Had an electrician start a rewire pre Xmas that is not yet complete so he needs to go back to finish. Something I’ve just thought about is our next job is to get a new hot water tank fitted as the current one is not working - the electrician has moved and installed a new fuse board. We have an EDF linky fitted also. Should I be asking the electrician to fit something on the fuse board to regulate the timing for a new balloon water heater or is it controlled remotely via the linky? thanks
Its controlled by its internal thermostat mainly but you could have a din rail mounted timer fitted if you ask. These are more expensive than externally mounted versions but I seem to recall @Badger a reason these mid way through the wiring timers are not liked, to do with direct wiring to the circuit breaker if I remember it.
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The heures Creuse “switch” is installed in the tableau - so yes. Obviously have them review/install the cable to your new water heater at the same time
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That would only apply if using the HC/HP though but well pointed out.
DIN mounted timer feed from its own breaker is the installation we have.
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In order to heat water using overnight cheap rate (Heures Creuses) you have a few things to consider/install.
Firstly, you need to subscribe to an energy contract that provides the HC option. Currently under EDF’s regulated tarrifs (tarif bleu) you can achieve that via their straight forward HC/HP option where you pay less for the 8 hours HC but pay slightly more for the daytime (Heures Pleines), or via the more complex but potentially cheaper Tempo option. See here for more details.
Secondly, you need to install a contacteur HC/HP in the tableau which then gives you the option to force the water heater on outside of HC periods, or to keep it switched off if you are absent.
The contacteur requires a connection of two wires to the Linky as it provides the switching to trigger it.
It is also acceptable to provide a suitable DIN rail mounted timer in the tableau instead of the contacteur (but not a plug in timer as water heaters should not be using a plug & socket conection). This allows you to vary the heating times of the water heater, which may be useful if you want to shift the load to the end of the HC period (it doesn’t need 8 hours to heat up). This is useful to to spread the load & keep your overall demand down if you have other heavy loads on during the HC period, charging an EV being one that is increasingly common.
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Badger just a quick question, hard wired external timer ok? Fully get plug and socket idea is bad.
That’s no problem. Go for it.
EDIT; Always make sure you use a timer that has an internal battery/memory to avoid the problem of a shifted time on period after a power cut.
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Many thanks Badger, hopefully the answer is also helpful to @becks5109 as well as maybe others 
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I think I’ve just discovered the purpose of the two random wires sticking out of my Linky, which sounds awfully like a euphemism.
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**you could also look at installing a [25A DIY Interrupteur Intelligent Compatible avec Alexa, Google Home, TUYA/Smart Life APP Contrôle à Distance, Commutateur Wifi
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thank you this is super helpful
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The Linky has it’s own contact for the immersion heater - new rules are arranged that it comes on at. 24h30, not the normal ‘cheap rate’ time
I’ve no idea where you’ve got that information from. It is not true.
Historically the HC periods were set to spread the load differently depending on local grid conditions. Some people might have had midnight to 08.00, some 23.00-07.00, some 22.00-06.00 & many other variations. There are some places where there are two HC periods - two hours at lunchtime, then 6 hours in the night.
These could/can not be negotiated, & only apply to the HC/HP dual tarif.
All Tempo supplies have an HC period of 22.00-06.00.
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