Immersion heater

[Slarti]

If your only way of heating the hot water, is it usual to leave the immersion heater on all of the time, or would I be better to turn it off when not required?

Slarti

[staffordian]

I've never needed to have it on more than an hour or two at a time, depending on how well the tank is insulated.

I very much doubt leaving one on 24/7 is efficient unless there is 24/7 showering in the house

[Slarti]

I've never needed to have it on more than an hour or two at a time, depending on how well the tank is insulated.

I very much doubt leaving one on 24/7 is efficient unless there is 24/7 showering in the house

It does sometimes seem as if it is one shower/bath after another as we come and go.

My instinct was to switch off unless needed, so that it what we'll do.

Cheers
Slarti

[JohnB]

Leaving it on will stress the thermostat, so it will fail quicker,

[moorfield]

My first flat in London (mid 90's) had no gas, so only an electric immersion heater tank. I just timed how long it took to heat up and left it on a timer clock. But if you own dividend paying shares in your energy provider, then leave it on 24/7 ...

[csearle]

I reckon that if your water tank could hold its heat indefinitely then it would make little difference to the bill (although I accept that it might make a difference to the longevity of the equipment). But as long as there is any heat-loss from the tank then all the time the water is hotter than the tank's surroundings there will surely be heat energy escaping into the air. So I feel that heating it up just before use would be marginally more efficient.

Chris
(No idea really.)

[tjh290633]

Bring back the Ascots

TJH

[jfgw]

As a very rough ball-park figure, I would guess you would save about 1kWh per day by using a timer rather than leaving the heater on all the time.

For a 900mm tall x 450mm diameter cylinder (the most common size), Telford quote a 70W heat loss,

http://www.telford-group.com/clear_down ... -50165.pdf .

This is equivalent to 1.68 kWh per day. Pipework will increase this.

I do not know the exact criteria upon what this is based but believe that an ambient temperature of 20 degrees C is assumed. Hot water should be kept at between 60 degrees C and 65 degrees C. This will give a 40 to 45 degree difference. The heat loss will be proportional to this temperature difference so the saving will depend upon how much the cylinder cools down. If, say, the cylinder cools down to 50 degrees, it will still continue to lose heat at a rate of over 1kWh per day. If you run a bath, however, the water in the cylinder may be much colder than this so the saving will be greater.

Bigger cylinders will lose more, as will older, poorly insulated ones (those with loose jackets).

Julian F. G. W.

[Itsallaguess]

When we had an immersion heater we used to make sure it was on for a couple of timer-activated periods a day, which was around the time we got up so we had good shower-availability (it came on a little before, actually, if I remember rightly), and also a second period around mid-afternoon to make sure we had enough hot-water for washing-up and maybe an evening shower if needed.

These periods generally made sure that we always had enough 'normal washing' hot-water for our general use through the day, and almost always provided enough 'shower-hot' water if we wanted a quick impromptu shower.

For any planned-shower, we often used the 1-hour boost facility anyway, no matter how hot we thought the water was in the cylinder. We didn't worry about any potential for overheating, as the element-stat would take care of that anyway. Using the boost facility always meant that you had a good slug of 'proper hot-water' for an enjoyable shower.

I can't remember many times at all when we didn't have the correct temperature of water for what we wanted using the above process, and whilst we knew that heating water using electricity was expensive, we didn't seem to have massive electricity bills.

We've moved over to a combi-boiler now, and re-gained the space taken up by the immersion heater. A win-win situation after the initial expense of the boiler-swap.

We were pretty good with remembering to use the 1-hour boost facility, but obviously this means that if we weren't as good at remembering to use it, then we may well have had more periods where shower-water was either a bit colder than we'd have preferred, or perhaps wasn't available for long at all, so I guess the answer to this type of question is going to revolve around how good a routine you could get yourself into, and if that's a struggle then perhaps a third automated timer-period would be warranted.

I'd still recommend that timer-solution over having it on all the time, however. Leaving it on as opposed to using a timer, in my mind, would be like putting the kettle on constantly just in case you want a cup of tea at some point....

Cheers,

Itsallaguess

[Dod101]

I have an old fashioned oil fired boiler which heats the water and central heating as required. I would not dream of heating hot water all day and so have a timer, doing much the same as Itsallaguess. I heat water twice a day much as Itsallaguess describes. What I do not understand is why even with a combi boiler he would 'regain the space taken up by the immersion heater'. Does he no longer have one? Are combi boilers infallible?

Dod

[jfgw]

Depending upon where your cylinder is and the weather, the heat given off might be useful. The cylinder is just acting like a small radiator. You might want to swap your LEDs for GLS lamps too for the next few days if your boiler is kaput!

Julian F. G. W.

