MK dimmers v the others

[Keith D]

Hi, I have just returned an MK £27 2 Gang 2 Way (single gang plate) white dimmer to B&Q as I thought it was more than I needed. It was one that could handle low voltage stuff but it added £15 to the cost from what I could see. Anyway, after getting the refund I proceeded not to be able to find a 2G 2W MK white dimmer just for mains halogen. I was a bit puzzled since the B&Q 'Varilight'? range had both options plus the soft start facility. I'm trawling the Internet at the moment having trouble finding any sign of an MK dimmer other than the expensive one! It has made me think of a couple of questions : Are MK worth the trouble ? For no particular reason I've convinced myself that I should buy MK and only MK. Also, what other brands can the group recommend - ideally a quality build with a nice smooth action. The varilight ones are a tad too loose. Is there such a thing as a decent white 2G 2W single plate soft start mains only dimmer - it's not too much to ask :-) ? ... or am I going to have to brave the crowds again and purchase the originally returned unit once more ? Is there a website that you guys 'n' gals can recommend that sells absolutely every switch known to man. I've already tried TLC-Direct and no joy there I'm afraid.

Thanks for any help, Keith

[Andy Hall]

I used MK grid type modular dimmers (4500 series) and switches for my kitchen, one for each group of mains or LV halogens of HF mini fluorescents as appropriate.

The dimmers soft start and the advantage of the grid arrangement is that you can have whatever arrangement of switches you like.

I standardised on using MK wiring accessories some while ago and rarely buy anything else - I do think that the extra cost is worthwhile. Having said that, I don't buy from B&Q but from an electrical wholesaler where I have been able to get them to sharpen their pencils on pricing.

Another aspect is that the designs are around for quite a long time. I don't trust store brands, simply because they will change vendor at the drop of a hat, making it impossible to match existing fittings.

.andy

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[Keith D]

Thanks for the replies. Is there an on-line shop that sells the full MK dimmer range or am I going to have to go back to B&Q to re-purchase the original over-specified dimmer :-( ? Is there a mains only downlighter double dimmer from MK or am I going to have to buy the LV capable one ?

Keith

[Keith D]

Thanks Andy. I'll have a good look at these.

Keith

[Rick Hughes]

Inteterseting - as I have had a LOT of failaure of MK dimmers - they still work as switches but fail to dim.

Rick

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[Andy Hall]

Curious. WHich one? They do have a 10 year warranty.......

.andy

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[The Natural Philosopher]

Yes. Had this with non MK dimmers. Candle bulbs arc over when they go and rip the triac guts apart. Replace with bigger triac.

MK don't do electronics I think - the dimmer modules are probably bought in by them from elsewhere.

In reality you need a 20A plus triac to control e.g. a 2A load :( So the MCB trip goes before the triac, not the oher way about.

[Dave Liquorice]

This is just Murphys Law in action.

Section 14 Part 4 Rule 12b "Any semiconductor device protected by an MCB will protect the MCB by failing first."

[IMM]

Who makes the 20A triac units?

[Christian McArdle]

I use Crabtree. I would have used MK, but they don't their standard double socket with the switches in the right place with dual earth and DP switches. If you want Sec607/DP, you have to have the switches outboard, which looks rank. Even like for like, I think the Crabtree ones look better than MK anyway.

have good action on the switches. My only gripe is that the screw terminals are at an angle, which requires a very specifically sized and shaped screwdriver to tighten up so that the driver doesn't foul the casing.

Christian.

[Andrew Gabriel]

This will also increase the minimum load the dimmer can dim correctly. However, it won't increase the maximum load, which is governed by heat dissipation, not size of triac (you will find all dimmers are fitted with triacs which can handle much more current than the rating written on the dimmer).

An MCB takes half a mains cycle to trip. It depends what the prospective short circuit current is at that point in the circuit, and if the triac can take that for half a mains cycle. A larger one is more likely to, but it's not a dead cert. For an (expensive) X10 DIN rail mounting dimmer, I have put a (cheap) 3A (B3) MCB next to it. The dimmer has had no problems, but then I don't know if it would have without the MCB. The MCB trips in preference to the dimmers 3A fuse. The MCB protects only the light on that dimmer -- you don't want a B3 MCB protecting a whole lighting circuit.