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hot water serviced by electric immersion heater - what does this mean?

(39 Posts)
beaglesaresweet Tue 18-Mar-14 23:59:33

PigletJohn, yet another 'ignorant' question to you, or anyone else who wants to reply.

What does the above means - if there is an older non-combi boiler for the heating in a house, but water is not by boiler, is this a normal thing (and is the immersion heater in some way dependant on the boiler or is it a totally separate system? ). From what I've read so far on here from PJ, they usually co-exist. If they are not linked at all, how reliable is immersion heater, and how expensive to replace if it goes wrong - again would it involve also replacing the boiler?
Also are these heaters very small? surveyor couldn't see it - I assume it's in the loft conversion but the closed-in voids aer tiny there - how could he not see it there if opened? If it's not reachable in the converted loft, isn't that a problem?

specialsubject Wed 19-Mar-14 10:15:43

an immersion heater is one that is 'immersed' in the hot water tank. It heats the water and is run by electricity. The immersion is usually there as a backup to the boiler - so if the boiler goes wrong, you have a way of getting hot water until the boiler is fixed. Immersions are expensive to run, the only feasible way to do it is to heat overnight on economy 7.

they are cheap to replace.

I hope you aren't saying that the surveyor couldn't find the hot water tank! Where is the tank?

ShadowOfTheDay Wed 19-Mar-14 10:21:52

immersion heaters are usually in the water tank in an airing cupboard - they are powered by electricity and if that is the only way to get hot water it will be expensive...

we used to have our heating done with a gas "back boiler" - it heated the radiators and provided hot water to a water tank which we could "top up" with an immersion heater in the same tank.

Combi boilers do away with the need for a tank and heat water directly on the way to the tap... (mainly... ours has a small pre heated internal tank so the water is hot when you turn on the tap)

Madmog Wed 19-Mar-14 10:29:22

We had one when we bought our house. It wasn't on a timer so had to remember to keep switching in on and off, so it wasn't heating all day. You may be able to get a timer these days.

beaglesaresweet Wed 19-Mar-14 12:01:22

thanks, specialsubject - how much more expensive proportionately to combi boiler (I only had them so far)? Probably he didn't mention the tank - I saw a cylinder next to the boiler when viewing, but if water tank us separate not sure where it is - the converted loft probably - the surveyor said 'seems to be serviced by el.immersion' - so I assume he couldn't access the tank in the void. To me it sounds like a problem when tank/immersion are hard or impossible to reach!

All the vendors are saying that it's cheaper/more efficient to use boiler+immersion to heat the house, so I'm confused.
Shadow - no back boiler there.

Madmog, what a faff though, having to switch on/off! Is that just by electric socket nearby, or do you have to reach the water tank?

specialsubject Wed 19-Mar-14 12:54:38

'seems to be' is not good enough from a survey. Get back to him and ask him to provide the information that you paid him to provide.

once upon a time when electricity was 2p a unit and I had economy 7, I used to heat water overnight with it rather than use a gas boiler. I don't think that makes sense any more. I now live in a house with oil-fired heating and hot water, still working on the maths but oil is pretty similar per unit to gas and we have a new efficient boiler; so the immersion is only there as standby. Left it on by mistake for a month, electricity bill was £41 instead of the usual £30!

most immersions are 3kW so they will cost 3 x your unit price per hour that you have them switched on.

adagio Wed 19-Mar-14 13:08:40

Immersion is literally a kettle, I am actually impressed specialsubject only had a bill for an extra £11 after leaving it on for a month - I seem to recall our was quite a few hundred quid more than we expected (this was a while ago, in a flat which had leccy only and we forgot to turn it off).

I would not personally choose an immersion other than a back up, as that bill took us two years to clear..

Oh and it looks like a round bit sticking out of the water cylinder with a cable coming from it.

Is the boiler definitely heating only? Forgive me if I am stating the obvious but there are broadly two gas systems - conventional and combi. Both are 'now' condensing (i.e. if installed in the last 15 years or so recycle heat by condensation rather than spitting it out of the vent). Conventional means radiators+storage of hot water, can be a back boiler behind a fire, or a boiler you might recognise as a boiler on a wall somewhere. You can still buy non combi boilers now - I did - I prefer a nice warm airing cupboard and a tank of warmish water at all times (even in a power cut as it stays warm!)

Combi as Shadow has said heats the water on demand with no storage.

When I say storage, I am meaning large copper cylinder jobby hopefully covered in a layer of insulation. There will also be other storage tanks bobbing about one for cold feed and probably one for the radiators assuming it's a gravity system.

Personally, I would go back to the surveyor. You said there was something next to the boiler, that could well be hot water storage tank. If you had the boiler make and model number you could google what sort it is.

PigletJohn Wed 19-Mar-14 13:12:59

you say you saw a hot water cylinder next to the boiler.

A cylinder is recognised by its shape, it is not a tank. Quite likely there is a cold-water tank in the loft, it will probably be rectangular.

