Dimming 40x 6 watt LED BULBS ON ONE DIMMER

[aaelectric]

Hi all,
i am installing a varilight 12 way grid switch panel for shop fitters who are putting around 40 6 watt mega man dimmable bulbs in a shelving unit. Client wants them on one switch so 40x6 is 240 watts but can i use a trailing edge 400w dimmer from varilight. I know dimming led are different to halogen. What are your thoughts?

 

[Octopus]

will the MCB handle the start up current if they are all switched on at once?

 

[aaelectric]

Well it will be a type c but how can i work out start up power??

 

[aaelectric]

10amp mcb and dimmer is soft start. Its just about 1 amp of power

 

[Octopus]

Well it will be a type c but how can i work out start up power??

Ask the manufacturer? I would be wary of having so many on 1 switch!

Imagine it was 50w lamps and 40 of them it would be 2Kw - so from a design point of view you have too many on one circuit to begin with IMHO

 

[aaelectric]

Yea i know what your saying but if they were 50w they would have to be on different circuits but there 6 watts

 

[Octopus]

I'd wait for more responses but putting 40 LED's on one dimmer is bound to end in tears...

 

[SJD]

I often use Varilight V-Pro dimmers for LEDs, just looking at the instruction sheet that comes with them. While rated at 400W (1-gang) or 250W (2-gang) for incandescants, for LEDs it says to derate and suggests max 10 per gang, or max 100W, whichever is lower, in the absence of LED-manufacturer-specific instructions.

Now I've occasionally exceeded this a little, e.g. I did one room with 11 LEDs (totalling 77W) on one of these dimmers, but I really think trying to get away with 40 LEDs is asking for trouble. In theory they turn off with overload, but in practice I've found they sometimes blow up.

 

[aaelectric]

Ok so if 20 even on one switch is 120 watts you still think that would be too much. I am going to ring mega man and varilight on monday and see what they say.

 

[shanky887614]

cant you swap them to fittings that have a network cable to dim them?

then could power up via contactor

 

[Richard Burns]

This link is to the megaman site where they have lists of which dimmers are compatible with which lamps including maximum and minimum lamps, if you can find the lamps you are using this will tell you if the varilight is suitable for how many lamps.

 

[aaelectric]

cant you swap them to fittings that have a network cable to dim them?

then could power up via contactor

The power is not the problem as its around 3 amps all in but how do i know what start current will be and why is dimming led different to halogen wattage wise ? If it was fluorescent i wound understand because once they heat up the pull small power but to heat up they take a lot, but led do not need a start up??

 

[Richard Burns]

An LED is a diode, when a diode conducts it exhibits a very low resistance to the circuit and in a basic circuit design would effectively be a shirt circuit across the supply, positive temperature coefficient resistors are one way of limiting the current because they resist more as the current rises and so limit the maximum current as they heat up, however the initial state of the circuit is an effective short circuit and the current rises rapidly until it is clamped, this may be only for a few milliseconds but it is something to be aware of so that the circuit is designed to cope with high inrush currents on start up.

 

[Rockingit]

There are lots of 1kw+ dimming modules available for not that much (Scolmore do a 2kW one for about £60ish if I remember right), just use one of those instead on it's own dedicated circuit, with the 'knob in the panel' just being a remote for it on ELV.

 

[mayfair]

Think rockingit has the most economical and practical solution. but id be very unsure about them been on one switch . As the unions used to say One out all out !