PIR Sensor and CH flue

[nazn]

Hi there,

I have recently installed 2 floodlights that are to be controlled by an independant sensor. I am having major probs with the sensor sensing the exhaust fumes every time the boiler is used.

The sensor is located approx 4ft from the flue outlet at a right angle so te flue blows in the direction of the sensor. I have moved the sensor higher up and today built a metal shield around the flue to vent the fumes upwards all to no avail. I can't really move the sensor elsewhere as it's current location is the best spot for it to pickup any 'dancing bears' (from a previous post!)

I would appreciate any suggestions on how this problem can be tackled.

Msny thanks

Naz

[woodglass]

can you locate the sensor so that it is detecting the area lower than the flue. i.e. not looking at the 'hot' emmisions from the flue.

woodglass...

[r.p.mcmurphy]

fit a condensig boiler....colder flue, less likly to triger pir. even better is if you install a long flue at the same time as the boiler's fitted to divert flue gases upwards rather than straight out.

downside is cost. but at least your less likly to be burguled and lower gas bills!

steve

[Tom]

Are you sure that the PIR is being triggered by the hot flue gases or is it being triggered by the boiler spark affecting the electronics of the PIR? Just a thought! it may be worth eliminating before you take any expensive action. Otherwise use a different type of sensor, must be cheaper than a new boiler. Tom

[nazn]

I am not too sure about the boiler spark triggering the sensor, the boiler is quite old and has a permanent pilot rather than a spark thingy (sorry I don't know what this device is called but know what you mean...I think). I am not the market for a new boiler, if I was then it would be the condensing type, then again slightly off-topic... what's the average to get a return on a condensing boiler?

I have also considered moving the sensor lower than the flue outlet, but this would be too low and IMO an easy target for anyone to get at it (less than 2m). This unfortunately seems to be my only option,

Many thanks Naz

[Dave Liquorice]

Mask of the parts of the lens that look in the direction of the flue? Bits of insulating tape on the inside should do it.

[BIG NIGE]

Your PIR is looking for a moving heat source, the exhaust from your boiler is a moving heat source, you have to stop the sensor seeing the area where the exhaust flows before it cools (in all wind conditions) this will mean moving or masking of the PIR.(unless of course you fancy moving the boiler)

[Ian Stirling]

Insulating tape may be transparent in the IR - comes from the pigment being well under the wavelength of the IR. Metal backed tape will totally obscure it.

However, simply pointing the PIR away may work.

[nazn]

I am now considering moving the PIR further down the building, this will however mean part of the side fence will not be covered by the PIR. This will be approx 1.5m from the flu with the sensor pointing away from the flue.

Thanks for all the suggestions

Naz