Hi,

Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Will it damage the bulbs or photocell, or both? Is it due to a
higher start up current?

Only looking to switch 22watts on one photocell and 52watts on a
separate circuit.

Is it worth the risk?

Hoping someone can explain this one!

Many thanks


Matthew

On 14 May 2007 05:09:13 -0700 someone who may be Matthew
wrote this:-

Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Alternatively one can get dusk to dawn luminaires designed for bulbs
like the 2D.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Largely because some of them avoid having a connection to the
neutral conductor to save a few pence.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On May 14, 1:24 pm, David Hansen
wrote:
On 14 May 2007 05:09:13 -0700 someone who may be Matthew
wrote this:-

Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Alternatively one can get dusk to dawn luminaires designed for bulbs
like the 2D.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Largely because some of them avoid having a connection to the
neutral conductor to save a few pence.

--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Cheers David,

Unfortunately the lights are already installed and wired in.


Largely because some of them avoid having a connection to the
neutral conductor to save a few pence.

Should they work with CFL's, but its not recommended etc?

Thanks

Matthew

In article om,
Matthew writes:
Hi,

Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Will it damage the bulbs or photocell, or both? Is it due to a
higher start up current?

It's due to the photocell expecting to power itself by passing
a low current through the filament during daylight hours. This
doesn't work with compact fluorescents. It would probably stop
the photocell working properly, and might damage the CFL longterm.

Look for a professional quality one of the type used in streelamps
which have a neutral connection and relay to switch the light,
and will be rated for something like 1000W. Here are some which
you can add to an existing luminaire...

http://cpc.farnell.com/jsp/search/pr...sp?sku=LA02802
http://cpc.farnell.com/jsp/search/pr...sp?sku=LA02803
http://cpc.farnell.com/jsp/search/pr...sp?sku=LA01127
http://cpc.farnell.com/jsp/search/pr...sp?sku=LA02228

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article om,
Matthew wrote:
Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Because they are designed to replace a switch, and therefore have no
discrete neutral to complete a power circuit to operate them. They obtain
the neutral via the much lower resistance of a filament bulb in the 'off'
state. CFLs have a much higher 'off' resistance so don't 'bleed' through
enough current.
That's the usual reason. Other reasons may be the electronic switching
can't handle the inductive load of a CFL.

--
*Time is the best teacher; unfortunately it kills all its students.

Dave Plowman London SW
To e-mail, change noise into sound.

On May 14, 1:32 pm, (Andrew Gabriel)
wrote:
In article om,
Matthew writes:

Hi,

Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Will it damage the bulbs or photocell, or both? Is it due to a
higher start up current?

It's due to the photocell expecting to power itself by passing
a low current through the filament during daylight hours. This
doesn't work with compact fluorescents. It would probably stop
the photocell working properly, and might damage the CFL longterm.

Look for a professional quality one of the type used in streelamps
which have a neutral connection and relay to switch the light,
and will be rated for something like 1000W. Here are some which
you can add to an existing luminaire...

http://cpc.farnell.com/jsp/search/pr...sp?sku=LA02228

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Ah, I see.

That explains why the light in the study, which has a security switch
on it (photocell and random timer) flickers slightly during the day
with a CFL in it. They were in when we moved in, so never even
thought about them not working with CFL's.

Looks like I'll have to replace them (the switch)- now the house is
about 95% CFL's.

All makes sense now!

Cheers,

Matt

On 14 May 2007 05:31:00 -0700 someone who may be Matthew
wrote this:-

Should they work with CFL's, but its not recommended etc?

Depends on the photocell, for reasons already explained. Get the
ones that will work properly, often the more expensive ones.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 14 May, 13:42, Matthew wrote:
On May 14, 1:32 pm, (Andrew Gabriel)
wrote:
In article om,
Matthew writes:

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?


Will it damage the bulbs or photocell, or both? Is it due to a
higher start up current?

no and no

Looks like I'll have to replace them (the switch)- now the house is
about 95% CFL's.

All makes sense now!


The other option is to put one filament lamp and the rest CFL on each
photocell. The filament lamp can be 15w if preferred - or even lower.


NT

On Mon, 14 May 2007 13:37:30 +0100, "Dave Plowman (News)"
wrote:

In article om,
Matthew wrote:
Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Because they are designed to replace a switch, and therefore have no
discrete neutral to complete a power circuit to operate them. They obtain
the neutral via the much lower resistance of a filament bulb in the 'off'
state. CFLs have a much higher 'off' resistance so don't 'bleed' through
enough current.
That's the usual reason. Other reasons may be the electronic switching
can't handle the inductive load of a CFL.

Maybe the photocells could be connected to a relay and that could
operate the lamps?

M

On Tue, 22 May 2007 10:24:17 +0100, Mark
wrote:

On Mon, 14 May 2007 13:37:30 +0100, "Dave Plowman (News)"
wrote:

In article om,
Matthew wrote:
Looking to fit a photocell(s) to some outside lights, which contain
low energy (CFL) lamps.

Many of the photocells say they are not suitable for Low Energy
Bulbs? Why is this?

Because they are designed to replace a switch, and therefore have no
discrete neutral to complete a power circuit to operate them. They obtain
the neutral via the much lower resistance of a filament bulb in the 'off'
state. CFLs have a much higher 'off' resistance so don't 'bleed' through
enough current.
That's the usual reason. Other reasons may be the electronic switching
can't handle the inductive load of a CFL.

Maybe the photocells could be connected to a relay and that could
operate the lamps?

A relay works by being inductive itself... :-)

--
Frank Erskine