Immersion Heater Timer

[kali291]

Hi. Can anyone help me please?
I have bought a timer to control my immersion heater, and assume that it should be connected between the heater and the fcu. The timer has L N in and out, and a common earth which suggests installation should be easy, but the exiting outlet from the fcu to the heater has four core wire, not three. Do I need a different type of timer, or is there a way that I can use this one?
Any advice would be appreciated.

 

[davy_owen_88]

How is it wired into the FCU? Are there 2 cores going into the live terminal, or is one core unused? Just copy the existing wiring.

I put my immersion timer before the FCU, this way the neon from the FCU shows when the immersion is on.

 

[kali291]

How is it wired into the FCU? Are there 2 cores going into the live terminal, or is one core unused? Just copy the existing wiring.

I put my immersion timer before the FCU, this way the neon from the FCU shows when the immersion is on.

The fcu has 'sink' and 'bath' options, and 2 separate live out terminals.

 

[Taylortwocities]

So you must have two immersions then, one long one and one short. Or one in the top and one in the bottom of the tank.

Which heater do u want to time, or is it both?

 

[kali291]

So you must have two immersions then, one long one and one short. Or one in the top and one in the bottom of the tank.

Which heater do u want to time, or is it both?

I only have one heater,but it is marked 'dual element' During the summer I would need to have both working. I have an oil fired Stanley range which has no option on it to heat the water in the tank without heating the radiators.

 

[davy_owen_88]

You could:

1) wire both elements into the timer so that they both come on at the same time (whether this is viable depends on the rating for each element and the maximum current rating for the timer).

2) wire just one of the elements into the timer and leave the other element disconnected (you'll have to decide on which one to use... (the bath element is the longer of the two and that heats the whole tank. The sink element is shorter and is mainly there to reheat the top of the tank for hand/dish washing purposes).

3) Buy another timer and wire both elements to separate timers.

 

[ColJack]

or do as sugested above and put the timer before the FCU....

problem solved..

 

[Softus]

If you truly have a dual-element immersion heater, then there should be two flex cables going to the element. The elements are different lengths - the long one is wired to the 'bath' output and the short one to the 'sink' output.

BTW, whether it's summer or winter you wouldn't normally use the boost (aka 'sink') element at all - this is for those times when the main source of heat has been turned off (e.g. while on holiday), and you want to heat a small amount of water quickly.

If you have to add some flex then make sure you use butyl-sheathed flex.

 

[davy_owen_88]

or do as sugested above and put the timer before the FCU....

problem solved..

Unless the problem he wanted to solve was to set each element to come on at separate times - main element for an hour in the morning and then the small element throughout the day to top it up.

 

[kali291]

or do as sugested above and put the timer before the FCU....

problem solved..

Not quite. This is Ireland we are talking about. Although only one mains feed into the fcu, it has been used as a junction box to run another circuit off