Installation instructions
ElectroMAX - Alternative products

How does the Heatrae Sadia ElectroMAX work?

Alternatives to the Heatrae Sadia Electromax


Electromax combined hot water system

The Electromax unit by Heatrae Sadia is a neatly packaged solution to hot water and central heating were the only fuel source is electricity.

The internals of Electromax

Housed within the Electromax cabinet are essentially two systems. One system provides electrically heated hot water to circulate around a wet central heating system (radiators or underfloor heating). The second system provides mains pressure hot water courtesy of an electrically heated unvented cylinder. The Electromax also contains necessary ancillary vessels, controls and pumps that allow the Electromax to perform it's function.

Advantages of Electromax

The single biggest advantage Electromax can offer rests with it's neat design. More or less everything your property will need (limited by the performance specifications of the unit) to manage your hot water requirements housed within a unit that looks uncannily like a fridge. These clean aesthetics have obvious appeal especially if the unit is to live it's life in full view.

Other advantages include the unit's ability to exploit off-peak electrical tariffs, heating domestic hot water overnight when electricity is at it's cheapest.

No need to worry about a flue pipe either. With no fumes to duct away (as you would need with a gas boiler) the unit is less bother to install.

Considerations and issues with Electromax

On the face of things Electromax can appear to be a gift from heaven. Everything to do with hot water in a convenient cabinet. But you should consider certain responsibilities you will inherit as soon as you install one of these units.

Suitability of an Electromax

Electromax is suited primarily to apartments (and very small houses) because of it's heat output - a 9kW central heating output is unlikely to be sufficient to heat a moderately sized house. The all-in-one space saving design does it's best to minimise the usage of valuable space and will fit neatly almost anywhere.

Locating an Electromax

Remember, this baby houses an unvented hot water cylinder. Unvented cylinders require a vent pipe capable of carrying steam at pressure to the outside of the building in case they go wrong. And while we are on this subject there are one or two other things you might consider.

Liabilities and expenses for Landlords

More often than not an Electromax will be installed in an apartment or building with multiple occupation. Multiple occupation by it's nature multiplies the risk and therefore the liabilities an unvented device carries with it.

The risk to which we allude is officially recognised by way of Building Regulations (Section G3) whereby any vessel that contains more than 15 litres of hot water under pressure (unvented cylinders) must be installed, commissioned and certified by a person competent to do so by definition of the regulation (you must also notify your local Building Control that an unvented device is being installed to a property).

In English this means such a device may only be installed by a qualified person. The reason: An unvented cylinder could explode if the safe operational temperature and/or pressure is exceeded should the unit develop a catastrophic fault. For this reason a temperature/pressure relief valve is necessary on all unvented cylinders to prevent such a scenario. Furthermore, the operation and condition of the unit must be inspected annually to ensure such safety equipment is fully functional. This obviously means an ongoing cost of ownership and the liability associated with injury that could be caused should the unit explode. Please click on the following links to see what happens when an unvented cylinder exceeds the critical point of safety....





There are numerous documented cases of death and injury caused by unvented hot water cylinders. This is why the G3 Building Regulations exist. And there in a nutshell is your problem. If you are a landlord you need to consider whether you want to take onboard responsibility for such a liability - albeit rare because of regulation.

Please note, the Electromax when installed and maintained correctly will provide you with exactly the service it claims. It is not our purpose to call into question the ability of this product to perform. We simply wish to draw your attention to the realities of the equipment and demonstrate alternatives from which you may wish to choose.

Options and alternatives to Electromax

The simplest way to examine your options is to firstly split the functions of the Electromax into component parts.

Essentially the Electromax has two main functions (excluding any control equipment) - Hot water for central heating and domestic hot water for bathing.

It is of course possible to provide both functions by other means. For example, electric central heating can be provided using an Amptec electric boiler - indeed this is more or less how the Electromax does it.

But more interesting are the options available to provide domestic hot water. The Electromax as we have discussed contains an unvented hot water cylinder which provides mains pressure hot water. As it is our purpose to look for similar alternatives we shall pursue other devices with a similar function rather than complicate matters by introducing all other cylinder types. So, we turn to a product known as a Thermal Store.

What is a Thermal Store?

A Thermal Store is a device that provides mains pressure hot water but the process by which it does so is very different to an unvented cylinder. Indeed, the beauty of a Thermal Store is the fact that it is 'open vented' - this is to say it is vented to atmosphere, or described another way it is at atmospheric pressure. This key factor means that a Thermal Store is inherently safe because there can never be an unsafe pressure build up within the unit leading to an explosion (the problem you could have with an unvented device). By the nature of the way a Thermal Store works there is never 15 litres of hot water under pressure at any time so the G3 Building Regulations do not apply. Because there are no pressure issues (and never any pressure that might need releasing) a Thermal Store does not need a safety valve venting to the outside of the building (like an unvented cylinder does). In short, a Thermal Store gives you the advantages of mains pressure hot water without any of the dangers.

How does a Thermal Store work?

An untrained person would be excused for mistaking a Thermal Store for a normal copper cylinder. After all, they look very similar but the way they work differs immensely (almost in reverse).

A Thermal Store is what it claims to be - a store for thermal energy. In this case a cylinder full of water is used to hold said energy. The claim that an open vented store can produce mains pressure water looks like a contradiction initially until you examine the very simple process. By immersing a large and very efficient heat exchanger within the hot water in the thermal store a process is created whereby mains pressure cold water passing through the heat exchanger draws energy from the store, emerging at the outlet as mains pressure hot water. It is that simple. The process is entirely safe.

There are numerous products that exploit the principle of thermal storage and over the years it has become a preferred method because of the inherent performance with safety.

Schematic of a 'Direct' Thermal Store

So what are your alternatives to an Electromax?

You need to ask yourself several questions before you decide.

Firstly, does it really matter how your system appears? Will it be visible or tucked away in a cupboard? The aesthetics of hot water devices are rarely an issue, but the might be!

Secondly, do you have a good mains water supply to the property? If your incoming supply is poor then a mains pressure systems might be the last thing you should consider. (If you would like further advice on this matter please contact us)

Thirdly, do you want an unvented cylinder in your property?

Fourthly, does it matter if the functions of electric central heating and electric domestic hot water are contained in the same unit or produced by separate pieces of equipment?

Thermal stores are available in many shapes and sizes and with a range of extra functions. You are always welcome to call for more detailed advice, but you might like to begin your mission of discovery by looking at the following that will provide you with electric central heating or electric mains pressure hot water utilising a thermal store.


Amptec Electric Boiler

Electric central heating boiler



Mains pressure hot water from a thermal store in a metal cabinet

Torrent Multifuel

Multifuel thermal store by Gledhill

Cylindrical thermal store with additional connections for other heat sources

Combination T' Store

Combination Solar Thermal Store Cylinder

Cylindrical thermal store with integral cold water header






Mains Pressure

Gas Fires

Electric Fires

Hot Water Cylinders

Thermal Stores

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