Domestic Hot Water Systems
There is a wide and potentially bewildering variety of systems for supplying hot water in houses and flats (Domestic Hot Water or "DHW"). These include
- Conventional systems with a large tank in the attic and a hot water cylinder
- Combi Boilers
- Unvented (e.g. Megaflo)
- Thermal Stores or Heat Banks
- Solar Hot Water systems
- Gas multipoint heaters (like old Ascot types)
and more ....
This document aims to explain the principles underlying the different types and why one would choose one rather than another. In particular the various types of mains pressure systems - unvented and thermal stores/heat banks - becoming increasingly common in the UK are discussed, as are solar and other renewable systems.
This article describes the main features of DHW systems and explains terms used in describing such systems. Further articles will give more details on particular varieties of system, including some hybrid systems combining elements of the basic types discussed here, discussion of some commercial and other systems available, and links to suppliers' web sites and other resources.
Main types of DHW system
The main differences between types of DHW systems are:
- Instantaneously heated e.g. combi boilers, multipoint ('Ascot'-type) instantaneous gas water heaters, instantaneous electric water heaters
versus
- Stored heat e.g. systems with some sort of hot water cylinder
and
- Mains pressure water e.g. combi boilers, unvented ('Megaflow' type) cylinders
versus
- Low pressure with stored water e.g. conventional: tank in attic and hot water cylinder in airing cupboard
The pros and cons of these systems are:
PRO | CON | |
---|---|---|
Instantaneous |
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Stored heat |
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Mains pressure |
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