Heat detector placement - skylight

[xpabu]

Hi

I've just had an extension built, building control want to confirm "[there has been consideration of] the heat reservoir effect of the skylight when installing the heat detector."; unfortunately the electrician who installed the detector is now on long term sick (but did sign off his work beforehand) and the builder's replacement electrician  (subcontractor) is saying a full assessment of the house will be required for them to comment.

I've attached a photo; the cooker/hobs are to the right of the picture--I can see building control's point but don't know how to assess if this is in guidelines or not. I've tried to reach out to a few other electricians but they're not interested as there's no other work required. 

Thanks in advance!

Paul

 

[Sharpend]

I would suggest that it is in an inappropriate area as is. I would have sought to install it in a more central position and should be a minimum of 300mm away from the edge of the opening. I would look to fit it between lights 2&3 of long side at possibly 500-600 away from edge. 
where it is will be potentially be subject to greater heat as it is has the tall cupboard adjacent which will trap heat above it, it is also closer to the wall which again will create a warm spot. 

 

[xpabu]

I would suggest that it is in an inappropriate area as is. I would have sought to install it in a more central position and should be a minimum of 300mm away from the edge of the opening. I would look to fit it between lights 2&3 of long side at possibly 500-600 away from edge. 
where it is will be potentially be subject to greater heat as it is has the tall cupboard adjacent which will trap heat above it, it is also closer to the wall which again will create a warm spot. 

Thanks--that's really helpful: I actually thought the detector may 'miss' any heat as it would go into the skylight area first--but you suggest the opposite and in fact it may actually alarm easier in its current location.

Thanks

Paul

 

[Sidney]

I would be seekig advice from the manufacurer. Some state 300mm and/or 150mm away from walls, light fittings etc. Edges like that aren't mentioned in the installation instructions.

 

[xpabu]

I would be seekig advice from the manufacurer. Some state 300mm and/or 150mm away from walls, light fittings etc. Edges like that aren't mentioned in the installation instructions.

Yeah--that's a good idea. I assume building regs override the manufacturer (you'd hope would the manufacturer always align with regs...). Thanks

 

[binky]

I would have thought heat flowing past detector is more likely to trigger the alarm, but I suppose that would depend on where the fire is. 

AICO have on line guides for installation.

 

[Geoff1946]

Unless I'm mistaken heat detectors don't trigger on temperature, but detect rapid rate of change (probably only increase), of temperature.

In event of fire this is likely to be concentrated on a flat expanse of ceiling rather than by a point of ventilation such as that skylight.  

I would definitely be going for manufacturer's instructions though.

 

[SPECIAL LOCATION]

As binky said AICO have loads of support into both hard-copy & online...

Such as:-

https://www.aico.co.uk/technical_support/alarm-siting/

Guinness

 

[xpabu]

Excellent, thank you everyone, really appreciate your help. Will look at the Aico online stuff.

 

[Bruspark]

Having a look back through my info this manufacturer seemed to have covered your situation   http://greenbrook.co.uk/product-pdfs/AHPM_Ins.pdf

If possible I would get the (/an) electrician to wire a second identical alarm in the 'cathedral' bit  as they show, as close as possible to the room centre without also being in full sunlight, 
and linked to the existing one.  I hope it will then be difficult for building control to think of a case in which neither alarm would go off 

HTH

 

[Fleeting]

The problem here is the void dropping away by the detector and how this affects the performance of the detector. On a flat ceiling heat can readily accumulate around the device however the void can produce a chimney and possible vortex effect drawing heat away from the detector. This drawing of heat can be considered the reservoir effect whereby it is drawn away from the detector and pooled into the void until sufficient heat is accumulated into said reservoir to equalise and drop down to cause the detector to activate. 

 

[xpabu]

Thanks all-- I think you are spot on, @Fleeting --think that's exactly what building control are talking about. Will try and get someone to install a second one in the 'cathederal' bit! Will let you know how i get on.

 

[Fleeting]

Thanks all-- I think you are spot on, @Fleeting --think that's exactly what building control are talking about. Will try and get someone to install a second one in the 'cathederal' bit! Will let you know how i get on.

Probably speculation on my part but the unusual situation and visualising what may happen in the event of a fire it seems to make sense but then again it could be off the mark.

 

[Murdoch]

the builder's replacement electrician  (subcontractor) is saying a full assessment of the house will be required for them to comment.

that’s utter garbage.
 

They could simply assess the circuit the heat alarm is on and check the MIs for you

the question is why it’s where it is? Where is the oven and hob?