Garage Lighting

[daveyrach]

Morning All

I have recently moved into a new house, in the garage there is power and lighting. There is a 2.5mm Twin and earth running to a socket just inside the door then 1.5mm Twin and earth running to a fused box and then onto the switch and lights etc which as i understand in correct. My question is there are 2x 4ft strip light in there and they flicker but they are nearly new and there is only a 13A fuse in the holder, is this big enough as the junction box is rated at 20A.

Cheers

[DarrenSV650S]

The cable from the socket to the fuseholder should be 2.5mm. The fuse should be 5A.

That isnt what is making the lights flicker though. How new are they? Sounds like they could do with new tubes and starters

[timwilky]

So let me try and understand exactly what you are saying.

You have a single 2.5 T&E feeding a 13A socket. From this socket there is a 1.5mm T&E that goes into a "fused box" and onwards to a light switch/ fluorescent tubs.

OK that fuse feeding your lights is far too heavy. Swap it for a 5A.

Tubes do go but only cost a couple of quid. If they don't start then again starters go etc.

My real concern would be where does your garage get its power from and how. for instance mine is fed though armoured 6mm directly from the distribution unit in the house into a 2 unit distribution in the garage from where I then feed sockets and lights.

The main distribution board has a 32A breaker and the garage has a 16A and 6A.

[daveyrach]

So let me try and understand exactly what you are saying.

You have a single 2.5 T&E feeding a 13A socket. From this socket there is a 1.5mm T&E that goes into a "fused box" and onwards to a light switch/ fluorescent tubs.

OK that fuse feeding your lights is far too heavy. Swap it for a 5A.

Tubes do go but only cost a couple of quid. If they don't start then again starters go etc.

My real concern would be where does your garage get its power from and how. for instance mine is fed though armoured 6mm directly from the distribution unit in the house into a 2 unit distribution in the garage from where I then feed sockets and lights.

The main distribution board has a 32A breaker and the garage has a 16A and 6A.

The garage gets it power from the main RCD box in the house it is not armoured or anything as the house and garage are linked by a porch type thing so cable runs thru the roof space.

The lights are very new only 2-3 weeks old, they were installed by our landlords electrician. Mind you he didn't touch anything that was already there just put the tubes up and connected em up.

[timwilky]

So the single socket is wired back to the house distribution unit. Is it off its own mcb (What size) or is it sharing a breaker with an existing ring main. The problem with the second scenario is the breaker may be too big to protect a spur as it was sized for the ring.

[daveyrach]

So the single socket is wired back to the house distribution unit. Is it off its own mcb (What size) or is it sharing a breaker with an existing ring main. The problem with the second scenario is the breaker may be too big to protect a spur as it was sized for the ring.

It has it own breaker in the fuse box and is labelled 'Garage/Outhouse' not sure on the size though. It literally feeds a single socket then straight off that to the switch via the 13A fused box then onto the 2x 4ft tubes.

[keith_d]

The current rating should be printed on the front of the MCB. For a 2.5mm spur this should be 20A or less.

[daveyrach]

The current rating should be printed on the front of the MCB. For a 2.5mm spur this should be 20A or less.

Thats fine but what about the 1.5mm fused lighting which runs off of the 2.5mm spur? What should that be rated at? Currently mine has a 13A fuse in it.

[Specialone]

Its perfectly right to use 1.5mm T&E for the lights from the socket to the fused spur.
As others have said, its very important for this to fused at 5amps or less.

You can run upto 32amps off 2.5mm but you aint gonna use that, but i suspect its probably 16amp at the main box.

The flickering is another issue, could be its not been fitted well, the tubes arent fully engaged in their holders or the starters or tubes may be iffy.

[daveyrach]

Right, i am going to change all the switch and pattress boxes as they are made of this brownish brittle plastic which is cracked but i will change fuse for 5 amp. Light switch is so old is the old round brown ones which feel really mechanical. I have been out there a while tonight doing 'bits' and they stop flickering after a while, could it be just that they are cold and once warmed up they're OK?

