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Home > Archive > Electrical code Compliance > June 2005 > Light Dimmer Isolation requirements
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Light Dimmer Isolation requirements
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| radon1111@hotmail.com 2005-06-20, 12:25 pm |
| It seems that Domestic light dimmers incorporate a mechanical switch
for isolation ( and a minimum dim level ) to ensure that an OFF light
really is OFF. Scene setting dimmers - with remote controls etc, do not
always seem to have this isolation feature.
Certainly many larger dimmer units only have isolation at the wiring
hub via a circuit breaker - and not at the local control position.
Is this feature detailed or specified in any standard, if so which one?
Any other info appreciated.
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| phil-news-nospam@ipal.net 2005-06-21, 12:25 pm |
| On 20 Jun 2005 01:29:53 -0700 radon1111@hotmail.com wrote:
| It seems that Domestic light dimmers incorporate a mechanical switch
| for isolation ( and a minimum dim level ) to ensure that an OFF light
| really is OFF. Scene setting dimmers - with remote controls etc, do not
| always seem to have this isolation feature.
|
| Certainly many larger dimmer units only have isolation at the wiring
| hub via a circuit breaker - and not at the local control position.
|
| Is this feature detailed or specified in any standard, if so which one?
| Any other info appreciated.
Where dimming is done by chopping the waveform, which is generally the
case in any efficient dimmer, it is possible, with more cost, to ensure
that the waveform has no time of passing current. Cheap dimmers can't
quite do that. Once you are getting into scene control systems, then
the cost isn't so much to get a real "off". Still, if you really want
a true disconnecting off, add a switch ahead of the controller. You
then lose features time remote control and timed scene changes.
--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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| Dale Farmer 2005-06-21, 6:25 pm |
|
radon1111@hotmail.com wrote:
quote:
> It seems that Domestic light dimmers incorporate a mechanical switch
> for isolation ( and a minimum dim level ) to ensure that an OFF light
> really is OFF. Scene setting dimmers - with remote controls etc, do not
> always seem to have this isolation feature.
>
> Certainly many larger dimmer units only have isolation at the wiring
> hub via a circuit breaker - and not at the local control position.
>
> Is this feature detailed or specified in any standard, if so which one?
> Any other info appreciated.
Theatrical dimmers use a number of different technologies to reduce
the current. They also have what is called a pre-heat setting, that leaves
a couple percent of the current flow even when at nominal 0% which
keeps the lamp filaments warm. This reduces the warm-up time to get
to the desired light level when it does come up, and is supposed to
reduce thermal stress in the lamp, extending it's lifespan.
So pretty much any recent manufacture theatrical dimmer system will
be constantly bleeding a little power to the loads. Some background
for your question would be good. If you want to speak to some experts
on theatrical dimmer systems, post the question on rec dot arts dot theatre
dot stagecraft newsgroup.
--Dale
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| radonix 2005-06-22, 6:25 pm |
| Yes - most of this I am aware of. I really was trying to find if there
are any international standards which define the legality or otherwise
re providing an air gap isolation when a system is aparently 'off'.
In a domestic or similar situation, who would be liable if someone got
a shock from a light fittting, if the 'off' setting was actually
causing some leakage.
A typical wall switch dimmer has a clearly defined 'off' click' which
corresponds to a mechanical switch. There are some remote control wall
dimmers ( touch dimmers ) which perhaps dont have the physical
isolation when set to off - so I guess it must be ok. None the less, I
recall reading somewhere about the requirements to go from 'off' to say
20 percent to avoid any uncertainty as to whether the power was really
off or not.
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| Dale Farmer 2005-06-23, 6:25 pm |
|
radonix wrote:
quote:
> Yes - most of this I am aware of. I really was trying to find if there
> are any international standards which define the legality or otherwise
> re providing an air gap isolation when a system is aparently 'off'.
> In a domestic or similar situation, who would be liable if someone got
> a shock from a light fittting, if the 'off' setting was actually
> causing some leakage.
>
> A typical wall switch dimmer has a clearly defined 'off' click' which
> corresponds to a mechanical switch. There are some remote control wall
> dimmers ( touch dimmers ) which perhaps dont have the physical
> isolation when set to off - so I guess it must be ok. None the less, I
> recall reading somewhere about the requirements to go from 'off' to say
> 20 percent to avoid any uncertainty as to whether the power was really
> off or not.
For the purposes of USA code, theatrical lighting is supposed only to
be serviced by qualified personnel, so they are expected to know the
proper procedure to safely deenergize the equipment for service.
Check your local country's electrical code for specific details. the
closest
thing to international standard would probably be the IEC.
--Dale ( Who isn't a lawyer, so don't count this as legal advice )
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