For an underground car park, which obviously will be totally dark all the time without lighting, any form of PIRs or timers is totally useless.
Even if you want to still have these PIRs or whatever, a 2 minute delay is far too little - 20 minutes would be more like it, to cover those situations already mentioned such as people waiting in their cars and plenty of others.
This means in reality, the lights will be on most of the time anyway, and savings from these timers or whatever will be tiny.
20 fluorescent tubes would be approx 1kW load, and even if they were on for only 60% of the time (in reality it would be far more), you are only saving about £1 per day - £365 per year. It will be many years before the savings even cover the cost of the PIRs, timers and switches, not to mention the increased maintenance costs incurred in replacing the tubes far more often, cleaning the PIRs every month and replacing items damaged by vandals etc.
The car park should already have some form of emergency lighting to cover power failures etc., so good luck wiring timers and PIRs into that without extensive and expensive modifications. If no emergency lighting, then it's only a matter of time before someone is injured due to falling down in the dark and the massive compensation claim arrives shortly afterwards, which more than likely won't be covered by your insurance due to the negligent lack of lighting.
Even if you want to still have these PIRs or whatever, a 2 minute delay is far too little - 20 minutes would be more like it, to cover those situations already mentioned such as people waiting in their cars and plenty of others.
This means in reality, the lights will be on most of the time anyway, and savings from these timers or whatever will be tiny.
20 fluorescent tubes would be approx 1kW load, and even if they were on for only 60% of the time (in reality it would be far more), you are only saving about £1 per day - £365 per year. It will be many years before the savings even cover the cost of the PIRs, timers and switches, not to mention the increased maintenance costs incurred in replacing the tubes far more often, cleaning the PIRs every month and replacing items damaged by vandals etc.
The car park should already have some form of emergency lighting to cover power failures etc., so good luck wiring timers and PIRs into that without extensive and expensive modifications. If no emergency lighting, then it's only a matter of time before someone is injured due to falling down in the dark and the massive compensation claim arrives shortly afterwards, which more than likely won't be covered by your insurance due to the negligent lack of lighting.
