Replacing Immersion Switch

[JohnB75]

Hi all

Newbie here so please be kind! I hope I'm in the right section for this.

Just bought a new (old) house and I'm starting to look to do some of the immediate jobs that need doing and I need some help with an immersion heater control. At the moment, it is a simple switch on the wall to turn the heater on or off. I want to change this to a timer and have bought a Timeguard NTT03.

I can understand the instructions for the new timer but the problem is I can't understand the wiring of the existing switch which just isn't making sense to me. Picture attached to show the existing wiring.

The new timer just needs a live and neutral in and a live and neutral out. But the existing wiring has a live and neutral in and the then a yellow wire that appears to link the live and neutral out with a black wire also leading from the live out.

I'm probably being really thick but can anyone help me out?

Thanks in advance for any help!
John

 

[EFLImpudence]

The yellow wire is just for the neon light - wired to outgoing L & N so that it lights when on.

It looks like only the Live is switched - Red to Black.

The Neutral in and out must be connected out of the picture. Can we have a wider shot?

 

[JohnB75]

Hi, thanks for replying so quickly. Another couple of pictures below. Nothing but yellow going into N2.

 

[ericmark]

Red line in.
Black line out.

Blue it seems negative and only there to work the neon.

I am worried about time switches on immersion heaters as if it switches hea off too soon could allow legionnaires to develop. Better just insulate the cylinder better.

 

[EFLImpudence]

There must be another connector/junction box somewhere.

Where does the flex from the immersion go/connect?

 

[JohnB75]

Been on a hunt and I found another two of the same switches on the wall in the cupboard where the water tanks are. Pictures attached. Sorry they're not great.

There are two tanks, two immersion heater switches in the cupboard and two immersion heater switches in the kitchen.

All the wiring looks normal i.e. there is a live and a neutral going into the in/out terminals.

So does this mean the switches in the kitchen that I want to replace are just there to control the second switches up in the water tank cupboard?

 

[bernardgreen]

While upgrading the system it would be sensible to check that the immersion heater has a safety overheat cut out as well as the thermostat that switches off the heater when the required temperature has been reached. The safety overheat cutout prevents the wate boileing if the thermostat fails to turn of the heater

If not then seriously consider the immersion heater with one that does have the safety over heat cut out ( new immersion heater must have one fitted )

 

[EFLImpudence]

Can't say from here.
You will have to determine which switch does what and in what order.

If you want to fit the timer in place of the first picture, then

Red to L
Blue to N
Black to SL
Nothing to N out

It looks like the wires could be reconfigured at the other end of the cable so that this switch could be completely removed.

However, it would be better if a switch was able to turn off the timer.

So it might be better to fit the timer in the cupboard after one of the switches there.

 

[JohnW2]

....I am worried about time switches on immersion heaters as if it switches hea off too soon could allow legionnaires to develop.

I think you're probably being over-cautious/'OTT'.

'Immersion time switches" have been in widespread use 'for ever'. A substantial number of people (like me) use E7 (or similar) to heat water, and that's generally only 'on' for 7 hours per day. I'm no authority, but I would imagine that if the water in the cylinder is raised to a temperature high enough to kill the bacteria for at least a few minutes every 24 hours, that ought to prevent any problematic proliferation of Legionella.

Kind Regards, John

 

[JohnB75]

Hi EFL

Thanks for all your help (and everyone else too!).

I've played with the switches and it appears to work like this:

1. If the switches in the cupboard with the tanks are switched on, but the switch in the kitchen is off, the immersion heater is off. If the switch in the kitchen is on, the immersion heater is on.

2. If the switches in the cupboard with the tanks are off, it doesn't appear to matter what the switches in the kitchen are doing i.e. on or off, the immersion heaters remain off.

EFL, using your wiring above and having nothing to N out, does this create any more of a risk than it presently does with the switch in place which also has nothing in N out? Is this not required because of what appear to be secondary but master switches in the cupboard with the tanks?

Thanks again for helping
John

 

[EFLImpudence]

1. If the switches in the cupboard with the tanks are switched on, but the switch in the kitchen is off, the immersion heater is off. If the switch in the kitchen is on, the immersion heater is on.
2. If the switches in the cupboard with the tanks are off, it doesn't appear to matter what the switches in the kitchen are doing i.e. on or off, the immersion heaters remain off.

Ok.

EFL, using your wiring above and having nothing to N out, does this create any more of a risk than it presently does with the switch in place which also has nothing in N out? Is this not required because of what appear to be secondary but master switches in the cupboard with the tanks?

The two Neutral terminals on the timer will just be a connector and will not be switched.
The Neutral is only required for the timer to work.

The present Neutral is obviously ony a link from the main wiring at the other end of the cable.

The red and black similarly must split the Live at the same place - much like a light switch cable if you know about that.

 

[JohnB75]

I think I follow (sorry). So if I wire as you say, which appears to mirror the existing switch wiring, the timer should work and will simply be a replacement for the existing switch with no major issues (hopefully!)?

 

[EFLImpudence]

Yes.

I have just noticed -

 

[JohnB75]

Brilliant. Thank you so much. I shall try this tomorrow and see what happens!

Thanks again for helping to guide me on this. Much appreciated.

 

[EFLImpudence]