Immersion - How best to use it

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BazFitz

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Hi Folks

My immersion comes on for 3 hours during the night. That just about gives us enough hot water for the day. Lately we've started putting it on for a bit in the evening as well. Some people have advised me to just stick the timer on all the time on the basis that it's actually cheaper to maintain a tank at a certain temperature rather than heating a cold tank up every day.

Does anyone know what the best approach is (i.e. the most economical)?

Thanks.
 
BazFitz said:
Some people have advised me to just stick the timer on all the time on the basis that it's actually cheaper to maintain a tank at a certain temperature rather than heating a cold tank up every day.
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That sounds like nonsense to me. I would be disinclined to leave it (anything bar the fridge & freezer) on at night. Do you even have a night-saver electricity meter? If not then you're not saving anything. I just use it as needed, it heats up quickly.
 
It's cheaper to heat it up as needed, rather than maintain a constant heat. When you use some of the water, the new cold water has to be heated up anyway.

Think about a kettle, would it be cheaper the keep this boiling for when you want a cup of tea, or just heat it up as needed?

In light of recent (largely unreported) events in Japan, I've really being keeping an eye on energy usage. Energy is probably too cheap.
 
michaelm said:
That sounds like nonsense to me. I would be disinclined to leave it (anything bar the fridge & freezer) on at night. Do you even have a night-saver electricity meter? If not then you're not saving anything. I just use it as needed, it heats up quickly.
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Yes, we have a night saver meter. It seems to take quite a while to heat up though and I'd prefer to have hot water on demand rather than having to manage a limited amount.

Thanks for the advice, Folks.
 
Turn it off completely. It is the most expensive way to heat hot water. Use your oil or gas to heat hot water. You will have more hot water in 1/4 of the time.

Immersions have a 3kw element therefore it is the same as boiling water in the kettle. It costs the same.
 
Shane007 said:
Turn it off completely. It is the most expensive way to heat hot water. Use your oil or gas to heat hot water. You will have more hot water in 1/4 of the time.

Immersions have a 3kw element therefore it is the same as boiling water in the kettle. It costs the same.
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Not an option but thanks for your input.
 
Immersions are VERY efficient, when kept free of limescale and any other contaminants, they can be around 95% and upward efficient as practically all the energy inputted is converted to heat and directly transferred to the water.

Regardless of heating source it is vital that the cylinder is well insulated.
 
They maybe efficient as in the heat transfer rate etc, but they would still be the dearest way to heat water when compared with gas/oil
 
On an analysis I done a couple of weeks back on gas
It costs me flat rate of 20 cent for 15 minutes of hot water using 1 radiator
It costs me 70 cent for 1 hour of heat supplied to all the radiators (7) at 21 degrees.

Does anyone know how much it costs to heat the water through the immersion? I dont use mine as it takes nearly an hour to heat up.
 
DGOBS said:
They maybe efficient as in the heat transfer rate etc, but they would still be the dearest way to heat water when compared with gas/oil
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I would agree with you there, I disconnected 2 electric showers in the house and connected them directly to the hot water tank which is heated by oil. I cut my electricity bill by over a third.

Mind you the price of oil has since rocketed but I still think it is cheaper to heat the water by oil rather than electricity.
 
There must be a problem with your immersion. When I heat the sink section it takes about 20 minutes. I have a good supply of hot water for several hours.
I use timer for the above. It is on for 30 minutes in the morning. I have it timed for 30minutes at 5pm for dinner preparation.
Even if you like continuous hot water, using a timer for 30 mins. every few hours would give you a constant supply.
Showers need considerably more. I dont find the immersion efficient to heat for showers. Electric showers are very efficient. Browtal
 
alexandra123 said:
Does anyone know how much it costs to heat the water through the immersion? I dont use mine as it takes nearly an hour to heat up.
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As stated above, 3Kw/h on bath, meaning it'll use 3Kw per hour. 2Kw/h on sink. How much are you paying per Kw/h for your electricity? Usually around 16c.

