Correct Contactor and MCB

[richard1barker@]

Hi All
I am going to be installing some high bay lighting which will consist of 3 x 400w metalhalide fittings so 1200w in total with runs of approx 60 meters in 2.5mm cable. I will be wiring the circuit via a 20amp contactor with a control circuit of a two way switch system to activate or pull in the contactor coil when swicthed on. Could anyone advise me on the size and type of RCBO to use for the lighting circuit and if when the switch is used to turn the lights on if it will trip one or both RCBOs in use.(One RCBO for light circuit and one for switching circuit)

 

[Guest55]

rcbo for commercial lighting ?
i'd sack off that idea no messing.
;-)

 

[Darkwood]

How are you wiring the fitting ?

Over 3ph (1 per phase)
Looped together off 1ph and 1 mcb
Wired on individual mcb's same phase

What make of Dist board are you connecting to?
You say RCBO is there any reason why your using this as oppose to mcb's?

The easy one to answer is the control circuit will be quite happy on a 6amp (b) device in 1mm or 1.5mm cable.

 

[guest119]

Emergency lighting, frogeyes etc?

 

[iamelectric]

r you only putin up the 3 fitting or rows of 3

 

[richard1barker@]

Hi Darkwood thanks for the response I'm wiring the fittings as already mentioned with RCBOs 1 for lighting circuit and 1 for switchiing circuit. These will be on different phases, the make of board is wylex 3 phase and I'm using RCBOs as its wired in twin and earth with no mechanical protection

 

[Brightspark2]

10A rating?

d I'm using RCBOs as its wired in twin and earth with no mechanical protection

How are the cables being run? buried in wall?.

 

[richard1barker@]

What about start up on the ballast in the metal halide fittings would that need a 10 amp type c ? and the cables are tie- raped to tray and on steel perlings in a industrail unit

 

[ayjay]

why do you need rcbo,s?

 

[richard1barker@]

So it complies with 17th edition

 

[iamelectric]

why are u using a contactor? even with the start up current you are under 10amps 1.8 times 1200w , theres no need for a contactor or to be split over 3 phase

 

[Darkwood]

High pressure metal Hallide 3no'

20amp(c)
16amp(d)


This is relevant to SQ-D mcb's and will ensure no nuisance tripping again i asked you the manufacturer of the DB as this does sometimes change the values of mcb rating.

Also you seem to be going about this the wrong way, you should determine the required mcb first when calc for inductive loads then work of the cable size etc after once you know the protective device rating.

Are you cables to the lights buried at any point ? i can understand your control circuit to switch possibly requiring rcd protection but surprised you need it to the lighting.

 

[iamelectric]

16amp C type , no contactor , 20 amp metal clad grid switches

 

[richard1barker@]

Thanks again for response Darkwood as I've wired it in 2.5mm this won't be a problem which is why I put a bigger size than normal even though I should have checked first to be sure. Also have u ever heard of two RCBOs tripping each other when used in this way on a contactor if on same or different phases?

 

[Brightspark2]

What about start up on the ballast in the metal halide fittings would that need a 10 amp type c ? and the cables are tie- raped to tray and on steel perlings in a industrail unit

Yes 10A type C

Also you dont need RCD protection on the cables ran to the fittings then. The no mechanical protection bit in BS7671 is referring to when burying cables within a wall.