need is a single phase, 110/220 3 wire generator right. please help i need to get this straight in my head.
Backup Power Sizing
- Thread starter coke03p
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Re: Backup Power Sizing
Most generators that you get from a rental yard that caters to construction or entertainment are going to have a switch in them that configures them as 208Y120 (what you want) or 480/277 (what you don't want!). Smaller ones also do 240/120 at (I think) 66% of their rated capacity. I'm talking traler mounted units here, if you are getting units meant for hardwiring, you will have to hook it up for the correct voltage. Don't forget proper grounding no matter what you do!
As usual, check all voltages (twice) before you bring your load online. If that switch is in the wrong position, god's pitty on you!
Good luck in Texas!
Most generators that you get from a rental yard that caters to construction or entertainment are going to have a switch in them that configures them as 208Y120 (what you want) or 480/277 (what you don't want!). Smaller ones also do 240/120 at (I think) 66% of their rated capacity. I'm talking traler mounted units here, if you are getting units meant for hardwiring, you will have to hook it up for the correct voltage. Don't forget proper grounding no matter what you do!
As usual, check all voltages (twice) before you bring your load online. If that switch is in the wrong position, god's pitty on you!
Good luck in Texas!
Re: Backup Power Sizing
Yes you can use 2 legs of the 3 phase 120/208 into the panel. How do you think the utility power got there? It is single phase (2 legs and a neutral) of a 3 phase service.
If you can get high enough in the distribution panels in the building and connect to a 3 phase panel, the load can be balanced over all 3 phases. If the generator is not big enough, or the building is damaged etc, you'll just have to use single phase.
In any case watch the load (amps) on each line and do not exceed rating. The engine will only be loaded at most at 2/3 of its capacity, and the set will only supply 2/3 of its KVA capacity when using only two lines.
Yes you can use 2 legs of the 3 phase 120/208 into the panel. How do you think the utility power got there? It is single phase (2 legs and a neutral) of a 3 phase service.
If you can get high enough in the distribution panels in the building and connect to a 3 phase panel, the load can be balanced over all 3 phases. If the generator is not big enough, or the building is damaged etc, you'll just have to use single phase.
In any case watch the load (amps) on each line and do not exceed rating. The engine will only be loaded at most at 2/3 of its capacity, and the set will only supply 2/3 of its KVA capacity when using only two lines.
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- Windsor, CO NEC: 2017
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Re: Backup Power Sizing
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