All electric flat - immersion water timers

Jay_c_2

Hi Guys, I have been searching everywhere for a answer but find conflicting answers everywhere.
I have just moved into a 1 bed flat, which is electric only so I have to use a immersion timer for my hot water. I have a single rate meter so no economy 7. My question is how long do people heat their hot water for? At the moment I set mine to come on 5-8am so I can have a morning shower, and have some hot water at night.

Is this to long, do I need to shorter the time? Some people suggest leaving it on all the time, others just have it on for a few hours. Also there are two elements top and bottom is either cheaper? Sorry about the many questions I just don't want sky high bills :beer:

Nada666

Do you have control over each element separately? If so it is the 'top' element you use for a small amount of water and both for a whole tank. The boiler should adjust elements itself when both are on. But you may only need both elements if you want a bath - a shower or washing up over an evening should only need one.

If you are a single person then three hours may be a little long in the morning - an hour of the top element should be more than enough for a shower. Top up in the evening only when needed.

Your comfort and your use is what matters - if you are not having a bath or shower last thing at night you can always just use a kettle for the washing up if the boiler runs out.

Alternatively this may be too fussy and you can just switch it on for a couple of hours morning and early evening and relax.

(Google the model of your boiler to find a manual to check your own controls.)

pooch

Jay_c wrote: »

Hi Guys, I have been searching everywhere for a answer but find conflicting answers everywhere.
I have just moved into a 1 bed flat, which is electric only so I have to use a immersion timer for my hot water. I have a single rate meter so no economy 7. My question is how long do people heat their hot water for? At the moment I set mine to come on 5-8am so I can have a morning shower, and have some hot water at night.

Is this to long, do I need to shorter the time? Some people suggest leaving it on all the time, others just have it on for a few hours. Also there are two elements top and bottom is either cheaper? Sorry about the many questions I just don't want sky high bills :beer:

Leave it on all the time mate - otherwise you are having to waste a load of energy heating it all up

Oh and what heat might escape only goes to heat the flat, so you save on space heating too.

:cool:

Joyful

Don't leave it on all the time. As soon as a colleague of mine switched hers on only when needed her usage went down a lot.

GolfFoxtrot

Due to our set up our emersion heater is on for all 7 hours of the economy 7 hours. This uses around 10 kWH or about 60p per day, personally I'd rather have a little too much water heated at night rather than pay more to boost during the peak hours of E7.

Cardew

Modern well insulated Hot Water Tanks lose very little heat.

They are tested to a British Standard(BS) and your figure might be displayed on the tank. Typically that figure is a loss of between 1kWh to 2kWh over a period of 24 hours with the water held at 65C.

So in practice your losses will be below that shown above, and also as stated the 'lost' heat warms the fabric of the house.

Whilst it will obviously save money to have the hot water timed, it is not a huge amount.

Jay_c_2

Thanks all...
I tried setting it to heat up for only 3 hours and I have no hot water at all today ive had it on for another two hours and its still cold. Will be leaving ot on for the 5 hours overnight as before I think.

colinsmithathome

Dear J,

there's something wrong!
Two hours should easily be enough to heat up even a large tank,

regards,
Colin

diamond_dave

Have you checked that the thermostat is set right? Remove the boss covering the immersion and you will see the thermostat underneath. Perhaps it just needs to be set higher.

PlutoinCapricorn

I am all electric too. I have just had a new heater put in.

I can heat either a half or the whole tank.

It is very well insulated: I had it on for four hours one Sunday for a bath, and still had warm (not hot) water on the following Wednesday morning.

Richie-from-the-Boro

Assuming its an exposed PartL cylinder leave it on. A 200 litre cylinder @ 65°C it will lose a max of about 2kW per 24 hours which is about 12p, however it will lose less than that because the time distance between charges is 17 not 24 hours and its prolly in an airing cupboard with a closed door.

PartL Water Cylinder - off peak rate

- Cylinder type - direct - no timed on peak immersion heater, 2 x 27 inch :



A PartL should have two [ top & bottom ] heater bosses [ bit you screw the heater into stats into] The usual 30mm foam insulation that most non E7 standard cylinders are sprayed with has poor insulating qualities and [older] can give off poisonous gasses in the event of a fire and will naturally decompose in the greater scheme of things. Flexilag or equivalent used in PartL cylinders outperforms the polyurethane foam by up to 40%.

The element in the bottom will give you tank full of boiling water, the element in the top will give you only 10-gallon / 45 litres of angry bubbling boiling water if you are lucky. Whilst it is a truism that switched off is always cheaper than switched on, unless you are away on holiday I see no real meaningful savings in turning the timed E7 off peak water off, and in 35 years have never done so, even in the summer months. My PartL tanks were and are always given a really good extra jacket. I have in that same 35 years never used the 'on peak' top immersion heater ever. It just does not make economic sense you can have 365 days a year of boiling hot water by simply letting the correct spec tank & controller do its thing, after all heating the water overnight at the off peak rate would give me a tank full of hot for the same price as the 10-gallon / 45 litres tank of hot I would get for two hours on the standard tariff.

PartL Water Cylinder - on peak rate

- Cylinder type - direct - no timed off peak immersion heater, 2 x 27 inch :

Looking at the same graphic above, using the "I'll only heat the bit I need" basis will heat only the top immersed element and give about 10-gallon / 45 litres [or less] of a tank of hot water. That hot water will cost more on two levels. The 'on peak' rate we will agree is at (1) least twice the off peak .. .. but .. .. it will also cost more because (2) the way convection works it will be heating water that cools 'inside' the tank then needs to be re-heated.

Liquid, such as water, is heated from the bottom, the layer of water closer to the heat source expands and hence becomes less dense compared to the water layer above it. Expanded water is less dense than the surrounding water and therefore it rises. The cooler regions of the water in the upper part of the flask, being denser, sink. This movement of liquid due to a difference in density sets up a convection current.

So the heated [ hot ] water pushes up and forces the cooler water down over the thermostat which in turn is heated until the whole volume of the tank reaches your pre determined setting then the stat switches the leccy off. Its a bit atomic science and the random motion of atoms and all that, but sufficient to say that's why the top down element is rubbish at heating a full tank of water.

NOTE01 : In addition to twin and single, there exists a~n~other kind of dual called usually a ermmmm dual which is a two-in-one element on an E7 controller that uses the bottom of its two elements in the off-peak mode and the top in the on-peak mode.

NOTE02 : 10-gallon / 45 litres can be very much more depending on the size of the tank fitted, obviously a 1500mm x 450mm is going to be less than a 900mm x 450mm.

NOTE03 : Information only. The new 2010 PartL spec is [Part L1A] or for replacement only [Part L1B], there will be old spec cylinders still in the supply chain.