Thermal Store Cylinder Versus Hot Water Cylinders

We get lots of enquiries regarding thermal stores, big and small, using every heat source imaginable. We explain about thermal storage cylinders to potential customers for hours per month and have realised that customer, Architects and Plumbing & Heating engineers really don’t know what they are.

What are the advantages?

So what is a Thermal Storage Tank? It’s a small or large cylinder used to store thermal energy. The tank is filled with primary central heating water opposed to potable hot water (tap water) which you will find in a convential hot water cylinder.

Below is a list of heat sources  /  energy sources that can be connected to a thermal storage tank, you can have 1 heat source or link up multiple.

1. Wind Turbine (Heating tank through immersion heaters)
2. Solar PV (Heating tank through immersion heaters)
3. Wood (biomass) through dedicated pellet, chip and log boilers
4. Wood fuelled boiler stoves
5. Wood fuelled masonry stoves / heaters
6. Pellet boiler stoves
7. Solid fuel, coal, anthracite, etc
8. Gas mains or LPG
9. Oil
10. District heating (heating the thermal store or multipul thermal stores through one centralised boiler)
11. Thermo electric generation (heating tank through immersion heaters)
12. Heat pumps, ground, pond and air
13. We are experimenting with compost coils, where decomposing vegetation heats water within a coil, which in turn produces low temperature energy to the thermal store.

We receive many enquiries from home owners or business owners who have gas or oil boilers with convential steel white radiators. The customer will generally come to us because they require seemless integration of a wood fuelled boiler stove or pellet stoves with the intent to reduce summer burning as well as reduce reliance on gas and oil consumption. This may sound challenging, but Gondwana has unrivalled experience in these types of systems.

Years of experience has toned and perfected the way we design and install these heating systems meaning that our customer get a custom heating solution with unrivalled quality and energy efficiency.

This can be acheived by a variety of methods. Specifically Gondwana believe there are 2 quality methods to achieve this.

1. A coil is incorporated within the thermal store, cold tap water passes through the coil which is surrounded by hot central heating water, this indirectly warms the cold tap water to create hot tap water. The hot water leaving the thermal store is then blended down to a safe temperature.
2. A small tank is suspended within the thermal store, the small tank has a bottom pipe and top pipe. The bottom pipe feeds in cold tap water while the top pipe supplies hot tap water to the property. This option is generally used where there is very high hot water consumption, luxury large homes, wee hotels etc and industry.

1. No expensive mandatory servicing
2. Unvented cylinders require qualified personnel to fit, maintain and certify. Thermal stores don’t require this.
3. Mains pressure hot water
4. Thermal store cylinders are typically much better insulated than hot water cylinders
5. Multiple heat sources can be combined easily, allowing you to use cheaper energy sources to heat your property.
6. Solar thermal and other renewables can be incorporated which can benefit heating as well as hot water to taps (You don’t get that option with a unvented hot water cylinder).
7. When heating demand is low, heat can be drawn from the thermal store without firing up the boiler, meaning less boiler use (cycling).
8. Longer boiler lifespan
9. Reduced fuel consumption due to boilers hard working in condensing mode
10. No large heat leak radiators wasting your heat (solid fuel installs).
11. Safety. Systems can be vented or sealed depending on heat sources used. Equally different heat sources can be separated through coils within the thermal store, meaning some vented or sealed.
12. A thermal store enables you to use low temperature heating circuit which typically save homeowners 20% off there heating bills.
13. Future proof. A quality thermal store is future proof, enabling you to incorporate different heating technology’s as the world changes.
14. Safety. Additional safety features can be incorporated like overhead coils (scorch coils) within thermal storage cylinders, this gives systems an additional layer of safety and can prevent overheating in solid fuel and solar installs.
15. Thermal stores can be made of a different materials and different sizes depending on the size of the property, door widths, dhw demand, heat demand etc. Sizes range from 50 litres to 200,000 litres
16. Thermal stores can heat multiple buildings from one thermal store. This means simpler installs as well as energy savings.

I have a wood burning boiler stove and a vented hot water cylinder as well as steel radiators. The system works but I burn lots of logs and my home is cold when the fire goes out.

How can a thermal store help me?

By piping the wood burning boiler stove directly to thermal store with dhw coil. You can get rid of the unvented hot water cylinder, meaning mains pressure quality hot water to your taps. Your radiators will then be heated directly from the thermal store, without the need for large / oversized heat leak radiators in upstairs rooms or attics.

By using a thermal store you will be saving the energy within the thermal store for times when you need or want heating, meaning when the fire goes out you can still have heating.

With this type of system you can also corporate solar thermal and or a electric immersion heater. This would allow you to heat your radiators and tap water with the sun. An electric immersion can also be incorporated into this system, for times you are not using your wood burning boiler stove. This can be run by mains electric on a reduced tariffs. Or for those of us who have solar pv, hydro and wind turbines run for free.

I live in a large Victorian townhouse with 2 gas boilers, some radiators and some wet underfloor heating. The boilers (one boiler heats hot water cylinders and the other boiler heats central heating water to the radiators and underfloor heating) are on their last legs. The system works fine but boilers are constantly on and off, which my gas donkey has ensured me has reduced their life span.

We also have a 2 unvented cylinders, but are often running short on hot water.

Can a thermal store and Gondwana help us be more comfortable and help us save some money through reducing our gas consumption?

Of course.

We would install a large thermal store with large dhw coil to ensure first class mains pressure hot water to your taps.

We would install 1 quality, high efficiency condensing gas boiler to heat the thermal store, loading valve and balancing valves would be fitted to ensure correct flow through the boiler as well as ensuring a protected return temperature. This keeps the boiler running in high efficiency condensing mode, meaning you actually get the manufacturers efficiency rating.

We would then install a low temperature circuit to the radiators and underfloor. This enables us to fit an intelligent heating controller that calculates the energy needed to keep the home at the set temperature, meaning the home can be kept at the desired temperature while using cooler water temperature. This typically saves homeowners 20% off there fuel bills.

Other advantages of this system are when small amounts of energy are needed at low temperatures, for example, underfloor heating. The hot central heating water is drawn from the thermal store to satisfy the underfloor heating. This means the boiler is not being turned on and off (cycling) which wastes gas as well as being very inefficient because the boiler rarley gets into condensing mode.

But by using a thermal store the boiler only gets the thumbs up to run when there is a substantial drop on the thermal store, meaning less gas is burnt, less ware and tear on boiler and therefor increased lifespan. You could also incorporate other renewable heat sources to further reduce costs like solar thermal.

So has the hot water cylinder had its day? In short, yes.

Gondwana install and sell a range of thermal storage tanks for every situation from domestic to commercial. We source our thermal stores from 3 suppliers and manufactures to ensure we can offer you the best product for your situation.

We invite you to get in touch should you need assistance with a full package or sales and design help.

Owner and engineer Dave Adams.

— Thanks to customers who let us take pictures of our products in their home as well as MacDonald engineers and our swizz partners for images.