# Can I Use a 60 Watt Bulb in a "40 Watt Max" Fitting?

• Civilian2
In summary, if you want to use a bigger wattage bulb, leave the globe off. Otherwise you might have a fire problem.
Civilian2
Gday,

This is a very simple question and it should only take one sentence to answer. It's not worthy of these forums, lol, but despite my efforts I cannot find an answer through google.

If a light fitting says '40 watt max' and I stick a 60 watt bulb in it, will that have any adverse effects? I assume what will happen is that only 40 watts of power will be fed into the bulb thus not fulfilling the bulbs potential brightness, but I'm unsure and thought I better ask before I do it.

No, it's a heat consideration. A 60-watt bulb generates more heat than a 40-watt bulb, and if you use it you'll be putting more heat into the globe than it is designed to handle. You'll still get the same light output from the 60-watt bulb that it would give in any other circumstance.

KM

If you want to use a larger wattage bulb, leave the globe off. Otherwise you might have a fire problem.

Thanks for your response. I'll simply go and buy some 40 Watt bulbs, lol.

Assume you have a 120volt supply. The bulb resistance will cause a particular current to flow ($$I=V/R$$) and this will result in a certain amount of power being dissipated ($$P=VI=V^2/R$$). This means that a 40watt bulb has a specific resistance resistance ($$R_{40W}=V^2/P=120^2/40=360\Omega$$) and that the resistance of the 60W bulb is different ($$R_{60W}=V^2/P=120^2/60=240\Omega$$). The 60W bulb will cause ($$I_{60W}=V/240=0.5 Amps$$) to flow, compared with ($$I_{40W}=V/360=0.33 Amps$$).

The fitting doesn't know the difference, but it is possible that the difference in current could damage light wiring or that the extra heat could damage plastic fittings. A more significant effect depends on the cold resistance of the bulbs (before they are turned on) because this determines the initial current. The higher wattage bulb has lower hot resistance and so probably has lower cold resistance. The higher starting current may cause you to blow more bulbs.

It probably won't hurt (I have just replaced a 25W bulb with a 60W bulb because that was all I could get) but if you are the careful sort then follow the manufacturer's directions.

## 1. Can I use a 60 watt bulb in a 40 watt max fitting?

It is generally not recommended to use a bulb with a higher wattage than the maximum recommended for a fitting. This can cause overheating and potential fire hazards. It is best to stick to the maximum wattage indicated on the fitting.

## 2. What will happen if I use a 60 watt bulb in a 40 watt max fitting?

Using a bulb with a higher wattage than recommended can cause the fitting to overheat, potentially leading to damage or fire hazards. It is best to use the recommended wattage for safety purposes.

## 3. Can I use a lower wattage bulb in a 40 watt max fitting?

Yes, it is safe to use a lower wattage bulb in a fitting with a higher wattage limit. However, the lower wattage bulb may not provide the desired level of brightness.

## 4. How do I know the maximum wattage for a fitting?

The maximum wattage for a fitting is usually indicated on the label or packaging. If not, you can also check the manufacturer's specifications or contact them directly for the information.

## 5. Can I use an LED or CFL bulb with a 40 watt max fitting?

Yes, you can use energy-efficient bulbs such as LED or CFL bulbs in a fitting with a 40 watt maximum. These types of bulbs use significantly less wattage while still providing the same level of brightness.

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