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Cylinder Connections: Tables, Calculators & Glossary
Connection Size Table
| Thread Size & Type | Male/OD | Female/ID |
|---|---|---|
| ½" BSP | 20.7mm | 19.2mm |
| ⅜" BSP | 16.6mm | 15.0mm |
| ¾" BSP | 26.1mm | 24.2mm |
| 1" BSP | 32.8mm | 30.4mm |
| 1 ¼" BSP | 41.6mm | 40.0mm |
| 1 ½" | 47.6mm | 44.9mm |
| 2" | 59.3mm | 56.9mm |
| 1 ¾" | N/A | 50.8mm |
| 2 ¼" | N/A | 63.0mm |
| 15mm Compression | 20.7mm | 19.2mm |
| 22mm Compression | 28.3mm | 26.7mm |
| 28mm Compression | 34.6mm | 32.6mm |
Cylinder Capacity Calculator
By typing in the height and diameter of the cylinder excluding insulation, we can determine the aproximate volume of water it can store.
Accurate Cylinder Measurement Calculator
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.)
Height (mm)
Cylinder height is specified from the base of the cylinder to the highest part or the dome excluding port connections and insulation.
Diameter (mm)
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 × 2 + Cylinder Diameter = Total Diameter
Insulation (mm)
Nominal 50mm insulation is recommended for most standard units, however custom depth can be specified between 35mm and 100mm. Keep in mind that larger units must have thicker insulation to match ERP requirements.
Material Grade
Material grade relates to the working head and metal thickness, i.e. distance from the base of the cold water feed tank to the base 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.
Hot Water Draw Off
22mm and 28mm Compression connections come complete with cap nut and olive, 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.
Top Entry Immersion Heater
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.
Shower Outlet
This can be specified rather than the use of a Surrey flange or Essex flange. These are 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.
Boiler Flow & Return
Boiler flow and return connections 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).
Boiler Control Stat
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 an aqua control thermostat. This allows for more accurate control of the water temperature. It is more efficient than the traditional strap-on type control thermostat.
Cold Feed
A cold feed is the cold water inflow into the tank. 22mm and 28mm compression connections come complete with cap nut and olive, avoiding additional costs by having to use tank connectors.
Mid Entry Immersion Heater
The connection size for the mid-entry immersion heater, also known as a boost 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.
Bottom Entry Immersion Heater
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 High & Low Flow Connections
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.
Opposite Side Primaries (OSP) Connections
Opposite side primaries are generally used in old systems and are very rarely encountered any more.
Drain
Used to drain the tank. Please avoid using a drain with a tapered thread or overpacking with PTFE Tape.
General Info & Advice
We advise you to avoid placing connection ports close together or overlapping other connections as there is a limitation on the proximity of the fittings but will also ease the manufacture and installation of the cylinder.
Please ensure both O’Clock position and Connection type are entered correctly before submitting your design; this will help to ensure an accurate quotation.
All compression fittings come with cap nut and olive, avoiding additional costs of tank connectors.
Important Information
- All female connections are parallel BSP thread and taper fittings should not be used.
- Excessive use of sealing materials (PTFE tape) can and will stretch the connections which can cause fracture of the brazing materials possibly creating a leak.
Need assistance? Our Sales Team can help answer any questions you have