Immersion question

davecampbell

My immersion heater also has no thermostat.
If it gets left on by accident, the water comes out scalding - so you find out quick.
I'm on my own and have just started using it in the morning rather than the gas boiler.
Boiler burns 20Kw and needs half an hour to get a bath.
Immersion heater burns 3Kw and takes the same time.
Not bothered about having any leftover hot water, I can use the kettle if I need some for washing up.


Dave

macman

It does have a thermostat, it's just not working. That is a major safety hazard which you should get fixed immediately.

Pincher

http://www.tlc-direct.co.uk/Main_Index/Wiring_Accessories_Menu_Index/Timers_Index/Immersion_Heater_Timers_2/index.html


As for sorting it out properly, well......

I thought replacing an element was easy, and then the CORGI guy and I
twisted the cylinder so much trying to free the element, that slow leaks appeared,
subsequently flooded the flat below.... And I had to replace the whole cylinder for about £1,500
including labour.

The developer probably left plenty of other surprises 13 years ago.

Cardew

macman wrote: »

It does have a thermostat, it's just not working. That is a major safety hazard which you should get fixed immediately.

Amen!

If it had no thermostat the water would boil.

Flyboy152

grahamc2003 wrote: »

Sheesh - i'd say get someone round to check it out - sounds a right dangerous bodge somewhere. I wouldn't turn it on at all, just in case you forget to turn it off when it's hot.

Most immersion heaters don't have thermostats, but they all have thermal cut-outs.

Norman_Castle

My immersion heater also has no thermostat.
If it gets left on by accident, the water comes out scalding

If the thermostat is set too high the water will come out scalding.

Flyboy152

MarrowFarmer wrote: »

Yeah did sound a bit odd, lived there for 6 years and knew nothing of said heater . It's just a switch on the wall right at the back of the airing cupboard. It seems to be working mind and if it ties us over for a few days then I'm happy.

:eek: Did you never wonder what the switch was for? Do you have the gas boiler on throughout the whole year?

Flyboy152

MarrowFarmer wrote: »

The house is about 13 years old and I'm pretty sure the GCH is standard install for all the houses round here so I can only assume it is there for emergency use only (like now) but it does seem odd to have no thermostat, will get one stuck on just in case someone mashes the switch in future. In the mean time though anyone know how long it should take to heat the water?

No, it's for use during the summer months, when you don't need the gas boiler on.

Flyboy152

Cardew wrote: »

Supplementary question - how big is your tank!!!!

Assuming you have a 3kW immersion heater try 90 minutes.

Bear in mind when using a shower that you may have to ajust the temperature from where you have it when the tank was heated by gas CH

That's a very long time to heat a standard hot water cylinder.

Pincher

Remember the immersion element only heats the top half/third of the cylinder. So if you have the typical 180 litre cylinder, you are heating about 90 litres. Let's say you start with lukewarm water of 20 degrees.

1 Cal = 4.19J
1kWh = 3,600kJ

To raise 1 ml by 1 degree is 1 Cal = 4.19J
To raise 1 litre by 1 degree is 1kCal = 4.19kJ
To raise 100 litres by 1 degree is 100kCal = 419kJ = 0.116 kWh

A 3kW immersion element is generating 3kWh/60 = 0.05kWh per minute. 0.116 /0.05 = 2.32 minutes.

So it takes 2 minutes 19 seconds to raise 100 litres by 1 degree.


In 90 minutes, 90 / 2.32 = 38.8 . So Cardew would have heated the water to 69 (= 20 + 38.8 ) degrees, with 80 litres at the bottom not so hot.