OP, 3 hours is way to long to heat water on the immersion heater. How big is your cylinder?

Typically it should take 30 to 40 mins to heat an average cylinder to 65 degrees C.
 
rockofages said:
As stated above, 3Kw/h on bath, meaning it'll use 3Kw per hour. 2Kw/h on sink. How much are you paying per Kw/h for your electricity? Usually around 16c.

OP, 3 hours is way to long to heat water on the immersion heater. How big is your cylinder?

Typically it should take 30 to 40 mins to heat an average cylinder to 65 degrees C.
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Thanks, ROA.

To be honest, I've no idea how big the cylinder is. It looks pretty standard to me (i.e. similar in size to others I've seen - about 4 feet high and 2 feet in diameter).
 
I heat my tank for 1.5 hours 7.30am - 9am to get the night save rate.
this gives hot water all day and enough for a good deep bath at night but if we use a bit more water during the day I do have to boost it on an evening for 15 mins for the bath.

As with other posted i change to a timer to stop us using the electric shower and it has cut out power usage by a good bit.
 
bluemac said:
I heat my tank for 1.5 hours 7.30am - 9am to get the night save rate.
.
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Are you sure this will get you the night rate? From [broken link removed]
The hours during which the day and night charges apply for non quarter-
hourly metered customers are controlled by time switches at the
customer’s premises. The day rate is applicable to kWh metered between
8.00 a.m. and 11.00 p.m. (GMT). As no alterations are made to time
switches at the beginning and end of summertime, the hours during the
summer time are one hour later (i.e. 9.00am to 12.00am). For quarter-
hourly metered customers day rates apply 8.00 am to 11.00pm summer
and winter.
Click to expand...
 
BazFitz said:
Thanks, ROA.

To be honest, I've no idea how big the cylinder is. It looks pretty standard to me (i.e. similar in size to others I've seen - about 4 feet high and 2 feet in diameter).
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In that case it should take no more than about 40 mins max. Bear in mind that the immersion heater will never be able to heat the tank all the way to the bottom.

Complainer said:
Are you sure this will get you the night rate?
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It will in the summer (ie now), but not in the winter as Nightsaver ends at 8am during the winter (ie when the clocks change).
 
rockofages said:
As stated above, 3Kw/h on bath, meaning it'll use 3Kw per hour. 2Kw/h on sink. How much are you paying per Kw/h for your electricity? Usually around 16c.

OP, 3 hours is way to long to heat water on the immersion heater. How big is your cylinder?

Typically it should take 30 to 40 mins to heat an average cylinder to 65 degrees C.
Click to expand...

Not quite true. A standard 30 gallon (136 litre) copper cylinder will require 8.72kW to heat from 10°C to 65°C (∆T 55°C) in one hour, therefore a 3kW immersion will take just under 3 hours to heat completely. In 30 to 40 mins, you will have only heated 46 litres of water from cold to 65°C.

To put this into prospective, a shower will have a flow rate of approx 8-10 litres per minute, whilst a power shower will have a flow rate of double this.

A 26kW oil or gas boiler will have all 136 litres heated to 65°C from cold in approx 20 mins.
 
BazFitz, a friend of mine was telling me for years that leaving the immersion on constantly was the way to go, I tried it 3 years ago and haven't turned it off since as it has made no major difference to my elec bill and the constant hot water is so handy. Try it for a month or two and see what you think. I think it's more efficient in the long run because you're only heating the amount of water you have used rather than possibly letting a whole cylinder of water go cold to then heat it up from scratch a few hours later. Give it a try,
 
That was a very interesting post Shane007.
Do you believe hippy1975's post makes sense?
 
Leaving the electric immersion on constantly. Hopefully the immersion thermostat won't fail, which could lead to catastophic circumstances with collapse of polythene cold water storage cistern. See case in the UK a couple of yrs ago,
 
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