(DIY) Help with connected fire alarms

[J40NYR]

Morning all

I hope this question isn't too basic...I think I'm sure but thought it would be wise to check.

I've fitted a couple of fire alarms that are wired, one at the top of the stairs one at the bottom.

First one I fit was downstairs, all was fine.

When I fitted the upstairs one the power on the downstairs one went off!

re-looking at the wiring upstairs I can see it has 2 sets of wires. One set presumably is the live feed which is the old standard of black and red with an earth. The second set had me confused, it was Red, blue and yellow with an earth.

The fire alarms are not earthed so I simply bent those wires over to not confuse my (easily confused self)

I am taking a guess that the wires that I had terminated into a block originally are actually going to the fire alarm at the bottom of the stairs, am I right in thinking I just join the red wire to the phase 1 wire going into the terminal block for the alarm, and the same for the blue/negative wire and that will then continue the power to the other alarm?

I know this is overly simple but better to be cautious I guess

Just out of interest, why would a fire alarm not be earthed?

Thanks

Jonny

 

[littlespark]

What make are the alarms and are they designed to be interconnected?

The alarms don’t need an earth, (double insulated, mostly plastic) but the earths have to be connected together.

 

[westward10]

Can you show pics of the alarm terminals.

 

[J40NYR]

I'm glad you've said that, I haven't actually joined the earths so I will do that as soon as I get back.

The new alarms are wired Google Nest alarms, they do not need an interconnect wire they simply need mains power.
[automerge]1584182286[/automerge]
That's upstairs

 

[Mike Johnson]

Sounds like someone ran out of T&E and used an intermediate switch cable, have you check the cable in the lower unit to see if it match's the bent over cables in the upper unit.

 

[telectrix]

I'm glad you've said that, I haven't actually joined the earths so I will do that as soon as I get back.

The new alarms are wired Google Nest alarms, they do not need an interconnect wire they simply need mains power.
[automerge]1584182286[/automerge]
That's upstairs

the R/Y/B cable is, as you say, the interlink between the alarms. it's L,N, and signal. as the don't appear to need the signal interlink, just use the R and B for L and N.
as littlespark said, the earths should be connected together in the upstairs deotector, but not coneected to the detector itself.

 

[J40NYR]

Difficult to see as it is really tight downstairs because of the daft plugs that nest supplies. Yes I am pretty sure that red and blue are connected to that alarm.

So is it as simple as sticking the Red (live) and blue (neutral) cables into the existing plugs that have the hot wires already connected into upstairs. Join the earths together and all will be well?

Thanks guys for your responses, really appreciated

 

[westward10]

Where are all those block connectors unenclosed in the ceiling space.

 

[davesparks]

Those connectors should not juts be pushed into the ceiling like that, they need to be enclosed in a suitable box. Either a joint box or a backbox cut into the ceiling.

The earth's must be sleeved and joined together so that every point of connection has an early present.

Unused conductors in a cable should be isolated at both ends and ideally connected to earth.

 

[J40NYR]

Ok, understood.

Once I've fitted up the wires that are currently loose into the existing blocks that are supplying power, the only wires that will not be conncted will be the yellow lead that won't be connected to anything either side, the earths which will be connected and sleeved upstairs (I understand as the green and yellow 'jacket' over the cable), the only loose wire will then be the earth cable downstairs that was originally stuck into the alarm.

Do I just bend that back and leave it?

 

[telectrix]

Do I just bend that back and leave it?

sleeve it Gn/Y and terminate in a connector. as davesparks pointed out, the connectors should all be enclosed, something like a wagobox. but that's not critical.

 

[Mike Johnson]

Just one more thing to do, is sack your plasterer.

 

[davesparks]

sleeve it Gn/Y and terminate in a connector. as davesparks pointed out, the connectors should all be enclosed, something like a wagobox. but that's not critical.

Is it not? Have they amended the regulations again to say that connections and single insulated conductors no longer need to be enclosed?

 

[telectrix]

Is it not? Have they amended the regulations again to say that connections and single insulated conductors no longer need to be enclosed?

they should of course be enclosed, but there's thousands like that done by DIY Dave. it's not exactly life threatening, is it?

 

[littlespark]

I believe he means it’s not critical to be a branded Wagobox. Any generic enclosure will suffice. Such as a dry lining box. Just not taped up

 

[davesparks]

they should of course be enclosed, but there's thousands like that done by DIY Dave. it's not exactly life threatening, is it?

There are many things we do which aren't exactly life threatening if they aren't done, it doesn't mean it's ok to ignore them.
Not fitting earth sleeving is also not exactly life threatening, and in this case not connecting the earth's isn't exactly life threatening.