Mike Dolt Enterprises
Mike Dolt Enterprises
User: Electric-Light, Location: Ware Shoals, South Carolina
Asked on: Monday, May 2, 2011 at 10:48 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:53 am EDT
Question: Some CFLs say it on the package, some don't.FEIT brand shows the same count-limit regardless of size. Both the 13W and 26W version warns:"Never use more than 25 lamps per 20A branch circuit".These use bulk-storage rectifier front-end and look the same as switching power supply to the line. Measured power factor is 0.55 and I'm guessing THD is between 100 and 130%, pretty typical for bulk storage rectifier front end load.so, the 13W version uses 24VA, which basically means 5A/600VA limit per 20A circuit, which doesn't make sense, because higher power switching power supplies, such as LCD TVs and computers can exceed that amount in single device.What is the basis for this limitation? Is there anything in the code about this?
Basis for the Limitation
The limitation of "never use more than 25 lamps per 20A branch circuit" likely stems from the following factors:
High Inrush Current
CFLs have a high inrush current when they are first turned on. This surge of current can overload the circuit if too many lamps are connected.
Power Factor
CFLs with bulk-storage rectifier front-ends have a low power factor, which means they draw more current than their rated wattage.
Harmonic Distortion
These CFLs also produce harmonic distortion, which can interfere with other devices on the circuit.
Overheating
If too many lamps are connected to the circuit, the total load can exceed the circuit's ampacity, causing overheating and potential fire hazards.
Code Requirements
The National Electrical Code (NEC) does not specifically address the number of CFLs that can be connected to a branch circuit. However, it does have general requirements for lighting loads:
Branch Circuit Ampacity
The ampacity of the branch circuit must be sufficient to handle the total connected load.
Overcurrent Protection
The circuit must be protected by an overcurrent protection device (e.g., circuit breaker or fuse) rated for the circuit's ampacity.
Additional Considerations
Manufacturer's Recommendations
The manufacturer's warning label should be followed for the specific CFL product being used.
Circuit Condition
The condition of the branch circuit should be considered. Older or damaged circuits may have reduced ampacity or insulation resistance.*
Other Load on the Circuit
Other devices or appliances on the same circuit can contribute to the total load and should be factored in.
Conclusion:
While the NEC does not specify a limit on the number of CFLs per branch circuit, the manufacturer's warning of "never use more than 25 lamps per 20A branch circuit" is likely based on the potential electrical hazards associated with high inrush current, low power factor, harmonic distortion, and overheating. It is important to follow the manufacturer's recommendations and consider the condition of the circuit and other loads when connecting CFLs. Flag for review