Immersion Heater - Two Switches Help

[SallyRutland]

Hello all

I have just moved in to a new rental accomodation in the UK. The accomodation has no gas and is purely run on electricity. I think all of my hot water is heated through an immersion heater (a 'Heatrae Sadia Megaflo DD210' pictured below).

I am trying to reduce my electricity useage as I had a rather nasty shock last month. I've been advised that it is could be due to the immersion heater as I think it had been set so that it was running 24/7.

The immersion heater has two connections to the mains. Both of these connections have been switched on.

I think 1 is linked to a control panel. Since the nasty shock, I played around with the control panel so that the immersion heater is programmed to be on for 6 hours a day (3 hours in the morning and 3 in the evening). This switch is labelled '12HR IMMERSION'. I have no idea whether this programming has had any effect.

There is a second switch labelled '24HR IMMERSION'. I am not sure what this switch does. I am worried that if this is needlesly switched on then I will get another huge electricity bill.

I have played around with the two swithces:
When I switch off 'Switch 2' (24HR), there is an immediate difference in the sound of the Immersion heater.
When I swtich off 'Switch 1' (12HR) there is no difference in the sound of the immersion heater. There is also no audible difference when the heater programmer switches from 'off to on' or vice-versa.

I am worried that my Immersion Heater might continue to be heating up water 24/7 (and therefore incurring huge quantities of electricity).

Would anyone be so kind to advise? Unfortunately I am clueless with this stuff but really want to avoid another nasty shock next month.

Thank you in advance,
Sally R

 

[ETAF]

you have 2 immersion heater elements within the tank
Both are wired up - one to the Box marked 12 hours and one direct to the 24hour switch
turn the 24hr one off
now it should only heat up to the timings you mentioned.
the immersion heaters on the TANK are factory set to 60C - so once the tank reaches 60C they should turn off - or NOT switch on
Unless someone has changed those temperature settings


thats my DIY take on your setup - sure more professional members will be along

you should be able to also see on the electric meter - when they are drawing current - some will flash a light faster - not sure what meter you have

 

[JohnD]

I've been advised that it is could be due to the immersion heater as I think it had been set so that it was running 24/7.

No, that won't be the cause. The Megaflo is so well insulated that even when fully hot, hardly any energy escapes (unless you keep running the hot water or have a leak). Once it is hot, the thermostat turns off and it stops using electricity until it gets cold.

Electric heating, however, is very expensive.

If you have "economy 7" or some modern equivalent where your night-time electricity is cheaper than daytime, use as much as you can during the night. This will (should) be the lower element in your cylinder, so turn the upper one off because it will (should) be the high-price daytime supply.

The Megaflo will (should) be so big tnat if you fully heat it during the night, it will provide enough hot water to last all day. If it runs out you can turn on the upper one for a small top-up.

If you do not have cheap night time electricity, it makes no difference.

Check your tariff and meter. Look at your electricity account online.

 

[ianmcd]

The 24hr switch should be ON and the 12 hr Switch OFF, it takes little energy to top up what you have used but takes a lot to keep heating from cold so small timed bursts like you have set cost more to run, leave it on 24hrs, its cheaper, the top immersion is to top up the cylinder if you have used up all the hw that has been stored overnight at the cheaper rate

 

[SallyRutland]

Thank you all.

I do not have an 'Economy 7' tariff. I have standard variable. I will contact my supplier tomorrow though to see if I can switch.

Does that mean, currently, I should leave the '24 HR' switch on and only switch on the '12 HR' one if a top up is needed?

Sally R

 

[ianmcd]

Thank you all.

I do not have an 'Economy 7' tariff. I have standard variable. I will contact my supplier tomorrow though to see if I can switch.

Does that mean, currently, I should leave the '24 HR' switch on and only switch on the '12 HR' one if a top up is needed?

Sally R

yes

 

[Johntheo5]

Assuming the 12 hour immersion element is on the top, except big demand for HW, shouldn't there be a little less losses than keeping the whole cylinder hot at all times.

 

[Rodders53]

The Megaflo is so well insulated that even when fully hot, hardly any energy escapes (unless you keep running the hot water or have a leak).

"Only" 1.43 kWh per 24 hours according to the brochure for the 210DD
So that's 30 minutes of heating neeeded each day for a full tank on the bottom immersion (24 hour).

