Immersion heater - timer wiring

[pretzelz]

Hi all,

I've bought an electronic timer to replace the on/off switch for my immersion heater.

The timer switch has N L-IN L-OUT and to the existing switch are a different set of wires, with some going to the switch-fuse.

Could you kindly shed some light about which goes where to connect up this timer? (The timer must have a built in 13a fuse)

From wall to original switch:

Untitled

• pretzelz
• 14 Mar 2012
• 1

Back of new switch:

Untitled

• pretzelz
• 14 Mar 2012
• 1

Many thanks!

 

[riveralt]

Could be wrong but I will have a stab at it:

L In - is your supply Live conductor.
L out is your load live conductor (the immersion)
N - both neutrals in here.
Unless there is somewhere to connect the earths they should be sleeved and joined in a terminal block.
Make sure circuit is dead before you start work.

Is there a requirement in the instructions to have some means of isolating the circuit - 20Amp switch??

 

[17thman]

I agree with riveralt.

However if the the manufacturer says that it must be fused to 13Amps, then instead of a 20Amp switch, then a 13A switched fused spur instead at some point before the timer unit.

 

[EFLImpudence]

(The timer must have a built in 13a fuse)

Why?


Assuming a 'usual' immersion heater ( 3kW ) on a circuit protected by 15A/16A device, it should not have a 13A fuse.

You should fit the timer between a 20A DP switch and the immersion.

Not replace it.

 

[EFLImpudence]

Are you sure that is an immersion timer?

They are normally 16A.

 

[pretzelz]

my answers might be a bit delayed as racing around getting ready to leave for Russia in 7 days.

The timer says it is built 13A. When that blows, it will need a new timer. The immersion heater is on a 16A ring. I don't know any other details about the immersion heater, it is buried in a cupboard which I've never opened since buying the house. I was very much hoping I could just replace the manual on off switch (almost same size as a light switch) with an automated switch, ie, this timer I've bought.

Most timers on Ebay seemed to be 13A.

I read on another post that it is ok to have a 13A fuse, but that it will blow now and again and need replacing. (a previous post wrote once every 18 months) - I'm only planning on using the immersion for 1 hour a night in the AM when electricity is cheaper.

 

[EFLImpudence]

http://www.ebay.co.uk/itm/LOGIC-16-..._Cooling_Air&hash=item3a713ab392#ht_598wt_820

You need to keep the switch anyway.

 

[pretzelz]

by looking at the picture of the existing wiring, would it be the main three wires at the top which would go into the main three sockets on the timerswitch? And what would happen to the redundant 2 wires connecting the existing fuse. (since the new timerswitch will have a fuse inside)

If you could look at the existing colours and tell me which colours you think would go where, that would be appreciated. However, I will for myself take a closer look (a friend was checking it out for me earlier) and clarify which colour is current connected to what, based on the markings.

Many Thanks!

 

[riveralt]

by looking at the picture of the existing wire, would it be the main three wires at the top which would go into the main three sockets on the timerswitch? And what would happen to the redundant 2 wires connecting the existing fuse. (since the new timerswitch will have a fuse inside)

Many Thanks!

Do you understand what I mean by Supply and load?
There will be a supply cable that comes to the switch/fcu from the consumer unit - this will contain a red/black and earth cable.
There will be a load cable that goes from the switch to the immersion heater - this will contain a red/black and earth cable.
So the Red supply goes into L in.
The red load goes into the L out.
The supply and load black cables together go into the N.
The earths need to be sleeved and connected together.

If you do not understand this then you should not be messing about installing the timer.

 

[pretzelz]

yes, I understand this, thank you. I never dive into a job anyway without first trying to understand the advice, and cross check it etc. I tread carefully when learning. Certainly anything to do with wiring.

 

[riveralt]

yes, I understand this, thank you. I never dive into a job anyway without first trying to understand the advice, and cross check it etc. I tread carefully when learning. Certainly anything to do with wiring.

In that case what do the manufacturers instruction say regarding providing a means of isolation.
Does it say you have to utilise a 13Amp Fused Connection unit?
A 20Amp Dual Pole Switch or nothing?
What does it say about cable size and MCB rating?
And is the immersion on its own circuit?

 

[ban-all-sheds]

The timer must have a built in 13a fuse

There's no "must" about it.

the new timerswitch will have a fuse inside

No it won't.

 

[JohnW2]

the new timerswitch will have a fuse inside

No it won't.

Not a replaceable fuse, I agree, but they nearly all have wired-in 'fusible links' as part of their guts.

Kind Regards, John.

 

[EFLImpudence]

If it states '13A' on the timer then it is not suitable for an immersion heater.

If it does not state 'immersion heater timer" on the pack then it is not suitable for an immersion heater.

 

[ban-all-sheds]

If it states '13A' on the timer then it is not suitable for an immersion heater.

It does, and the maker says it is.

If it does not state 'immersion heater timer" on the pack then it is not suitable for an immersion heater.

See the 3rd page.