Wiring wi-fi switch + manual dual immersion switch

[iahzg]

Hi all. 1st time poster. This has been partially covered on some rather old threads, so I decided to start a new one.

I posted in the screwfix forum but didn't get any answers. Hopefully I will get some here...

The current set up is dual immersion with manual Horstmann Quartz 7 (electricity only in flat). I want to replace the controller with a smart switch and a manual bath/sink on/off switch so that I can have a "smart" immersion.

I would like another pair of eyes to run through my plan and diagram if you don't mind and also opinions on a couple of things.

1. I plan to place the smart switch above the Horstmann and the manual dual switch below, the latter between mains and heater.
2. The Horstmann is protruding almost 6cm from the wall inside the hot press so I was thinking a ~45mm surface box for the slim dual immersion switch.
3. The plan for the smart switch is a 47mm dry lining flush box as it is already chunky enough.
4. With 2. and 3. both switches are still inside the hot press door frame.
5. I will be using 3-core 2.5mm2 cable to connect both switches: Is there a min/max distance between them or length of cable recommended?
6. I will be using the existing element cables. I presume this is OK.
7. What are L1 and L2 at the back of the manual sink/bath switch, i.e. which one is which? It's a BG Nexus 800 Series. I have assumed L1=SINK in my diagram.
8. If I understood correctly, I need to connect the L OUT with the COM at the back of the manual switch. Can I just cut a length of the brown wire from the 3-core 2.5mm2 cable for this and does it have to be a min/max length?
9. The 2 element neutrals go into the same N OUT terminal of the manual switch.
10. I will have 2 earths into the same terminal on the smart switch and 3 into the same terminal on the manual switch [SEE EDIT].

Since I made the diagram, I have discovered that there is an earth cable running separately from the 2 white ones connected to the elements. Am I right in assuming both elements' earth wires run together in the yellow and green sleeve and that the white ones are 2-core?

I would appreciate your replies.

 

[EFLImpudence]

Firstly:

I cannot find a BG Nexus 800 series sink/bath switch. Have you a link?

I presume the shaded area on your smart switch is a fuse.
13A fuses sometimes don't like immersion heaters so you would be better without one.

 

[EFLImpudence]

The current set up is dual immersion with manual Horstmann Quartz 7 (electricity only in flat). I want to replace the controller with a smart switch and a manual bath/sink on/off switch so that I can have a "smart" immersion.

Do you still have Economy & or similar?

1. I plan to place the smart switch above the Horstmann and the manual dual switch below, the latter between mains and heater.
2. The Horstmann is protruding almost 6cm from the wall inside the hot press so I was thinking a ~45mm surface box for the slim dual immersion switch.
3. The plan for the smart switch is a 47mm dry lining flush box as it is already chunky enough.
4. With 2. and 3. both switches are still inside the hot press door frame.
5. I will be using 3-core 2.5mm2 cable to connect both switches: Is there a min/max distance between them or length of cable recommended?
6. I will be using the existing element cables. I presume this is OK.
7. What are L1 and L2 at the back of the manual sink/bath switch, i.e. which one is which? It's a BG Nexus 800 Series. I have assumed L1=SINK in my diagram.
8. If I understood correctly, I need to connect the L OUT with the COM at the back of the manual switch. Can I just cut a length of the brown wire from the 3-core 2.5mm2 cable for this and does it have to be a min/max length?
9. The 2 element neutrals go into the same N OUT terminal of the manual switch.
10. I will have 2 earths into the same terminal on the smart switch and 3 into the same terminal on the manual switch [SEE EDIT].

1. Ok I think. but the Horstmann will be gone won't it?
2, 3 & 4. Irrelevant - what ever fits.
5. Ok. No, proximity and length irrelevant.
6. Yes, if they are ok.
7. As above. Link to switch? Do you not have the instructions?
8. Yes, that will do. Length irrelevant.
9. Yes.
10. Ok.

