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Garden lights and Connecting to Existing Armoured Cable From Dimmer Switch

Postby Smw111 » Sat Mar 24, 2018 7:18 am

Hi, a forum newbie here. Looking for some advice please. My new house has a armoured cable running from a dimmer switch, under the lawn and coming out to a black sealed junction box in a flower bed at the bottom of the garden. It’s not connected to anything from there. I’d like to do something with it but not sure what I need or how many lights it will support. I appreciate you may need more information but would be grateful for any advice. Thanks!
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Simply Build It

Postby Mr White » Sat Mar 24, 2018 12:51 pm

Sadly, it is not a case of "It will support X number of lights" since it depends on various factors, e.g.

1) Wattage of lamps you intend to use.

2) Size of the actual cable

3) Distance of actual cable run.

4) The dimmer switch

I shall expand on the above points.

1) You could have say two high wattage lamps to light all of your garden (and probably most of your neighbours garden) but equally you may want to have say twenty 10w lamps dotted around the garden as "markers" you really have to decide what you want to do, choose the lights then see can the cable support your choice.

2) The size of the cable determines how much current it can safely carry. It looks like it is 1mm but it may be 1.5mm or even 2.5mm. it will be written (embossed) on the cable itself.

3) The longer a cable is, the more that voltage drop will occur. Some lights will not work at all if there is too much voltage drop. Also too many lights can "drop the voltage" as well. The actual cable run needs to be measured. ( A close approximation will do, but it must take into account the actual cable run, its twists and turns)

4) Not all lights can be dimmed, and not all dimmers can dim all lights.
It is down to the actual lamp and any "associated parts" as to if it can or can not be dimmed. An example: Some LED lamps say they can be dimmed, others say non dimmable. (So it depends on the type of lamps you choose)

Also there are two types of dimmer. Trailing edge and Leading edge.

Leading edge were the "first" household type of dimmer and as such are very common, they have no problem dimming "ordinary (incandescent) lamps but can not dim most LED lamps. These dimmers are also very basic in construction.

Leading edge dimmers are made primarily for "Modern day" lamps that can be dimmed, to this avail these are more sophisticated in their construction.

All dimmer switches have a maximum wattage rating that they can work safely with, so not only should you consider which lamps you can have but also how many the dimmer can work with.
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Postby Smw111 » Sun Mar 25, 2018 6:37 pm

Great answer, than you Mr White.
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