Combination Cylinders | Hot and Cold Water Storage Cylinders

Combination units combine both the hot water storage section and cold water storage tank in an integrated unit. They are often suited to multi-storey developments, where space is limited or simply wherever the installation of the header tank is going to prove difficult. Combination Units are available in direct, indirect, primatic or Thermalstore type. Other options are also available to meet customers' particular needs including

Economy 7 specification, split header tanks to support the central heating system's feed and expansion, and additional connections (e.g. for shower supply or secondary return)

Indirect Coil-

By definition, Indirect cylinders are fitted with a spiral heating coil designed to work in conjunction with domestic gas /oil boilers, heat pump as well as solid fuel heating appliances. Heat is transferred to the potable water contained within the cylinder via a spiral coil that acts as the heat exchanger keeping the potable bathing water and the contaminated system water separate.

Other compatible heat inputs can be in the form of solid fuel appliances such as wood burners or multi fuel stoves. As most of these systems rely on natural thermo syphoning to achieve the circulation of heated water through the coil (as opposed to a circulation pump), the spiral coil needs to be 28mm and have a continuous fall to minimise the risk of any air traps or air pockets from forming within the coil.

Insulation-

Our polyurethane foam insulation can be applied up to a thickness of 75mm deep and is the most environmentally friendly type available. Rather than the more common blowing agents that are used in spray foam applications , such as CFC, HCFC and HFC .Our spray system uses water as a blowing agent. The code for sustainable homes states that materials must have an ozone depletion potential of zero and a global warming potential of less than five. As a result of the water used in our spray system , our insulation has an ozone depletion potential of zero and a global warming potential of one.

British Standard- Manufactured in accordance with British Standard, BS 3198 and in compliance with Part L of the Building Regulations, these cylinders combine a high performance heating coil (where applicable) with low heat loss, factory applied insulation, to provide a highly efficient and effective way to store and provide domestic hot water.

When ordering a particular cylinder its worth taking into consideration upgrade options or requirements as listed below, a marginal cost now can save a considerable amount over the life of the cylinder.

Material-

Material grade is important to consider especially in areas of hard or aggressive water quality, by designing a cylinder from thicker material can prolong the life of the cylinder.

Connections-

There are a wide variety of connection sizes available and its worth taking the time to refer to our Connection Size List before ordering a direct replacement cylinder. If you are unsure, then the simplest option is to specify the cylinder with 22mm or 28mm compression connections, this saves buying extra plumbing fittings and any worry over ordering the incorrect size connections.

Connection layout-

We understand how difficult it can be to install a cylinder with pipes that are inaccessible, by specifying connections in the most convenient places will not only save money on materials but make the the install easier.

Additional connections-

Specifying additional connection such as a shower or a secondary return connection can save not only the trouble of fitting an Essex flange but also cost as well. Each unit can come complete with a Byelaw kit, a float valve (with a plastic or copper float), immersion heater(s) and a drain valve if required.

Quick recovery coil-

For situations that need faster than usual heat-up times or where a large boiler is installed, these cylinders can be supplied with a larger than usual coil, designated as a “Quick Recovery” coil. There is also a benefit if you have a space and volume restriction due to cupboard size, by having a quick recovery coil fitted and timing the boiler to come on when there are peak hot water demands, this will replace the volume used whilst bathing or showering. These units not only improve on heat-up times but also reduce boiler cycling times which in turn will maximize the boiler’s efficiency, this can make a significant saving over the year.

Gravity Coil-

For cylinders that are intended for use with a solid fuel appliance, a 28mm gravity coil is required with connection sizes of 1" or above. It is important to specify that the cylinder is intended for gravity use when ordering, we will then carry out a test to ensure the coil is compatible for gravity use.

Insulation-

Daily heat loss can be in the region of 5c and higher depending on the insulation depth of the cylinder and the store temperature, by adding extra insulation up to 75mm deep will save on daily heat loss over life span of the cylinder.

Bespoke-

Matching customers' requirements is particularly important when space is at a premium, so the most common customisation for a hot water cylinder, is the “mixing and matching” of the various heights and diameters that we offer. As additional parts of a Bespoke design, the customer is able to specify a number of options including coil sizes (where applicable), connection sizes/positions, insulation thickness, whether it is manufactured from copper or stainless steel (see our Copper vs. Stainless Steel page for a comparison), and the finish of the unit (the metal case being the premium option). We can offer design drawings prior to manufacture to ensure that all connection sizes, positions and functions are to the customer's requirements.

Combination cylinders are available in a range of heights (from 825mm to 2000mm) and to the specific diameters listed below (all sizes stated are excluding insulation):

400mm Diameter
HeightDiameterLiterage (Hot)Literage (Cold)
900mm 400mm 67L 16L
1050mm 400mm 91L 16L
1200mm 400mm 91L 32L
1300mm 400mm 103L 32L
1400mm 400mm 114L 32L
1500mm 400mm 127L 32L
1800mm 400mm 166L 32L
450mm Diameter
HeightDiameterLiterage (Hot)Literage (Cold)
900mm 450mm 85L 20L
1050mm 450mm 115L 20L
1200mm 450mm 115L 40L
1300mm 450mm 130L 40L
1400mm 450mm 144L 40L
1800mm 450mm 210L 40L
500mm Diameter
HeightDiameterLiterage (Hot)Literage (Cold)
1500mm 500mm 200L 50L
1800mm 500mm 260L 50L

All height and diameter measurements are excluding insulation, other cylinder sizes are available upon request.

