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CFLs and rental properties.

Discussion in 'Hobby Electronics' started by kreed, Mar 31, 2009.

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  1. kreed

    kreed Guest

    Ran into a friend today who works as a property manager in a local
    real estate agency.

    He brought up the subject of CFL's and specifically there had been
    several complaints from tenants about them burning and smoking when
    they failed. Apparently "loud bangs" had also happened in some cases
    and at least one CFL "had literally exploded".

    Also mentioned , (the failure?, or just a shitty plastic to metal
    joint ?) had caused the white plastic bases to disintegrate, leaving
    the bayonet part stuck in the light fitting, the rest, hanging from
    the wires, no (safe) way to remove it, and needing an (expensive) call
    to an electrician to remove the thing, the cost of which ended up on
    the landlord.
    The language used to describe this situation was VERY far from polite.

    He also claimed that there were several tenants that had bought (one
    had in excess of 100 bulbs) quantities of incandescants, based on word
    of mouth about them being withdrawn from sale, and not wanting to use
    these "shitty" new ones. Poor light quality (of CFL) was also
    mentioned by some.
    (he had seen boxes of stored incandescent bulbs during property
    inspections and asked). He said that for his own use, he had already
    bought a "significant quantity" from Haymans, following all these

    I told him of the dimmer problem as best as I could in laymans terms
    (he isn't a technical person at all) and I advised that they arrange
    with property owners to get any dimmers removed from all their rental
    properties ASAP. He promised me he would check if the premises that
    had had the catastrophic bulb failures had been using dimmers.

    I also told him of the "flashing" problem, he remembered hearing
    complaints of intermittently flashing CFL's in bedrooms, - noticed
    because he noticed in a property inspection one woman had stuck a
    black cloth into a wall light fitting to avoid having to put up with
    flashing at night while trying to sleep. (great potential fire hazard
    I reckon)

    Not surprisingly, the electricians they use didn't seem to have a clue
    as to why. I advised a double pole switch.

    His opinion was (quote) "It's the fucking CFL's should be banned, not
    the normal light bulbs".
  2. Sylvia Else

    Sylvia Else Guest

    That would often be a major wiring job. It's quite common for the
    neutral wire not to go anywhere near the switch.

    Except that I'd have to suspect that the flashing is a result of the
    switch being in the neutral wire, possibly with the live wire not going
    anywhere near.

  3. Jasen Betts

    Jasen Betts Guest

    that sounds like overkill and would be kind of hard to retrofit.
  4. Jasen Betts

    Jasen Betts Guest

    there can be enough capacitance between the live and switched live in
    the run from the socket to the switch to provide current enough to
    make the lamp charge up and flash.

    "grounding" the switched live to neutral when the switch is off would
    stop the flashing but that requires another conductor to the switch.
  5. Sylvia Else

    Sylvia Else Guest

    Resistor (of appropriate quality) across the inputs to the CFL?

  6. KR

    KR Guest

    To respond to both posts:

    (note - I am talking Australian standard switches and wiring methods,
    other countries might be different.)

    Jasen -
    Like you, I did originally think of shorting the switched active to
    neutral when "off" too, however it was pointed out to me that typical
    AU light switches are not rated sufficiently for connecting the active
    and neutral directly to both the NC and NO terminals (insulation may
    break down or arc between the "throw" terminals potentially causing a
    short or a fire). This was also mentioned in one of SC's recent
    articles on DIY house wiring.

    In almost all domestic light circuits I have seen locally, both the
    active and neutral come back to the switch plate and the main active
    and neutral are available there too, hence the double pole switch
    would probably be the easiest and quickest method in these cases.

    I have seen one light circuit where the main active and neutral were
    present at both ends (switch and bulb) and a single (switched active)
    wire ran to the light socket from the switch.

    A resistor (or small bulb like a standard 240v mains rated neon "on"
    indicator wall plate insert) may be able to be connected between the
    "throw" terminal (the position it is in when light switch is in the
    off position) and neutral, this way the switch "throw" terminals
    would never be directly across the actual mains, solving that problem.

    In normal use, the indicator/resistor would never actually come on,
    also avoiding greenies predicable howls of protest that it "wastes

    I suggest using the neon indicator rather than just using a carbon
    resistor from DSE, because neon its approved for fixed wiring type
    240v use, (therefore safer if there is a catastrophic failure ), is in
    its own insulated case, readily available, has screw terminals built
    in etc.

    Installations where there are 2 way switches, motion sensors, wired in
    timers and so on are a bigger problem. you could then probably put the
    neon indicator insert directly across the bulb socket in the ceiling,
    or obtain a suitably rated "bleed" resistor.
  7. KR

    KR Guest

    Well... As long as the neon starts to conduct at a lower voltage
    than the CFL "starting" circuit................
  8. Sylvia Else

    Sylvia Else Guest

    Don't neons have a resistor in series anyway?

