How do I splice an alarm into mains power supply?

[mo2]

Read this: http://www.diynot.com/pages/el/el012.php to see if the socket can be used.

If so you will need:

2.5mm twin and earth cable

0.5mm flex

FCU with 3 amp fuse

1 Gang pattress box

2 Gang pattress box

Mini trunking


Be sure to have the power off before trying anything.

The best way to take a spur off the socket is to mount it on a pattress box so you mount mini trunking right next to it. From the socket to the FCU, use 2.5mm twin and earth and from the FCU, use flex to the alarm.

 

[bernardgreen]

Since I want to do this myself, how exactly do I create a spur into the socket?

Fitting a switched fused outlet as a spur to a socket on an existing ring main is within the ability of a DIY person. But is NOT a task to be started without being FULLY aware of the method and ALL the critical things that have to be taken into account for safety in the future.

Installing the wired alarm system is relatively easy task and has few dangers even if a serious error is made. ( other than connecting the mains to the wrong terminals ).

So maybe you should consider using an electrician to install the mains supply and you concentrate on the alarm wiring.

Take care when deciding where to place the sensors and do not be tempted to place them where it makes the wiring easier. If a sensor is placed where it can "see" through a window onto the road then a passing car may set trigger it.

 

[username132]

Thanks for the help and advice so far.

I still have two points of confusion:

a) if the original socket already has a pattress box, and the FCU comes with a pattress box, are those okay to be striken from the list (otherwise I don't understand where they're needed)

b) the instructions at http://www.diynot.com/pages/el/el012.php state "Once the wire is coming out of the mounting box, remove the existing two cables from the socket and twist the conductors together with the new spur cable" but if I twist together the spur cable and socket supply cable, wont I end up with a non-functional socket?

Thanks again.

 

[bernardgreen]

if I twist together the spur cable and socket supply cable, wont I end up with a non-functional socket?

YES so you have to put the three wires into the terminal on the socket and tighten the screw.

Reds and or browns into the L terminal and the blacks and or blues into the N terminal And the earths to the earth terminals.

 

[username132]

Okay, I understand. Thanks. How do I make a square-shape hole in brick for the FCU and associated pattress to be embedded?

 

[mo2]

Okay, I understand. Thanks. How do I make a square-shape hole in brick for the FCU and associated pattress to be embedded?

Are you sure you want to do this, because if you are not burying the cable, then connecting it can look quite messy.

If so, do a search - my opinion is a chisel for thermalite, hammer and chisel for something a bit harder, or even better an SDS drill and chisel bit.

 

[Steve]

a screwdriver will be fine for chasing thermalite blocks. Anything heavier and you'll be looking at a hole through the wall.

 

[username132]

I found some info here: http://www.diynot.com/pages/el/el017.php

I think I'm gonna go for surface mount ! Don't want to spoil mum's recent redecoration.

Just to make sure I've been paying attention. I open the double socket cover, bring in wire through the top of the box to their respective terminals where they're added to the wiring holes (like you have in a rewirable plug) and screwed in place with the original cables?

Here is an artist's impression ((I've never seen behind a double gang socket cover).

 

[mo2]

Yup, loosen the screw, insert it, and do it up really tight.

 

[username132]

And when it comes to drilling a hole in the wall from the master bedroom to the outside, through which to pass the bell box cable, how do I patch up the hole afterwards?

 

[bernardgreen]

Drill the hole from INSIDE the house and drill it sloping downwards so the hole outside is a inch or two LOWER than the hole inside. ( this stops water running along the cable and making a damp mark on the inside wall )

The outside hole should be hidden by the bell box so the cable is not exposed to view. ( exposed cable can be tampered with and the alarm by-passed )

But your comment about the cnnection to the socket worries me.

Do NOT put a surface cable into the TOP of the socket. It looks untidy and if the hole is too large around the cable dirt and debris can get into the box behind the socket and possible lead to a short.

Put cable into the under side of the socket or the side as low as possible.

BUT I SAY AGAIN use an electrician to do this small but very critical part of the job. You HAVE to get this bit connected properly..... A burnt socket would damage your mum's re-decoration. Poor connections in the back of a socket can over heat due to current passing through the connection on route to another socket.