Backfeeding 120/240V service from new 208V 3phase service

M

monitaverma

Member
Existing service at the house is 800amps, 120/240V, 1-phase. There are (4) existing panelboards. We are doing remodeling, and all HVAC units are new, 240V, single phase. After one year there is going to be service upgrade to 208V, 3phase. What are my options to back-feed existing service board?

  • Install 225 kVA transformer (208-3phase to 120/240V 1-phase) and back-feed 800amps, 120/240V, single phase service. Problem with option is that this transformer is not readily available in the market.
  • Install small size transformer and back- feed each of the existing panelboard.
  • Feed all existing panelboards from new 208V, single phase. Provide buck boost transformer to all HVAC units to convert 208V to 240V single phase.
 
C

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
monitaverma said:
Existing service at the house is 800amps, 120/240V, 1-phase. There are (4) existing panelboards. We are doing remodeling, and all HVAC units are new, 240V, single phase. After one year there is going to be service upgrade to 208V, 3phase. What are my options to back-feed existing service board?

  • Install 225 kVA transformer (208-3phase to 120/240V 1-phase) and back-feed 800amps, 120/240V, single phase service. Problem with option is that this transformer is not readily available in the market.
  • Install small size transformer and back- feed each of the existing panelboard.
  • Feed all existing panelboards from new 208V, single phase. Provide buck boost transformer to all HVAC units to convert 208V to 240V single phase.
Click to expand...
Are you the homeowner? GC? or EC?

Three phase to single phase transformer is not happening. You would be using a single phase to single phase transformer.

Most HVAC equipment is designed to run on 208V or 240V.

You can keep the existing single phase panels but will need to balance the loads over the 3 phases. AB - BC - AC.........
 
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