Electrical Load Question

[crokett]

The basement heaters are on a 220V 20A circuit. As per the nameplate ratings, they total 15A when all are on together. They are zoned to 3 different t-stats and AFIK are either on and drawing their max ratings or off, there is no in between. My FIL wants to add another heater with a rating of 5A to bring the total to 20 possible A. Question is, do I need to add a new circuit and rebalance them ? The heaters are a resistive and therefore predictable load, not variable like motors are.

[master53yoda]

The basement heaters are on a 220V 20A circuit. As per the nameplate ratings, they total 15A when all are on together. They are zoned to 3 different t-stats and AFIK are either on and drawing their max ratings or off, there is no in between. My FIL wants to add another heater with a rating of 5A to bring the total to 20 possible A. Question is, do I need to add a new circuit and rebalance them ? The heaters are a resistive and therefore predictable load, not variable like motors are.

minimum circuit ampacity is amps x 125% so 16 is maximum amps on a 20 amp circuit. If you add that heater to the circuit you will blow the breaker if it is on much more then 10 minutes with the others. You should add a new circuit.

good luck