Twin Coil Cylinders – unvented or vented twin coil hot water cylinder range

A twin coil cylinder or a twin coil hot water tank is a hot water cylinder that has a twin coil or two inter wound coils installed within the hot water cylinder, which indirectly heats the domestic water inside the tank via two heat sources for the heat transfer. They can be unvented or a vented cylinder and are also known as a twin coil calorifier.

They are intended for utilizing two external heat sources energy sources combined (a traditional gas or oil boiler, solar thermal, heat pump, etc.) that heat the water that is stored inside the tank by passing hot water or fluids through the internal coils to heat the domestic water inside via heat transfer.

More commonly, the water is heated indirectly by a traditional boiler, be it a gas boiler, wood burner – (must be an open vented system if solid fuel is used to feed the hot water cylinder – you can’t use a unvented twin coil cylinder on solid fuel), or oil boilers suitable to feed the appropriate power to the upper coil, sometimes referred to as the boiler coil, whilst the lower coil of the twin coil calorifier is often powered by solar panels or a heat pump, which are low-carbon, and is often referred to as the solar coil.

Although you can also use these dual coil cylinders range as solar cylinders, with both coils being fed by a solar system to lower fuel bills.

These low heat loss twin coil cylinders are designed to have the domestic hot water heated indirectly and are suitable for both gravity and pumped heating systems.

Dual coil hot water heating systems

Whichever way you want to power our dual coil hot water cylinder range will depend on the heating systems available, such as heated water via a traditional boiler central heating or solar heating system, and you can also have a backup hot water heating via an immersion heater or immersion heaters depending on the dual coil hot water cylinder’s size.

Twin coil hot water cylinder

Optionally, an immersion heater can be installed into the cylinder via the immersion bosses to top up a heat pump or solar system or to back up a boiler in the event of a boiler breakdown to ensure heated water.

Our boiler coil or solar coil (solar thermal) both have a 1″ BSP coil suitable for a pressure of 25 bar and a temperature of 200°C.

This twin coil hot water cylinder range has an ErP rating of “B” or “C” for low heat loss depending on the size of the model and includes one immersion boss for an optional electric immersion element to back up or supplement any solar thermal systems.

Users continue to have many benefits by saving money with reduced energy bills throughout the storage tank’s lifespan thanks to the over-dimensioned, rigid, mould-injected PU thermal insulation, which keeps DHW storage temperature constant for extended periods of time without requiring any additional energy input by reducing any heat loss.

Hot water cylinder twin coil range

From 300 litres to 1,500 litres, our indirect twin-coil cylinder range has high-efficiency heat exchangers with a large surface area. Designated the CV- M” twin coil hot water cylinder range.

Our dual coil cylinders feature two separate coils for heat transfer, rather than two interwoven coils that can affect each other’s performance.

The thermal insulation is rigid, mould-injected PU (CFC/HCFC-free, 0.025 W/m°K) for low heat loss to reduce energy bills.

Optional immersion heater – for backup heating, especially if you’re using these cylinders as solar cylinders only, i.e., using solar to feed the traditional boiler coil at the top of the unit.

These dual coil cylinders all come with extra connections, such as a secondary return connection – a 1″ BSP hot water return for models of 300 to 500 litres and a 1 1/2″ BSP hot water return for models of 800 to 1,500 litres.

Depending on the size of our multi coil hot water cylinder, they may be fitted with extra immersion bosses or extra bosses for temperature sensors as bespoke options.

 

Technical dimension data

The 800- and 1000-litre capacity tanks include a removable insulation system that allows them to pass through 800 mm-wide doors.

Dual coil cylinders performance based on 85°C primary flow 

With each 1″ bsp coil suitable for temperatures up to 200°C – most commonly they are fed at lower temperatures – i.e., 85°C or so

Cylinder coil performance data

Full output data for the lower coil (solar coil) and the upper coil (boiler coil) rising water from 10°C to 60°C.

Full details on our twin coil hot water cylinders can be found on page 17 of the following brochure for 300 to 1,500 litre indirect twin coil cylinders.

Enamelled Domestic hot water cylinders brochure from Flexiheat UK

We also do a double-coil cylinder range in stainless steel – thus, no sacrificial or permanent anodes are required – which cuts down on maintenance. The performance of the coils in our stainless steel twin coil calorifiers is also slightly better than our enamelled range. This range is designated the GX-M2 twin coil stainless steel cylinder range.

In areas with naturally soft water conditions such as west Wales, Scotland, and the northwest and southwest of England, where the water is very soft, you should use a stainless steel twin coil cylinder rather than a glass-lined (enamelled) version.

Stainless steel hot water twin-coil indirect cylinders are the best of the best, as with stainless steel there are no sacrificial or permanent anodes required to protect the tank lining, which glass-lined units require. Stainless steel units can be used everywhere.

Please see page 25 for general data and pages 28 and 29 for their twin coil hot water flow rates performance figures on the following brochure –

Stainless Steel cylinders for domestic hot water production and storage brochure Flexiheat UK

For our 1,500 to 6,000 Litres duplex stainless steel multi-coil  hot water cylinder range, please see page 42 of the above

Technical data for the larger twin coil hot water cylinders / double coil hot water cylinder range.

Twin coil vented cylinder

As standard, our twin coil tanks come as a “twin coil vented cylinder”, which means that as the water heats up and cools down within the cylinder, the vent pipe allows the water in the tank to expand and contract.

It is also a safety system that lets water expand and flow into the expansion tank if the water heater gets too hot. Vented dual coil hot water cylinders can be ideal for retrofit applications where no pipework changes are necessary.

Twin coil hot water solar cylinders

These twin coil cylinders can also be used as a twin solar cylinder, whereby both coils can be connected to solar panels or a solar system, rather than a gas or oil fired boiler suitable for the upper coil. Solar cylinders are leading the way in low-carbon or zero-carbon hot water systems, as the water is heated by the sun’s energy. So, if you have solar panels, you can, if desired, use these as twin coil solar cylinders, with each coil being a solar coil as such.

Twin coil unvented cylinder

These days, an unvented hot system is the most popular in the UK, as it takes the mains water pressure directly to be heated.

This kind of twin coil unvented cylinder is directly supplied with water from the mains. Mains water enters the bottom of the cylinder directly, eliminating the need for a tank in the loft.

The benefit of this indirect twin coil cylinder is that it supplies water under mains pressure, which is typical in most UK properties, so there are no hot water pressure problems.

Our dual-coil hot water cylinder range can be made into an unvented twin coil cylinder by the simple installation of an unvented kit on the unit.

Contact us

Should you require any more assistance, information, check stock, or get prices on the best twin coil cylinder range on the UK market, please don’t hesitate to contact our customer service sales team on 01202 822221 or use our e mail contact above on the web page for our email form.