Mike Dolt Enterprises
Mike Dolt Enterprises
User: BigMike, Location: Las Cruces N.M.
Asked on: Thursday, October 27, 2005 at 3:09 pm EDT
Answered on: Thursday, May 9, 2024 at 12:46 pm EDT
Question: At the job site, we have a 240V high leg delta transformer that feeds numerous buildings. We added some three phase roof top units and they are not functioning properly. We measured the L-L voltage at the panel and it had:A-B: 254VB-C: 242VA-C: 243VWe told the utility about the problem and they don't seem willing to help the client out saying their voltage is "within spec". One option I was thinking of was installing a single phase transformer between A-B to reduce the voltage. Someone else mentioned using a UPS ($$$$$$$) which Im not even sure that would work. Should I just push back and say to replace with single phase roof top units? Anyone else have a better solution?
Understanding the Issue
The measured voltages indicate an imbalanced delta transformer, which is providing uneven voltages to the three phases. The utility's voltage may be within their specification, but it is not suitable for the proper operation of the three-phase roof top units.
Possible Solutions
1. Single-Phase Transformer (SWER) This is a viable option. Installing a 240V single-phase transformer between A-B will reduce the voltage to 120V, which is suitable for the roof top units. However, this solution only addresses the voltage issue and does not correct the transformer imbalance.2. UPS System While a UPS system can provide stable voltage, it is not typically used to correct transformer imbalances. Additionally, the cost of a UPS system is significantly higher compared to other options.3. Replace with Single-Phase Roof Top Units This is a straightforward solution that eliminates the need for voltage adjustments. However, it may require significant modifications to the existing electrical system and may be more expensive than other options.
Recommended Solution
1.
Communicate with the Utility
Explain the issue and provide the measured voltage readings. Request the utility to investigate the transformer and correct the imbalance.2.
Consider Single-Phase Transformer (SWER)
If the utility does not resolve the issue, install a single-phase transformer between A-B to reduce the voltage for the roof top units.3.
Monitor and Inspect
Monitor the voltage regularly after implementing any solution to ensure proper operation. Inspect the transformer and electrical connections regularly for any signs of imbalance or deterioration.
Additional Considerations: Consult with a qualified electrician for proper installation and safety measures. Consider the load requirements of the roof top units to determine the appropriate transformer size. Ensure that the transformer is rated for outdoor use if necessary. Flag for review