FCU for security control panel.

[mevtickin3]

Hey guys,

I need a 3 amp FCU fitted for a new alarm control panel. I've looked at my electrics in the location where this is due to be installed and think I found something suitable.

There is a single spur from the ring main, which goes to a unswitched FCU/outside power socket. Could I use that cable, by adding a junction box and my new unswitched FCU?

Also, under Part P can I carry out this work or do I need a Part P electriction to do this for me, I did read up on this, but found much conflicting information. The location in this instance is a garage.

Thanks in advance. River.

 

[Spark123]

It sounds like you are wanting to add a spur to a spur which is not allowed. It is not advisable to run an alarm from the fused side of the existing spur in this case either taking into account what else it is supplying. You may however run another spur directly from the ring circuit. The work is not notifiable to your LABC under part P of the building regs providing you are not adding to a circuit in a kitchen or a special location such as a bathroom.

 

[mevtickin3]

Thanks for the reply..

I'm proposing to add the 3 amp fused spur from a single mains cable that's been spurred from the ring-main. This currently feeds an external socket, but I would put a junction box in before that so the single spur would feed a FCU for the alarm AND a socket.

I guess this would be 2 outlets from a single spur which you advise is not good.

So I need to sput off somewhere else, OR extend the ring-main?

So it would look like this:

 

[Steve]

Put the top FCU in the place of the junction box. Then all is well.

That FCU then feeds another FCU and a socket. this is fine.

 

[mevtickin3]

Thanks for the help Steve.

Here's my revised version. Can I put the 3 amp FCU in first, as that much simpler to cable, as the FCU & socket is already in place?

So I am right in saying that you can have a FCU feed multiple other FCU's, but not spur from a spur off the ring main?

What's the reason for this? Is it because the entire circuit after the first FCU is protected by a fuse (just interested

 

[Steve]

a 2.5mm T+E can carry 27 amps maximum optimum. More than one accessory on a spur on a 32 amp circuit must have additional protection, normally afforded by a 13 amp FCU at the source of the spur. Your diagram is the opposite of what i said to do.

The socket doesn't need its own FCU.

The source FCU should be 13 amps, protecting both legs.

The security alarm needs its own FCU, rated at 3 amps or whatever the manufacturer requires.

 

[mevtickin3]

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[mevtickin3]

Thanks Steve, really appreciate your help.

Can I leave the 13 amp FCU on the socket (as it's already in place), and ADD a 13 amp FCU at the source of both legs? Otherwise I'd have to remove the existing FCU and re-site it elsewhere on the cable.

Also, I take it the FCU input is the 2.5mm T&E and I wire both legs to the output of the FCU?

 

[kevnurse]

Can I leave the 13 amp FCU on the socket (as it's already in place), and ADD a 13 amp FCU at the source of both legs? Otherwise I'd have to remove the existing FCU and re-site it elsewhere on the cable.

Yes, you can do that. However, to save money you can replace the existing FCU with a 13A junction box and fit the FCU onto the spur where you have drawn the new 13A FCU. Doing this you only need to buy a 3A FCU and a 13A JB.

 

[Steve]

A 13 amp junction box?

River, your final diagram is OK, but I say again, the outside socket does NOT need its own FCU!

 

[kevnurse]

Oops, I meant to write a 20A JB. Costs less than £1. The OP recognizes that if he removes the existing FCU, that he will have a break in the circuit, so thats why he wants to keep it there, rather than rewiring that part of the circuit. I'm suggesting that by using a JB in its place and refitting the FCU at the point of spur he can make better use of resources.

 

[mevtickin3]

Thanks guys, you've really helped at lot.

It's great that you guys take the time to help people out on here. Keep up the good work! Mucho Respecto.

River.