Breaker Masking
Why you need to know what’s on your plugin solar circuit.
-----------------------------------
Breaker masking happens when solar power flowing backward into a circuit makes the circuit breaker “think” less current is flowing than actually is. The breaker may not trip when it should.
Example:
- Circuit is protected by a 15A breaker.
- You plug in a 1,200W (10A) solar source.
- A device on the same circuit draws 12A from the home.
- Solar pushes 10A backward, so the breaker sees 12A – 10A = 2A.
- Even though 22A is actually flowing THROUGH the wires, the breaker only “feels” 2A and does NOT trip.
- That can overheat wiring.
HOW TO MANAGE THIS
------------------
The key is ensuring your solar does not combine with other appliances on the same circuit in a way that masks the real current. Solutions include:
- Using a dedicated circuit with no other loads.
- Using a smart breaker or Smart Plug monitoring.
- Keeping your solar system small enough that masking risk is low.
WORKSHEET – IDENTIFYING WHICH OUTLETS ARE ON THE SAME CIRCUIT
--------------------------------------------------------------
Instructions:
Turn off the breaker for the outdoor outlet you are planning on using and walk your home to see which outlets lose power.
​
Breaker Number: ____________
​
For each outlet/light/appliance, check the correct box:
- Dead (on this breaker)
- Still Working (different circuit)
​
ROOM / OUTLET LIST
------------------
​
Location: ___________________________
â–¡ Dead â–¡ Working
​
Location: ___________________________
â–¡ Dead â–¡ Working
​
Location: ___________________________
â–¡ Dead â–¡ Working
​
Location: ___________________________
â–¡ Dead â–¡ Working
​
Location: ___________________________
â–¡ Dead â–¡ Working
Also add up the wattage for any lights or other appliances that are on that circuit. For example a wall heater, TV, etc.
Notes:
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
If using a 15 amp circuit start with 1,800 watts and subtract the wattage from your solar plugin system. If the balance is greater than all the appliances remaining on the circuit you are fine. You must also factor in plugging in appliances like a vacuum cleaner or a space heater (approximately 1,200 watts).
Example:
15amp circuit = 1,800 watts.
400 watt plugin system - 1,800 – 400 = 1,200 watts available
800 watt plugin system – 1,800 – 800 = 1,000 watts available
Note: A 20amp circuit = 2,400 watts
Solutions –
1. Have a dedicated circuit installed.
2. Mark all the outlets on the circuit to prevent any large appliances from being plugged in or only use chargeable devices (we only have a rechargeable vacuum).
3. Purchase a NEC smart breaker from Craftstrom. Www.craftstrom.com ($200).