Indirect Cylinder - Standard Specification (Plain)
Indirect Cylinder - Standard Specification (Insulated)
Indirect Cylinder - Specification Drawing
• For use in Domestic Properties
• For use with solid fuel appliances
•Can be specified for a gravity system
Indirect Vented Cylinders are heated by a boiler of some sort which heats water within a coil of the cylinder. They are also fed from a cold water feed and expansion tank usually situated in the loft space within the property. These cylinders are generally classed as low pressure cylinders due to the low static pressures better known as working head. The working head is determined by the distance between the feed tank’s water level, and the draw off point on top of the cylinder.
The working head of a cylinder determines which of the three grades of copper it should be manufactured from;
• Grade 1 is the heaviest or thickest grade and is specified for a working head of 25 metres.
• Grade 2 which is specified for a working head of 15 metres
• Grade 3 which is specified for a working head of 10 metres.
Grade 3 cylinders are usually specified and are more than adequate for general domestic properties. Although you may also come across Grade 4 or Medium Duty cylinders, both have now been superseded by the Grade 3 cylinder since 2002.
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.
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.
Manufactured in accordance with British Standard, BS 1566-1 : 2002 and in compliance with Part L of the Building Regulations, these cylinders combine a high performance heating coil 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 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.
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.
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.
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. A Surrey or Warrick flange while easy to install are considerably more expensive than having an extra connection added when specifying a cylinder.
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.
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.
Due to the uncontrolled heat input and high temperatures that a solid fuel appliance can emit over prolonged periods of time, it is recommended that a metal feed and expansion tank is installed as opposed to the more common plastic types. For more information on our copper and stainless steel header tanks, please see our Header tank page.
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
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.
Indirect cylinders are available in a range of heights (from 400mm to 2000mm) and to the specific diameters listed below. Please see our Slimfit products for small diameters (all sizes stated are excluding insulation):
300mm, 350mm, 375mm, 400mm, 450mm, 500mm, 600mm
Variable height from 400mm to 2000mm
Copper Grading Options
Grade 1 (25mtr Mwh), Grade 2 (15mtr Mwh) and Grade 3 (10mtr Mwh)
Shell Connection Sizes Available
1/2", 3/4", 1", 1 1/4", 1 1/2", 2", 15mm, 22mm, 28mm
50mm to 75mm
Coil Heating Surface (Indirect)
Relative to cylinder size (General Guidance - 25 minute recovery)
Coil Working Pressure (Indirect)
3/4", 1", 1 1/4", 1 1/2", 2", 22mm, 28mm
Coil Connection Sizes Available
All height and diameter measurements are excluding insulation and all connection port heights are approximate.
For smaller diameters, please see the Slimfit Page
HeightDiameterNominal LtrCold FeedBoiler FlowBoiler ReturnSecondary Return
900mm 400mm 96L 100mm 450mm 100mm 700mm
1050mm 400mm 120L 100mm 500mm 100mm 800mm
1200mm 400mm 135L 100mm 650mm 100mm 950mm
1500mm 400mm 170L 100mm 650mm 100mm 1200mm
1800mm 400mm 210L 100mm 1100mm 100mm 1450mm
HeightDiameterLiterageCold FeedBoiler FlowBoiler ReturnSecondary Return
900mm 450mm 120L 100mm 500mm 100mm 700mm
1050mm 450mm 144L 100mm 550mm 100mm 800mm
1200mm 450mm 166L 100mm 650mm 100mm 800mm
1500mm 450mm 210L 100mm 650mm 100mm 1200mm
1800mm 450mm 260L 100mm 1150mm 100mm 1350mm
HeightDiameterLiterageCold FeedBoiler FlowBoiler ReturnSecondary Return
1200mm 500mm 204L 100mm 800mm 100mm 950mm
1500mm 500mm 260L 100mm 850mm 100mm 1200mm
1800mm 500mm 320L 100mm 1100mm 100mm 1450mm
2000mm 500mm 360L 100mm 1100mm 100mm 1650mm
HeightDiameterLiterageCold FeedBoiler FlowBoiler ReturnSecondary Return
1200mm 600mm 204L 100mm 800mm 100mm 950mm
1500mm 600mm 375L 100mm 1000mm 100mm 1200mm
1800mm 600mm 450L 100mm 1100mm 100mm 1450mm
2000mm 600mm 510L 100mm 1100mm 100mm 1650mm
Cylinder height is specified from the base of the cylinder to the highest part or the dome excluding port connections and insulation.
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
Material grade relates to the working head and metal thickness, i.e. distance between the feed tank’s water level, and the draw off point on top of the cylinder. Grade 3 is standard for most properties whereas Grade 1 and 2 are used for higher working heads or for longevity of the cylinder.
This is the top centre connection on the dome of the cylinder, there are a wide variety of connection sizes and its worth taking the time to read our Connection Size List before ordering a cylinder, if you are unsure then the simplest option is to specify the cylinder with 22mm or 28mm connections already attached to the cylinder, avoiding additional costs by having to use tank connectors. If a surrey flange is being used, the requirement of a 1" female connection must be specified.
All female connections are parallel BSP thread and taper fittings must not be used.
The connection size for the top 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.
This can be specified rather than the use of a Surrey flange or 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 bottom feed connection on the side wall of the cylinder, there are a wide variety of connection sizes and its worth taking the time to read our Connection Size List before ordering a cylinder, if you are unsure then the simplest option is to specify the cylinder with 22mm or 28mm connections already attached to the cylinder, avoiding additional costs by having to use tank connectors
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.
Direct flow and return connections were used with traditional solid fuel appliances in certain regions of the country and were specified with 1" Male or Female connections. They are generally not required anymore unless the cylinder is being replaced for use in an old system.
Opposite side primaries are generally used in old systems and are very rarely encountered any more, these units can be confusing to determin due to the flow connection being on one side and a return connection positioned on the opposite side.
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.
Hot Water Draw Off
Top Entry Immersion
Boiler Flow & Return
Boiler Control Stat
Mid Entry Immersion
Bottom Entry Immersion
Direct High Flow Conn.
Direct Low Flow Conn.
Opposite Side Primaries
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.
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.)
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.
PRODUCT OPTIONS & UPGRADES
SIZE & SPECIFICATION
Northern Road Industrial Estate
Tel: 01636 678 437
Fax: 01636 678 964
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