Switch 'Unsuitable for use with Fluorescent lighting'

[Nilly]

I want to change the regular light switch in my dark under-stairs cupboard for door-operated switch so that the light comes on when I open the door. Simple really.

There is a single bayonet light fitting in the cupboard which is currently fitted with an 18W CFL bulb. Even if I were to put a 100W incandescent bulb in the fitting the current draw would be less than 0.5A

So (noting that other retailers do exist) I find this:
www.tlc-direct.co.uk/Products/FM142W.html
a 1A push-to-break surface door switch but it says 'Unsuitable for use with Fluorescent lighting' How is this so? Does it mean those old-school fluorescent tubes or a CFL bulb in a bayonet or both? What is it about a fluorescent light that makes the properties of a simple on/off switch relevant?

It's bigger 2A brother, which oddly is 10 pence cheaper:
www.tlc-direct.co.uk/Products/FM143W.html
does not seem to suffer from the same limitation - so I'll be buying one like this, but I'm just curious!

 

[winston1]

Older florescent lights fitted with a choke have a large inrush current and can produce a large back emf when switched off which could damage the switch.

As an aside fluorescent or CFL lamps are unsuitable for your situation. Frequent switching on for a few minutes at a time will drastically shorten their life. Fit a LED bayonet lamp.

 

[Iggifer]

Older florescent lights fitted with a choke have a large inrush current and can produce a large back emf when switched off which could damage the switch.

As an aside fluorescent or CFL lamps are unsuitable for your situation. Frequent switching on for a few minutes at a time will drastically shorten their life. Fit a LED bayonet lamp.

wot 'e said

 

[ericmark]

I also agree.

 

[333rocky333]

I dont,

you just derate a normal switch for the inductive load, the 2 amp resistive load switch is likely good for 1 amp inductive load , aprox 50 percent
The amount of times you operate the switch is unlikely to have any noticable effect on a moderrn tubes life.
Have you considered led bulkheads
https://www.googleadservices.com/pa...ahUKEwiM9Onev-7VAhWhBsAKHbGhAzMQvhcIPw&adurl=

 

[bernardgreen]

the 2 amp resistive load switch is likely good for 1 amp inductive load

Current wise that may be correct. Voltage wise the switch has a maximum breaking voltage. As mentioned inductive loads create a large back EMF when the switch breaks the current and the energy in this back EMF creates an arc as the contacts move apart. Rapidly opening contacts will break the arc before it can do significant damage to the contact pads. Where the contacs move slowly the arc will be there long enough to do significant and accumalative damage to the pads.

 

[JohnW2]

There is a single bayonet light fitting in the cupboard which is currently fitted with an 18W CFL bulb. Even if I were to put a 100W incandescent bulb in the fitting the current draw would be less than 0.5A ....
a 1A push-to-break surface door switch but it says 'Unsuitable for use with Fluorescent lighting' How is this so?

Older florescent lights fitted with a choke have a large inrush current and can produce a large back emf when switched off which could damage the switch.

wot 'e said

I also agree.

I dont, you just derate a normal switch for the inductive load, the 2 amp resistive load switch is likely good for 1 amp inductive load

....As mentioned inductive loads create a large back EMF when the switch breaks the current and the energy in this back EMF creates an arc as the contacts move apart.

Virtually everyone seems to be talking about large inductive loads - which would have been the case with fluorescent tubes using large ('old') wire-wound chokes as their 'ballast'.

However, the OP has an 18W CFL, which is surely neither highly inductive nor of sufficient power to do any harm to a "1A" switch. I would personally have no hesitation in using such a switch for an 18W CFL.

Kind Regards, John

 

[ericmark]

Virtually everyone seems to be talking about large inductive loads - which would have been the case with fluorescent tubes using large ('old') wire-wound chokes as their 'ballast'.

However, the OP has an 18W CFL, which is surely neither highly inductive nor of sufficient power to do any harm to a "1A" switch. I would personally have no hesitation in using such a switch for an 18W CFL.

Kind Regards, John

I did hesitate myself, with a modern ballast they now need to be electronic anyway, the old inductive ballast has gone, so yes there seems to be no reason any more with any fluorescent to use contacts rated at higher voltages, however with any switch mode device first the AC is turned to DC and it charges a capacitor, so as to inrush it may still have one, depends on the quality of the device.

So now to nitty gritty how do you know what is inside a CFL? In general a fluorescent tube gives out between 75 and 95 lumen per watt, mainly dependent on the ballast used, I have two 8W CFL at my side rated 400 lumen, this is extremely low efficiency, made by Osram but no date, states made in China. Opening the packet all they have is a questionnaire asking how many energy saving light bulbs one has fitted in the last year, there is nothing saying electronic, and they are quite heavy, since never been used, not inclined to open bulb just to see what is inside, however there is a good chance these were sent to my dad when Manweb or Scottish power tried to push energy saving bulbs by sending free bulbs to old age pensioners.

Since only 50 lumen per watt and heavy think there is a good chance it has a wire wound ballast inside?

 

[JohnW2]

I did hesitate myself, with a modern ballast they now need to be electronic anyway, the old inductive ballast has gone, so yes there seems to be no reason any more with any fluorescent to use contacts rated at higher voltages, however with any switch mode device first the AC is turned to DC and it charges a capacitor, so as to inrush it may still have one, depends on the quality of the device.

Indeed. Yes, a CFL will have a bit of an 'inrush' current, but when the running current is (well, assuming {incorrectly!} a unity PF) around 80 mA, that inrush current is not going to be enough to worry a "1A" switch - and they ('modern' CFLs) are also far too light to contain a component which would have a significant inductance.

So now to nitty gritty how do you know what is inside a CFL? .... I have two 8W CFL at my side rated 400 lumen, this is extremely low efficiency, made by Osram but no date, states made in China. ... Since only 50 lumen per watt and heavy think there is a good chance it has a wire wound ballast inside?

I also have (somewhere!) a couple of very old (probably ~30 years), very large, low power and quite heavy CFLs made by Phillips which I have never used. However, I'm not sure that they are heavy enough to have an inductive 'ballast'. Assuming that one didn't want to use a hammer, one would have to measure the PF to find out - maybe I'll try that later, if I can find them!

Kind Regards, John

 

[ericmark]

If I can find a BA22d table lamp I will have a go, but not at home so not sure what is here.
Philips between 0.73 and 0.80 power factor power between 7 and 9 watts.
Osram 0.80 power factor watts on turn on 7 dropping to 3W.
Both look the same other than writing and both ratted 8W.
The max load shows 7 watt and 0.04 amp.
235 volt.

 

[winston1]

I also have (somewhere!) a couple of very old (probably ~30 years), very large, low power and quite heavy CFLs made by Phillips which I have never used. However, I'm not sure that they are heavy enough to have an inductive 'ballast'. Assuming that one didn't want to use a hammer, one would have to measure the PF to find out - maybe I'll try that later, if I can find them!

Kind Regards, John

The Philips SL series from that time did indeed use inductive ballasts. I recently had one fail (wear out) after 24 years. Can't complain really. They came in SL9, SL13, SL18, and SL25, the number referring to the wattage. Rough equavilant to 40, 60, 75, and 100 watts.

 

[JohnW2]

The Philips SL series from that time did indeed use inductive ballasts. I recently had one fail (wear out) after 24 years. Can't complain really.

Ah yes. If I can find them, I'm pretty sure that the couple I have (unused) are SL9s.

Kind Regards, John