Ron Lowe wrote:

"Mungo "Two Sheds" Toadfoot" wrote in message
...
I changed the screw-thread 60w tungsten bulb for an 11w low energy job and
now it won't turn itself off. Any ideas why?

Si



A fundamental difference between regular tungsten lamps and low-energy ones
it the current required to light them up.

A tungsten lamp is a low-impedance device, which requires a reasonable
amount of current to light up.

A low-energy lamp can illuminate with a minimal amount of current : even
minimal leakage current in some cases.

It seems that the PIR switching device has enough leakage current in it's
'off' state to light the low-energy lamp.

You need to change the PIR device to one with a lower leakage, or put back
the tungsten lamp, or do some electronic trick-****ery perhaps involving a
relay, or spoons.

--
Ron

Just to expand on Ron's and other's comments and try to make it
clearer there are two sorts of PIRs you'll find in the shops.
Expensive (properly designed in my opinion) ones require a live and a
neutral and provide a switched live output. These will work with any
sort of bulb. They do pretty much what you'd expect in that they are
a load on the circuit in the normal way, the current they consume goes
"in" the live and "out" the neutral. But that does mean you need a
neutral.

Now nasty ones are a bit different. They are designed as a kludge for
retrofitting in place of a normal light switch. In this situation you
might well find that there is not a handy neutral as typically only a
live and a switched live wire are taken down to a switch as good old
fashioned switches have no need for a neutral. This type of PIR uses
the light bulb itself as a path to neutral with its power flowing "in"
the live and "out" of the switched live, through the bulb and then to
neutral. The trick works fine for normal bulbs as they offer a path
to neutral but they will not give off any light with the tiny currents
involved.
As soon as you fit a low energy bulb in place of the incandesant all
bets are off. Some low energy bulbs don't provide a low enough path
to complete the circuit in their off state so the PIR doesn't work at
all. Some provide a low enough resistance path to complete the
circuit but will still glow a bit at the currents involved. Some will
charge up an input capacitor and give off a flash every so often as
the voltage across it gets high enough to strike the lamp which
discharges the cap, rinse and repeat.

As others have said however you might find that if the light is only
now on for very short times anyway you are OK with a normal bulb. My
hall lighting works this way and I'm very happy with it. The total on
time per day now is probably about 10 minutes whereas previously the
low energy bulb was on all evening.

Hope that helps,
Calvin