[ sparks and paint spray/fumes don't mix ]
Any electricians shed any light (pardon the daft pun) on this one?
I need to wire up 28 x 58 watt 5ft fluorescent tubes (our new paint booth). They are twin fittings, i.e. 14 of them.
What cable should I use and what switch/switches and breakers.
Now before a bright spark says multiply 58 x 28...........I know that! I mean I assume I have to allow for startup current, they are switch start
units not electronic start.
My "gut feel" is that 1mm cable, through two switches, and to a single 16amp mcb, would do the trick.................
Don't want to do it all and then it fail the wiring check when I have to get that done though!
Lastly, is it still legal under part P to use old colours cable? I thought it was but just wanted to check as I have a full roll of old colours 4 core
2.5mm swa that needs using up! (PS obviously I am referring to 3 phase colours here, though I guess the same rules apply anyway)
[Edited on 17/9/10 by NS Dev]
They sell 1.5 t&e usually for lighting. Have you got the light fittings suited to hazardous locations ?
I hope they are the proper lighting for a paint booth [ sparks and paint spray/fumes don't mix ]
you cant run 1.0mm twin on a 16 amp mcb mate!
quote:
Originally posted by jacko
I hope they are the proper lighting for a paint booth
You can use 1.5 swa or 2.5 if you like though the 1.5 is fine current wise.
You don't really want to be glanding that off, in and out of every fitting though, what a potch. If it's doesn't warrant SWA,
don't use it.
Don't use t&e either, that's a bad job really, it's for houses. One of the neatest and easiest ways is flex and stuffing glands,
it'll be wired really quickly, much easier to terminate and the glands don't allow for dust ingress should that be important to you.
You can still wire in old colours I guess, assuming you fit the std "this installation contains wiring colours to 2 different versions of
BS7671" sticker, but you'd have to check, but running 2.5 SWA for the sake of it as it's free - no ta!
Stick it on a 10A C breaker (1.5mm flex) and you'll be fine for those lights I'd have thought and the cable is safe.
ATB
Stott
PS, then again, what do I know, take my advice with a pinch of salt. 
[Edited on 17/9/10 by Stott]
quote:
Originally posted by daniel mason
you cant run 1.0mm twin on a 16 amp mcb mate!
quote:
Originally posted by Stott
You can use 1.5 swa or 2.5 if you like though the 1.5 is fine current wise.
You don't really want to be glanding that off, in and out of every fitting though, what a potch. If it's doesn't warrant SWA, don't use it.
Don't use t&e either, that's a bad job really, it's for houses. One of the neatest and easiest ways is flex and stuffing glands, it'll be wired really quickly, much easier to terminate and the glands don't allow for dust ingress should that be important to you.
You can still wire in old colours I guess, assuming you fit the std "this installation contains wiring colours to 2 different versions of BS7671" sticker, but you'd have to check, but running 2.5 SWA for the sake of it as it's free - no ta!
Stick it on a 10A C breaker (1.5mm flex) and you'll be fine for those lights I'd have thought and the cable is safe.
ATB
Stott
PS, then again, what do I know, take my advice with a pinch of salt.
[Edited on 17/9/10 by Stott]
quote:
Originally posted by jacko
I hope they are the proper lighting for a paint booth
Lighting cicuits should be protected by a 6AMP mcb, not a 10AMP !
Old colours are not allowed normally, but ask the question of whoever is to do the inspection?certification, would hate you to wire up swa, only to
be told it cannot be certified!
quote:
Originally posted by slingshot2000
Lighting cicuits should be protected by a 6AMP mcb, not a 10AMP !
Old colours are not allowed normally, but ask the question of whoever is to do the inspection?certification, would hate you to wire up swa, only to be told it cannot be certified!
A 10amp mcb is fine with 1.5mm t&e or flex. All new circuits should be covered by a 30 mA rcd to achieve the correct disconnection times , unless your cable is mechanically protected. Your not allowed to use the old coloured cable , sticker or no sticker it's a good few years old already even before you've installed it , any good sparky would not put his name on a test sheet with that on it. Go to edmonsons or newye and eyre it's only about £2 per mtr
Sorry to butt in, but surface run cables are excluded from RCD protection. Only buried cables should have them unless earth sheilded or deeper than
50mm.
You can still fit one for extra shock protection but its not a requirement. Disconnection times are improved by better earth loop impedance. So
generally using larger cables. RCD's are used if you cannot get the earth impedance down low enough to operate a regular fuse, but its bad
practice in a normal installations i.e one not using an earth electrode.
The required max impedance figures for each fuse type/size are in the regs book.
Your fuse/cable size will depend on the method of installation and enviromental temps as well as required current. There are factors in the regs to
apply to the cable.
As for cable colours, as long as the new colours are used at the termination in the form of sleeving, you can use any colour you like for the
cable.
Sorry, just done my 2391 testing and inspection and this stuff is fresh in me brain!
[Edited on 18/9/2010 by nitram38]
why not run 2 seperate circuits? on 2 x 6 amp mcb's
just a main from the fuse board to one switch, controlling half the lights
and another main from fuse board to a second switch controlling the other half!
also if the lights will be hanging from chains i would fit some sort of plug and socket arrangement at each fitting to enable them to be taken down
easily!
