How to Find the Number of Incandescent Lamps in a Circuit?
How to Determine the Number of Incandescent Lamps in a Branch or Final Sub-Circuit?
If the current rating of a branch circuit or final sub-circuit has already been determined, and the proper cable and wire size has been installed according to that rating, you can calculate how many light points (lamps) can be connected to the circuit.
The following example and associated formula can be used to determine the number of lamps or bulbs that can be installed on a final sub-circuit or branch circuit:
Calculating the Number of Incandescent Lamps in a Circuit
230V/240V Circuits
Suppose we need to install 100 W light bulbs in a home, office, or hall for general lighting. The current rating of the specific final sub-circuit is 5-amp, and the supply voltage is 230V (120/240V in the US). The maximum number of lamps can be calculated using the following formula:
Power Rating of the Circuit (V × I) / Load Power in Watts (P)
Number of Lamps = (Supply Voltage × Current Rating of Sub-Circuit) / (Power Rating of Incandescent Lamp in Watts)
= (230V × 5A) / 100W
= 11.5
This means you can install 11 incandescent lamps, each rated at 100W, on a 5A, 230V branch or final sub-circuit.
120V Circuits
Now, we need to find the number of incandescent lamps that can be connected to a 120V, 15-amp branch circuit.
(120V × 10A) / 150W
= 8
In this case, the maximum number of incandescent lamps that can be installed on the branch circuit is 8.
Note:
- Final sub-circuits and branch circuits are designed based on maximum demand, meaning they are rated to handle the maximum power consumption when all connected appliances are in use.
- The Power factor is considered unity because incandescent lamps have a purely resistive load.
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If we want to install both kind of lamps(florescent and incandescent) then what is the formula? and in case of florescent lamp why we multiply the ratings of lamps by 2??? plz feed back me at live007messenger@mail.com thanx in advance
If you want to install both kind of lamps… Simply use
(Supply voltage * current rating of the sub circuit) / ((2* power of fluorescent lamps)+ power of incandescent lamps)
i.e. use the highest power rating.
How many are Fluorescent lamps incandescent lamps?
These are the minimum numbers of the different type of lamps which has to be installed in the final sub circuit…. There is another post for finding the number of fluorescent lamps and tube lights. In case of mix lighting points and bulbs with different wattage rating, use the highest power rating for division to be safe.
Please can some one send a detailed wiring diagram of ring mains circuit for lighting points for me. Not power ring circuit but lighting ring mains.