Domestic HOT Water.
A Specifier’s Guide
Every home needs a ready and adequate supply of hot water, for bathing, washing and cleaning. The means of providing this supply should ideally be energy efficient, environmentally friendly and maintenance free.
Storage, in an insulated copper cylinder, is the modern means of ensuring that a plentiful volume and flow of hot water is available and, with recent technological advances in design and construction of hot water systems, storage will remain the choice of discriminating specifiers.
In order to help you, the specifier, choose the most appropriate hot water storage system for your development we have compiled this brief guide to the options available to you. Some will be familiar to you, the tried and tested BS 1566 indirect copper cylinder for instance, but others may not be. If you would like further technical information or assistance in selecting the most suitable option for your development call us, we will be only too pleased to advise.
At the heart of the hot water generating system is the insulated copper cylinder, this includes copper combination units.
The cylinder is constructed from copper sheet to BS EN 1653. The joints are either welded or brazed with a zinc free alloy and the screwed connections are of copper to ensure total immunity from dezincification.
In aggressive waters an aluminium rod can be specified to provide maximum corrosion protection, this coupled with coppers inherent corrosion resistance ensures the cylinders long service life and durability.
Every cylinder is tested to 1½ times the pressure under which it is intended to operate. BS 1566 specifies cylinders according to 4 different grades, each suitable for different operating pressures.
The Building Regulations require all hot water storage cylinders to be insulated. This insulation is usually provided by a foam coating which maintains a heat loss not exceeding 1 W/L of capacity. Foams have been developed which are totally free of harmful CFCs.
Schematics are for illustrative purposes only. Hot water system design should follow the recommendations of the product manufacturers.
Standard cylinder.
The standard cylinder, specified in BS 1566, is suitable for replacement of older inefficient models. Higher heat exchange efficiency, leading to faster re-heat times and prevention of rapid boiler recycling, together with improved thermal insulation, leading to reduction in heat losses, mean that the modern standard cylinder will provide an energy efficient hot water storage system over a long service life. From 1st July 1995 the heat exchanger surface area in a cylinder must be at least equivalent to that of a BS1566 cylinder.
Cylinder capacities range from 74-210 litres.
High performance cylinder.
High performance cylinders in a range of sizes up to 210 litres are suitable for straight forward replacement of standard models and in the new build situation. The benefits include reduction in fuel usage due to the reduced boiler cycling, reduction in heat loss from the stored hot water due to the high performance insulation and improved supply of hot water.
The storage capacity of cylinders selected for each application depend upon the quantity of hot water required for simultaneous draw-off.
Fast re-heat for bath filling at high flow rates and ideal for use with high efficiency and condensing boilers.
Thermal storage system.
Integrated thermal storage is the generic term for a British development which supplies both heating and mains pressure hot water in a most cost effective way. By dramatically reducing boiler cycling and giving much faster response times to demands for heat it can reduce the fuel usage by between 5% and 15%. Integrated thermal storage is specifically recognised in the NHER software. It works by putting a store of primary water between the boiler and the radiators; cold water is passed through the store at mains pressure to generate high flow hot water.
The smaller capacity thermal stores are suitable for 1-2 bedroom homes with showers only and the larger thermal stores for 4-5 bedroom homes with bathrooms and en-suite showers. Thermal stores should be selected from those tested and badged to indicate that they comply with the Performance Specification for Integrated Thermal Stores and Hot Water Buffer Stores currently issued by British Gas.
Thermal store capacities range from 80-210 litres and the systems can deliver flow rates of between 18-30L/min.
Integrated boiler system.
An integrated thermal store with its own dedicated boiler is ‘the ultimate combination’ for the domestic market. It takes up less space compared to a traditional system. Feed and expansion are accommodated by a tank sited conveniently above the appliance. Hot water is supplied in the same manner as the thermal store. During summer operation the central heating can be switched off and the thermal store still provides hot water.
The hot water is provided at mains pressure and with fast re-heat times and high flow rates it provides an efficient package.
Smaller units are suitable for 2-3 bedroom with bathroom and en-suite shower whilst the larger units for 3-4 bedrooms with 2 bathrooms where simultaneous demand may be encountered.
Volumes of up to 150 litres stored hot water are available and flow rates of 20L/mm are achieved.
Unvented, mains fed, system.
These systems offer mains pressure balanced hot and cold water supply. The unvented unit does not require water to be fed from a cold water cistern in the roof space and so can be sited anywhere within the property. Heating performance of the unit is excellent with quick re-heat times, typically 20 mins from cold, and very low heat losses from the stored hot water.
Smaller capacity units are suitable for 1-3 bedroom homes with bathroom and the larger units for 4-5 bedroom homes with 2 bathrooms and en-suite showers.
The unvented unit is capable of delivering high flow rates, in excess of 30L/mm.
All of the previously illustrated systems provide energy efficient methods of producing as much hot water as is required, when it is required. High efficiency heat exchange coils prevent wasteful boiler cycling and also reduce water re-heat times. The factory applied cylinder insulation, as well as being eco-friendly, ensures that heat losses from the stored hot water are very low, which is a particular advantage when water is heated electrically during off-peak periods. A correctly sized cylinder will provide hot water at high flow rates, even when other outlets are being used simultaneously.
Copper cylinders for hot water storage
| A | B | C | D | Capacity L | Typical applications | |
| Standard Cylinder | 4 | 4 | 4 | 4 | 74 and upwards | Suitable for all domestic properties |
| High Performance Cylinder | 4 | 4 | 4 | 4 | up to 210 | Suitable for all domestic properties will give faster recovery & reduced boiler cycling |
| Thermal Storage System | 4 | 4 | 4 | 4 | up to 210 |
Suitable for most property types with multi-bath/en-suite facilities |
| Integrated Boiler System | 4 | 4 | 4 | 100 120 135 180 |
Suitable for flats/starter homes through to mainstream housing types | |
| Unvented, Mains | 4 | 4 | 4 | 4 | 80 and upwards | Suitable for most property types including multi-bath/ en-suite facilities |
The capacities and typical applications above are intended as a rough guide and information regarding individual products and their suitability for particular applications should be obtained from the manufacturers:
A Albion
Shelah Road
Halesowen
West Midlands
B63 3PG
Tel: 0121 585 5151
Fax: 0121 501 3826
B Elsy & Gibbons Limited
(Combination units only)
Simonside
South Shields
Tyne and Wear
NE34 9PE
Tel: 0191 4270777
Fax: 0191 427 0888
C Gledhill Water Storage Limited
Sycamore Estate
Squires Gate
Blackpool
FY4 3RL
Tel: 01253 401494
Fax: 01253 349657
D Range Cylinders
Tadman Street
Wakefield
West Yorkshire
WF1 5QU
Tel: 01924 376026
Fax: 01924 385015
WMA Energy Advisory Board, Verulam Industrial Estate, 224 London Road, St Albans, Herts. AL1 1AQ
