Fitting Immersion Timer.

Sleepy

We have an old fashioned on/off, sink/bath immersion switch in the hot press that I'd like to add a timer to.

As I understand it, the normal practice is to fit a timer before the immersion switch but on opening the faceplate, I was able to see that the gas boiler in the same hot-press takes it's power from the same outlet via a fused switch. I can't make out all the other wiring as I don't want to open up the boiler, but it appears the pump and boiler controls then take their power from the boiler unit.

As such, if I place a timer before the immersion switch, that timer would also be affecting the gas boiler, which I obviously don't want.

I'm assuming the solution to this is to install a junction box (something like this?) where the existing immersion switch is (at the power source), then taking one cable from that to boiler via the fused switch and another to the immersion switch via the timer.

While this seems pretty straight-forward and makes sense in my head, I thought it best to run it by the more knowledgeable posters here, make sure I'm not missing anything or inadvertently creating a fire hazard / issues with current regulations and get pointers in terms of the type of junction box I should be using.

aido79

Sleepy wrote: »

We have an old fashioned on/off, sink/bath immersion switch in the hot press that I'd like to add a timer to.

As I understand it, the normal practice is to fit a timer before the immersion switch but on opening the faceplate, I was able to see that the gas boiler in the same hot-press takes it's power from the same outlet via a fused switch. I can't make out all the other wiring as I don't want to open up the boiler, but it appears the pump and boiler controls then take their power from the boiler unit.

As such, if I place a timer before the immersion switch, that timer would also be affecting the gas boiler, which I obviously don't want.

I'm assuming the solution to this is to install a junction box (something like this?) where the existing immersion switch is (at the power source), then taking one cable from that to boiler via the fused switch and another to the immersion switch via the timer.

While this seems pretty straight-forward and makes sense in my head, I thought it best to run it by the more knowledgeable posters here, make sure I'm not missing anything or inadvertently creating a fire hazard / issues with current regulations and get pointers in terms of the type of junction box I should be using.

Current regulations would most likely prohibit anyone who is not an REC from doing this job but your method of doing it would be correct.
It would be preferable in my opinion to have the immersion and gas boiler on separate supplies or at the very least having the gas boiler on a fused spur if this isn't possible.

Sleepy

Am I mixing up terminology or does the fused switch between the supply and the boiler not count as a fused spur?

aido79

Sleepy wrote: »

Am I mixing up terminology or does the fused switch between the supply and the boiler not count as a fused spur?

My apologies. I missed that part in your post.

Sleepy

So, I wired it up as above last weekend and had thought it was a success as the LED in the Immersion switch lights up when the timer is set to always on or is inside the time window set by the timer.

The gas boiler is working perfectly and I've double-checked all the wiring connections and they're all as tight as can be. I copied the wiring at the back of the bath/sink switch from what was there before:

L & N into the power in connections
N from the the immersion lead connected to the N out
L out connecting to COM with a link wire (didn't need to change this)
Bath and sink wires (black and brown) fitted to 1 and 2 out
Both Earth wires connected to the earth on the switch.

As far as I can tell, I've connected everything correctly, and given that the light comes on when it should, it would indicate to me that it's getting power so I'm now wondering if I'm dealing with a dodgy thermostat or heating element on the immersion itself. Did some googling which indicated there should be a reset switch on the thermostat but it doesn't appear to have one (it's a COTHERM Type:TSH 111 which Google has next to nothing on bar that I can see the company which made it have been bought out and rebranded years ago so I'm guessing it's pretty old!).

My gut instinct is to fit a replacement thermostat but don't want to go down the path of replacing various bits that I don't know for certain are broken. Is there some way of testing that the thermostat and element (a) are actually getting power and (b) are working?

Sleepy

Any tips on how to select the correct new element to fit?

Sleepy

Got it last night - the neutral connection to the immersion needed to be doubled over and tightened. All working now.