I was about to install a dimmer switch module (MK K4501 BSS BLV) to
control a group of 4 low voltage halogen downlighters that are each
supplied via their own individual ( 220 volt a/c to 12 volt DC)
transformer.

But, the installation instructions says that the dimmer should not be
used in a circuit with more than 3 transformers.

Can someone, who knows about electricity theory please explain the
reasons behind this limitation. And, if more than 3 were connected,
what would happen?

VT

On Tue, 14 Jul 2009 12:08:38 -0700 (PDT), Vet Tech wrote:

Can someone, who knows about electricity theory please explain the
reasons behind this limitation. And, if more than 3 were connected,
what would happen?

Real transformers as in lumps of iron with wire warpped around them
have fairly hefty inrush currents, toridial (donut shaped)
transformers commonly used in lighting applications have really big
inrush currents. They also produce a spike when switched off. Either
or both of these could kill the semiconductor switch in the dimmer.

Are your lighting transformers large and heavy (lumps of iron with
wire) or small a light (electronic power supplies)? The latter won't
have the inrush or spikes but they might object to being dimmed...

--
Cheers
Dave.

In article
,
Vet Tech wrote:
I was about to install a dimmer switch module (MK K4501 BSS BLV) to
control a group of 4 low voltage halogen downlighters that are each
supplied via their own individual ( 220 volt a/c to 12 volt DC)
transformer.

But, the installation instructions says that the dimmer should not be
used in a circuit with more than 3 transformers.

Almost certainly only applies if actual transformers - the switch on surge
with these is vast and you usually have to half (or more) the dimmer
rating with them. If you changed them (or even a couple) to electronic
'transformers' the restriction doesn't apply. One of these to supply 2 x
50 watt units costs under a tenner.

Can someone, who knows about electricity theory please explain the
reasons behind this limitation. And, if more than 3 were connected,
what would happen?

--
*24 hours in a day ... 24 beers in a case ... coincidence? *

Dave Plowman London SW
To e-mail, change noise into sound.

On 14 July, 22:46, "Dave Liquorice"
wrote:

Are your lighting transformers large and heavy (lumps of iron with
wire) or small a light (electronic power supplies)? *The latter won't
have the inrush or spikes but they might object to being dimmed...

--
Cheers
Dave.

I will have to move some furniture and lift floorboards to check what
type of transformer(s) I have. It may be a few days but I'll be back.

VT

In article
,
Vet Tech wrote:
I will have to move some furniture and lift floorboards to check what
type of transformer(s) I have. It may be a few days but I'll be back.

Electronic types are normally installed through the hole for the fitting -
to allow easy changing in event of a failure. Conventional transformers
are usually too big for this.

--
*It's not hard to meet expenses... they're everywhere.

Dave Plowman London SW
To e-mail, change noise into sound.