Immersion heater advice needed

SteveCritten

Yes Neil I have left my heating on with the only control being the room thermostat to test it and the bill wasn't significantly different to turning it on for a few hours in the morning and a few hours at night.

LauraL

In theory you're right, in practice what you save with the timer might be irrelevant compared to the cost of the timer and of the electrician.

If you really want to save money just LOWER the hot water THERMOSTAT! It take less energy to heat up the water from 20 to 30 deg than from 30 to 40, etc. The warmer the water, the more energy is needed to heat it further.
Normally heaters are set 60degC, but in the mixer you use cold water to bring it down again to 37-40, which is a shameful waste.  it would take much less energy to warm up to 37-40 the whole amount of water. Ideally you would want to minimise as much as possible the mixing with cold water in the tap.
The downside is that the tank will empty faster. If I were you i would set the heater at 50, then depending on your needs you can adjust and overall you will save.

Personally, I use a combi boiler where i can set the hot water at 39 so it comes straight from the hot water tap at "shower" temperature. Better than a bloody thermostatic tap....

One more thing to consider is the pure cost of energy. If you have some energy contract where using energy at night is much cheaper than during the day, then the timer is necessary and you can heat the hell out of that water so that you don't need any extra kick during the day!!

SteveCritten

But Laura I thought that if the hot water is in a tank it is set to 60 degrees plus to stop bacteria and bugs breeding such as legionella?

stephenc

That is correct. If you have a tank, then at least once a week, the water should be heated to around 60C to combat legionella.

SteveCritten

Thanks Stephen didn't realise it only had to be once a week.

IronGiant

It sounds like a bit of a chore, unless you gave it a manual boost once a week you'd have to have two heater circuits one timed and temperature set for the weekly boost and another for daily use.  Either that or a complex thermostat/timer combo that probably doesn't exist for hot water supplies.  That and the fact you'd probably end up scalding yourself once a week when you forget it's nearly twice as hot as usual.  With modern efficient insulation you may as well leave the temperature set at 60 deg all the time, no?.

SteveCritten

Have to agree IG I hardly spend anything on gas as it is so we would be talking penny's.

johntheexpat

My advice would be to lag your tank again.  And then do it again.  And perhaps one more time just for luck.  (Which is what I have done.  My tank is in a cellar, which while it never gets cold down there, never gets particularly warm either.  And it is a relatively new (2  yrs) tank.  But without the additional insulation, there was a noticeable background warmth in the cellar.  Insulation isn't expensive (I bought a couple of jackets from Wickes for not a lot) and then wrapped some rockwool around it.  Tied it all in and voila! as they say.
Now, when the economy 7 kicks in at midday, I can watch the meter and see no noticeable increase in consumption (ie the water has stayed hot enough for the immersion heater not to kick in)

Timers will always make a difference, but with an easily attainable level of insulation, you can make that difference insignificant.  And then you also have the luxury of constant hot water.  So, for perhaps twenty quid, perhaps a bit more but not much more, you can save the money you would have spent on a timer, save on electricity and have constant hot water.

stephenc

I have solar thermal, so try to have as much of my hot water heated by the sun. The tank thermostat is set to 50c, but once a week or so, I bump it up to 60c, just in case.

chipper

Well it sounds good but it's not correct.
It takes 1 kcal to raise 1kg (~1 litre) of water by 1 degree C.
In other words it takes exactly the same amount of energy to heat water from 20 - 30c as it does to heat it from 30 - 40c.