[Specialone]

Could be, mine do that in my garage when its really cold.

[daveyrach]

Yeah i think it is that

[Kilted Ginger]

Are they brand new lights, or old lights that have just been installed?

flickering tubes tend to be caused by faulty / dying starters.

Its very unlikely that the wiring / switches / sockets are causing any problems.

You should be able to see the starter on the side of the light, when its flickering, remove the starter, if it lights and stays lit then its the starter. they are the cheapest and easiest bit to change, so start there.

Regarding the fuse rating etc. The fuse is there to protect the downstream wiring and fittings. It is also to discriminate and protect the larger circuit.

The mcb in the distribution board will probably be a 20 or 16a. so anything smaller than that in the spur for the light is fine. Yes a fuse rating close to the load it is protecting is advisable but as long as it is smaller than the next upstream one and bigger than the capacity of the downstream cabling its fine. without going looking up tables 1'5mm twin and earth running on the surface will be rated for about 20amps (22 iirc) so your 13a is fine, but for 2 4ft 36w lamps it is overkill, lets just say you can run a 1000w kettle from a 5a fuse.

[daveyrach]

No they were brand new i watched them come out of the boxes.

[Kilted Ginger]

No they were brand new i watched them come out of the boxes.

Strange then, if by flickering you mean on and off rather than varying shades of illumination i would still start with the starters.
Nothing outside of the fitting should cause it to flicker. The only other thing you could check as it sounds like a very old installation, is that you are actually getting 240v plus (could be up to 260 depending on where you are in the country) its very unllikely though.

[Stuuk1]

Very much doubt it's the switchgear. Unless you can hear any kind of arching going on...

All this advice about starters... You don't find too many new fluorescent tube lights with starters. All the fitting I install at work are self starters with just the ballast.

If you watched them being unpacked then perhaps it was a dodgy batch.

Call the sparky and ask him, he may have put lots of these up.

If the lights flicker for too long the ballast can get fairly hot and sometimes fail, so I'd recommend calling the sparx.


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[keith_d]

Thats fine but what about the 1.5mm fused lighting which runs off of the 2.5mm spur? What should that be rated at? Currently mine has a 13A fuse in it.

The 1.5mm cable would be fine with a 13A fuse, but I would still change it for a 3A fuse. Not to protect the cabling, but because it limits the current a faulty ballast can draw. The lights themselves will be less than 200VA (a typical 4' fluroescent is 75VA) so they require less than 1A.

However, as several other posters have commented, the flickering is unlikely to be due to supply problems. If it goes away when they've been on a while I'd suspect the tubes.

[daveyrach]

They aren't on/off it is varying shades, only slightly though, but as I say after a while it stops which is what made me think it may be due to them being in the garage where it is cold.

[Kilted Ginger]

They aren't on/off it is varying shades, only slightly though, but as I say after a while it stops which is what made me think it may be due to them being in the garage where it is cold.

Thats the tubes then. they have probably installed fittings that have been designed for indoor use and spec for operating temperatures as such. Nothing you can do about it. You'll stop noticing it after a while.

[daveyrach]

Thats the tubes then. they have probably installed fittings that have been designed for indoor use and spec for operating temperatures as such. Nothing you can do about it. You'll stop noticing it after a while.

Ahh i see, well technically they are inside, its just cold, suspect they'll be fine in the summer time.

[Kilted Ginger]

I fitted lights spec'd for external use in my garage, rated -5 to 27degs, last winter -20, they did what you're describing but settle quickly.

[daveyrach]

I fitted lights spec'd for external use in my garage, rated -5 to 27degs, last winter -20, they did what you're describing but settle quickly.

My garage is warmer than outside and it was 3oC this morning here down south, so prob 4-5oC in garage. But as you say settle quickly.