High frequency lighting with low frequency fittings

Henryp · Nov 28, 2021

The bulb in my bathroom went the other day. It's a fluorescent 2d 4 pin that says 50hz on the fitting. I looked for a similar bulb to replace it, however none of them mentioned anything about frequency. When I received the replacement I bought, it had 50 to 60hz crossed out on the packaging and 20khz ticked. Is this a definite no to use in my fitting or just inefficient. If a definite no, what bulb should I go for instead?

dogbob · Nov 28, 2021

We're going to need some more information to be certain, but if the bulbs are basically the same type, you should be fine with the new bulb.

We know that 50Hz or 60Hz means the power mains frequency. I believe (but can't be certain from afar) that 20kHz means the switching frequency of the electronics inside the bulb, just above the frequency that humans can hear.

To be certain, we need the part number of the old and new bulbs. Even better, you need to make sure that the new bulb has the same part number as the old one. Even if most of the characters are the same and the shape is the same, that doesn't mean that it is interchangable.

There is a possibility that the bulb you bought is intended to work with electronics outside the bulb. In that case, it would be absolutely wrong for your fixture. But if that were so, it would not have the same part number.

By the way, I have a fluorescent fixture in my kitchen that takes two 4-pin bulbs. Those bulbs would fail every 6-9 months. I got sick of that, so found LED replacements with the same physical size and pin pattern on Amazon. These install into the same fixture BUT they required that I remove (bypass) the ballast inside the fixture. The bulbs came with instructions for how to remove the ballast. It was easy and worked the first time. These LED replacements have been working flawlessly for 5 years. I hope I never need to buy any fluorescent lamps again in my life, for anywhere.

Henryp · Nov 29, 2021

dogbob said:
We're going to need some more information to be certain, but if the bulbs are basically the same type, you should be fine with the new bulb.

We know that 50Hz or 60Hz means the power mains frequency. I believe (but can't be certain from afar) that 20kHz means the switching frequency of the electronics inside the bulb, just above the frequency that humans can hear.

To be certain, we need the part number of the old and new bulbs. Even better, you need to make sure that the new bulb has the same part number as the old one. Even if most of the characters are the same and the shape is the same, that doesn't mean that it is interchangable.

There is a possibility that the bulb you bought is intended to work with electronics outside the bulb. In that case, it would be absolutely wrong for your fixture. But if that were so, it would not have the same part number.

By the way, I have a fluorescent fixture in my kitchen that takes two 4-pin bulbs. Those bulbs would fail every 6-9 months. I got sick of that, so found LED replacements with the same physical size and pin pattern on Amazon. These install into the same fixture BUT they required that I remove (bypass) the ballast inside the fixture. The bulbs came with instructions for how to remove the ballast. It was easy and worked the first time. These LED replacements have been working flawlessly for 5 years. I hope I never need to buy any fluorescent lamps again in my life, for anywhere.

Thank you! I've taken a couple of photos of the bulbs, new and old:
the wilko is the old and the philips is the new. Also I was wondering what the cylindrical philips device was, I've heard the term 'starter' thrown around in the context of fluorescent bulbs but I wasn't sure if that's what it was.

Alas, were I in my own accommodation I'd steer clear of fluorescent bulbs, but I'm replacing a bulb in a flat I'm renting (otherwise I fear I will be in the dark for many weeks)