Switch problems
- Thread starter rodders1965
- Start date
Sponsored Links
No, cable A is part of a 2-way switch circuit for your landing light.
You should confirm that cable B really is going to your loft light be some careful testing with a multimeter.
Sounds good...
No! One terminal for line & the other side of the switch will therefore be a switched line. Connect the neutral from the loop-in to the neutral from the light fiting using a e.g. a choc block.
Never connect a neutral to any single pole light switch terminal!
Yes, you got there. It's looping in at the switch.
What replies did you get to that? Can you supply a link? Some of the questions do raise an eyebrow!
e.g.:
What is 20A cable? Cables' current rating depends on a whole host of factors that I won't enumerate here, but there are plentiful links to useful material on many posts, mainly supplied by ban-all-sheds which should be compulsory reading
What sort of socket? A domestic 13A socket on a lighting circuit is not appropriate and should be reserved for ring or radial circuits supplying sockets, protected accordingly. (Although I did see one on a boat once supplying 12V DC!).
You should keep to same cable size as the rest of that lighting circuit, will which conventionally will be 1.0mm2 or 1.5mm2 protected by a 6A or 10A MCB. Mixing cable sizes on a lighting circuit is wrong.
The appropriate place for a fuse in these circumstances would be in an FCU as described below.
20A junction box is fine if your lighting circuit is conventional.
Fusing: The aerial amp will have a very low power rating (a few watts at most), and the instructions will probably recommend a 3A fuse (even though it should never draw anything like 3A after switch-on). To conform to the letter to the MI, you would likely need to protectd it with a 3A fuse.
I reccommend you get a switched FCU with a neon, put a 3A fuse in it, connect the amp via the flex outlet, mount the amp to something convenient and consider it a fixed appliance. This way you protect the amp by its correct rated fuse, don't have to bother with round-pin 5A sockets.
An the legality/safety side, you must be competent to do and test the work and follow BS7671. You should be able to supply evidence of both of these. This work is not notifiable given the information supplied.
OK today I isolated the mains and rewired the landing light switch as Echoes recommended. Reconnected the supply and the landing light switch works fine with the new single gang two way switch plate I put in place of the old one. The loft light is now permanently on, which is what I expected having taken it out of the switch setup to create a permanently live feed to the loft.
Having traced the wire in the loft to the light, I again cut the power, went back up into the loft and cut this wire near loft floor level. I wired this end near the floor into a junction box. From this I ran some 20A cable to a single gang one way switch. I then rerouted the now cut wire from loft light into the new single gang one way switch, with red to L1 and neutral to the neutral using a choc block. The live from the junction box is to the com terminal and the two earths to the earth terminal. Reconnected the power and nothing works. How can I test the current using a multimeter correctly I have a Rapitest M1015B meter rated to a MAX of 300V/250Ma.
Having traced the wire in the loft to the light, I again cut the power, went back up into the loft and cut this wire near loft floor level. I wired this end near the floor into a junction box. From this I ran some 20A cable to a single gang one way switch. I then rerouted the now cut wire from loft light into the new single gang one way switch, with red to L1 and neutral to the neutral using a choc block. The live from the junction box is to the com terminal and the two earths to the earth terminal. Reconnected the power and nothing works. How can I test the current using a multimeter correctly I have a Rapitest M1015B meter rated to a MAX of 300V/250Ma.
Sponsored Links
When you say 'nothing works', does that mean that the landing light doesn't work either?
Let's eliminate the obvious: are you sure you cut the right cable (B in your picture) in the loft? I'm pretty sure you haven't done this.
Re-check your wiring at the landing switch.
Your wiring sounds right, and you should have this:
[code:1]
LANDING JUNCTION LOFT LOFT
SWITCH BOX SWITCH LIGHT
o-------------L-------------o------------L----------o/ o-----------------SL
o-------------N-------------o------------N----------o--o-----------------N
[/code:1]
The only changes you should have made between 'working as expected' and 'nothing works' is the installation of the JB and the Loft switch in cable B. The electrical circuit you have now should be exactly the same as you had before - only the loft switch has moved from landing to loft.
At risk of teaching you to suck-eggs, set meter to 300V AC range.
With the circuit energised should measure :
At landing switch: 240V COM - N
At JB: 240V L-N
At Loft switch: 240V COM-N
An afterthought: when you cut the power, did you switch off the MCB, then cut the cable, then connect up, then switch the MCB back on? If you have the lighting circuit on an RCD, chances are you tripped that RCD when you cut through the cable by introducing a brief N-E short circuit.
Let's eliminate the obvious: are you sure you cut the right cable (B in your picture) in the loft? I'm pretty sure you haven't done this.
Re-check your wiring at the landing switch.
Your wiring sounds right, and you should have this:
[code:1]
LANDING JUNCTION LOFT LOFT
SWITCH BOX SWITCH LIGHT
o-------------L-------------o------------L----------o/ o-----------------SL
o-------------N-------------o------------N----------o--o-----------------N
[/code:1]
The only changes you should have made between 'working as expected' and 'nothing works' is the installation of the JB and the Loft switch in cable B. The electrical circuit you have now should be exactly the same as you had before - only the loft switch has moved from landing to loft.
