Hot water cylinder & immersion problems - 2 switches

[Lauragraham92]

Is your shower electric ?

Yes!

 

[CBW]

Is your shower electric ?

Yes!

Then that’s not going to deplete the hot water from the cylinder.

 

[Harry Bloomfield]

We have electric radiators (all electric flat) - but luckily haven’t had to have them on yet!

You need storage heaters, to make E7 worthwhile.

 

[ericmark]

It looks to be a better insulated tank to mine, I have not until last few months used electric to heat the water, but used oil, in the summer it would switch on three times a week for ½ hour a time, but would normally cut out after 20 minutes, it was only used for hand washing, and boiler is 20 kW, it was not really enough so water only warm.

So around 7 hours a week with a 3 kW immersion would keep water warm for hand washing, my showed is around 10 kW and used for around 20 minutes a time, so a shower will need around another 3.5 hours to heat the water. So two people who both shower every other day one would consider it would need the immersion to run for at least 5 hours a day to get all the hot water required.

I now use electric for domestic hot water in the summer, I can't in the winter as no way to turn central heating hot coil off, I use no timer, it is left switched on 24/7, however there is a sensor on the supply cables so it only heats water when would would otherwise be exporting power from solar panels. It does tell me how much I am using and how much used, and also says when the thermostat has switched off, it says water hot, so I know when it is working, and I found the thermostat had been set too high and the over temperature trip had turned off the immersion heater, if this happened to your lower immersion heater you may not realise it has tripped.

With my system it can use much less than 3 kW due to the solar iboost+ which controls it, so hard to see from the electric meters if working, not got a smart meter yet, but would assume they do have some thing like this

which shows you what you are using, maybe something like this

so you can see if the immersion is using power. I will admit my standard electric meter is a bit useless, the old wheel type you could see the change in wheel speed, but newer types harder to see what you are using.

I would have thought with all electric you would have a variable tariff, and today to get a variable tariff you need a smart meter, except it seems in Scotland where economy 7 can still be installed. But going by what I use to heat water seems likely simply not left on long enough.

 

[ianmcd]

Yes!

you wont have an electric shower and an unvented electric HW cylinder, post a pic of your shower

 

[terryplumb]

Thanks both. The boiler was fitted in February this year by the previous resident.

Do you mean the hot water cylinder was fitted in February this year ? It would be odd to have an instantaneous electric shower ,unless the previous resident planned to change it and never got around to doing so. Show us pics of the shower.

 

[Lauragraham92]

Sorry - we don’t have an instantaneous electric shower, it takes time to heat up the tank before there is hot water for a shower.

 

[ericmark]

Working out how long a 300 watt item has been running for is hard, the orange line is how much I am using and I can just about see when the heat pump tumble drier kicked in. But with 3000 watt it is reasonably easy to see when it has been running, see when I boiled the kettle to fill the flask, so I assume the same is true with smart meters, it should be easy to see when the thermostat cuts in and out when heating the water. So one should be able to see how long it takes, and if the immersion is working. Before have solar panels and with no smart meter it was harder, I had to use a clamp on meter on the meter tails to see what was going on, but it seems unlikely one can heat 40 gallons of water in 1½ to 2 hours, calculator here it seems it will take over 4 hours even at 65ºC if you went to 80ºC then over 5 hours.

I found my water will remain hot for two days, so there is little point in heating just the top of the tank, or using a timer unless you have a flexible tariff, simply switch it on and leave it on. With a flexible tariff then yes heat when electric is cheap, but other wise simply leave it running.

 

[Rodders53]

Looks like a 200 litre cylinder: TSMD 200: https://www.tdlonline.co.uk/docs/Tempest/Tempest-Direct-Data-Sheet.pdf

That has a heat loss of 1.85 kWh every day - and a 3kW immersion need to be on for 37 minutes to make up that heat loss alone, once the cylinder is up to temperature (60 C). The spec sheet states a reheat time from 10 C to 60 C of 116 minutes (6 kWh on the bottom element). Thus your approx 2 hours daily in two 1 hour sessions is never going to quite 'cut it' if you use most of that 200 litres in the day via showers etc.,..

It is possible the immersion thermostat never cuts out as the water never reaches the required set temperature.

That bottom timer looks to have two lots of only three segments set for ON periods: from 0645 to 0730 and 1615 to 1700. If I'm correct no wonder the water is never hot enough.
Top timer is not set to be on ever, which for E7 would be correct. But it may be ideal for an evening hand and dish washing boost?

You may need to time the HW to come on at least 2 hours before you plan to shower and possibly a lot longer if you want to reheat the water used.

Do you have a smart meter for your electric? If so you can use that to check that both elements work by watching the increase in consumption when operating. Otherwise it may need someone competent to use, say, a multimeter to check that mains is reaching the element(s).

However I believe this is a case of trying to be a bit too frugal with energy use. Possibly