Immersion heater (smart?) timer

gabbro86

Hi all,

We'd like to stop using our gas boiler to heat our water, and use a pre-existing immersion heater during times when electricity is cheap (we're on Intelligent Octopus Go).

Setup is in the picture:

What's the best (and most cost-effective) product out there? Would it just be a case of swapping the current "dumb" on/off wall switch?

Rodders53

That would be correct… That 13A fused switch is wrong anyway… they (13A fused connections) overheat in use… (think Granny Charger and why they are limited to 10 Amps). If the immersion is fed from its own 16A MCB (or RCBO) then a 20A DP switch would be better from the heat viewpoint.

The ubiquitous immersion heater timer is the not especially smart Timeguard (or similar devices) but has the same potential 13A fuse overheating issue and is usually a simple swap.https://www.cef.co.uk/catalogue/products/4297839-supply-master-24-hour-fused-spur-timeswitch

Do you REALLY want to use and put wear onto the EMERGENCY BACKUP immersion heater in your cylinder? It may mean that it doesn't work when you really need it. Such immersion heaters aren't cheap to replace, either.

Gas and IOG rates are not really that far different and the off peak EV charging pricing is only going up.

Albermarle

Are you sure that even low cost electricity is cheaper than gas ?

FrugaiMacDugal

Doesn't look like there is a timer in the set up.

So, you would need a timer, then set to come on during your cheap rate, you can then adjust timer according to usage.

Have a look here.

tacpot12

https://youtu.be/521Vuoa2p2g?si=3VXkR1-rOB6xBKN-

QrizB

https://forums.moneysavingexpert.com/discussion/comment/81912154#Comment_81912154

IOG is 7p/kWh and 100% efficient, so roughly equivalent to gas at 5.8p/kWh and 80% efficiency.

Albermarle

https://forums.moneysavingexpert.com/discussion/comment/81912520#Comment_81912520

So for the OP, no savings for switching.

QrizB

https://forums.moneysavingexpert.com/discussion/comment/81912524#Comment_81912524

I don't know how much the OP is paying for gas, and it's not mentioned in this thread. Have they given this info elsewhere?

gabbro86

Apologies, I posted quickly between work meetings and didn't give all details…

And kinda missed the biggest one, which is that we also have a 9.5 kW solar array and a Tesla Powerwall 3 battery 😁

IOG off-peak tariff is 7.5p/kWh (which we use to charge the battery at night). I'm on Octopus Tracker for gas, which has meant below 5p/kWh per gas until the Iran War… more like 7p now and wondering whether it'd be better to change tariff.

https://forums.moneysavingexpert.com/discussion/comment/81912138#Comment_81912138

@Rodders53, why do you say that's an "emergency backup" immersion heater? Is it less reliable than others?

Newbie_John

https://forums.moneysavingexpert.com/discussion/comment/81912345#Comment_81912345

ive been using it for the past two years. Easy to install yourself, easy to manage in the app - and I've used mine with Agile 😅

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/81912543#Comment_81912543

By 'emergency', I understand Rodders meant that it would only usually be used if your gas boiler broke down.

No, it isn't any less likely to fail than any other element.

If you get significantly cheaper leccy than gas, then by all means use the immersion. Yes, it'll fail after a few years of intensive use, and you'll likely need a G3 plumber to replace it, and the tank will need draining, but hey...

In addition, have you considered a solar immersion controller that will divert any excess PV to the immersion? Ie, any PV power that is not otherwise being used in the house, or charging up the battery, will automatically be sent to the immersion. All excess power will be used, so on a dull day it'll heat the tank more slowly, but it should mean no more wasted PV. By 'wasted', I mean sent to the grid for other folk :-)