Hi Mars,

To be able to install an immersion heater, your buffer first of all must be able to accommodate one. Have a close look at the buffer to see if there is a suitable socket into which an immersion heater could be installed. Check the socket size is the same as the immersion heater.

Since an immersion heater is in direct contact with the water, it would also be necessary to drain down your system prior to installation. You would then need to remove the plug from the socket and install the immersion heater in its place, after which the system can be refilled and leak tested.

Are you looking to provide an extra 3kW of water heating capacity on occasion Mars @editor? The Grant LLH can be used purely as a 11.5l volumiser. It has a 3kW immersion heater plus a relay, which can be controlled as an output from a ASHP control aux contact or independently via thermostat, pipestat, timer, whatever. Grant see to like to fit LLHs regardless of whether they are needed. 😉 It's wall mount vertically installed unit.

CITYPLUMBING.CO.UK "https://www.cityplumbing.co.uk/p/grant-system-combined-volumiserlow-loss-header-70kw-kit-hpidsysllhkit/p/626692"

Grant System Combined Volumiser/Low Loss Header 70kW Kit HPIDSYSLLHKIT | City Plumbing

Grant combined volumiser/low loss header 70kW kit which creates hydraulic separation. The unit cleverly
maintains the correct flow rate through the heat pump
and can provide a suitable volume of system water that
allows the heat pump to fully modulate

https://www.grantuk.com/media/5080/grant-combined-volumiser-low-loss-header-installer-uk-doc-0184-rev-1-0-november-2022.pdf

Thanks for the feedback above. I took a closer look at our hot water cylinder and buffer, and double checked it against the manual, and the available "hole" that at the bottom of the tank where I was hoping to fit the immersion is received for probes/sensors, so that's not going to work. Bummer. 

Posted by: @editor

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Thanks for the feedback above. I took a closer look at our hot water cylinder and buffer, and double checked it against the manual, and the available "hole" that at the bottom of the tank where I was hoping to fit the immersion is received for probes/sensors, so that's not going to work. Bummer. 

Hi Mars,

Am I correct in assuming that you wish to use some of your spare solar PV generation for heating purposes? There could be several ways that may be possible.

The most efficient way would be to install a smaller A2A heat pump (AC basically), which can be run in preference to your main heat pump on sunnier days. This is the route we went down to reduce our gas consumption.

A less efficient, though much cheaper method is to use one or more convection heaters, preferably supplied via your power diverter. Some of our heating today was by this method.

A less efficient and more expensive alternative would be incorporating a heat store, with immersion heater, into your present heating system, which could be heated up via solar PV, or heat pump on cheaper tariff overnight, or during daytime when your heat pump may be more efficient.

@editor are you trying to store spare PV for heating later? To hold a meaningful amount of energy in a water buffer, compared to the size of the heat demand over a day of your house (given you have an 18kw heat pump, I assume its quite a lot) , you will find you need a BIG buffer. If you do the maths with the heat capacity of water it's likely 1000+ litres. 

or are you trying to give yourself a "direct electric" input into your heating circuit - e.g. if your heat pump is faulty / struggling and you just need a way to get some heat in (and not worry about efficiency at that point) ?  thats do-able but in a different way - inline electrical water heaters exist that are intended to be used in a central heating loop (a.k.a. "electric flow boilers"). or as other's have said there are LLH / buffers that have immersions built in if a replacement is an option.

depending on the size and shape of your existing buffer it may even be possible to cut an immersion into it but thats definitely outside DIY skills IMO... probably better to get another buffer with an immersion fitted to start with.

Let us know your objective.