Help with wiring zwave switch for water heater (240V)

Moin,
I hope this is a suitable group for this kind of question. If no, suggestions are welcome.
I'd like to automate our storage/tank water heater using some home automation system using zWave.
Local power is 240V 50Hz
The Water Heater is rated 220V-240V 2.5-3kW
(which in my calculations may end up just above 13A)
Originally, the water header was just connected directly to the incoming power supply via a 2-throw wall switch (for both the L and N wires, ground connected through inside the switch housing.
I was planning to use a Fibaro FGS-213 switch for this
http://products.z-wavealliance.org/products/1871
It is rated at 8A tops, so it cannot be used with the heater as load directly
So I got a contactor:
Schneider TeSys LC1K09 10M7
http://www.datasheetlib.com/datasheets/lc1k09.html
which is rated:
| [Ie] rated operational current | 9 A AC AC-3 for power circuit at <= 440 V
Since the water heater is an AC-1 load, it can handle up to 20A, which should be sufficient.
I am using two poles of the 3-pole contactor so that in Open both the LIVE and NEUTRAL of the water heater are disconnected (just like with the 2-throw switch it replaces)
The Fibaro also has a switch connection which allows for local switching of the load...
This is the wiring diagram I came up with:
https://www.dropbox.com/s/5r0sbaj5iqz5qz5/wiring1.pdf?dl=0
I would like to know if that is doable, and whether I am missing anything..
1. Can I just connect all the N leads together like that? or do I need anything to protect the N ports of the Fibaro and the NO (14) of the contactor from any current?
Same for the Ground?
2. I am unsure about what colour leads to use for all connections.
Incoming LIVE i brown. that much is clear. what colour wire should I use between the FIBARO's load connector (Q) and the contactor's A13 NO control gate?
Same for the leads to the switch connected to the Fibaro's L and S1 ports?
The whole thing will be housed in a :hager plastic enclosure with a metal DIN rail. do I need to ground the DIN rail inside this enclosure? Afaics the contactor has no ground connection to the rail itself..
thanks to all

On 01/05/17 17:30, Mathias Koerber wrote:
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If UK Mains, try the newsgroup uk.d-i-y

On 2/5/17 12:30 am, Mathias Koerber wrote:
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I'm from OZ so we have different codes but I would use the L3 terminal as the common neutral and run the wire from there to the remote switch and the coil of the contactor. There is no need to have protection in the neutral, I suppose you could put a 5amp fuse inline for the Fibaro but it would be overkill IMHO and would not protect the Fibaro just the wiring to it.

On 1/5/2017 7:30 ??, Mathias Koerber wrote:
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I'll do my best as I am in Greece and you obviously aren't... 1.yes, the N is the common and are all wired together and they aren't allowed to be disconnected while the live is connected, because the N will become live...there are no fuses or circuit breakers needed in the neutral. 2. usually you use the same as hot (brown) or red at least here. you can get a special contactor for rail mounting in a enclosure with just 2 poles, for 20 A AC1 because the one you picked is 3 phase which is overkill and might be longer so the cover of the enclosure might not fit.here they are called storage heater relays (another word for contactor)because they were used in house enclosures for that purpose.for instance-schneider A9C20732, with nominal current 25 A.2 pole and with the size of a circuit breaker. their cost is ~20 euros.

On 1/5/2017 7:30 ??, Mathias Koerber wrote:
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BTW, you don't need to ground the rail, as its only purpose is holding the elements (circuit breakers etc.) and usually might not become live or come into contact with humans. for ground purposes you use the ground rail (ditto for neutral) of the enclosure...