Before we start: lets start with the terminologies, the rules and myths so you can understand how all this works
A wet back – hot water jacket – water booster – these are pretty much all the same thing.
They are traditionally made from stainless steel or copper and hold (on average) 1ltr of water.
They are installed within the firebox and as the fire is going, the water passes through the hot water jacket – which is heated by the fire.
They are all LOW PRESSURE and CAN NOT be connected to mains pressure hot water systems.
The average hot water jacket will heat up to 2.5 to 5kW of water
Wood Heaters MUST be tested and approved for a hot water jacket to be installed: you can not install these into any heater.
A Wood boiler
These are larger size hot water jackets and heat a lot more water.
These are made from steel and require inhibitor to prevent rusting.
These vary in size and are purpose made to suit the boiler
These vary in size form 8kW to 80kW
You can get different styles of wood boilers from
Myth - You can’t heat your water with a wood heater or wood stove
Fact – Yes you can … Pretty much all wood cookers ( or wood stoves ) are available with a wet back option to heat water
Wood heaters MUST be tested and approved to have a Hot Water jacket installed
Myth - I can retro fit this to my existing wood heater
Fact - Only if the wood heater is tested and approved to have a hot water jacket fitted
Myth – The hot water systems give you bad hot water pressure
Fact – Actually this is wrong: there are different types of hot water systems on the market, some give you gravity feed (low pressure) some have heat exchanges that give you mains pressure (or pump pressure) hot water to your home
Myth – You can't use solar with a wood stove
Fact – Again, this is incorrect, you can: there are different types of hot water services available that have Solar for heating your hot water when the sun is out
Myth – The bigger the hot water jacket – the better the hot water
Fact – No: if your hot water jacket is over sized and you don't use the water - all you do is boil the water
Myth - I can run hot water & radiators off any system...
Fact - Yes and no...its all about heating the right amount of hot water to heat the amount water you need to do your hot water and radiators
Myth - Can I use the hot water to heat hydronic (radiator) panels
Fact - Yes
How does it heat the water?
Its very simple - hot water is lighter than cold water...so when you light your fire, the fire starts to heat the water.
As the water is getting hotter and hotter, it starts to rise, this is called Thermosyphoning
All the hot water jacket does is heat water, it does not store the water.
So as the water is heating, it then rises into a storage tank
The hotter the fire; the more water is heated
The size of the hot water jacket (or Hot Water Boiler) will determine the actual amount of hot water per hour that can be produced.
Different types of Hot Water Tanks
There are many different sytle of hot water tanks available : they all offer different solutions for your home
Low Pressure In Roof Tanks
These tanks offer a coil of copper, on average 36mts long, inside the tank – this acts as a heat exchange and is heated by the low pressure water
You use the water from the heat exchange as you would your normal water supply that offers you now pressure to the hot water to your taps
The water in the tank is still Low Pressure and is heated by the wood stove or wood heater
These tanks are available all plumbed so you can combine:
Centra Coil Tanks
The Centra Coil tank is a versatile tank - suitable for many installation options
The body of the tank is a S/Steel construction: Offering 315Ltrs of domestic hot water at pressure...all heated with a bottom manifold (coil) at low pressure.
The coil of copper in the bottom of the tank has the hot water for your boiler/stove running through it; which then heats the main tank
By setting up the coil on a low pressure system, you can connect the Centra Tank to any make or model wood heater with a wet back - wood stove or wood boiler
The Centra Coil comes complete with
How this tank works...
There is a coil of copper in the base of the tank - the hot water from your wood stove or hydronic system uses this coil to heat the S/Steel hot water tank, like an element, but it's a hot water coil rather than an electric element.
There is an additional electric element in the tank that you can set up on Off Peak, for times your wood stove is not operating
On Roof Tanks
Vacuum Tube Solar panels have proven themselves with offering a higher return of solar energy than standard flat panel solar systems...
Up until now, Vacuum Solar was never really suited to connecting to a Wet Back (Low Pressure Hot Water System) from your Wood Stove or Wood Heater
The Ultimate Solar Vacumm System has been purpose built to connect to a Low Pressure Hot Water system - for any make or model wood heater or wood stove
With two models to choose from
There are a number of ways to plumb these systems
The basic rules are:
The system is designed to work in this way
Gravity systems is also known as Thermosyphon systems. It's based that hot water is lighter than cold water - so as soon as there is a temperature increase: the hot water will naturally rise.
As soon as the boiler or stove is slight, 100% of the water will naturally rise into the storage tank - this natural circulation will happen because hot water is lighter than cold water.
Once the water temperature reaches 70°C - 75°C, the thermostat (which is on the hot flow line) will then turn the pump on (which is on the return line) and start to pump the water into the radiators.
Depending on the set up (how many radiators you have) the pump does not use all the hot water...it will only pump 40% - 60% of the water to the radiators, the balance is continuing to go to the hot water storage for your domestic use
How the Domestic Coil Works
Water in storage tanks naturally laminates - the hot water is always hotter in the top 1/3rd of the tank
The "MP" coil is submerged in the hottest part of this water and the heat from the storage (or hydronic water) is transferred through the copper pipe to the domestic water.
Different length coils are used (18 or 36Mr) which will determine how much domestic water you have on demand.
By Adding Solar Hot Water to the system; you have created an "Off the grid System"
Different brands and your location will determine the solar impact on this system
The Solar WILL NOT assist the Hydronic part of the system: it will only assist with the domestic requirements