Hot water advice - Immersion Heater

CinderKona

HI all
My new house has a traditional boiler and immersion heater, and in the past I have been spoilt by having a combination boiler and constant hot water.
How long do I need to leave the immersion heater on for - is it an all day and night thing? They'll be only 2 of us and, after covid, we expect to be out all day - so maybe a couple of showers a day..
Also, I can see that the immersion heater has no jacket I imagine a quick dash to Screwfix is urgent

[Deleted User]

You leave it on not at all.

It's only there in the event your boiler breaks down. It's a very very expensive form of heating water. Think of it as a huge kettle.

Reed_Richards

Doesn't your traditional boiler provide you with hot water as well as central heating?  That is the tradition, with the immersion heater only there for emergency use.  But if not I think it will probably take about two hours to bring the tank back up to temperature.  Modern hot water cylinders are clad in insulating material and don't really need a jacket as well.  If yours is very old it might be worth considering getting a new one and plumbing it in so you boiler can provide that hot water, much cheaper than heating with electricity. 

CinderKona

Ah ok. I only switched on for some 20 minutes and I suppose it needed longer to hear the water via the boiler. I supposed it needed an immersion heater too.
Yes it is cladded already but it was mentioned in the homebuyers report that it needed a jacket.

Reed_Richards

If it was completely cold then it will take some time to heat the tank using either the boiler or the immersion heater.  The boiler should be faster and will certainly be cheaper.  But it probably won't give you central heating whilst you are heating the tank so wait until the house warms up unless you need hot water urgently.  Most tanks will be big enough that you won't use all the hot water in a day but if you use a lot the water may go from hot to tepid.

I'm not sure you should trust the Homebuyers Report; if you post a picture of the tank then people on the forum can comment on whether or not it needs a jacket.      

Ectophile

Look at the price per kWh you're paying for gas, then look at the price per kWh for electricity.  You really don't want to be using electricity to heat the tank unless your gas boiler has broken down.

Set the timer on the boiler to heat the water once or twice a day and you should be good.  If the boiler's any good, it will heat the tank in an hour or less.

matelodave

AS R_R says, the average tank should take around two to two and half hours from stone cold to heat to 60 degrees, a gas boiler will use around 6-7kwh of gas at 3p = 21p whereas the immersion will use about 6kwh at 15p = 90p.Therefore you dont want to use the immersion heater at all if you can help it.

Try setting the timer to heat the tank for around 1.5-2hours before you get up so you've got plenty of hot water for your morning ablutions and then see how long it lasts, if neccessary put in on for another hour or so later on if you run out.

If you dont waste hot water, dont let it run down the sink, rinse stuff in cold water rather than hot, take shorter showers or shallower baths you might be able to get away with only heating the tank once a day.

btr30

if if there is obvious heat loss from the cylinder, i.e exposed copper, then a jacket will be needed. If the pre-formed insulation is in good condition it should be ok.
The other thing to look for is the setting on the cylinder thermostat. If it is set too low it will shut down valve before cylinder reaches required temperature. I would recommend setting hot water time for approx an hour before you get up, and maybe another hour in the evening to maintain plenty of hot water when you are going to use it.
The immersion should only really be used in the event of a failed boiler

CinderKona

HI all,
Did a hot water test today, and all was well after a few hours, so no need to employ the immersion heater. It has a hard foam lagging which seems intact, so no jacket required there as well.
thanks for all the advice - very useful.

McKneff

My boiler which is about 7 years old gets me a bath ful, of hot water in 25 minutes, bliss

greyteam1959

Just shows you what rubbish the Homebuyers Report was then.