Install timer in DB board with inline breaker


Old 04-08-15, 05:48 AM
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Question Install timer in DB board with inline breaker

Hello all,

I've bought a timer to use with my geyser/water heater and think I understand the correct installation but am a bit puzzled by the current setup and would appreciate some input to understand it better and make sure my plan is correct.

I'll start with pictures because they'll help with my questions.

I should state this board is in South Africa so regulations would be UK based with some variations (historically SA uses UK wiring). Supply is 220V. All wiring is 2.5mm (excluding house supply)

Please excuse my paint brush diagrams / markups.

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I want to install the timer in the last picture to automatically turn my geyser on/off based on the set timings. I would also like the option of turning off a breaker to stop the geyser all together (holidays; etc).

My primary question is around the 60A dual breaker (highlighted in yellow square) - why is it there? The geyser is fed from the 60A breaker. The 60A neutral goes to the neutral bar but the 60A live is fed from a 15A breaker (highlighted in green square).

What's the point of the 60A breaker? Surely the 15A breaker will trip before the 60A so the 60A is only useful to isolate the neutral? Why would you want to do that? Shouldn't the neutral go directly to the neutral bar? Is there some clever reason a geyser/water heater needs this setup or is it wrong?

As far as I see it I can just remove the 60A breaker and wire the timer in it's place, as follows:

Timer neutral from neutral bar
Timer live from 15A breaker feed (so I can switch it off during vacation)
Geyser neutral to neutral bar
Geyser earth to earth bar
Geyser live to timer output

Is the wiring as simple as that? Can I remove the 60A breaker all together?

The only downside with this method is when I switch off the 15A breaker the timer switch will eventually lose power and i'll need to reprogram it, that's not a big problem.

I guess I could avoid that by connecting the live output of the timer to the 15A breaker (mains -> timer -> breaker, rather than mains -> breaker -> timer) but that becomes a more difficult install because the 15A breaker is wired directly to a live bar so I would need to move it and I don't have the fittings.

I'm prepared to live with reprogramming a timer once in a while but want to make sure there isn't a good reason there is a 60A breaker inline with a 15A one and why the neutral is running through this breaker.

Any help is appreciated!

Old 04-08-15, 05:53 AM
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This was my first post. I didn't realise the images would be resized. Links to the full size images are below:

DB Photo:
Timer Photo:

Old 04-08-15, 09:02 AM
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Welcome to the forums.

I can see where you drew in wiring but don't see anything behind it. Can you post just a pick of the panel with no highlights ?

What is the amperage of the heater and will the timer be able to handle it ?
Old 04-09-15, 07:43 AM
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Hi Pete,

Here is the original photograph:

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I don't know what the amperage of the heater is as I can't get into my loft as the moment as I don't have a ladder (just moved).

The live is attached to a 15A breaker so it shouldn't be any higher than that. The timer supports upto a 21A resistive load so it should be ok.

It makes me wonder why there is 2.5m^2 wired into a dual 60A breaker as the wire will burn out long before that breaker kicks in. I read somewhere that South Africa specification requires the geyser (water heater) be isolated so I think that's why it's attached like this.

I hope the additional photo clears up any questions.

At this point i'm thinking of leaving the load attached to the 60A breaker and taking the live feed from the 15A breaker and passing that through the timer then wiring the timer neutral to the neutral bar.

That way I can flip the 60A breaker to turn off the geyser but the 15A breaker will keep the timer powered and still offer protection on the live connection. I don't know if the timer has a breaker in it, I doubt it.

Thanks for your help.


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