On Sun, 24 May 2009 18:26:05 +0100 someone who may be "Johnny
OneSpanner" wrote this:-

The police recommend a sodium lamp, but are the CFL-based floodlights also
suitable?

Depending on the particular sodium lamp, sodium lamps are likely to
have a lower life-cycle cost due to the lower running costs for a
given lighting level. OTOH it will be more difficult to achieve an
even level of illumination with sodium lamps, as fewer will be
needed for a given level of illumination. However, fewer lamps may
mean less wiring depending on the particular circumstances.

I would go for sodium lamps, there is a selection at
http://www.tlc-direct.co.uk/Main_Index/Lighting_External_Index/Lighting_Floodlight_Index/Commercial_Lighting/index.html

Sodium lamps with dusk-til-dawn sensors seem to be quite thin on the ground,
should I use a separate sensor?

They have advantages and disadvantages, the main disadvantage being
that if it fails there will be no light at all, or light all day. If
you go for one drive a relay/contactor from it and use that to
switch the lamps.



--
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