FITZGERALD’S SENSOR OCCASION
With the increasing Government focus on energy efficiency and the amendment
to the Building Regulations, Approved Document L2, it is now necessary to
consider intelligent switching of lighting, and as a result, the benefits, including
the economical and environmental savings to the end user.
The present…
Until now, sensor options have been very limited, the traditional
PIR, a passive
device monitoring infrared radiation patterns, being the most common.
Incapable of sensing through solid objects, PIR technology places the sensor
outside the main housing of the light fitting, where it may be prone to
vandalism. Also, many exterior PIRs are IP54 rated at best, but are used to
control fittings with an IP65 rating, so the overall rating of the fitting is
compromised. Sensors separate from the luminaire can also look unsightly
adding to wall or ceiling clutter.
The future?
Fitzgerald Lighting now makes a range of products using the latest
Microwave
Sensor technology. Their new Occupancy Sensor option utilises a sensor head
mounted internal to the light fitting. Safely protected from the elements and
external damage, this option compromises either the product’s IP rating, vandal
resistancy, nor its aesthetic appearance.
How does it work?
The microwave occupancy sensor works by emitting a constant stream
of very
low power, high frequency radiation. It then monitors the radiation it receives,
which is reflected off solid objects in the surrounding environment. Changes in
the pattern of received radiation indicate movement and triggers the sensor.
The power density emitted by the microwave is less than 6% of the permitted
level at a distance of only 50mm from the face of the sensor head, making this a
very low power (and so safe) device. (As laid down in ANSI IEEE C95.1)
So what are the ideal applications?
Possible applications for this product are wide ranging. Some applications
where energy savings within lighting are required, demand more than just your
average PIR where it could be inappropriate, vulnerable, look unsightly, or
costly to install.
Recent installations include an educational establishment which had ramps
installed for wheelchair access. The ramps were for occasional use but had to
be extensively lit. So as not to have a high level of illumination at all times,
luminaires with microwave occupancy sensors were used. The luminaires were
positioned at a low level so as to be appropriate for wheelchair users; however
in this position the fittings were prone to being knocked. By having the sensor
within the luminaire it was protected from damage, and due to its low level
position, did not trigger unnecessarily.
Other typical application examples include corridors in schools, hospitals etc,
which don’t require high illumination levels when not occupied. By having
luminaires with an internal microwave occupancy sensor fitted, situated at
either end of the corridor wired in parallel, automatic switching of all the
luminaries takes place as soon as presence is detected. When used in areas
such as car parks, underpasses and stairwells which may be prone to vandalism,
other harsh conditions, and the occasional football, an internal microwave
occupancy sensor enables the luminaire to retain its IP rating, vandal resistancy
and negates the need for external detection components which themselves
could be easily damaged, as well as the initial installation time and costs.
Other external applications include porches, access ramps, door areas and
paths.
What other benefits?
- Quicker installation. Old-fashioned PIRs can be more expensive to install.
First you install the lighting, then the sensor. With the sensor already fitted in
the luminaire, there is only one installation to complete. Less time on site, less
risk of mistakes.
- Variable time-out. The delay before switch-off can be varied by the installer,
between 1 to 30 minutes.
- Lux level threshold. Adjustable light level sensor to control the threshold level
at which the load will be switched on.
- Variable sensitivity. To help prevent false triggering, or the sensor responding
to movements on the far side of a partition wall, the sensitivity can be adjusted
up and down.
- Presence or Absence detection. Each sensor can operate in presence or
absence mode. Presence mode switches on and off automatically in response
to movement and ambient light level. Absence mode requires the switch-on to
be manual, but the switch-off is automatic. Building Regulations, Approved
Document L2 specifically favours absence detection, because this mode is even
more energy efficient then presence detection.
- Manual override. There is a manual over-ride facility (essential in absence
detection mode), and the sensor head also has an IR receiver, making it
compatible with FLG Exodus hand-held remote controls.
- Switching capacity. The sensor includes a high power relay so that you can
use the sensor in one fitting to switch a number of separate luminaires.
Building Regulations, Approved Document L2
The recent amendment to the Building Regulations, Approved Document L2
specifically favour absence detection, Section 4.5 covers lighting controls and
quotes:
“Where it is practical, the aim of lighting controls should be to encourage the
maximum use of daylight and to avoid unnecessary lighting during the times
when spaces are unoccupied. …”
Part L2 of the building regulations increases the need for energy efficient
lighting. Variables to take into account include lamps types, control gear
efficiency, luminaire design, good use of daylight and effective use of lighting
controls and intelligent automatic switching.
And finally -
The microwave occupancy sensor is available within popular Fitzgerald
ranges
including Purlieus, Jupiter, Lodestar and Weatherpack. These fittings are all
designed for exterior use so the internal sensor is ideal in that it upholds the
installation and its vandal resistance. The microwave sensor is also available in
a selection of interior luminaries including the Municipal, Premier, Opaque and
Defa range.
On a final note, beware of imitations! There are microwave sensors available on
the market, incorporated in luminaries, which may not offer the features that
the Fitzgerald products do. They only offer presence detection, they have no
facility for a manual switch override and because they operate at a different
frequency from the Fitzgerald sensor, tend to trigger when rain falls on the
diffuser, which in a typical British Summer will mean very often!
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