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I don't understand my house's lights


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Hi all,

Hope everyone is well.

I have a strange request for you today.  I need you to help me understand the lighting system in my house.  So, it’s a normal downlight system with one exception – and this is the part that causes confusion – the downlights have a solar & battery backup for loadshedding that works well but it raises questions in my mind.

 Let me share what I DO know:

·         Downlights are MR16 GU5 (12V AC DC) and all work off the normal light switches.

·         Solar panel on roof, connected to charge controller in roof connected to 100ah in roof.

·         Also in the roof is a 12V Power Supply (Xytron GK-250-12).  Ouput 12VDC, 21A.

·         From the main DB board, 230V is connected to this power supply.

·         The power supply also has 3 pairs of V+ and G which I assume is DC out channels with a mess of wires connected.


Here’s what I’m trying to figure out:

·         How is the battery connected into this system?   When AC goes off there’s a seamless transition – lights stay on and still work off the normal light switches.  From the charge controller, a set of wires come off the “Load” terminal into the mess of wires around the 12V power supply but I can’t tell where they end up or what they’re connected to.  Surely they can’t just be spliced onto the Power Supply’s output?   The battery will also draw too much on the supply if not fully charged.

·         How the fuuuudge are the normal light switches integrated into this system?  Normally, DB board output goes to the lightswitch panel for a certain room and then out to the light itself. In my case, I assume, there is only one output from the DB board to the central 12V power supply and from there, there is an ouput to each light switch for each room and then from there a line out to each group of downlights for that light switch.   That makes sense, BUT, does that mean I have 12V lines connected into the house’s light switch conduits and switches?   Not CoC?   There is no transformer at the downlight unit itself.


Not sure if there’s anyone around here who may have a similar setup or perhaps just know what conventions are with such a setup.  I can’t figure it out.

Reasons for me asking is this:   I’m curious and always want to understand everything (especially my own house), if my house has compliance issues I’ll need to fix it, I want to expand the system to one or two rooms that don’t have the downlights, I’m considering conversion to GU10 and I’m considering a full-house solar system and don’t know how that will impact the current lights.

Any thoughts?

Much appreciated


Edited by Christoff83
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  • Christoff83 changed the title to I don't understand my house's lights
  • 2 weeks later...

Basically you need to go and look. Take some photos. I can only guess at what is in your roof so please bear that I am making assumptions based on likelihood:

However, 12v down-lighters are a common thing. They have a transformer that takes the 240V AC and steps it down to 12V. In your case it appears the 12V Power Supply (Xytron GK-250-12) is performing this function.

Normally the switch on the wall is going to open or close the circuit on the 240V AC side of the transformer / power supply. Turn off the light switch and there is no mains voltage AC going in and no 12V coming out of the transformer / power supply.

Many downlight setups share transformers because they are expensive and can easily power more than one bulb.

Where it gets interesting in your case is the battery. Forget about the charging side of the battery as that has nothing to do with your quest to understand your lights. Focus on how the battery is connected to the load.

What is connected to the battery? The battery can only supply 12V DC so this is what I would trace. Perhaps (speculation!!) the power supply can take 12 V DC in as well?

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Just a couple of thoughts,

Lighting transformers produce 12v AC whereas a battery produces 12v DC so I'm not sure how the changeover between the two would be seemless. Standard light switches aren't rated to switch ELV DC. they don't have internal arc quenching and there's a good chance the current may be too high for them.

ELV (12V) and LV (230V) circuits need physical separation.

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