Options for Smart Timers/Switches for Immersion Heaters & Storage Heaters (potential IFTTT)?

FreeBear

mmmmikey said: Although AFAIK nobody is advocating doing anything against the law here I think it's fair to say (and hopefully most here would agree with) that if you DIY this you'll be working at the more dangerous end of what you're allowed to do and need to have this firmly in mind and be honest with yourself about your own competence in this area.

240V is considered "low voltage" in many circles. Some of the stuff I occasionally work on have 20kV or more floating around.. Fortunately, low current, but still enough to give you a nasty kick. That said, there are real dangers working with high currents & mains voltages, so the warnings are well placed.

Bendo

Scrounger said:

I'm really pleased with my improved immersion heater setup with additional Tapo control.   I'm on Octopus Agile for electricity and it means that I can heat the water on the cheapest energy slots anytime, even in the middle of the night.   Plus I can run hot water cylinder 'legionella cycles' on any Agile -ve price slots even when I'm away from home and the water then usually cold.

I'm a  big fan of Tapo stuff, but I have got a few tapo plugs where the relay sometimes sticks. Usually refusing to turn on to be fair, but I think I've had one refuse to turn off. That could result in expensive usage if that happened to you.

Scrounger

Bendo said:

Scrounger said:

I'm really pleased with my improved immersion heater setup with additional Tapo control.   I'm on Octopus Agile for electricity and it means that I can heat the water on the cheapest energy slots anytime, even in the middle of the night.   Plus I can run hot water cylinder 'legionella cycles' on any Agile -ve price slots even when I'm away from home and the water then usually cold.

I'm a  big fan of Tapo stuff, but I have got a few tapo plugs where the relay sometimes sticks. Usually refusing to turn on to be fair, but I think I've had one refuse to turn off.

This is usually caused by overloading, that's why I use the contactor to do the 'heavy lifting'.

Bendo said:
... but I think I've had one refuse to turn off.  That could result in expensive usage if that happened to you.

True, however the the immersion thermostat will limit the 'damage', it's not as though the tank will boil dry!

If it bothered me I could always incorporate another remotely controlled contactor to short the immersion supply and trip the 16A breaker - I do monitor my electric usage when away on my phone (sad, I know!).

It hasn't happened yet and easily a risk I'm willing to take (never away for long anyway).


Scrounger

ch_152

Thanks all, and very wise words @mmmmikey .

It seems, however, like there's little other options for anything over 3kW? Are these kind of things (a contactor switched by a relay) something your average electrician is going to understand and be able to do? Seems quite niche...


With regard to the DIN rail relay switch as linked earlier by @FreeBear. Would this essentially just replace the MCB in my consumer unit (currently 16A)?

https://shellystore.co.uk/product/shelly-pro-2/.  - linked again for reference

mmmmikey

ch_152 said:

Thanks all, and very wise words @mmmmikey .

It seems, however, like there's little other options for anything over 3kW? Are these kind of things (a contactor switched by a relay) something your average electrician is going to understand and be able to do? Seems quite niche...


With regard to the DIN rail relay switch as linked earlier by @FreeBear. Would this essentially just replace the MCB in my consumer unit (currently 16A)?

https://shellystore.co.uk/product/shelly-pro-2/.  - linked again for reference

Hi, it really depends on the electrician, no problem round here. Most of the local electricians do a mixture of domestic and commercial wiring, e.g. in shops, farms, GP surgereis, small industrial units and so on. This kind of arrangement is common place in those kind of environments - think of things like fryers in chip shops, milking machines in farms, electrical lifts in garages and so on. That said, if you really are confident in what you're doing I wouldn't stress about it unduly, just do it with your eyes open and be aware of your own limitations and the risks. The point of my post wasn't to put you off, really just to flag up the risks as it's very easy to focus on the technical solution and not give enough thought to the safety aspects.

FWIW I think a contactor in a suitable enclosure powered by a Tapo plug is an excellent way to go. Fairly easy to wire up - the thing I'd watch out for is to make sure there's some kind of strain relief on the cables going into the enclosure with the contactor in. You can get all the bits you need from Screwfix or Toolstation. Also make sure you use heat resistant cable for the final leg of the connection to the storage or immersion heater, again easily available from Screwfix etc.

FreeBear

ch_152 said: With regard to the DIN rail relay switch as linked earlier by @FreeBear. Would this essentially just replace the MCB in my consumer unit (currently 16A)?

https://shellystore.co.uk/product/shelly-pro-2/.  - linked again for reference

No. It would not replace an MCB in the consumer unit as it doesn't have any overcurrent trips. You could wire it in alongside an MCB, but you are unlikely to have the space (in the CU) and you'd have a pedant NICEIC electrician having a hissy fit as the Pro-2 has not been tested & certified by the CU manufacturer.

Much better to put it in a standalone box - You can get some with an integral DIN rail, or simply cut a length of DIN rail to suit.

A competent electrician that works on industrial control systems should be well versed in wiring up a contactor or DIN rail mounted relay. They are pretty standard fare for electric motor control (or any other high current device).

mmmmikey

.....something like this....

https://www.screwfix.com/p/wylex-nh-ese2-ip40-2-module-unpopulated-din-enclosure/32311

mmmmikey

....and here's a suitable double pole contactor....

https://www.screwfix.com/p/british-general-fortress-20a-dp-contactor-no/6654p

(only one module wide but the enclosure will have a blanking plate for the unused slot)

FreeBear

mmmmikey said:

.....something like this....

https://www.screwfix.com/p/wylex-nh-ese2-ip40-2-module-unpopulated-din-enclosure/32311

4 module box - https://www.superlecdirect.com/switchgear-and-control/breaker-boxes/616-europa-components-ip20-4-module-insulated-enclosure/

Box with clear lid - https://www.superlecdirect.com/8875-wiska-adaptable-weatherproof-box-320x250x135-ip65-grey-clear-lid-6887lh/

Your local electrical wholesaler should have a selection on the shelf.