Mike Dolt Enterprises
Mike Dolt Enterprises
User: highpowered, Location: los angeles
Asked on: Tuesday, March 15, 2011 at 3:00 am EDT
Answered on: Tuesday, May 14, 2024 at 2:49 am EDT
Question: Client has asked a question without giving me all info needed but here goes160 amp appleton 4pinw/sleeve 240v 4 wire=200 amp rated fused disconnect(125%)-Existing 30kva transformer line is 480/277v-also have a mobil office needs 120v 20 amp im assumingmy calculation is 40 amp line breaker 80 amp load breaker@120/208. this dosnt make sense?i dont think the 30kva is enough for that type of load? is there any way to configure existing transformer to carry a 200 amp240v load plus the mobil office?id appreciate any help im tired and its been a long time since i did a transformer calc
Transformer Capacity Calculations
The existing 30kVA transformer with a 480/277V secondary cannot handle a 200A, 240V load plus the mobile office's 120V, 20A load.
200A, 240V Load
200A x 240V = 48,000VA
Mobile Office Load
20A x 120V = 2,400VATotal Load: 48,000VA + 2,400VA = 50,400VA
Transformer Rating
50,400VA > 30,000VA (transformer capacity)
Circuit Breaker Calculations
Your calculations for the circuit breakers are correct based on the information given:
Line Breaker
40A (125% of 32A calculated load)
Load Breaker
80A (125% of 64A calculated load)
Possible Solutions
To provide power for the 200A load and the mobile office, the following options can be considered:
Upgrade Transformer
Replace the 30kVA transformer with a larger one that can handle the increased load.
Use a Separate Transformer
Install a separate transformer dedicated to the 200A load, leaving the existing transformer for the mobile office and other loads.
Reduce Load
Determine if the 200A load can be reduced to a level that the existing transformer can handle.
Maximize Load Distribution
Ensure that the loads are evenly distributed across the transformer phases to minimize voltage imbalances.
Additional Considerations: The wire size and conduit used for the 200A load should be rated for the expected current. Proper grounding and bonding should be implemented to ensure safety.* A licensed electrician should perform all electrical work and verify the system's compliance with electrical codes. Flag for review