If there is a cylinder next to a boiler, the cylinder will almost certainly be heated by the boiler. It is usual for a cylinder to have an electric immersion heater that you can use if/when the boiler is out of action (this is much more convenient than having a broken combi). However energy from electricity costs about three times as much as energy from gas.

The colour of a HW cylinder has a meaning. What colour is yours?

Bramshott Wed 19-Mar-14 13:13:32

Check the timer thing - my DB's new-build flat has an electric immersion and no timer hmm.

specialsubject Wed 19-Mar-14 13:15:34

I only got away with a bill that low because the water was also being heated by the boiler. What a muppet, have now labelled the switch!

crazykat Wed 19-Mar-14 13:41:46

We had an immersion heater and left it on constantly for hot water. It wasn't that expensive to run - about 30p per day - which was cheaper than using the boiler to heat up the tank.

If you only switch it on when you want hot water it costs a fortune as it has to heat all the water in the tank from cold. If you leave it on it has a thermostat which keeps the water at a set temperature and turns on and off so isn't using electric all the time, just to maintain temperature.

beaglesaresweet Thu 20-Mar-14 18:22:08

thank you for all replies.
It's def immersion, and cold water tank is in loft.
PJ, the cylinder is wrapped in dark grey or similar dark colur. What does that mean?
Still don't know re timer.
interesting, crazycat, will bear that in mind.

PigletJohn Thu 20-Mar-14 18:37:21

Dark grey is not one of the usual colours. Bare metal, red,yellow, green and blue, or sometimes a white metal casing are usual.

Could someone have wrapped an old blanket round it?

PigletJohn Thu 20-Mar-14 18:59:37

The hot water cylinder is quite easy to see, the immersion heater is quite small, and might Not be easily visible if the cylinder has been wrapped up.

I bet your cylinder is heated by the boiler. You can easily improve the cylinder insulation.

Have you moved in yet, or are you just looking?

PigletJohn Thu 20-Mar-14 19:22:15

all you will see of an immersion heater, if you expose the domed top of the cylinder, is the round cap which will probably be black plastic and about 4" in diameter, with a white or black electrical flex coming off it and going to a switch on the wall. Not all cylinders have an immersion heater, but it is very common.

If the cylinder has truly been swathed in some dusty, moth eaten old blanket, a dainty surveyor may have been unwilling to disturb it.

beaglesaresweet Fri 21-Mar-14 21:06:23

there's definitely immersion heater, vendors confirmed. I'm not there yet, so still deciding. It may have been dark-blue/green, I saw it from a distance and it was inside cupboard (not well-lit).
Now transpires there is cold water tank in loft.
It's just if immersion is not good for a string shower pressure, I may want to change to combi, not sure yet.

PigletJohn Fri 21-Mar-14 21:12:45

you can get a powered shower with its own pump, that runs off a tank and cylinder, but it's too early yet to decide until you've had a good look at what you've got.

TypicaLibra Sat 22-Mar-14 12:36:56

crazykat, that must have been a while ago surely? Last winter I had my immersion on all the time as I didn't know how expensive it would be, and my bill was £100 pm, now I barely use it at all - just use the back boiler to heat the water, and I've got the leccy bill down to about £35 pm.

PigletJohn Sat 22-Mar-14 13:19:40

if the hot water cylinder is very well insulated, it will not lose much heat. However energy from electricity costs about three times as much as energy from gas.

I suppose if you don't have baths, or if the immersion heater runs only to fill the cylinder overnight on economy 7, then 30p a day might possibly cover it, but it does sound very low.

If you have a back boiler, which is likely to be very old, you may have an old and badly insulated cylinder and pipes, which will waste a lot of heat.

TypicaLibra Sat 22-Mar-14 15:02:30

PJ, I suspect my back boiler was put in in about 1980 as I know that was when the house was last updated significantly. With mine, whilst you're probably right about it wasting heat, it is powered with free wood which is obviously a redeeming feature!

Also we do have lots of baths which was probably why the electricity usage last winter was so astronomical.

PigletJohn Sat 22-Mar-14 22:01:40

What colour is the cylinder?

beaglesaresweet Sat 22-Mar-14 22:34:35

Is that ti Typical, PJ?
I did say 'my' cylinder is wrapped in dark-green/possibly blue, didn't look closely. So what would that mean?

PigletJohn Sat 22-Mar-14 23:53:39

I was asking about Typica's colour.

Dark green/blue doesn't sound right. Have another look when you can. There are pale green, and pale blue, stiff foamed plastic, perhaps it is one of them.

Dark I don't know. Might be paint, might be an old rug, might be that there's a lot of dirt hiding the colour, might be that lighting is poor.

If it is plastic foam, you can mark it with your thumbnail if you press hard.

PigletJohn Sat 22-Mar-14 23:57:06

this is the colour of a typical modern blue one.

The older green ones were paler.

WTFlike Sun 23-Mar-14 00:06:47

I leave my immersion on all the time. My electricity costs about €15 a week, which is ok in Ireland.

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