[Itsallaguess]

What I do not understand is why even with a combi boiler he would 'regain the space taken up by the immersion heater'.

Does he no longer have one? Are combi boilers infallible?

Hi Dod,

No, I don't have an immersion heater any more, following the installation of our combi boiler. The boiler delivers hot-water on demand and doesn't need a storage vessel at all.

Nothing is infalible, of course (although our Vaillant combi has been fantastic for many years now), and we've always ensured we have an electric shower above the bath, and this is actually what we use all the time now, with baths using combi-hot-water limited to our son for the most part, who seems to be able to find the time and justification for one more than we do, but I do grant that if I came in covered in mud after football, as he often does, then I'd be back having a bath now and again in a flash!

I can't imagine us moving away from a combi/electric-shower set-up to be honest, it seems to deliver the best mix of instant hot-water for our day-to-day needs, with the built in benefit of having two bathing options even if one of them develops a problem.

Cheers,

Itsallaguess

[vrdiver]

If you have a solar panel, you can link it to your immersion heater so that any unused electricity from the panel gets diverted to heat your water tank. E.g. https://www.thegreenage.co.uk/optimmers ... on-heater/ (just the first result from a google search of "solar panel immersion heater").

Never tried it - was wondering if any LFs had, or if it was a technical nightmare in the making?

VRD

[gryffron]

If you have a solar panel, you can link it to your immersion heater so that any unused electricity from the panel gets diverted to heat your water tank. E.g. https://www.thegreenage.co.uk/optimmers ... on-heater/ (just the first result from a google search of "solar panel immersion heater").
Never tried it - was wondering if any LFs had, or if it was a technical nightmare in the making?

It's technically quite feasible. Of course, many of us are still getting premium rate for solar generation, so using our own power would be a very UN-Foolish thing to do. Financially better to do the opposite.

Gryff

[vrdiver]

many of us are still getting premium rate for solar generation, so using our own power would be a very UN-Foolish thing to do. Financially better to do the opposite.

Gryff

I thought you got the FIT for all electricity generated, whether it was exported to the grid or consumed?

VRD

[csearle]

If you have a solar panel, you can link it to your immersion heater so that any unused electricity from the panel gets diverted to heat your water tank. E.g. https://www.thegreenage.co.uk/optimmers ... on-heater/ (just the first result from a google search of "solar panel immersion heater").

Never tried it - was wondering if any LFs had, or if it was a technical nightmare in the making?

Not exactly the same but I helped out on a friend's job (on a farm) where they have a wind turbine charging an array of batteries, which are then used to supply power (at 240V) for the farmhouse. Excess energy is dumped into a two-bar electric heater on the outside of an out-building.

The farmhouse was being re-built with membrane all around so that its heat-loss was ultra-low. Wet under-floor heating was installed throughout.

One of the jobs we did (apart from re-wiring the place) was to direct the excess energy from the wind turbine to an additional immersion heater until its stat switches-off, after which it is directed to the dummy load as before.

Regards,
Chris

[richlist]

I have solar pannels, a 14 panel array on my roof. We also have the additional hot water solar boost system. Both are excellent. We get cheaper electricity, free hot water, use less gas because were not using gas to heat water, get a payment for solar energy from our energy supplier and get a feed in tariff payment from the government.

The feed in tariff assumes that you export 50% of total solar production to the grid......even if you don't export anything, you get paid on 50% of total production.

Anyone with....solar panels + hot water solar system + battery back up for night time use + electric car charging......Will probably export virtually nothing to the grid but still get paid a FIT based on 50% of total solar production.

It's the best kept secret around......

[Dod101]

I have solar pannels, a 14 panel array on my roof. We also have the additional hot water solar boost system. Both are excellent. We get cheaper electricity, free hot water, use less gas because were not using gas to heat water, get a payment for solar energy from our energy supplier and get a feed in tariff payment from the government.

The feed in tariff assumes that you export 50% of total solar production to the grid......even if you don't export anything, you get paid on 50% of total production.

Anyone with....solar panels + hot water solar system + battery back up for night time use + electric car charging......Will probably export virtually nothing to the grid but still get paid a FIT based on 50% of total solar production.

It's the best kept secret around......

Can I ask what sort of net cost was this to you? Presumably there is also a subsidy for the capital cost of the installation.

Dod

[richlist]

Installation costs have fallen dramatically since around 2011.......and so have The feed in tariffs. The installation cost to me (in October 2017) of the 14 solar panels with inverter and all the necessary bits and pieces was around £4900. The additional hot water solar boost installation was another £200. There is no additional subsidy available as far as I'm aware. FIT is guaranteed for 20 years.

[Dod101]

Thanks richlist, not outrageous and actually unlike wind turbines, it has little or no impact on the landscape. Maybe they ought to be more widely publicised.

Dod