One for the electricians.
I am about to embark on swapping my workshop twin 5' fluorescents with LED replacements.
We have had this discussion before but I don't recall anyone else experiencing this problem (I have had contact weld switching 2x twin
5foot lamps). Farnell do a flock of inrush suppressors but I don't know which if any to use or whether the thermal output requires a separate enclosure.
What's the question exactly?
If you are fitting LEDs I wouldn't expect any problems with inrush currents or switching under load. So just a regular switch would be fine.
Are you changing the whole fitting or retrofitting LED tubes? You may find it easier to change the fitting, but otherwise you need to bypass the fluoro control electronics and just put the LED tube across the live and neutral.
Theo
Inrush current is a known issue with LEDs. It's why the specifications for LEDs list it. May not matter for ordinary domestic use but all too easy to think that it's only the power and stable current that matters when looking at big loads. Can trip MCBs too.
Indeed. I have in mind using NTC thermistor current limiters to limit the inrush current. I will have up to 6 twin 5' fittings on each circuit.
>
If you use NTCs you'll need to calculate what you need. Another option is to use relays, so power goes through a protected power R for a moment before direct mains is applied. In the latter setup one must ensure it behaves safely if the relay stays in the resistor position.
I need to piggy back on this thread. The old Thorne single and double fittings for the big diameter tubes I have seen swapped with just a removal of the starter. However, there are fittings in a room we do not own, whose tubes are tired and weedy now. Both have Electronic Starters that stop that flashing and hence come on all at once. Can we simply replace these with LED ones that fit, or does the high voltage from the ballast unit cause problems with this. Don't want to end up with no light at all in somebody elses room. And the nightmare of lumens and colour temperature is extremely confusing. Obviously, we have sighted people at that place and so we do need light enough to read by, but nothing that causes eye strain. Brian
In message <tt7abg$1r1s1$ snipped-for-privacy@dont-email.me, Brian Gaff snipped-for-privacy@gmail.com writes
Wait for the experts Brian but you can either ignore or simply short out an inductive ballast.
The electronic ones need to be re-wired to bypass the ballast circuit.
Various diagrams available on line for the sighted.
IIRC Tim planned to keep the old gear in the fittings so the calculation is not so simple (and for a DIY circuit beyond me in any event).
There are "universal" LED tubes that can be used with either type of ballast.
And even more "universal" ones that can be used with either or none:
In message snipped-for-privacy@outlook.com, Robin snipped-for-privacy@outlook.com writes
Hmm. 5' version comes in a £32 odd locally. Might be worth it for Brian.
Yes, I should have said I had Brian in mind. Though I expect you'd get a discount for 10 off :)
You should not get inrush current issues except with electric motors, incandescnet bulbs or large capacitors in a SMPS.
Certainly never with fluorescents.
You generally get large inrush currents with non dimmable LED lamps.
You can also get large inrush currents with fluorescents, they sometimes have a large power factor correction capacitor of many uF straight between live and neutral.
I think a zero crossing style switch would be best! Then any 'inrush' would be over a full half cycle.
I'd thought the best agricultural solution was a knife switch - with hammer to hand ready if it plays silly buggers :)
But if the MCB will cope with the inrush current I'd be inclined to suck it and see with the switch given I think Adam said before he hasn't met problems with them in practice.
I guess a lot depends on the robustness of the switch. I'm using exterior twin gang which are fitted with microswitches.
Not exactly the environment for electronic switchgear and still fed from rewireable fuses!
CPC Farnell are momentarily boxing up my order.
Now some real knowledge.
The inrush on a single 6 foot LED tube blows a 3 amp fuse!
Also, despite strong cardboard tube protection, they don't survive transport very well. Two broken out of 3 supplied:-(
That's odd. I have 5x 5 foot LED tubes in my loft, on a 2 amp fuse in a FCU (total about 50W). Never considered inrush current, the fuse has never blown.
These are the most basic (cheap) kind, just LED tape in an enclosure, probably with a simple capacitive dropper.
Are yours perhaps fancy enough to have their own constant current controller? Was it a quick blow fuse?
Theo
Normal domestic fuse in the fitting. The only unusual feature might be the shortness of the feed cable from a 30 amp ring.
At £11.99ea. not likely to be anything fancy.
I don't think that's a truth universally acknowledged :)
What make and model of tube?
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