Just a thought , I had to get my old workshop rewired by a qualified electrician to keep my insurance company happy , It may be yours will expect the same?
quote:
Originally posted by nitram38
Sorry to butt in, but surface run cables are excluded from RCD protection. Only buried cables should have them unless earth sheilded or deeper than 50mm.
You can still fit one for extra shock protection but its not a requirement. Disconnection times are improved by better earth loop impedance. So generally using larger cables. RCD's are used if you cannot get the earth impedance down low enough to operate a regular fuse, but its bad practice in a normal installations i.e one not using an earth electrode.
The required max impedance figures for each fuse type/size are in the regs book.
Your fuse/cable size will depend on the method of installation and enviromental temps as well as required current. There are factors in the regs to apply to the cable.
As for cable colours, as long as the new colours are used at the termination in the form of sleeving, you can use any colour you like for the cable.
Sorry, just done my 2391 testing and inspection and this stuff is fresh in me brain!
[Edited on 18/9/2010 by nitram38]
quote:
Originally posted by rusty nuts
Just a thought , I had to get my old workshop rewired by a qualified electrician to keep my insurance company happy , It may be yours will expect the same?
quote:
Originally posted by daniel mason
why not run 2 seperate circuits? on 2 x 6 amp mcb's
just a main from the fuse board to one switch, controlling half the lights
and another main from fuse board to a second switch controlling the other half!
also if the lights will be hanging from chains i would fit some sort of plug and socket arrangement at each fitting to enable them to be taken down easily!
I think Rusty's point was not about the necessity of a rewire, but that his insurance company required electrical work to be done by a qualified
spark. Worth thinking about. I'm not really up to speed on commercial installations/insurance matters though. Are you expecting to get a spark in
afterwards to test, inspect and issue all the paperwork?
The reason most lighting circuits (at least domestic) dont exceed 6A is the roses and or switches may only be rated at 6A - it's not just the MCB
and cable on a circuit, ya know 
. Most domestic switches are rated 10A nowadays, but it's still uncommon to see circuits over 6A. Commercial is
a different matter, but check the ratings of fittings etc if you're going over 6A. Personally I'd make this lot at least two, possibly more
6A circuits on at least C-type MCBs ELI permitting.
Using old colours would have to be listed as a departure from the regs on the EIC/MWC. You need a good reason for making the departure and it must not
reduce safety. For example an acceptable reason for using old colours could be that the existing installation uses old colours and so sticking to old
colours reduces the possibility for confusion and therefore increases safety. Because you have some kicking about wouldn't wash imho, especially
if the rest of the installation is new colours. Sleeving all the old colour cable with new colours at the terminations might make it acceptable -
would be up to the inspecting spark (if that's you fine!).
Thanks Liam , That's exactly what I was trying to put over.
In fact, thinking about it, and bearing in mind I'm a sad geek, I'd definately have it on three circuits. One with 4 lights, one with 8
lights, and one with 16 lights. Then you can have binary dimming with combinations of the three switches as per this logic table...
S1 S2 S3 Lights
0 0 0 0
1 0 0 4
0 1 0 8
1 1 0 12
0 0 1 16
1 0 1 20
0 1 1 24
1 1 1 28
How totally awesome is that?
I'll get me coat
[Edited on 18/9/10 by Liam]
quote:
Originally posted by slingshot2000
Lighting cicuits should be protected by a 6AMP mcb, not a 10AMP !
quote:
Originally posted by Liam
I think Rusty's point was not about the necessity of a rewire, but that his insurance company required electrical work to be done by a qualified spark. Worth thinking about. I'm not really up to speed on commercial installations/insurance matters though. Are you expecting to get a spark in afterwards to test, inspect and issue all the paperwork?
The reason most lighting circuits (at least domestic) dont exceed 6A is the roses and or switches may only be rated at 6A - it's not just the MCB and cable on a circuit, ya know
Using old colours would have to be listed as a departure from the regs on the EIC/MWC. You need a good reason for making the departure and it must not reduce safety. For example an acceptable reason for using old colours could be that the existing installation uses old colours and so sticking to old colours reduces the possibility for confusion and therefore increases safety. Because you have some kicking about wouldn't wash imho, especially if the rest of the installation is new colours. Sleeving all the old colour cable with new colours at the terminations might make it acceptable - would be up to the inspecting spark (if that's you fine!).
I may stand to be corrected BUT IIRC the start current multiplyer for fluorescent tube was 1.8 ( Form memory)
So 28 x 58 x 1.8 =2923 watts/240 volts
Is 12.2 amps approx. so your cable and switchgear will need to be able to handle 16 amps ( or nearest sized mcb)
^ yeah I think that's right, 12.2 at startup, 7ish running, so 10A C type and 1.5 flex will cope just fine.
The flex is rated at about 16A depending on manufacturer and the trip charectaristic of a C type curve breaker should allow for the startup current
without tripping
ATB
Stott
Stott
if it did trip the breaker, you could always up it to 16A and back down to 13A via a fuse.