Diameter Options

350mm, 375mm, 400mm, 450mm, 500mm, 600mm

Height Options

Variable height from 825mm to 2000mm

Copper Grading Options

Grade 1, Grade 2 and Grade 3

Shell Connection Sizes Available

1/2", 3/4", 1", 1 1/4", 1 1/2", 2", 15mm, 22mm, 28mm

Insulation Thickness

35mm to 75mm

Coil Heating Surface (Indirect)

Relative to cylinder size (General Guidance - 25 minute recovery)

Coil Working Pressure (Indirect)

3.5 Bar

Shell Connection Sizes Available

1/2", 3/4", 1", 1 1/4", 1 1/2", 2", 15mm, 22mm, 28mm

3/4", 1", 1 1/4", 1 1/2", 2", 22mm, 28mm

Coil Connection Sizes Available

Glossary

Combination height is specified from the base of the cylinder to the top of the cold section, it is also worth making a note of the depth of the cold section in order to get the correct replacement unit.

Cylinder diameters are specified excluding port connections and insulation material. Only listed diameters are available.

For the total diameter of a cylinder including insulation, use the following formula; Insulation Depth x 2 + Cylinder Diameter = Total Diameter, or to find the replacement cylinder diameter , please refer to our online cylinder calculator.

Nominal 50mm insulation is recommended though custom depth can be specified between 35mm and 75mm

Uninsulated units are available upon request.

Material grade is important to consider especially in areas of hard or aggressive water quality, by designing a unit from thicker material can prolong the life of the unit.

This is one of the higher connections mounted on the side wall of the unit, and as there are a wide variety of connection sizes, its worth taking the time to read our Connection Size List before ordering a unit, if you are unsure then the simplest option is to specify the cylinder with 22mm or 28mm connections already attached to the unit, avoiding additional costs by having to use tank connectors. All female connections are parallel BSP thread and taper fittings must not be used.

This can be specified rather than the use of an Essex flange and is generally positioned in the upper part of the cylinder and fitted with an internal air ingress prevention device. All compression fittings come with cap nut and olive, avoiding additional costs of tank connectors.

A secondary hot water return connection is generally specified on systems with long pipe runs to wash facilities. Secondary return circuit provides hot water on demand and avoids wastage of cold water, eliminates dead legs in the system and reduces the risk of legionella. This system must be powered by a bronze circulating pump.

Boiler flow and return are connections that are fed from a heating appliance such as a boiler, wood burner or range type cooker. It is most important to specify 1" or 28mm connections and upwards for gravity flow and return circuits to ensure no airlocks occur within the internal coil of the cylinder (Please specify gravity flow and return in the additional information box if necessary).

The connection port is a ½" Female connection that allows for a screw in pocket that is supplied with the boiler control stat, usually specified as aqua control thermostat. This allows for more accurate control of the water temperature and is more efficient than the traditional strap on type control thermostat.

This is the valve positioned in the upper cold section of the unit and will require a 22mm hole for the ball valve connection to pass through. We can punch this hole as an option but generally no holes are punched in the cold section of the unit unless requested by the customer

The connection size for the mid entry immersion heater is 2¼" BSP female. An encoloy immersion is advised for use in hard water areas or for longevity. For particularly aggressive water conditions such as high chlorine or acidity, a titanium immersion heater is advised.

The connection size for the bottom entry immersion heater is 2¼" BSP female. An encoloy immersion is advised for use in hard water areas or for longevity. For particularly aggressive water conditions such as high chlorine or acidity, a titanium immersion heater is advised.

Direct flow and return connections were used with traditional solid fuel appliances in certain regions of the country and were specified with 1" Female or Male connections. They are generally not required anymore unless the cylinder is being replaced for use in an old system.

Self explanatory. Please avoid using a drain with a tapered thread or over packing with PTFE Tape.

This is the position specified looking down from above the cylinder as shown on the 'Plan View', 12 O'Clock being at the rear.

This is a screened warning overflow connector that allows for the expansion overflow, this requires a hole diameter of 27mm to pass through. We can punch this hole as an option but generally no holes are punched in the cold section of the unit unless requested by the customer

Height

Diameter

Insulation

Material Grade

Hot Water Draw Off

Shower Outlet

Secondary Return

Boiler Flow & Return

Boiler Control Stat

Ball Valve Cold Feed

Mid Entry Immersion

Bottom Entry Immersion

Direct High Flow Conn.

Drain

O'Clock Position

Byelaw 30 Kit

Capacity Calculator

Uninsulated Diameter Calculator

This calculator is designed to assist the specification of a cylinder by determining the amount of hot water available from a cylinder of a specific size; this can be particularly useful in situations where space for a cylinder is limited.

Please note - When calculating the hot water volume, a measurement must

be taken of the hot water section only and not the overall height.

This calculator is designed to assist the specification of a cylinder by determining the size of the cylinder from it's circumference and insulation thickness; this can be particularly useful in situations where a replacement cylinder is required, but due to the insulation it is difficult to determine the size of cylinder required.

Please note - The final figures are approximate and should be rounded to the nearest standard diameter (375,400,450 etc.)

Tapping Chart

To assist with determining the correct size connection for replacement units or units to fit your current system, we have created a table of external and internal thread sizes.