5amp Lighting circuit with no power

[rwatney977]

I have a 5amp lighting circuit throughout my flat which should power a total of four 3-round pin outlets. The 5amp circuit also powers two smoke alarms (backed up by battery). It is my guess that the circuit also powers the lights under the cupboards in my kitchen.

MCB switch is on. Cycling the switch turns the light on the fire alarms on and off so there is power in the circuit. However, after removing the switch and sockets for the 3-pin outlets, there is no voltage to the switch or outlets.

Additionally, there is no power to the switch for the lights under the kitchen cupboards and no power to these lights either (all these lights have been removed and powered up to check the bulbs/units are working.

It seems strange that almost everything on this circuit isn't working. Could there be a break in all wires (expect the fire alarm?

Any ideas on how to find the fault?

 

[pc1966]

It is possible there is an additional non-obvious switch or fuse that is also in that circuit.

However, if you can't find a FCU (fused connection unit) or similar that has no other identifiable function then the best plan is to get someone in with proper test equipment to locate the fault.

 

[Pete999]

I have a 5amp lighting circuit throughout my flat which should power a total of four 3-round pin outlets. The 5amp circuit also powers two smoke alarms (backed up by battery). It is my guess that the circuit also powers the lights under the cupboards in my kitchen.

MCB switch is on. Cycling the switch turns the light on the fire alarms on and off so there is power in the circuit. However, after removing the switch and sockets for the 3-pin outlets, there is no voltage to the switch or outlets.

Additionally, there is no power to the switch for the lights under the kitchen cupboards and no power to these lights either (all these lights have been removed and powered up to check the bulbs/units are working.

It seems strange that almost everything on this circuit isn't working. Could there be a break in all wires (expect the fire alarm?

Any ideas on how to find the fault?

Is tgere an Fused Connection Unit FCO anywhere in the equation? could be the fuse has given up the ghost, blown, USM open circuit.

 

[rwatney977]

It is possible there is an additional non-obvious switch or fuse that is also in that circuit.

However, if you can't find a FCU (fused connection unit) or similar that has no other identifiable function then the best plan is to get someone in with proper test equipment to locate the fault.

Thanks for the quick reply. Just encase it help, attached is a photo of my MCB. I have no idea where a FCU would be installed...?

 

[SJD]

If the flat is fairly modern, maybe the live feed is wired from one light switch to another, and it would take just one break to disconnect all the round pin sockets & the kitchen lights. It might even be they were deliberately disconnected (on a recent job a customer asked me to do so as they never use them). It could even be they are disconnected in the consumer unit.

Edit: just seen the photo of the consumer unit, there should not be a MCB-sized hole in the front, it needs a blank fitting.

 

[rwatney977]

The building was converted into flats in 1998.

 

[pc1966]

Seeing the "5 amp" circuit has a 10A MCB for it makes me think there is a 5A fuse hidden somewhere. I could be anywhere, inside a cupboard, etc! Probably look like variations on this:

British General 900 Series 13A Switched Fused Spur & Flex Outlet White - Screwfix

Order online at Screwfix.com. Robust, square-edged profile. Supplied with screw cap covers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[cloverman]

You say 5amp and although 5 amp is written on the consumer unit, The MCB is 10amp unless my eye sight has shot it or I've missed something in your question.
If the circuit is fed from that mcb then I'm guessing like someone said that a FCU is install somewhere on that circuit

PC1966 beat me to it

 

[rwatney977]

Seeing the "5 amp" circuit has a 10A MCB for it makes me think there is a 5A fuse hidden somewhere. I could be anywhere, inside a cupboard, etc! Probably look like variations on this:

British General 900 Series 13A Switched Fused Spur & Flex Outlet White - Screwfix

Order online at Screwfix.com. Robust, square-edged profile. Supplied with screw cap covers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Thanks pc1966 - certinaly gives me something to look for. Still a little confused why the power still works on the fire alarms...

 

[DefyG]

I'm guessing like someone said that a FCU is install somewhere on that circuit

Either that or a junction box with loose wire where perhaps the smoke alarm circuit is connected!!!

 

[westward10]

5A at the consumer unit suggests it was/is for the 5A sockets, probably for lighting and were probably controlled through general light switches. It is possible this circuit has been ditched and used for the smoke detection, have they ever functioned.

 

[rwatney977]

I purchased this flat 9 months ago and this circuit has not worked since moving in and I do not know the history. I would be surprised if it has been ditched (lights under kitchen cupboards are particularly useful).

Have searched flat for FCU and found two. One is connected to the boiler (working). The other is located in a kitchen cupboard,as per the attached photos. 240v found even with the "5amp switch" on the consumer unit off. Could this unit be broken/relevant?
[automerge]1590350442[/automerge]
The 13A stamped on the black plastic seems to throw me off....although I'm not sure what this FCU is for...perhaps protecting the kitchen sockets/outlets?

 

[SJD]

This FCU looks like it supplies something that also has a switch somewhere else? From the socket circuit. Possibly the cabinet lights. Have you checked the fuse is OK?

If the fuse is OK, you could always try removing it, and see what now stops working.

 

[rwatney977]

FCU removed and all kitchen appliances now off. Fuse is clearly OK. Trying to think of another FCU...but running out of areas to check!

 

[pc1966]

It could be as westward10 said and it is long-disconnected, or it could be there is something you have not found yet. It is just possible (but unlikely) it was on a 13A plug with a 5A fuse, but as it is a fixed wiring circuit that would be pretty unusual/unacceptable to a professional electrician.

If you can find anything obvious it will take more testing to see if they are connected at all. If there is just a fuse blown then you would expect the neutral to be still connected to that circuit, but if a DP switch if off then not. However the earth should still be connected, but even that is not conclusive as there could be more than one earth path.

Of course testing is a potentially dangerous thing to do so unless you have appropriately rated test gear (CAT-III 300V at least) and know how to use it then best to call someone in when it is feasible to do so.