Posted by B Wooster on August 27, 2003, 12:06 pm
I am puzzled by the install instructions
on a dimmer switch I just bought (for regular bulbs).
It is a standard toggle switch, with a thin slider on the right.
It has a metal cover, with flanges (tabs) on left and right.
These tabs have to be broken off to install this switch
in a multi-switch panel.
The instructions say that if no side tabs are broken,
it supports 600W
If one of the side has its tabs broken off (to fit in a multi-
switch panel), then the power is reduced... I don't get this,
why?
If both sides have their tabs broken (need to do this if
this dimmer is going in between two other switches on the side)
then power capacity is reduced even more!
Why does breaking off side tabs reduce the power handling
capacity of a dimmer?
Posted by Larry on August 27, 2003, 7:20 pm
>bwooster47@hotmail.com (B Wooster) wrote in news:75cc51dd.0308270806.5bab00d7
>@posting.google.com:
>> Why does breaking off side tabs reduce the power handling
>> capacity of a dimmer?
>The metal tabs are for heat dissipation.
Bzzzzt. Wrong. The tabs are too small for that. But you were close.
They act as spacers. If they are in place there is sufficienct space
around the dimmer to allow proper air cooling. The only way they will
fit in a multi gang box is to break the tabs but then they are much
closer to the next switch. Less air space, less cooling.
Posted by Bert Hyman on August 28, 2003, 9:00 am
nospam@san.rr.com (Larry) wrote in
>
>>bwooster47@hotmail.com (B Wooster) wrote in
>>
>>> Why does breaking off side tabs reduce the power handling
>>> capacity of a dimmer?
>>
>>The metal tabs are for heat dissipation.
>
> Bzzzzt. Wrong. ...
Guess it's my fault for believing the manufacturer's documentation.
--
Bert Hyman | St. Paul, MN | bert@visi.com
Posted by Bob Rahe on August 28, 2003, 9:59 am
>>bwooster47@hotmail.com (B Wooster) wrote in news:75cc51dd.0308270806.5bab00d7
>>@posting.google.com:
>>> Why does breaking off side tabs reduce the power handling
>>> capacity of a dimmer?
>>The metal tabs are for heat dissipation.
>Bzzzzt. Wrong. The tabs are too small for that. But you were close.
>They act as spacers. If they are in place there is sufficienct space
>around the dimmer to allow proper air cooling. The only way they will
>fit in a multi gang box is to break the tabs but then they are much
>closer to the next switch. Less air space, less cooling.
Ummmm, and where do you think the heat is going to get cooled by the
air? On those tabs. They are the heatsink for the device.
The amount of heat transferred out of the device is directly
proportional to the surface area of the heat sink. The amount of heat
dissipated is proportional to the load on the device. Thus, given an
allowable temperature rise, the load limit (power capacity) is directly
proportional to the surface area of the heat sink.
--
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|Bob Rahe, Delaware Tech&Comm Coll. / |
|Computer Center, Dover, Delaware / |
|Internet: bob@dtcc.edu (RWR50) / |
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>@posting.google.com:
>> Why does breaking off side tabs reduce the power handling
>> capacity of a dimmer?
>The metal tabs are for heat dissipation.