At risk of teaching you to suck-eggs, set meter to 300V AC range.
With the circuit energised should measure :
At landing switch: 240V COM - N
At JB: 240V L-N
At Loft switch: 240V COM-N
An afterthought: when you cut the power, did you switch off the MCB, then cut the cable, then connect up, then switch the MCB back on? If you have the lighting circuit on an RCD, chances are you tripped that RCD when you cut through the cable by introducing a brief N-E short circuit.
Exactly that!! Bloomin heck Echoes thats spot on. Restored power but then after seeing the switch did not work, and checking all my connections again, I went back to the main supply box and yes one of the RCD's had tripped. Landing light now switches on and off from both downstairs and upstairs and the new light switch inside the loft now works on and off perfectly...hoorah. Just got to finish off the JB spur to the plug socket to be able to supply power to the mast head amplifier's power supply unit. Then it's all done.
One thing Echoes....though the PSU plug has a 3A fuse in it, should I have some sort of protection on the spur to the socket it will plug into or is the RCD that tripped earlier taking care of the originating feed wire from the landing light switch, which runs the loft light switch and the plug socket.
Thanks so much for your help so far. PS If you are any good with Mast Head Amplifiers then read my new thread on that!!
Well done - Good job!
That PSU plug is presumably a standard 13A plug wanting a 13A socket.
You must consider the possibility that someone may unwittingly plug in a high power appliance into such a socket, which would be dangerous and not obviously so, so you must address this risk. Therefore I suggest you don't use a 13A socket at all and do one of the following:
1) Cut the plug off and wire the flex into a switched FCU (3A) through the flex knock-out
2) Cut the plug off and fit a round pin 5A plug and socket on the lighting circuit, possibly via a 3A FCU.
3) If you *must* use a 13A socket, fit an FCU with a 3A fuse on the lighting circuit, take the load side of this to a single 13A socket and emblazen it with warning notices that this is for your amplifier only.
My preference would be (1) - 13A sockets are not appropriate for a lighting circuit, but I've done this to death now.
I'll now have a look at your next post....
Cheers!
That PSU plug is presumably a standard 13A plug wanting a 13A socket.
You must consider the possibility that someone may unwittingly plug in a high power appliance into such a socket, which would be dangerous and not obviously so, so you must address this risk. Therefore I suggest you don't use a 13A socket at all and do one of the following:
1) Cut the plug off and wire the flex into a switched FCU (3A) through the flex knock-out
2) Cut the plug off and fit a round pin 5A plug and socket on the lighting circuit, possibly via a 3A FCU.
3) If you *must* use a 13A socket, fit an FCU with a 3A fuse on the lighting circuit, take the load side of this to a single 13A socket and emblazen it with warning notices that this is for your amplifier only.
My preference would be (1) - 13A sockets are not appropriate for a lighting circuit, but I've done this to death now.
I'll now have a look at your next post....
Cheers!
Why not?
It's asking for the circuit to used for other than its intended purpose, and may overload it.
Could be mitigated by a 3A FCU and socket labelling, but as far as I understand, it is not acceptable to use a fuse or circuit breaker as a load limiting device.
Once again thanks Echoes I will probably go down route 1 as you suggest. I cant thank you enough for shedding light on all my problems and without your help I could not have done this so thanks very much.
Kind regards
Rod
Kind regards
Rod
Its a 3A plug for the PSU Echoes so I will go with a 3amp FCU instead of plugging thePSU intoa 13 amp socket
How would it be dangerous?
The protective device is there to protect the cables and nothing else. If too large a load was connected into a 13A socket connected to a lighting circuit then the protective device should operate.
I'm not a big fan of putting 13A socket outlets on lighting circuits but it's certainly not dangerous.
I think you've said it:
A fuse is not there to act as a load-limiting device.
I don't think that plugging in an appliance unsuitable for the circuit consitutes a fault, neither is the appliance operating in excess of its designed load. In this case the cable is certainly overloaded, but only because the design of the circuit allowed it to be.
In the OPs cirumstances of a dedicated socket in a loft, I happily concede that this is not an immediate danger. But given a blank sheet of paper, it's not how one would design it. Think we agree on that!
Discussion appreciated!
Totally agree with that: in the event of a fault or overload condition with some connected appliance, or the cable itself.
A fuse is not there to act as a load-limiting device.
I don't think that plugging in an appliance unsuitable for the circuit consitutes a fault, neither is the appliance operating in excess of its designed load. In this case the cable is certainly overloaded, but only because the design of the circuit allowed it to be.
In the OPs cirumstances of a dedicated socket in a loft, I happily concede that this is not an immediate danger. But given a blank sheet of paper, it's not how one would design it. Think we agree on that!
Discussion appreciated!
Certainly it wouldn't be my favoured option (although a previous boss appeared to be fond of such a design). If you wish you could even label it "TV AMP ONLY" or something similar.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
