Replace wired smoke alarms

MrMrMr111 · 13 Jan 2015

I'm wanting to replace the wired smoke detectors in the house for Nest protect ones.

The wiring is as follows on the original

The plug that connects to the actual alarm has a brown, white and blue on. This connects to a chocky block to red, blue , white/grey, and yellow as follows.

Brown---red (x2)

White---yellow

Blue---blue & white/grey

Now I know there is 3 (Delta 530sca?) and they use the interlink between them. The Nest protect only needs power as it's uses WiFi for communication between them etc.

So I expect red 2 are live, the blue is neutral, but what is the yellow and the white/grey?

What happens if I do these one at a time and disconnect the interlink will it alarm?

Thanks for any help
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flameport · 13 Jan 2015

The red should be live and the blue neutral - however this MUST be checked before connecting anything else there.
The yellow is probably the interconnect. As for the black/white or whatever - looks like some kind of bell wire or 'speaker' type stuff. No idea why that would be there, and it probably isn't mains rated either. Certainly requires further investigation - what is the wiring like at the other alarms?

If the new ones only require mains power, then the other unwanted wires can be disconnected. Ideally the other wires should be traced and totally removed, but if not possible, put the wires into some separate terminal strip.

Disconnecting the interconnect will do nothing. Unclear why you would want to do one at a time, since the new things will only be a couple of minutes to install.
Obviously all disconnecting etc. must be done with the power off.

RF Lighting · 13 Jan 2015

My wifi crashes from time to time. Not sure I'd trust my life to it

MrMrMr111 · 14 Jan 2015

I can understand the red and blue, but the white/grey I've no idea either. Haven't had chance to open up others to look at wiring yet.

Reason 1 at a time was ill be replacing them 1 at a time, and was worried if disconnecting the interlink it may alarm or something. Also I'm replacing them with Nest Protect, only bought 1 so far, until buy another.

bernardgreen · 14 Jan 2015

RF Lighting said:
My wifi crashes from time to time. Not sure I'd trust my life to it

I share your concerns..
If the fire has taken out the mains then the WiFi will be out of action ( unless battery backed )
Fires create ionised particles and in the high concentration that a fire can produce these can affect wireless communications.

MrMrMr111 · 14 Jan 2015

bernardgreen said:
RF Lighting said:

My wifi crashes from time to time. Not sure I'd trust my life to it

Click to expand...

I share your concerns..
If the fire has taken out the mains then the WiFi will be out of action ( unless battery backed )
Fires create ionised particles and in the high concentration that a fire can produce these can affect wireless communications.

Yes mine does to, but it is battery backed up, the WiFi part is used for the interlinking of numerous Nest protects I believe to "talk" to each other, they speak alarms, e.g. "the ground floor has smoke" Which is does by all the Nest protects, even to the top floor one.

So I presume the worse could happen is they don't "talk" to each other. I would hope Nest have thought about WiFi issues and the default that the Nest becomes just a normal smoke and CO alarm, even if no mains as well.

skotl · 14 Jan 2015

Presumably, though, the units will still shriek an alarm autonomously? (they're not relying on a remote wifi-controlled sounder)

bernardgreen · 14 Jan 2015

skotl said:
Presumably, though, the units will still shriek an alarm autonomously? (they're not relying on a remote wifi-controlled sounder)

But if the interconnect isn't working the shrieking alarm in the kitchen may not be loud enough to wake people asleep in the bedrooms before the stairs become impassable due to smoke / fumes / flames when the kitchen door burns through.

skotl · 14 Jan 2015

bernardgreen said:
skotl said:

Presumably, though, the units will still shriek an alarm autonomously? (they're not relying on a remote wifi-controlled sounder)

Click to expand...

But if the interconnect isn't working the shrieking alarm in the kitchen may not be loud enough to wake people asleep in the bedrooms before the stairs become impassable due to smoke / fumes / flames when the kitchen door burns through.

Ah - fair enough. We have interconnected alarms but it never occurred to me that they would all alarm if one detected smoke.

In that case, I fall into the camp that would be uncomfortable trusting this to wifi.

ban-all-sheds · 14 Jan 2015

I have a simple rule.

Never ever ever use wireless if wired is an option.

For anything.

flameport · 14 Jan 2015

The nest things do not require wifi to operate - it's only used to set up the devices.
If the wifi / internet / mains fails, they have batteries inside for power, and will still signal each other just like any other wireless smoke alarm.

The real benefit of them and the Nest thermostat is that they contain the All Seeing Eye of Google, so that your movements around the house and what you are doing can be monitored 24/7.

stillp · 14 Jan 2015

flameport said:
will still signal each other just like any other wireless smoke alarm.

Isn't that wifi?

ban-all-sheds · 14 Jan 2015

No - completely different frequencies and protocols.

stillp · 14 Jan 2015

Yes, I know that, but it's still wireless communication, subject to the possible problems mentioned.

bernardgreen · 14 Jan 2015

Equipment that uses Licence Exempt frequencies in both the 868 and 433 MHz bands is prone to interference both accidental and intentional from a wide range of equipment both legal ( compliant ) and illegal ( intended to be non compliant ).

The equipment may be designed to alert you when it finds its channel is blocked by other equipment but in the case of a fire alarm this is a problem.

If it bleeps quietly to alert you to being jammed then you are unlikely to be woken by it. Not a problem provided the house doesn't catch fire at the same time. To ensure safety if the system finds it is being blocked it has to go full alarm to ensure people are awake and alert while the alarm is out of action due to being jammed.

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Replace wired smoke alarms

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