Replace wired smoke alarms
- Thread starter MrMrMr111
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Confirmed with Nest that it doesn't have to have WiFi to work, it will use it own method, and also on the wired ones, if power falls, it will still work on its own battery.
If you use WiFi though, you can use the app for alerts etc
If you use WiFi though, you can use the app for alerts etc
And it's own method is ?
What does it do if it's wireless channel is blocked ?
What does it do if it's wireless channel is blocked ?
As has been said and implied, I think there is a terminological issue here. I imagine that "it's own method" is to use its own wireless capability - which, as you say, will involve a wireless channel which might possibly be 'blocked' at any point in time - such is the nature of the technology. I similarly image that the "WiFi" which "is not required" refers to the standard (usually internet-connected or, at least, network-connected) 'WiFi' system, which is not required for operation of the detectors, but can (if present and working) be used to interact with it.
Kind Regards, John
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They will still work independently though, I can imagine the alarms are quite loud also so would hear. Don't know specifics, but I can imagine due to laws that if the WiFi doesn't work and the use their "own" WiFi system it is quite robust, for safety laws?
If using their own wireless, it only has that to worry about, no other devices, of course it could get blocked our crash, but again imagine it's been tested so surely it works restart the link somehow?
If using their own wireless, it only has that to worry about, no other devices, of course it could get blocked our crash, but again imagine it's been tested so surely it works restart the link somehow?
It obviously depends upon the size and layout of the house, but I' sure that one quite often would hear a distant alarm. However, 'quite often' is by no means 'always'- and that, indeed, is presumably the reason for the requirement that alarms be interconnected.
If it's a reputable make, then one assumes that, as you say, they would be quite 'robust' - but, as bernard has pointed out, there is no way of ensuring that any such wireless connection is guaranteed to work at the moment it is needed. However, although I'm not particularly familiar with this area, I believe that wireless interconnection of alarms is permitted to 'the powers that be' are presumably less concerned than bernard that their communication channel may get 'blocked'.
Having said all that, I can but agree with BAS that, in whatever context, if a wired connection is in any way possible, it is always to be preferred to any sort of 'wireless' one. The modern obsession with 'anything wireless' is, IMO, not really very clever!
Kind Regards, John
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The usual reason to use wireless linked alarms is when it is impractical to fit the interconnect wiring.
It seems retrograde to fit wireless linked alarms where the interlink wire already exists!
It seems retrograde to fit wireless linked alarms where the interlink wire already exists!
Indeed and indeed. As I wrote:
Kind Regards, John
If the channel is blocked by transmissions from some other system the alarm can only "re-start" once the channel is clear.
The regulations that apply to licence exempt transmissions in the 868- 870Mhz do mean that the risk of blocking from a compliant system using two way communication is small.
Calculating the maximum delay in the interlink between fire / smoke alarms due to blocking from one or more nearby and compliant system does give a result that suggests there would be no significant delay ( from memory ) in 99.95% of incidents.
For the other 0.05 % the delay would increase the risk to the occupants by delaying but not preventing the interlink.
The problem is when the blocking is due to a non-compliant system which may transmit without any breaks for long periods. Various non compliant transmitters can be purchased from a variety of sources. Some are specifically intended to be used to intentionally block the 868 Mhz band for criminal and anti-social purposes.
An idea of many compliant 868 Mhz licence exempt items will be in use in the next few years can be found here.. ( 80 page PDF )
http://stakeholders.ofcom.org.uk/binaries/consultations/tlc/annexes/Final_report.pdf
An interesting "conflict" from a few years ago when some fire alarms interlinked on 173 Mhz ( which I if recall correctly required the issue of a licence and then the annual payment of a fee to be able to use the channel. )
A listed building ( Grade I ) had to be fitted with fire alarms connected to a fire control centre.
Conservation Officer stated it had to be wireless to avoid the need to "damage" the fabric of the building by running cables.
A fire safety expert said it would have to be wired as wireless could not be relied on and in the long term a few holes were less damaging than a fire that was not reported to the fire control centre in time to save the building.
The wired system was installed.
A listed building ( Grade I ) had to be fitted with fire alarms connected to a fire control centre.
Conservation Officer stated it had to be wireless to avoid the need to "damage" the fabric of the building by running cables.
A fire safety expert said it would have to be wired as wireless could not be relied on and in the long term a few holes were less damaging than a fire that was not reported to the fire control centre in time to save the building.
The wired system was installed.
Well which is it? Do they use WiFi to talk to each other or not? It would seem a ridiculous idea to use WiFi instead of something simpler, but then there are far too many people "designing" products these days who don't have the sense to come in out of the rain.
Do they know? Do they periodically try to send/receive signals to verify that they can communicate? Is there actually a link which needs to be established, or is a protocol of that level of sophistication not used?
Assuming that figure is roughly correct, it might be worth trying to put it into perspective ....
... in 2013, there were about 42,000 UK dwelling fires in the ~23 million dwellings - about a '1 in 550' risk. If all those homes had wireless alarms, and there was a significant delay in their communicating during 0.05% of those incidents ('1 in 2000'), then the risk of a particular dwelling suffering a fire during which there was such a delay in the alarm system in a year would be about '1 in 1.1 million' . To put that '1 in 1.1 million in a year' into perspective, the overall statistical risk of an individual dying on UK roads in 2013 was something like '1 in 37,000' about 34 times greater than the risk mentioned above (and the risk of being seriously injured on UK roads many times greater still).
If you constantly worry about the risk of being killed or seriously injured on the roads, you might possibly also want to worry about the far smaller risk associated with the "0.05%" bernard mentioned above.
Kind Regards, John
Or you might (quite rationally, IMO) decide that the price of avoiding RTA risks is pretty high, whereas the price of avoiding flaky wireless interlinks is not.
That is based on the blocking caused by adjacent and compliant systems. The effect of blocking from the non compliant equipment alters that 0.05% significantly. These may transmit for many minutes if the user holds the button pressed as they are intended to block all activity on the channel.
A compliant "other system" will not be transmitting for more than 10% of the time averaged over a very short period. ( per transmitter it is 1% but if a couple of units are chatting together the system is taking more than 1% of the time ). So the delay to the fire alarm will be a couple of seconds worst case. ( assuming it is a two way protocol and alarm messages that are not acknowledged are repeated by the sensor ).
One might indeed decide that - but so many RTAs (I gather we now have to call them RTCs!) are due to deliberate human behaviour and/or human error, I'm not sure what 'pretty high cost' methods of 'avoiding RTA risks' you had in mind.
Whatever, I have already agreed with you that, in virtually any context, wired connections are always to be preferred to wireless ones, unless there are really compelling reasons to the contrary.
Kind Regards, John
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