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URGENT! Downlight wiring advice

Discussion in 'Home Cinema Buying & Building' started by crashav, Mar 3, 2005.

  1. crashav

    crashav
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    I have had my living room ceiling renovated and replaced the original single 100W bulb with a grid consisting of 9 x 50W low-voltage downlights with individual transformers (60W assume electronic)

    I purchased a double dimmer (rated at 250W) from B&Q and the builder connected up the 9 downlights/transformers to one switch and a further 2 50W downlights/transformers on a separate circuit to the other switch.

    Following some stress testing last night it transpires that after 7 mins at max brightness the 9 downlights will switch off and then come back on again after 5 mins. This is clearly not right and at a guess the switch is being overloaded! The 2 downlights on the separate circuit are fine.

    Following some research today, I have discovered various gems of information which include having a maximum of 5 transformers on each circuit and only loading up the switch to 75% of it's maximum capacity.

    My best option appears to split off the 9 downlights into 3 circuits and wire each circuit individually to a switch rated at 250W at least. This would mean that I would need to install an additional double dimmer and have a configuration of 4 x 250W switches (2 x doubles) with 3 lights on 3 switches and 2 lights on the final switch.

    I would like some advice as to how best to wire up the lights before I blow them all up or worst set my flat on fire!! Could someone please help?!?

    Thanks
    John
     
  2. mhuk05

    mhuk05
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    9 x 50 = 450 watts - too much for your switch.

    Sounds like 1 switch will suppor up to 5 lights. 9 transformers does sound like a lot (in series?).

    Is it a big room? 9 x 50 watts is pretty bright! I've got 6 x 20W in my lounge and plenty bright.

    Can you get a higher rated triple dimmer?

    screwfix.com, tlcdirect, cpc.farnell.co.uk, maplins.co.uk
     
  3. mhuk05

    mhuk05
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  4. crashav

    crashav
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    Indeed, have realised switch just cannae cope with the power...

    Not a huge room, roughly 14 x 20 feet. I guess going from a single 100W to 450W is quite a big jump!!! :D

    Even if I fit 20W bulbs, the load is still rated at the transformer isn't it so will still be 450W and the switch will still blow?

    Thanks for the link and have had a look at some higher rated switches.

    Currently debating whether to go fo the triple 3 x 300W and a single 250W (for the other 2 lights in the dining area) or to go for two double 250W switches. Think that latter may be a cleaner look. What do you reckon?

    Thanks for the quick response! :hiya:
     
  5. richjthorpe

    richjthorpe
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    As said before, 450W is too much for a 250W dimmer.

    There is a company (Gemini) in Teddington that sells double dimmer switches with 400W rating and they can also upgrade a dimmer switch to 600W although I think this can only be done on a single dimmer and not a double. I was thinking of this when I installed 9 50W downlighters onto one 400W dimmer. The thing got quite hot at some times and I blew one switch, but the second one held up well.

    They do a range of brushed aluminium and chrome effect switches in:

    Single dimmer on single plate
    Double dimmer on single plate
    Triple dimmer on a double plate
    Quadrouple dimmer on a double plate

    http://www.electrical-suppliers.co.uk/

    HTH,

    Richie.
     
  6. rectorydp

    rectorydp
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    Not quite sure what sort of dimmers you want but you should be able to get 4 gang dimmers which would probably give you the cleanest look. TLC Direct certainly do a variety of 4 gang dimmers rated at 250w per gang. You can also get triple gang dimmers at 400w per gang.

    One of your deciding factors will be how it is all wired at the moment and how easy it will be to get extra wires to the switch. If a bundle of 4 cables is going to be tricky then you might want to look at ways of reducing the number.

    It is probably worth considering lower power bulbs as suggested by mhuk05 - you could then run several off the same transformer which should simplify things and allow you to use fewer switches.

    As to how it actually needs to be wired up that will partly depend on how it is wired at the moment if you want to minimise the disruption. You will need to wire back to all the switches unless you want to use some other method of dimmer control, eg x10, cbus etc.

    BR
    David
     
  7. Dave R

    Dave R
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    If you went with 20w bulbs, then you could run three of a 60w transformer as rectorydp suggests.

    And generally speaking, a 60w rating on a transformer is the maximum it can handle - connecting up one 20w bulb to it does not mean that it will still draw 60w, it should only draw 20w. Otherwise the remaining 40w would still have to go somewhere, and the only place it could go would be heat!
     
  8. crashav

    crashav
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    Ok, have been doing some further investigation and have discovered that the transformers are wire-wound, not electronic. TLC stock a dimmer for wire-wound transformers rated up to 630W so this should do for the main living room (max. 450W lights / 540W transformers).

    My only question is for the other groups of lights around the house where there are 2-3 spotlights per circuit using the same setup (i.e. 50W light on a 60W wire-wound transformer). I am using Varilight dimmers bought from B&Q which are apparently for Mains Voltage lighting only not LV lighting but appear to work fine.

    The thing I am worried about most is whether this is a fire risk? Or is the worst case scenario blowing transformers / tripping the circuit breakers?

    On a side note, the breaker box has started emitting a buzzing noise when the new lighting is switched on. I am guessing because there is a much larger loading overall on the house circuit now with all the new spotlights (17 x 50W lights x 60W transformers).

    Does this mean getting the circuit box upgraded or installing higher amperage(?) breakers?

    Thanks all for your help and advice.
     
  9. AverageJoe

    AverageJoe
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    I use a local company in Birmingham called Clearlight based in Erdington, Birmingham. I think they have other warehouses dotted around the country. I got a double brass dimmer rated 400W each and control a whole bunch of halogens off rach. make sure the transformers (if they are low voltage lights) are electronically dimmable (these cost slightly more but last much longer). Vaguely recall double dimmer was £30 ish - lot more than Homebase etc. but as you said, they are the cheapo 250W version. Not sure if Clearlight havbe a website but you coudl search web and/or give them a beel re mail order.
     
  10. andythepole

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    There is a company called ILES

    http://www.ileslimited.co.uk/

    that does a rotory type dimmer (one with a knob on it which you tap to turn on and then rotate to dim) that goes up to 1000Watts, They are a small company that have won the DTI design awards about 3 years running

    http://www.nesta.org.uk/ourawardees/profiles/3772/print.htm

    They also do some very nifty touch panel dimmers that can cope with quite a bit more power than usual dimmers.
    I have had to go with them as I have 12 50watt downlighters in one of the rooms in my house (it's a big kitchen).
     
  11. mrdimmer

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    The fact that your lights are turning off after 10 minutes or so means they are definitely overloaded (450W on a poor little 250W dimmer).

    As your transformers are wire wound, you will need an inductive load dimmer such as the 630W dimmer available from TLC Direct. Resistive load dimmers (most available) may not work. If you still want a double dimmer, TLC also stock a 2x300W dimmer which is also suitable for Low Voltage loads. Both these products are made by Varilight and will be also available from your local electrical wholesaler.

    John
     

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