The Nobo System 500 RX512 wireless receiver is wired to the upper immersion and on the "12 hour" immersions switch...
Google tells me that the Nobo System 500 is no longer made.
That upper immersion is intended for a 'topup' and is usually manually operated when on an economy 7 installation.
Looks to me like the numbers assign an RF ID to that switch to permit the wireless control-timer to operate it. (I have a similar set of wireless 13A sockets and remote control, a predecessor of 'smart switches').

OP should look for other Nobo-branded items and time controllers for that. For example https://www.upperplumbers.co.uk/PDF/Manuals/Controls/Orion512 manual.pdf is a link to the manual for a Nobo Orion 512 that mentions this controllable switch and that the device permits wireless multi-zone timer control of panel heaters and similar.

Then there's the lower element fed from the 24 hour switch... To heat a full tank of water - typically via an economy 7 switched supply circuit. Which the OP doesn't seem to have.
To make use of 'off peak' or variable time of use tariffs the 24 hour immersion would need a timer-switch (capable of the high current) inserted into the circuit (a bit like the one in the upper immersion circuit.

We need to know more about the OPs hot water use. Shower only or baths? How often. It may be that the full 210 litres is seldom/never required and that the upper only will be best (providing the control of it can be sorted). However if baths and frequently then the bottom may be needed. Once in a blue moon and a manual switch on/off is all that's needed.

Theory says it uses no more electric to leave an immersion on 24 hours as the thermostat will switch on/off as needed. BUT it uses more if the 'stat is set to 70C cf 60 C or a lower temperature even?
Losses on a 'half tank' using the upper immersion only will be lower too.
That it can be switched on via the timer may work well and reduce overall consumption based on the OPs hot water usage.

My 250 litre unvented HW tank gets reheated once a day around our morning shower time and lasts us for all other use (two adults). {Oil boiler so only on for about an hour.)
The 210DD electric spec states a heat up time of 102 minutes with both elements - that's 6 kW - in use to 60C. That'd need 3 hours for the bottom only, and a full tank of hot drawn off.}

 

[SallyRutland]

Hello,

My habits are usually a hot shower in the morning and a hot one at night. Very rarely take a bath and can't think of any other instances where a significant amount of hot water is used.

Because I do not benefit from Econony 7, and because it is well insulated, does that mean there is an arguement to turn off the '24 HR' element and purely rely on the programmable upper element (and programming it so that warms up water for when I need it).

Sorry if I misunderstand, and thank you all for assisting me.
Sally R

 

[ETAF]

is the shower a completely separate electric shower , which would be feed from mains cold water
Or does it use the hot tank water ? via a Powershower , Pump or a mixer tap on bath

 

[Johntheo5]

Yes, I would suggest definitely to go that route, use top "1/2" only.

 

[Rodders53]

Hello,

My habits are usually a hot shower in the morning and a hot one at night. Very rarely take a bath and can't think of any other instances where a significant amount of hot water is used.

Because I do not benefit from Econony 7, and because it is well insulated, does that mean there is an argument to turn off the '24 HR' element and purely rely on the programmable upper element (and programming it so that warms up water for when I need it).

Sorry if I misunderstand, and thank you all for assisting me.
Sally R

Yes. 100%.

I'd expect the green led light on that element switch shows 'mains on' and the adjacent led will light red when it is actually heating the water... The controller probably has a manual advance or boost switch to force it to go on. Check that operates as expected.

Caveat: a very long, very hot shower might use most of that 'half tank' of hot. Short showers will use less. The shower head will often make a big difference, too.
Frugal use may mean you can heat the tank once a day, or for shorter times twice. Experiment. (Ensure it's heated up for an hour or two before your morning shower, and beyond for a bit to reheat it to some extent, if not fully.
Some will say leave it on 24/7 and the thermostat will take care of things.

 

[Diver Fred]

Hello Sally. Whilst others have given you good advice I recommend you contact you landlord or the agent for guidance on how the hot water system operates to you best advantage. In fact there should be written instructions for the hot water (along with copies of other installed kit, heating, etc) in the tenants handover pack which you should have signed for.

A thought - how is your flat heated? Hot water radiators?