Author Topic: RTI of Heat Detectors  (Read 2928 times)

Offline GB

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RTI of Heat Detectors
« on: September 07, 2017, 03:02:02 PM »
Good afternoon all,
I am conducting some CFD modelling on a high pressure mist system within a 2 storey domestic environment which uses a heat detector as the activation device.
I have spoken with the manufacturer of the heat detector in order to determine the RTI of the heat detector with no success.
They did state that the detector was in accordance with BS 5446-2:2003 which was all the information they could provide.
Does anyone have any information on the RTI of heat detectors or what the standard RTI is of BS 5446?
I know that in the US the manufacturer should in accordance with NFPA 72 state the RTI however that does not seem to be the case here in the UK.

Would also like to hear from anyone who has done CFD of high pressure mist in a domestic property to share our woes ::)

Offline Phoenix

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Re: RTI of Heat Detectors
« Reply #1 on: September 07, 2017, 11:24:40 PM »
"The RTI is a measure of how quickly a detector's thermal element will respond when exposed to a gas temperature at or above its alarm threshold...
 
"...the current measurement standard for RTI values of heat detectors does not provide adequate results that can be used to accurately predict the response time of heat
detectors."
That's from 2011.

Water mist in a domestic environment?  What if the window's open?  Might be a hot day - What if the door's open as well and there's a draught blowing through the room?  Consider sprinklers instead.

Offline GB

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Re: RTI of Heat Detectors
« Reply #2 on: September 08, 2017, 08:51:38 AM »
Thanks Pheonix.

Do you know what the standard RTI value is in BS 5466?

I also appreciate and share your concerns in relation to water mist and ventilation conditions however BS 8548:2015 does have a ventilation test therefore if passed, deemed suitable to use. These systems are out there being installed and approved by AHJ's therefore we need to try and understand their strengths & limitations.

In addition to the CFD modelling I am planning a couple of live full scale burns to try and understand the systems better and conduct a small scale comparison study with the varying HP systems and conventional sprinklers.


Offline Phoenix

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Re: RTI of Heat Detectors
« Reply #3 on: September 10, 2017, 09:53:26 PM »
No, unfortunately I don't know what BS5446 says about RTIs.

It is good to hear that you are doing some research and it would be even better if we could all benefit from it.  Well done on that front.  I shall remain a sceptic until convinced otherwise.


Offline GB

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Re: RTI of Heat Detectors
« Reply #4 on: November 07, 2017, 03:04:37 PM »
I have since reviewed 3No high pressure water mist companies whose literature states that they comply with the BS.
They do not on a number of items - please beware of bogus claims by high pressure mist companies!!

Online John Webb

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Re: RTI of Heat Detectors
« Reply #5 on: November 07, 2017, 07:34:42 PM »
"The RTI is a measure of how quickly a detector's thermal element will respond when exposed to a gas temperature at or above its alarm threshold...
"...the current measurement standard for RTI values of heat detectors does not provide adequate results that can be used to accurately predict the response time of heat
detectors."
That's from 2011.
Water mist in a domestic environment?  What if the window's open?  Might be a hot day - What if the door's open as well and there's a draught blowing through the room?  Consider sprinklers instead.

Phoenix - what's the source of your quote re RTIs, please? Just that with sprinklers the RTI has been measured for some years with reasonable results and I'm a bit perplexed as to why a similar technique can't be used with detectors.
John Webb
Consultant on Fire Safety, Diocese of St Albans
(Views expressed are my own)


Online John Webb

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Re: RTI of Heat Detectors
« Reply #7 on: November 11, 2017, 10:06:17 AM »
I'll take a look next week - rather busy this weekend with several things.
John Webb
Consultant on Fire Safety, Diocese of St Albans
(Views expressed are my own)