Key Takeaways
- Voltage Matters: Equipment rated for 240V can fail when utility voltage exceeds safe limits (255V+ in this case)
- Measure Multiple Times: Taking voltage readings over time reveals developing problems that single measurements miss
- Document Everything: Specific voltage readings help utilities respond quickly to dangerous conditions
- Protection Options: Permanent voltage monitoring and surge protection can prevent expensive equipment damage
The Way It Works
The Proterra is a hybrid water heater system that utilizes both a heat pump and electric resistive heating elements to maintain domestic hot water at set point. This dual-mode operation provides efficiency through the heat pump while ensuring rapid recovery through resistance heating when needed. The system can be configured in several operating modes depending on user preferences and demand patterns. But we’re not here to discuss its operation – we’re here to find out why it was tripping.
The Problem And The Solution
After a quick visual inspection, everything looked okay except for telltale signs of overheating on the upper resistive element. This was the first clue that something electrical was amiss.
The tank is rated for 240V, but when I measured the incoming voltage, it read 255.4 volts – well above the acceptable range. After monitoring for an hour or two, the voltage had increased even further. I immediately informed the customer, who contacted the utility company. They showed up within an hour and corrected the situation. After the voltage reduction, the breaker hasn’t tripped again.
Check out this Instagram post and conversation on this topic.
Utility Over Voltage Is A Serious Problem
The utility company’s swift response demonstrates they take these voltage issues seriously, as excessive voltage can cause widespread damage beyond just one appliance. When voltage exceeds equipment ratings, it increases current flow through resistive elements, causing them to overheat and potentially fail. This accelerated wear affects not just water heaters but all electrical equipment in the home – from heat pump systems to sensitive control boards.
This case serves as an excellent reminder why taking multiple voltage readings over time, rather than a single snapshot measurement, can reveal developing problems that might otherwise go unnoticed. Just like we emphasize proactive maintenance scheduling to prevent failures, monitoring voltage trends can prevent catastrophic equipment damage.
Learn more in the following short podcast where this call is described in detail.
Side Note: Don’t Jump To Conclusions – Measure First (And Often)!
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