Plug In Wall Timers & Low Energy Fluorescent Lighting ??

[Aletank]

I have a tall standing Uplighter currently with a 60Watt bulb in - (Max Allowed)
I planned on fitting a 15Watt Low Energy Bulb and plugging it into a wall timer for when I'm out.
I've just read the instructions of the wall timer and under the Safety Warning/Instructions it says "The timer is not suitable for low energy fluorescent or discharge lighting"
Does anyone know what thats all about ? Does that mean its not safe to use low energy bulbs with it or they just won't work ?

Thanks For Any Replies

 

[B-max]

I have the same question!! I think the answer is that the switch can't handle as much current when the load is inductive (a fluorescent) than when its resistive. The question is would it be unsafe?

 

[andy]

I have the same question!! I think the answer is that the switch can't handle as much current when the load is inductive (a fluorescent) than when its resistive. The question is would it be unsafe?

it says not to use it for that kinda load. doesnt take much brains to relize it says that for a reason

 

[kendor]

might be a solid state timer? ie Triac output as opposed to relay contact, therefore not suitable for switching inductive loads.

 

[breezer]

triacs can aand do switch inductive loads (they have to be derated, but thay can do it)

 

[kendor]

triacs can aand do switch inductive loads (they have to be derated, but thay can do it)

Yes there are also other circuits using triacs such as dimmers that are able to drive inductive loads but they tend to cost more to achieve this so in the case of this timer it may be cheap and cheerful hence the warning. One of the reasons is that inductors cause a back emf and this tends to limit current flow if this current is limited too far beyond the triacs Holding current specifications then it will simply turn off causing an unstable highly chopped waveform which can be potentially harmful to both the device and what it is driving( low energy lamps usually flicker because of this). a more sophisticated and correspondingly more expensive system will be designed with extra circuitry to compensate for this, not the sort of thing found in your common or garden timer.

 

[Aletank]

so in the case of this timer it may be cheap and cheerful hence the warning.

Ha ha - yeah £6 for a 2 pack - Mechanical type were you push the pegs in.
So what could be the dangers ? set on fire ? trip a fuse ?

 

[kendor]

so in the case of this timer it may be cheap and cheerful hence the warning.

Ha ha - yeah £6 for a 2 pack - Mechanical type were you push the pegs in.
So what could be the dangers ? set on fire ? trip a fuse ?

If mechanical type then that suggests a mechanical switch type so it may be the contact gap is not sufficient to operate such lamps due to gap jumping by the high voltages involved.

 

[mapj1]

What you will find is it will work, at least for a while, BUT the contacts of the timer will arc (flash!) when the contacts bounce on opening-closing, and will slowly oxidise away. Eventually the contacts will fail, and the lights will not come on. However, if the lighting load is really small compared with the contacts normal rating, there will not be much energy in the 'flash' of the arc, and the contact life may still be acceptable.
The question is how many million operations will the contacts withstand before failing, at any given load level.
When contacts are rated professionally, there are usually two ratings, one for 'pure resistive' loads, like heaters, (limited by contact heating) and another (often lower by a factor of at least 2) safe rating when switching inductive or capcaitive loads (inductors create a back voltage on switch off, capacitors create nasty current surges on switch on (but so do cold lamp filaments.) this second rating is that which is limited by arc damage)
If no such double rating is written on the box, you would be wise to assume a safety factor of 2 or maybe even 3 should be applied, and underload the switch accordingly.
Mind you at that price you could replace the timers every few years and not worry to much about the reduced lifetime.
(the usual design lifetime at rated load is usually the guarantee period plus one week, he says smiling cynically... )
regards,
m.

 

[Aletank]

I been using it a week so far anyway - lol, it sounds like it is safe to use and just damage to the timer is possible. For what the timer cost I'll see how long it lasts

 

[jacko555]

What about a relay?

If you want to tinker, how about a trip to Maplin. A 15a relay, box, cable glands etc shouldn't cost more than a tenner.

You could make a good 'heath robinson' security setup here, just put a cardboard cut out of a person , and put it between your lamp and a window (curtains closed of course)

You could even add a CD playing the noise of a dog barking to the timer...

But seriously now. A Relay sounds like a cheap soloution.

 

[ban-all-sheds]

Wouldn't a relay coil be an inductive load?

 

[sdavies21216]

Wouldn't a relay coil be an inductive load?

I would have thought it would be resistive, but then again I guess it does induce magnetism into the other set of contacts, so it might be inductive I guess. Hmm.

 

[bernardgreen]

I would have thought it would be resistive, but then again I guess it does induce magnetism into the other set of contacts, so it might be inductive I guess. Hmm.

Both resistive and inductive. Magnetism induced in yoke to attract armature to move and operate the set of contacts.....

Posted: Mon Feb 07, 2005 6:34 pm Post Subject:
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What you will find is it will work, at least for a while

About 4 and half years later it may be still working

 

[ericmark]

Any electronic switching will need some protection from inrush when used with an induction load cheap devices may not have this built it.
However not all discharge lighting uses an inductive start and current limiting device some use a system similar to switch mode and convert the AC to DC than back to HF AC and then transform to required voltage for start and run. In which case the inrush may be quite different to the simple inductive type.
But these types also have their own draw backs mainly in the way a small current can be stored and then discharged causing a flash at regular intervals.
The warning could be for either. So although it may work with one compact discharge lamp it may fail with another.
It is unlikely to cause danger by using wrong types of bulb but it may blow the unit.