My chauff-eau holds 200 litres [c.50 gallons] and is a 2kw immersion-element water heater running soley on cheap rate 230VAC supply, presently about 7 centimes per kwh. Models range from 50 litres and up. I have 2 meters, the cheap rate automatically switching for all consumption in the off peak times, 1am-7am and 12pm-2pm, and times which, incidentally, I can choose within limits. During off peak only, a live [hot] signal appears from the off-peak meter and feeds to 3 breaker 'units', for want of a better description.
a] A 10A breaker to protect the signal/relay circuit. This is the lowest rated breaker now available in France, [ it used to be a 5A fuse in the old days].
b] A 16A [or as necessary] breaker to protect the immersion element circuitry.
c] The switching device itself, basically a 20A rated relay arranged so that cheap rate is only normally used for water heating, and occupying one breaker space. This has a 3-position slider switch to enable OFF/AUTO/OVERRIDE selection, the latter so you can heat water during normal rates if necessary. The slider automatically returns to the cheap rate position on getting the pilot signal, so you don't have to remember to switch back to auto from manual, which is neat.
Chauff-eaux [plural] are almost universally used here for domestic hot water generation, as it is by far and away the cheapest option. It is reliable, cheap to install, totally automatic and the insulation round the cylinder is so effective it will keep stored water hot for at least a week with no power.
And since France has 75% nuclear*/hydro generation, off peak is now cheaper than gazoil per kwh considering overall efficiencies.
Alan
* 58 nuclear reactors in 14 power stations.
[This message has been edited by Alan Belson (edited 05-03-2006).]