  9. F Murtz

    F Murtz Guest

    In Australia unless it has changed the practice was to take the active
    and neutral +earth to every light fitting point and send a twin to the
    switches therefore very rare to find a neutral at the switch.
  10. ian field

    ian field Guest

    Well... As long as the neon starts to conduct at a lower voltage
    than the CFL "starting" circuit................

    Most CFLs I've had apart used a diac starter circuit - AFAIK with a
    breakover voltage about 32V.
  11. ian field

    ian field Guest

    If you have a neutral at the switch plate, a single pole changeover will
    do - simply switch the lamp feed from live to neutral

    In the serious bodge category, if there's no neutral switch the feed to
    earth (I wonder how many lamps it would take to trip a ELCB?).
  12. KR

    KR Guest

    they do.
    I discovered that (at age 10) that if you dont have the resistor, and
    connect a neon across 240v, it tends to go "bang"
  13. Sylvia Else

    Sylvia Else Guest

    Did you do it multiple times to test this hypothesis, as part of the
    scientific method? ;)

  14. Davo

    Davo Guest

    I thought neons needed a fairly high start voltage? In which case a neon
    wouldn't do what you're trying to achieve. From what I've read, you're
    trying to stop a build up of induced voltage in the wires to the lamp.
    By having the neon in series with the resistor you essentially have an
    open circuit until the voltage is sufficiently high for the neon to
    conduct. That's why you have a starter and inductor in a normal
    fluorescent light, the operation of the starter causes the inductor to
    produce a high voltage spike that makes the tube conduct.
  15. Davo

    Davo Guest

    I'd suggest the wiring has been incorrectly done in the first place and
    needs to be fixed. A big part of the wiring regulations now states that
    if you have knowledge of bad wiring you have a legal obligation to get
    it fixed or disconnected. You can't "turn a blind eye" so to speak. In
    industry this is known as "duty of care".

    This is the sort of action that kills people. An electrician doing this
    would probably end up in gaol on a manslaughter charge.
    Not sure what you mean here but domestic ELCBs trip at 30mA.
  16. glenbadd

    glenbadd Guest

    Interesting. I have 2 CFLs on a 2-way circuit (at each end of a
    The CFL in one of the fittings flashes (very faintly every few
    The other one doesn't. Swapping over the CFLs indicates it is
    related to the fitting and wiring, not the CFL itself.

  17. Phil Allison

    Phil Allison Guest

    "Davo the Dickhead "

    ** Funny how the things work so well on the US 115 volt supply then - with
    just a series resistor.
    ** What case?

    You never posted one - cos you do not have one.

    ** False conclusion based on a silly false premise.

    ** Which occurs are what voltage ??

    Use Google if you like.

    ** Totally pig ignorant false comparison.

    Fluoro tubes are nothing like neon bulbs.

    ...... Phil
  18. Phil Allison

    Phil Allison Guest

    "Davo the Dickhead "
    ** I suggest you find out something about electricity before posting utter
    crap like this.

    Starting with how a neon bulb operates.

    Work your way up to stray capacitance and leakage current as you feel able.

    However, the complexities of a CFL are forever beyond a moron like you -
    so give up on them.

    ** Irrelevant CRAP.

    Davo the Dickhead is a just another pathetic "big noter" with a grab bag
    half baked facts.

    ** Wot a load of bollocks.

    All electricians know to treat installed neutral and live wires with the
    same respect and care.

    The public are never meant to touch either of them.

    ...... Phil
  19. Jasen Betts

    Jasen Betts Guest

    Last time I checked it was perfectly legal to run the live(red)+neutral(black)
    +earth(green+yellow) from the fusebox to the light fixture and then run a
    branch from there to the switch with a 2 conductor cable with just live(red)
    and switched live(white)

    As has been observed the capacitance between live and switched makes this setup
    less than ideal for use with CFLs.
    I doubt a cfl would conduct significant current if wired between earth
    and neutral, it does seem like a bodge though.

    would putting a Class X2 capacitor in parallel with the lamp be
  20. KR

    KR Guest

    Yes, that is correct and would stop the CFL from flashing (by shorting
    together the 2 lamp wires when power is off) , but the problem is that
    you cannot safely connect both the active and neutral directly to the
    2 "throw" terminals of a standard Australian light switch, there is a
    high risk of arc / breakdown between the 2 throw terminals, leading to
    a short and/or a fire.


    As I said in another post, using a resistor in series with the neutral
    to the throw terminal, or wall plate type neon insert (subject to its
    breakdown voltage being lower than the CFL's "start" voltage
    threshold) is the only safe way I can think of achieving a safe result
    with this method.

    the ideal solution would be for CFL makers to put a "bleed" resistor
    across the filter cap. I doubt it will happen though.

    Note - If trying this in any other electrical system, note that as
    well as the insulation breakdown switch, if you use any type of "make
    before break" switch, you would cop a dead short circuit across the
    supply - check the switch first before applying power.

    probably wouldn't trip an ELCB, but I wouldnt try wiring anything to
    the earth except things that are meant to be earthed. at least it
    would probably trip the ELCB if the switch insulation failed.
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