Wire an Axiom Digital Electric Timer to a Fused Spur


Postby Robertdodgson » Tue Mar 07, 2017 10:53 am

image.jpeg
New timer connections
image.jpeg
New timer connections
Hi all,

I'm have bought an axiom digital timer to replace a light switch that controls a lamppost in the front garden.

On removing the faceplate to the current switch it appears it is possibly part of a radial circuit with two twin and earth cables. See attached photo.

The new timer has 'L' , 'L out', 'N' and 'Not Used'

The instructions say wire from a fused spur. Does this mean I need to mount the timer next to the light switch and connect them together somehow?

Hope the photos help this make sense, any help is massively appreciated.

Rob
Attachments
image.jpeg
Wiring for current light switch
image.jpeg
Wiring instructions for new timer
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Postby ericmark » Wed Mar 08, 2017 12:49 am

One would normally use a fused connection unit (FCU) to make a fused spur. But with lighting in UK we would normally have just a 5 or 6 amp supply to a radial circuit so rather pointless creating a fused spur from a 6 amp supply, you would only do that if the supply was really for sockets.

In the main internal lights we only switch the line, and outside lights we switch line and neutral so it can be fully isolated so if you get water in the fitting you can switch off and still use other lights in the house without the outside lamp tripping the RCD.
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Postby Robertdodgson » Wed Mar 08, 2017 11:03 pm

ericmark wrote:One would normally use a fused connection unit (FCU) to make a fused spur. But with lighting in UK we would normally have just a 5 or 6 amp supply to a radial circuit so rather pointless creating a fused spur from a 6 amp supply, you would only do that if the supply was really for sockets.

In the main internal lights we only switch the line, and outside lights we switch line and neutral so it can be fully isolated so if you get water in the fitting you can switch off and still use other lights in the house without the outside lamp tripping the RCD.



Hi thanks for the information. Are you able to tell me the correct wiring for the inlets for both the fused spur and for the timer?

Thanks
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Postby ericmark » Thu Mar 09, 2017 10:30 pm

The reason I answered in general terms is I don't know where the supply comes from or where items are placed.

One has to look at the risks of water ingress, and where the supply comes from and design the circuit, the idea of just making it work is not good enough, it has to be safe and unlikely to cause problems latter.

So with a supply from an old fuse box with a 30A fuse I would use a RCD FCU and likely a 3A fuse, but from a consumer unit with RCD protection already in the consumer unit and fed from a 6A MCB with light where it's highly unlikely to get wet then simply replace switch with the unit you have.

If there is likely hood of water ingress then leave original switch and fit timer as an extra. But there is no one size fits all,

All electrical installations go through three stages. Design, installation, and finally inspection and testing, some forms allow one person to do all three and other forms can have three separate signatures.

Even if I could design it for you, I can't sign for the design, Some times we do make errors, I have just bought a MiHome light switch only to find back box is too shallow, so I have modified my design to include a new back box which I will likely get tomorrow. However I also found it was wired with three core cable so I may completely change the design.

In your case there are timers and fuse connection units built as one single unit, but I can't really say if what you have needs a FCU or not, only you know that.
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