fluoro lighting and timers

[djjd21]

hi all,

i have been asked to place a timer on an array of fluorescent lighting in a friends shop and would like a bit of advice regarding my proposed method of installation.at the mo i am a registered domestic installer but would like to be able to show this installation as an application for approved contractor status so here goes.
i have an array of 4 600mm2 modulars in the shop each with 4 tubes in which i am assuming are 18w lamps.i know that this sort of fitting has high starting currents which would likely be unsuitable for a domestic timer due to their low inductance capacity.
my question is this - can i place a domestic timer on the wall which in turn switches on a contactor to absorb the inductance of the lights or would the inductance still return back to the timer contacts and possibly make them fail?

hope you can help

 

[ericmark]

I have used contactors/relays before to switch 1.5Kw flood lights using a small photo cell and see no reason why you should not do same. Also very common where one wants one switch to work lights spread across phases.

 

[ColJack]

4 grid lights isn't going to take all that much start up.. you'd put them on one 6A rated switch after all..

just use an immersion timer.. or does he want it specific and accurate to the minute?

 

[RF Lighting]

You can use a contactor if you wish. A neat way of doing this is to get a DIN rail mounted time switch and DIN rail mounted contactor. Install them both together in a neat little enclosure.

You will need to make sure that the contactor is rated for inductive loads, and if it is not, then I generally make sure the contacts are rated to 10 times the load to be switched.

As has already been said, the easiest soloution would be to use a time switch with a 16A / 20A switching capacity such as an immersion heater time switch.

This one is rated for switching a 2A inductive load, which is plenty for your needs.

http://www.tlc-direct.co.uk/Products/TCGP24.html

 

[briwire]

I would echo what has been said-you don't need a contactor for that small a load.

 

[stuartsjg]

You could buy a contactor on its AC3 "Motor" rating then you would be sure it shouldn't burn out due to the lighting.

So if you have 2kW of lighting, get a contactor for at least a 2kW Motor.
If they don't have an AC3 or motor rating, over spec by 2-3 times

The costs of a big contactor are not very high:

http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Hager_Rcd_s_and_Contactors/index.html

http://www.tlc-direct.co.uk/Main_In...gear_Index/CMD_Main/CMD_Controls_5/index.html

As the whole point of a contactor is to isolate the surge current from the control circuit, there wont be any problems with the surge getting from the contactor contacts to its coil and into the timer switch.

You can get high power timers:
http://www.tlc-direct.co.uk/Main_Index/Timers_Index/Timers_Sangamo/index.html

 

[chimp]

Starting current will also depend on switch start of HF control gear in the light fittings.

If you done have to use a contactor don't as it is one more thing to go wrong.

I also aggree a din rail timer in an enclosure would be best.

 

[bernardgreen]

Just a thought. In rush current and possibly tripping the lighting circuit MCB if all the light switch on at the same time.

How are the lamps controled at the moment ? Is there one switch that operates all of them or are they divided among several switches. ?

If there is just one switch and they all switch on the the same time then one contactor and one timer will be OK as the MCB is coping with the inrush.

But if the light are at present switched on manually in groups then when the contactor switches them all on at the same time the inrush may be enough to trip the MCB.

A solution to that is two or more contactors each switching a group of lights. The timer controls only the coil of contactor one. The coil of contactor two is fed from the switched side on contactor one and so contactor two closes after contactor one has closed. Likewise contactor three coil operates from contactor two.