Someone help me understand my immersion set up!

7 Jan 2021
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United Kingdom
Hey! I moved into a new flat recently, and it is fully electric (which is new to me) and taking me some time to figure things out. I'd appreciate some guidance so I can feed back anything I need to my lettings agency.

So, I have an immersion tank with 2 switches. I've been investigating and understand that the lower heating element should be "off peak" and for the switch to be left on, and it will only fire up during off peak times. This is not the case (I have tested it against my smart energy meter and it heats the water any time of the day) so there can't be a timer fitted? It's pretty inconvenient to have to manually heat up water in advance. I know, first world problems...

I want to ask the landlord to fit a timer, but wanted to understand:

a. do I need one? I've also read that it should have a thermostat so will click off when it reaches a certain temperature. How can I confirm this or is this ALWAYS the case. If this is true, is it even efficient to have this on all day as it's only me in the flat?

b. If I should get a timer fitted, how much work is to have done?

Should also mention that when I moved into the flat I was on a single electricity tariff but have since moved to Economy 10 as I'm WFH so good to have some cheaper electricity during the day and not just the night. And the flat is only 4/5 years old.

Any helpful advice on electric heating also welcome - it's costing me a bloody fortune to even stay mildly warm. 20201203_144900.jpg 20201203_170957.jpg



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I want to ask the landlord to fit a timer, but wanted to understand:
You cant have a timer with economy 10, your supplier decides what is the cheap period and what isnt, the immersion heaters have thermostats inbuilt, you can have a timer fitted to the boost immersion, (top one) but as you are only there yourself it is false economey to use the boost
From your photo of the cylinder it's obviously been leaking at some time and from the rust rings around the heater elements it appears to be severely corroded (it's a lined steel sealed unit). If you intend staying there for a while I'd suggest asking your landlord for a replacement unit as that one is obviously on its way out. Plumber needs to hold a G3 certificate to do the job.

With respect to fitting timers, it's a minimal job for a sparky to do, located in the vicinity of the existing ON/OFF switches.
@ianmcd - thanks for the advice! But even with economy 10 right, the off-peak should only click on during the off peak periods determined by my supplier SSE (12-5am, 1-4pm, 8-10pm) So in theory I should be able to keep the the bottom switch on all the time, or all night and it will only heat during the off peak times? This is the part I am convinced isn't happening. So is this a tank issue or is this an SSE issue?

@Jackrae - thank you for your feedback. I will let my lettings agency know and request someone comes and checks on the condition of the tank.
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So in theory I should be able to keep the the bottom switch on all the time, or all night and it will only heat during the off peak times?

No, it is always live and will work at any time of the day. The cheaper tariff kicks in at specific times to reduce the cost on all sockets/outlets.
The old way E7/E10 it used to work was that there were 2 L/N cable connections into your fuse box and the heaters/water heaters were on a separate circuit and that was switched over by the meter at the low tariff periods.

Looking at yours then it's autoswitching on one circuit and as suggested everything clicks over to low tariff at the relative time.

You could put the lower immersion on a E7/E10 immersion time switch (would replace the lower switch in pic 2) so the heater would only come on during those low tariff times.


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