I have a project where we are providing a 3-phase, 480V generator plant for 3-buildings with each building having 2 services; 1-480V, 3-Phase Service and 1-120/240V service for each building. Aside from the obvious phase imbalance issues, can anyone comment on potential issues.
3-Phase Generator Plant serving 3-Phase and 1-Phase building services
- Thread starter Rwat
- Start date
- Location
- Bremerton, Washington
Is this the only power to the buildings?
Why not use 208Y/120 for the single phase?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Agreed. Very few modern loads must be supplied with 240v vs 208v.
TwoBlocked
Senior Member
- Location
- Bradford County, PA
- Occupation
- Industrial Electrician
Just don't underestimate the phase imbalance issues. This might not apply to you situation, but saw a facility with utility power and genny backup. 3-ph 480V going to a number of air compressors with Wye-Delta starters, and 1-ph 480 going to the primary of a 480/120-240 transformer going to an MCC. Everything was fine until one day the utility power was shut off for an upgrade. The Wye-Delta starters had a delay that was long enough that only the single phase transformer loaded the genny. The genny saw an imbalance long enough to shutdown, which was before the 3-ph air compressors came on. The work around was to open the primary breaker to the 1-ph transformer until an air compressor kicked in, then energize the transformer thereby feeding the MCC. The imbalance setting was changed to a higher setting (I forget just what, now) as a fix, at least temporarily.
With three buildings in your design, might never be an issue, but if for some reason two buildings are shutdown, it could be.
With three buildings in your design, might never be an issue, but if for some reason two buildings are shutdown, it could be.
Yes
All buildings on This part of the Base are fed like this.
The 480, 3-Ph and 120/240,1-PH are the services to each building
So you cant use 208 due to specs or something?
Its interesting this keeps coming up.
If you have to have 120/240, and you have to balance the 480 genny and your tight on capacity
then I'd go for a scott-t transformer and use 2 single phase feeders off it.
That would keep the genny balanced enough.
Its interesting this keeps coming up.
If you have to have 120/240, and you have to balance the 480 genny and your tight on capacity
then I'd go for a scott-t transformer and use 2 single phase feeders off it.
That would keep the genny balanced enough.
- Location
- Bremerton, Washington
At the generator, is there separate ocpd for each building? If so then the power to each building is a feeder. The service is from the generator to the first ocpd.
At least that’s my opinion
At least that’s my opinion
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I thought only utilities provide services, and all generator lines are feeders.
- Location
- Bremerton, Washington
I don’t know the current codes as well as previous, but in this case, isn’t the generator considered the utility? Wasn’t there a change for a location with no poco, like a remote cabin
Birken Vogt
Senior Member
- Location
- Grass Valley, Ca
I would like to know the answer to this question too if there was a change.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
You are correct. If there is no POCO, there is not a service.