Immersion wiring help- fitting a timer

[Vinco]

Afternoon all, sorry my first post is a question!! i did try the search function but couldnt answer my question fully

I have an immersion heater and it had a bath/sink double switch unit attached to it.

I want to fit a timer onto this to automate the controlling.

So, i picked up a timer (below) from B&Q

When i took the old wiring from the immesion heater i had a 3 core wire connected as below with a seperate earth wire running seperate into the switch

My question is, should i replicate this when wiring in the timer or do it differently?

Here is a pic of the immersion/stat from above (the blue line is the path the metal strip follows around the back of the stat - couldnt get an unfuzzy pic from above!) how it was wired can be seen in the above pic

and another

This must be a dual element yes? but with one thermostat?
Also, the immersion heater is 13amps, since ive been checking out this wiring issue i have seen a few people suggestion a 16amp unit?

Many thanks in advance!
Vince[/b]

 

[ericmark]

I would say there is a clue in the name "Duel Stat" and this unit is two thermostats built into one.

First point to make this set-up in not safe unless you have a metal header tank. Thermostats do fail and if they do most plastic header tanks can't take the heat and become soft and buckle with lethal results.

However all old houses with back boilers need to have metal header tanks anyway and the new non re-settable thermostats are a real pain when each time the water over heats in back boiler you need to replace the thermostat.

So you should have a four core cable feeding this unit Earth, Neutral, Live 1 and Live 2. One will go deep into tank and heat whole tank and the other will just heat top bit. So this cable should either go to twin timers or to bath/Sink switch and then to timer.

Without twin timers you can't select how much water to heat.

In Northern Island (Ulster) they have a very clever system where the heater is in it's own tank and it heats water from top down but this idea never caught on in the mainland.

So you need to make up your mind. Two timers or one and manual switch. The latter means you must remember to switch it before having a bath or of course you could fit timer on bath supply only so at all times you have hot water for sink and only hot water for bath at selected times.

With modern insulation the cistern does not loss much heat and normally the element is only timed either to use off peak power or to stop it activating just before central heating is due to start.