Okay, let's break down the calculations to determine if your panel has enough capacity for the two additional heat pumps.1. Calculate the Existing Load

5 HVAC units 40A/unit = 200A

2. Calculate the New Load

2 new heat pumps 43.8A/unit = 87.6A (This is the calculated load) 2 new heat pumps 50A/unit = 100A (This is the MOCP load)

3. Determine Total Load on Panel

Existing Load + New Load = Total Load 200A + 87.6A = 287.6A (Based on calculated amperage) 200A + 100A = 300A (Based on MOCP for new units)

4. Compare Total Load to Panel Capacity

Panel Capacity: 200A Total Calculated Load: 287.6A Total MOCP Load: 300A

Analysis and Conclusion

Based on the calculated amperage of the new units alone, you would exceed the 80% rule for the panel, which would mean the units could potentially overload the panel. Given that the new units have a 50A MOCP (Minimum Overcurrent Protection), the NEC would require you to use this amperage value to determine the actual load on the panel. Using the MOCP of 50A, you would be exceeding the panel capacity by 100A. Therefore,

you do NOT have enough capacity on your 200A panel to safely add the two new heat pumps according to the NEC.Important Considerations



NEC Compliance

You

must follow the National Electrical Code (NEC) for proper sizing and installation. Consult the most recent version of the NEC, specifically Article 440 (Air-Conditioning and Refrigeration Equipment). The MOCP provided by the manufacturer is crucial for code compliance. Voltage Drop

Consider the voltage drop that might occur with the increased load, especially with the new units being on the roof. Voltage drop can affect the performance and lifespan of the equipment.

Diversity Factor

It might be tempting to apply a diversity factor (assuming not all HVAC units will run at full load simultaneously). However, it is generally not advisable to apply a diversity factor to HVAC loads in this scenario. HVAC equipment is often sized to meet peak demand conditions, and relying on diversity could lead to undersizing and potential problems during hot weather.

Recommendations


Upgrade the Panel

The safest and most reliable solution is to upgrade the electrical panel to a larger capacity (e.g., 400A).2.

Subpanel

Consider adding a subpanel fed from the existing panel solely for the two new heat pumps. However, you'll still need to verify if the existing service has enough capacity to support the additional load on the original panel. This may require contacting your local utility company.3.

Load Shedding

This is generally not recommended for HVAC systems.4.

Professional Consultation

Engage a licensed electrical contractor to perform a thorough load calculation and determine the best course of action to comply with the NEC and ensure safe and reliable operation. They can assess the entire electrical system, including the service entrance and any other relevant factors.5.

Local AHJ

Consult with your local Authority Having Jurisdiction (AHJ) (e.g., electrical inspector) to confirm their interpretation of the code and any local requirements.

Disclaimer: Always consult with a qualified and licensed electrician for any electrical work.* Flag for review