Boiler has two switches, and both seem to be linked to an immersion heater?

[Josh9247]

I don't really know much about boilers, but I have just discovered that most boilers have two heating elements: a slow to heat, but cheap heating element which should always be left on, and an immersion heater which is very expensive to power.

My girlfriend's boiler (https://www.telford-group.com/product/tempest-stainless) has two switches but, following them to the boiler, both seem to be connected to something with 'immersion heater' written on it. Does anyone know which switch we should be leaving on?

 

[JohnD]

I don't really know much about boilers, but I have just discovered that most boilers have two heating elements: a slow to heat, but cheap heating element which should always be left on, and an immersion heater which is very expensive to power.

your description is not clear, and is probably wrong.

When you say "boiler" I think you mean "hot water cylinder"

Does the house have a gas boiler?

Does the householder have electricity with a tariff that gives cheap rate electricity at certain times, like the old "Economy 7"

 

[Josh9247]

your description is not clear, and is probably wrong.

When you say "boiler" I think you mean "hot water cylinder"

Does the house have a gas boiler?

Does the householder have electricity with a tariff that gives cheap rate electricity at certain times, like the old "Economy 7"

No, it doesn't have a gas boiler. She does have economy 7 though.

 

[JohnD]

in that case, the hot water cylinder will probably (should) have one element at the bottom, controlled by a timewsitch so it only comes on during the off-peak hours. This one should be switched permanently on, but the time control will prevent it using electricity during peak hours

and it will probably (should) have one element near the top, controlled by a manual switch, which should be switched off at all times except if you have used up all the hot water stored in the cylinder and need to top it up at high cost.

 

[Madrab]

It looks like what's called a direct unvented cylinder. It has 2 immersion heating elements, the one in the bottom is a full cylinder heater and heats the water using cheaper economy 7 tariff leccy overnight. The one at the top is classed as a booster, and is there for during the day when all the cylinders hot water has been used and you really need some hot water during the day but uses pricey standard tariff leccy.

The top immersion heater should really be wired up to a override booster switch which can run from 15mins up to 4hrs, switch dependent, that ensures it can't be left on and breaks the bank.