Since I made the diagram, I have discovered that there is an earth cable running separately from the 2 white ones connected to the elements. Am I right in assuming both elements' earth wires run together in the yellow and green sleeve and that the white ones are 2-core?

I do not really understand what you mean. Perhaps a picture? Just copy and paste.

Surely the element cables are flexible cables (not T&E) and the CPCs(earth wires) have their own green&yellow insulation.



The diagram is alright for what it is but I don't know that it is the best setup if the smart switch can only turn everything on and off.
What if you leave the other switch on 'sink' by mistake?

 

[ericmark]

I see no reason why that would not work. Only question is will it do what you want?

Smart switch turns all off/on. And right hand switch does same, would expect manual isolator before smart switch not after,

Left hand switch selects which element used.

 

[RandomGrinch]

I want to replace the controller with a smart switch

Have you decided on a smart switch yet?

Personally, as this is a switch controlling a high power element, for what may be an extended length if time; I would go for a switch from a reputable brand, rather than a cheap switch from Amazon.

Although expensive, something like this may be suitable?

WiFi Controlled 13A Fused Switched Spur - Tuya Compatible | Timeguard (SMFSTWIFITU)

 

[Harry Bloomfield]

I would like another pair of eyes to run through my plan and diagram if you don't mind and also opinions on a couple of things.

The only problem I can see, is the limited extra control that having the Smart Switch would provide. you with. Basically, you would have to have the manual switches correctly set, to enable use of the Smart Switch. I would want the SM able to override, or at least bypass the manual switch settings.

 

[iahzg]

Wow, thank you all for your replies! Just in case, I should mention I am in Ireland (Republic).

I cannot find a BG Nexus 800 series sink/bath switch. Have you a link?

Me neither!

7. As above. Link to switch? Do you not have the instructions?

I got it here and it didn't come with instructions. Maybe I should contact BG.

I presume the shaded area on your smart switch is a fuse.
13A fuses sometimes don't like immersion heaters so you would be better without one.

Although expensive, something like this may be suitable?

WiFi Controlled 13A Fused Switched Spur - Tuya Compatible | Timeguard (SMFSTWIFITU)

That's exactly what I got!

Do you still have Economy & or similar?

In Ireland you can have a day meter and a separate night meter like I do. Electricity at night is half the price (winter 11pm-8am/summer 12am-9am). But I don't think my controller is wired to turn on/off at set times like the storage heaters. It's all done via the controller.

1. Ok I think. but the Horstmann will be gone won't it?

It will be disconnected but I will leave it in place to cover the hole(s) and if whoever comes next wants it.

I do not really understand what you mean. Perhaps a picture? Just copy and paste.

Surely the element cables are flexible cables (not T&E) and the CPCs(earth wires) have their own green&yellow insulation.

I'm thinking those earth cables have nothing to do with the elements. Will they be connected to the controller though?

The diagram is alright for what it is but I don't know that it is the best setup if the smart switch can only turn everything on and off.
What if you leave the other switch on 'sink' by mistake?

The only problem I can see, is the limited extra control that having the Smart Switch would provide. you with. Basically, you would have to have the manual switches correctly set, to enable use of the Smart Switch. I would want the SM able to override, or at least bypass the manual switch settings.

The vast majority of times I only need a 15-20 min boost (top element/sink?) for a shower. I only heat the whole tank (bottom element/bath?) occasionally to prevent bacterial growth and when I have guests, which is not very often.

At the moment I have to manually turn on the Horstmann and set the 2h booster to whatever length of time I want, then switch it off manually or heat the whole tank unnecessarily at the next set time, which has happened too many times.

So my idea with the set up is to leave the dual manual switch "on" and "sink" all the time, except when I want "bath" and programme the Timeguard wi-fi switch to come on and off from my phone before I go to sleep or whenever and from wherever I want.

Either there's something I'm missing or the sink/bath has to be set correctly all the time and it doesn't really matter where the smart switch is?