Dimmer switch: two gang 400W / 220W -- possible?

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wrote:

Ah, I see, that would be because of the heat then. That's why you're not meant to put too many together over a certain rating.
SJW A.C.S. Ltd.
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All the TLC two gang dimmers seem to be 400 watt each - but not for LV use. The LV ones are 300 2 gang, 400 single.
I've got an old MK Superswitch somewhere that was 1000w in a one gang size, but again for GLS only. I'm surprised there's not a difference between plastic and metal plate ones these days - there used to be.
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wrote:

Andy, thanks this is very useful stuff. I also notice on tlc's website that MK do "Grid Dimmers for Low Voltage Lighting", with sliding control. Why are the ones you have pointed to not stated as being "dimmers for LV lighting"? You say they are suitable for LV lighting, which is good, but I'm curious as to why there is a specific grid range for LV lighting in the sliding type. Presumably the ones you have pointed to are suitable for LV lighting at their specified loading (i.e. the 400W dimmer will power 400W of LV lighting, not down-rated to something smaller as I have learned happens with certain dimmers powering LV lighting)?
[rest of helpful post cut for brevity]
Thanks. Mike
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I've not looked at the website, but the cat. lists separate MK types for ordinary and LV. They have the same TLC part numbers but with an LV suffix.
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On 2 Feb 2004 05:48:46 -0800, snipped-for-privacy@drmrb.fsnet.co.uk (Michael Brewer) wrote:

These are a generic part and not made by MK.

They make only the round knob type. These are suitable for mains and LV as long as a suitable transformer is used.

I've just been looking at this again, and dug out the notes that I wrote when I installed my own, following studying the GridPlus datasheet and a call to MK's technical department.
The modules are rated OK, the issue is getting the heat away.
http://www.tlc-direct.co.uk/Technical/DataSheets/MK/GridPlus.pdf
There is a row limit and a plate limit for the Grid system, and for a single row of 3 in a single box there is a total plate limit of 380W for halogen lamps of mains or LV, so the idea of two modules in a triple box won't work.
I reviewed how I did my layout and why. The top row has one 400W dimmer for some mains halogens and some standard switches. The bottom row has 250W dimmers, but they are each connected to no more than four 20W LV lamps per dimmer.
Overall, the lights being dimmed work out to just under the 600W plate rating.
So.... realistically, it looks like you will be back to two separate plates as the most practical solution.

.andy
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(Michael Brewer)

Isn't this slightly bonkers? They do a 400W double module that is above the plate limit of 380W all on its own. So just how would you accommodate a 400W module? Does that 380W plate limit only apply to powering halogens?

Hmm.
Cheers! Mike
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On Mon, 2 Feb 2004 20:56:44 -0000, "Michael Brewer"

There's a table in the data sheet.
For halogens, there's a plate limit of 600W for a 6 module grid for example.

.andy
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(Michael Brewer)

According to the datasheet, the row limit is only 380W until you get to a whopping 18 or 24 module plate. So presumably your 400W dimmer is not fully loaded either? Either that or your kitchen is a fantastic light extravanganza !

Who would have thought it would be so complicated? Until I got into this, a switch was a switch was a switch. Interesting though.
Another thing I learned by looking at the "standard" MK dimmer switch datasheet is that even though you might think that your dimmer switch will power your 400W total of halogens, it then says that it will only control a maximum of 4 transformers. Aaargh ! I was planning for each hologen to have its own transformer ! Is this transformer limit common to all dimmer switches? Please say no !
Mike
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On Mon, 2 Feb 2004 21:24:18 -0000, "Michael Brewer"

Well it is, but the 400W dimmer has 300W on it.

Normally grid switches are used in offices or other commercial applications. There are all kinds of modules available, and others which could be put together that are not compatible from a technical or a regulatory perspective.

The technology is remarkably similar at the power end of these. The control arrangements vary - for example soft start like the K4500 series has.
If you are going to give each halogen its own transformer, wouldn't it be easier to use mains ones?

.andy
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Michael Brewer wrote:

Yes. I have several and a three gang 400W dimmer. Made by Heritage.
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Is that 400W on each gang, or 400W total?
Mike
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Michael Brewer wrote:

400w each gang I think. Leastways I have 6x 50W LV's happily working off one bank, and 3 off another, and 3x40w candles on the third. All on one large plate - as in double mains socket size.
I have had a LOT of problems with that range at first tho - all the candle bulb equipped circuits have blown the triacs, but I got free upgraded modules and they are all fine now.
The LV stuff - running of electronic transformers - has been flawless.
Apparently candle bulbs do >10A when they blow and arc over for considerable periods. They ALWAYS trip my 6A circuits when they go.
I should add that the heritage replacement triac modules - now standard I believe- have been faultless.
I am not sure these are the ones I have, but here is a 400W double http://www.ryness.co.uk/Lists/accessories.html
I think the ones I have are from M Marcus - thats the manufacture - but they are not webbed up. I got them fromn cambridge electrical discount.
It seems that 400W on a single, and 300W on a double, is the order of the day. Or 400W on a triple on a big metal face plate.
My electronic transformers were part of a rather shoddy kit from the same shop (track units) and a big newey and eyere own brand electronic to drive the second bank of three LV's. The dimmers are nothing special, but the transformer units awere slod as 'fully dimmable' amnd in fact they are.
I suspect there are different things gong on with dimamble LV lighting - that is
(i) some electronics can't be dimmed. (ii) some electronics are designed to respond to the dimmer output correctly. These require no derating or specialised dimmers (iii) Toroids put a weird load on the dimmers, and probably need a specially designed and derated dimmer. Dimmers 'designed for LV' probably WILL work with toroids.
IME LV's put far less load on teh dimmers than incandescents. Mosrt have slow atrt up featires, and so don't surge. You can PROBABLY drive up to 8 50W LV's off a 250W dimmer in reality, tho it may get warm.

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