Any electricians around?!

Anyone got any experience with electrics? In particular hot water cylinders and an auto switch on a fuse box?

We have a hot water cylinder, and on the fuse box is a simple fuse switch, with ON, AUTO and OFF. (This:

However, since having a power cut, this doesn’t seem to be working on auto. If we set it to auto, our hot water runs out after a day… as if it’s not switching on when it should. It’s fine when “ON”, so it’s something to do with the timer I guess.

I’m guessing it’s supposed to switch on at set times when it’s cheaper rate. What I can’t work out is how it knows… I was expecting to see a timer, or a clock or something - that I suspect has been reset… but I can’t find it. Do you know if the fuse box would have a clock/timer inside it? Or do these switches work in a different way?

I’d appreciate any help you could offer!



I thought these things were controlled remotely these days. Radio waves or something?

Also known as a “contacteur jour nuit” as well as the 240V in and out these take a separate control input which is driven by contacts in the meter - there is no timer controlling this.

I suspect that the power cut has somehow damaged either the meter or your contacteur.

See for an explanation.

The distribution box should have a 2amp breaker switch which controls the auto function of the water heater breaker. This 2 amp breaker may have tripped when power was restored. Turn it to the off position and then back to the on position. Then, with the water heater switch set to auto, see if the meter starts to show increased usage of current when the cheap rate starts at 23.30hrs.
If so, then problem solved. If not, then as Paul says the fault is either with the 3 position breaker on the distribution board (your problem to fix), or with the command signal switch inside the meter which is the responsibility of the electric supply company. Should only take an electrician a few minutes to determine which item is at fault.

Thanks all!

Out of interest, if the connector is broken on the Linky Meter (The green one), would that mean that our house never has off-peak electricity and we’re being charged the full whack 24/7? Our last electricity bill was huge, which is why I started looking into it again…

Do you know if the cheap rate is just done at the electricty company (checking the time the electric was taken) or if the switch happens and is sent back to them automatically?

The meters just maintain two tallies and switch between them using the same signal that drives the switch - any power that you use during off peak hours will be charged at the heures creuses rate but, obviously, if the switching is broken you might not be making most effective use of the low rate period.

If the signal never arrives, however, you wont have any usage charged at the lower rate - but you should be able to spot that on the bill.

When the time comes for your electricity supply to switch over from ‘heures plein’ (daytime) to ‘heures creuses’ (night, ours is 10pm to 6am) Your supplier transmits a signal to your meter which switches it over.
The meter, in turn transmits a supply via a 2amp pilot wire to your distribution board. This supply switches your water heater switch (disjoncteur heures creuses) on, provided it is set to ‘auto’.
The most likely cause of your problem is that your disjoncteur hc has failed but, as has already been said it should not take long for an electrician to find the fault.

Just checked my bill, and there’s no mention of heures creuses or heures plein.

It’ll be annoying if I pay for an electrician to come check and the fault is on the box outside, not in the house … but seems I don’t have much option.

Thanks again everyone!

If you sequentially press the button marked + on the front of the Linky it will show you which tariff you are on, whether or not you have Heures Creuse / Heures Plein, which one of those it is currently recording against, how much has been used on each tariff since the meter was installed, the current usage in Watts, and the maximum usage at any one time in Watts since the previous midnight hour.
There should have been an instruction / information booklet left on-site by the Linky installer which explains all the various info that you can obtain from the meter yourself.

I’m on the plain tariff bleu so I’m guessing a bit but there should be mention of so many units at one rate and so many units at another.

If not then check your tariff and that you are on the correct one, plus what Robert said about the meter giving you the running totals.

Thanks! So after checking the meter, and calling around - it turns out that we were on a tarif that doesn’t have off-peak hours!! Crazy. Not sure how our hot water worked previously, but hey-ho.

They’ve switched us so we should be all good from 3am tonight. Case closed! Thanks all!

We are also not on a day/night tariff. We don’t use enough electricity through the night to warrant the higher daytime rates so although the night rate is cheaper it would have worked out more to switch.

Instead I put a timer on the hot water tank to heat it at useful times for us - it seems about 30 minutes per day is enough to keep the water hot for us.

I wish I’d know we weren’t on a day/night tariff! Our entire house is electric only, including the heating (from a rather rubbish reverse air-con unit that is on all day and night!) plus we have an inflatable hot tub that runs 24/7 - so makes sense to have a cheaper rate in the eve.


If you are running electrical items 24 hours a day just make sure you are not paying a higher daytime rate.

I had Mitsubishi ‘split’ units installed to provide warmth as well as coolth. Mitsi, I thought, I can do no better than/of. They work very well.

One of the room units failed due to a most bizarre cause. See below in case anyone has a similar set-up

Although I have just put my flat on sale, I played the officer and gentleman and had a similarly premium make fitted to replace it - Fujitsu. This is even better than the Mitsi! It takes half the time to produce warm air than the Mitsi did. It has an extra fan setting below ‘low’ which makes it pretty much silent.

No doubt Hi-Sense and other Chinese makes will eventually attain the quality level of Fujitsu/Mitsubishi/LG, but they are not there yet. Perhaps you have one of the Chinese ones? Air-con is one thing that is worth paying a premium for. It’s expensive to buy and expensive to instal. You want it to serve effectively for years.

This indoor unit failed because its condensation overflow was piped into a closed hopper also taking kitchen/bathroom/WC waste. In summer, the condensation runs down this pipe and flushes out gases which arise from the brown waste.

In winter, the condensation drains from the exterior units on the roof. The ‘summer’ pipe into the hopper, never getting flushed out, allowed gases into the room unit and rotted the heat exchanger. What shoud have been a matrix of shiny copper tubes was all black. All the gas gone.

A tap has been fitted on this pipe which must be closed when the unit is used as a heater and opened when used for cooling.

I’d check your actual tariffs including standing fees/tax. There’s an assumption “off peak” will be cheaper - I did the sums you need to be using a lot of electric “off peak” for it to be worthwhile these days. Yes the unit price overnight is lower - but the day rate… and the fixed charges outweigh those savings for many houses. It was once very worthwhile - now you may find you’re better paying standard tariffs. Inflatable hot tubs running 24/7 … might find that’s why your bill is huge whatever tariff.

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Absolutely - for us it is cheaper to be on a standard discounted tariff rather than a day/night tariff.