Category Archives: Solar installations

What is a hot water cylinder coil or heat exchanger?


What is a heat exchanger

The simple answer is, a coil or heat exchanger is a device that allows the transfer of heat between two fluids without having them come in contact with each other.

A standard immersion element is by default integrated into the average solar ready cylinder and is considered the primary heat source. When an external secondary heat sources such as solar, heat pumps or even gas boiler are used, most hot water cylinders will not have a heat exchanger to accommodate and potable water is heated directly within the tank.

Systems of this type (without a heat exchanger) are sometimes called “direct systems”, they can be a problem for a number of reasons:

  • The mains water may be corrosive
  • The mains water may be mineralised
  • Mains water will almost certainly have oxygen dissolved in it
  • The location where the system is used may suffer from frostscylinder_heat_exchanger

Corrosive water will attack the collector tubes, this process will be accelerated by any release of oxygen from solution in the water (gasses are less soluble in water at high temperatures). Minerals in the water will form deposits inside the collector tubes at high temperatures (in the same way that deposits are formed inside a jug or kettle). these deposits will eventually block your solar tubes, gas heat exchangers, pumps, valves and other system components.

Heat exchangers in closed loop systems are critical to the performance of the system and should be matched with the heat source (gas boiler or solar for example) being used and the flow rate through the circuit so that the heat being gained by the heat source is efficiently transferred to the potable water by the heat exchanger.

The most common type of heat exchanger is the coil heat exchanger this is integral to the storage tank, although sometimes external plate heat exchangers are used.

Here is one example of a double coil hot water cylinder which can be used for a solar system and gas boiler backup.




Upgrading your sacrificial anode when replacing a hot water cylinder.

hot_water_cylinder_anodeHow would you like to increase the life span of your current or new hot water cylinder by at least 10 years?

Sounds too good to be true? Every hot water cylinder contains a sacrificial anode which prevents the breaking down of the tank and components. As the name suggests “sacrificial” would mean that at some point it would have to be replaced to maintain this form of protection. In the image to the right you can clearly see the difference within 10 years of operation. Most house holders are not made aware of this fact and unknowingly allow the continuation and breakdown of their relatively young or new hot water cylinder.  By replacing this sacrificial rode you can easily add another 10 years to its operation saving significant cash by preventing the breakdown of metals.

The sacrificial anode (also called an anti-corrosion rod) is typically made of magnesium. It it used to attract corrosive elements so that the tank itself will not corrode as quickly. It can be replaced when it is badly corroded.

But when your hot water cylinder is installed in a tight spot with limited height which is the case in most scenarios, how can you replace this rode (typically over 1 meter length) without actually removing / disconnecting (which would cost you more than its worth) the hot water cylinder to fit it in?

Making it easy to change a cylinder anode when clearance is tight.

When is time to replace your sacrificial anodes you might be faced with several challenges. Either HWC_Anodeyou will have to drain and remove the hot water cylinders or you may have to put a hole through the ceiling above for access. So what is the solution? A flexible Anode! this specialized anode requires less than 250mm clearance and can be installed within 1 hour. So whether you have an exiting cylinder or getting a new one, why not ask to be upgraded to one of these allowing you to make the replacement when its due? Saving you cash long term!

Please ask our team about this upgrade which can be purchased for under $200 with a new installation.




What are Calorifiers?

A calorifier is a heat exchanger which heats water indirectly by circulating is over a heating coil or multiple coils. The source of heat can be water or steam, heated by an external heat source, contained within a pipe immersed in the water. the two bodies of water or steam do not mix. (touch each other)

In hospitals and factories where steam is already being generated for other uses is can also be used to heat the water by the indirect method.

The calorifier may be a continuous coil of pipe or a cylinder within a cylinder with an annular space between the two vessels.


With the vertical hot water cylinder, the steam enters the coil though the top connection. the strainer or grit trap removes any solid matter suspended in the steam. The steam then passes through the inlet valve which is thermostatically controlled. the thermostat prevents overheating or boiling of the stored water.

A steam trap, fitted near the outlet of the coil, prevents the steam from leaving the coil until is condenses.

In a hot water cylinder which contains a steam coil, the coil must be able to be removed for descaling. this is more likely to occur using steam because the coil is working at a higher temperature than with the conventional hot water system.

Hot water cylinders Ltd provide custom hot water cylinder (storage tanks) design and construction with integrated calorifiers at most demanded KW sizes. Our services include domestic and commercial applications. With water applications heat sources such as Heatpumps, Gas, Solar or steam can be applied. For more information please contact us on 0800 4 CYLINDERS.

Relocate your hot water cylinder (external) outside and add solar

Another great looking hot water cylinder installation! Green_glo_hot_water_cylinder

Internal low pressure hot water cylinder system completely  removed and relocated to the outside. This green glo is an external model designed to cope with exterior weather conditions. Designed with higher grade insulation and powder coated materials. Solar water heating was added to this installation ensuring maximum efficiencies. System design is indirect heating via an integrated heat exchanger. No power to get hot water on this installation! Also white UV tape was used to prevent breakdown of the insulation. Builder yet to build a structure surrounding the hot water cylinder to provide further protection. Great looking water cylinder installation guys well done!

Help my hot water cylinder is leaking!

The title to this blog are the words that were spoken when I picked up the phone. To make a bad situation worse it happened on the weekend. After a series of questions it was very obvious we had to get a technician to site. There are two things our costumers hate > 1 > not having hot water on the weekend and >> 2 >> the call out fee on the weekend.

Once the cover was removed the problem was quickly identified. Unfortunately this job required spare hot water cylinder parts not available from your “average” plumbing supplier. Back the following day to replace the faulty solar hot water cylinder. Due to the size of the job the call out fee was not charged and we were able to get the solar hot water up and running the same day 🙂 everyone happy again.