In the optional calculation methods 220.82(C) or 220.83, you're on the right track. Let's break down how to determine the amperage for a heat pump.You're correct in identifying the two key components: Compressor

12.4 Amps (This is likely the Rated Load Amps (RLA) or Full Load Amps (FLA))

Supplemental (Electric Resistance) Heat

2.3 Amps (This is likely the rating of strip heaters)Now, here's the critical part, the

NEC requires you to use 100% of the largest motor load plus 100% of the supplemental electric heat:Therefore, the total amperage for calculation purposes in 220.82(C) or 220.83 would be:12. 4 Amps (compressor) + 2.3 Amps (supplemental heat) = 14.7 Amps

Therefore, you would use 14.7 Amps in your calculation.

Important Considerations



Nameplate Data

Always rely on the

actual heat pump nameplate for the most accurate information. Look for terms like "Minimum Circuit Ampacity (MCA)" and "Maximum Overcurrent Protection (MOCP)". The MCA is a crucial number for sizing conductors, and it already accounts for the compressor and other loads that run simultaneously. MOCP will tell you what size breaker or fuse you need. Simultaneous Operation

The assumption here is that the supplemental heat can operate simultaneously with the compressor. This is generally the case, as supplemental heat kicks in when the heat pump struggles to meet the thermostat's setpoint.

In summary, your calculation of 14.7 amps is correct based on the information you provided (compressor RLA/FLA of 12.4 amps and supplemental heat of 2.3 amps). However, always verify this with the equipment nameplate data. Flag for review