Immersion Heater Timer Switch

[blueST]

Ican anyone recommend a timer or time limiter for our hot water immersion heater? We regularly leave it switched on by mistake. It never needs to run for more than a couple of hours, so something that will make it knock off automatically would help us stop wasting electricity.

Need something that doesn't require any alterations to the current 20a switch location as its on a tiled wall that I dont want to disturb. Ideally something thats a straight swap for the switch would be ideal.

There are a few products on Amazon that might do, but given the high power rating id prefer something from a reputable brand that wont burn my house down.

[dontlookdown]

Horstmann make good quality immersion heater timers in a range of sizes and specs.

Make sure you get a genuine one though. There are a few knocks off and 'clone' brands about that look and sound similar, but aren't.

[blueST]

Do you have a link to something suitable? I found this, but it says 3kw max which I dont think is sufficient.

Horstmann / Secure 30/60/120 Boost Timer - Heating Controls Online https://share.google/M2LujXzoWbMFO6ct8

[netherfield]

blueST said:

Do you have a link to something suitable? I found this, but it says 3kw max which I dont think is sufficient.

Horstmann / Secure 30/60/120 Boost Timer - Heating Controls Online https://share.google/M2LujXzoWbMFO6ct8

3 Kw standard for an immersion heater.

[Actual]

I recently installed a smart controller for my hot water immersion heater so that I can save using boiler heating oil and heat my hot water from midnight to 5am using my 5.49p per kWh EV tariff.

I used
Shelly Pro EM-50 Single-Phase Energy Meter (749AG)
Hager ESC225 25A Contactor
Hagar 6 Way Weathertight Enclosure IP55 c/w Din Rail

Controlled using the Shelly mobile phone app and Wi-Fi.

The Shelly has a dry contact relay which is used to turn the contactor on and off.

The Shelly also has a current measuring clamp which I fitted on the line wire to the immersion heater element so that I can see and measure actual power consumption.

The Shelly is not handling the high current load which is controlled directly by the contactor rated at 25 Amps.

Interestingly the water heats up and gets to temperature causing the immersion heater to turn off and then after a bit the hot water must rise to the top of the tank and the immersion heater turns on and this repeats for shorter and shorter cycles. No hot water is being drawn at this time.

I installed above the airing cupboard door.

There is an audible clunk when the contactor engages and disengages.

Electricity usage per day is around 4.2 kWh which is 23p per day or £84 per year (inc VAT) for hot water.

[OutInTheShed]

If you're on a single tariff, just let the immersion's thermostat switch itself off?

If your tank is well insulated, it won't lose much heat, so you won't save much by faffing with a timer.

If you are Economy 7 or some other time-variant tariff, go for it.

[Russet Grange]

I unstalled one of these a couple of years ago, seems like a decent quality product, and it has performed reliably:

https://www.tlc-direct.co.uk/Products/SMFST24.html...

[qgd]

How about something like this:


https://www.tlc-direct.co.uk/Products/SMSTBT4.html

[blueST]

Thanks for the help. I was concerned about replacing 20A switch with a device thats only 13A rated, but if thats ok then something like the above will be ok?

[dontlookdown]

blueST said:

Thanks for the help. I was concerned about replacing 20A switch with a device thats only 13A rated, but if thats ok then something like the above will be ok?

You should absolutely not do this, but I think you know that already.

[blueST]

I thought I did, but the posts above were starting to make me doubt myself. If I need to stay with a 20A rated switch, does anyone do one with a timer?

[Gone fishing]

Actual said:

I recently installed a smart controller for my hot water immersion heater so that I can save using boiler heating oil and heat my hot water from midnight to 5am using my 5.49p per kWh EV tariff.

I used
Shelly Pro EM-50 Single-Phase Energy Meter (749AG)
Hager ESC225 25A Contactor
Hagar 6 Way Weathertight Enclosure IP55 c/w Din Rail

Controlled using the Shelly mobile phone app and Wi-Fi.

The Shelly has a dry contact relay which is used to turn the contactor on and off.

The Shelly also has a current measuring clamp which I fitted on the line wire to the immersion heater element so that I can see and measure actual power consumption.

The Shelly is not handling the high current load which is controlled directly by the contactor rated at 25 Amps.

Interestingly the water heats up and gets to temperature causing the immersion heater to turn off and then after a bit the hot water must rise to the top of the tank and the immersion heater turns on and this repeats for shorter and shorter cycles. No hot water is being drawn at this time.

I installed above the airing cupboard door.

There is an audible clunk when the contactor engages and disengages.

Electricity usage per day is around 4.2 kWh which is 23p per day or £84 per year (inc VAT) for hot water.

There’s a Ogemray SW40 – 25A Shelly device now which pretty much combines everything above into 1 device, at least functionally. I like Shelly stuff and I’m considering it. It’s £25 and you can control from your phone, set timers, have a local switch, auto off after an interval, etc.

When we were having work done over the summer I used a 16a Shelly device to switch our immersion heater and it tripped its internal over temp protection occasionally, so you do need something like the ogemray or a contractor like you did, but it worked really wel

[Mr Pointy]

blueST said:

Thanks for the help. I was concerned about replacing 20A switch with a device thats only 13A rated, but if thats ok then something like the above will be ok?

What rating is the immersion heater & the breaker supplying the circuit? Immersion heaters are usually 3kW taking 13A & fed from a 15A breaker so a 13A rated switch like the Timeguard from TLS linked to above would seem adequate. If you want to go up to 20A rating then you are looking at contactors & that won't be a simple fit into your situation.

[The Mad Monk]

LAP Digital Immersion Timer from Screwfix.