Major Classifications
Definition: A hot water system can be defined as an installation of one or more water heaters, plus the associated cold and hot water plumbing, which can supply hot water to one or a number of outlets. This definition is general, and covers many types of water heater, each with advantages and disadvantages. Water heaters are generally divided into five broad classes:
Instantaneous Water Heaters
The instantaneous unit is designed to heat water only at the time it is being used, rather than relying on any form of storage. Instantaneous water heaters are normally connected directly to mains water supply. When a hot tap is opened, the flow of water activates a valve or switch causing gas or electricity to flow to heat the water as it passes through the system; this stops when the hot tap is closed. An integral water governor controls the flow rate of the water to the hot taps. These units can be single point heaters, as in a bath heater, or multipoint, supplying several outlets.
Storage Water Heaters
A storage unit is designed to hold a useful quantity of hot water in a thermally insulated container ready for immediate use. As hot water is used, cold water enters the storage tank to replace it. Reheating continues after the flow of hot water has ceased. These units can be designed either to store and supply hot water at mains pressure, or to store water at atmospheric pressure and distribute it by means of gravity. Again, these water heaters can be single point water heaters (e.g. sink water heaters) or multipoint water heaters. These are also known as "direct storage" units.
Heat Exchange - Coil Heaters
This type of unit consists of a heat exchanger, usually in the form of a coil of copper tubing immersed in a thermally insulated container of static heated water. Cold potable water, at mains pressure, passes through the heat exchanger and picks up heat from the stored water. The stored water is then reheated to bring it back to its original temperature. These are sometimes referred to as "indirect storage" units.
Heat Exchange - Calorifiers
Similar to coil heaters, except the location of the heating water and potable water are reversed. Hot water, generated by some remote appliance, passes through a heat exchanger immersed in a container of stored potable water. The stored water, heated by the heat exchanger, is drawn off when a hot tap is opened. The remote supply of hot water (which is often circulated through the heat exchanger by a pump) can be provided by a water-heating appliance (i.e. a boiler), or can be waste heat recovered from some other process. This type of hot water production is usually confined to commercial or industrial uses. These units are also "indirect storage" units.
Commercial Water Heaters (Boilers)
This method of heating water is similar to the instantaneous method. Water is heated as it passes through the water heater and may then go directly to the point of use or pass into an insulated storage tank. Circulation may be by natural convection but is more frequently pumped. Commercial water heaters are used where large quantities of hot water are required and are often connected to calorifiers to provide an indirect storage system.
The term "boiler" is commonly used to describe these appliances. The term "boiler" does not apply to appliances, which heat water or other liquids to a temperature lower than the normal atmospheric boiling temperature of the liquid.
Classifying By Storage Pressure
- Mains pressure units: Water is stored and delivered at mains pressure so hot and cold water is at the same pressure.
- Reduced pressure units (medium pressure): Pressure limiting valves, reduction valves, ratio valves or overhead feed tanks connected to the cold water connection of the water heater reduce the pressure of the delivered hot water to below that of full mains pressure.
- Gravity units (low pressure): A cold water cistern fitted to the storage tank ensures the water is stored at atmospheric pressure and gravity is used to distribute the hot water to the points of use. This system relies on the storage tank being located well above the draw off points.
Classification By Distribution Method
- Single point units: These are designed to supply water to one tap only. The water heater may be of the instantaneous or storage type.
- Multipoint units: These units have sufficient water flow capacity and thermal input to provide consistent supplies of hot water to several taps simultaneously. Again, these units may be of the storage or instantaneous design.
- Push through units: Also known as "free outlet" water heaters, these units store water at atmospheric pressure, but when the tap is opened mains pressure water is delivered. This is achieved by controlling the cold water supply to the water heater by what appears to be the hot tap at the point of use. On opening this tap, cold mains pressure water is allowed to enter the storage tank and push the hot water out of an uninhibited outlet at the point of use. When the tap is closed, the water in the storage tank returns to atmospheric pressure.
Simon Totterdell - Owner
Call Now - 99043074
Major Classifications
Definition: A hot water system can be defined as an installation of one or more water heaters, plus the associated cold and hot water plumbing, which can supply hot water to one or a number of outlets. This definition is general, and covers many types of water heater, each with advantages and disadvantages. Water heaters are generally divided into five broad classes:
Instantaneous Water Heaters
The instantaneous unit is designed to heat water only at the time it is being used, rather than relying on any form of storage. Instantaneous water heaters are normally connected directly to mains water supply. When a hot tap is opened, the flow of water activates a valve or switch causing gas or electricity to flow to heat the water as it passes through the system; this stops when the hot tap is closed. An integral water governor controls the flow rate of the water to the hot taps. These units can be single point heaters, as in a bath heater, or multipoint, supplying several outlets.
Storage Water Heaters
A storage unit is designed to hold a useful quantity of hot water in a thermally insulated container ready for immediate use. As hot water is used, cold water enters the storage tank to replace it. Reheating continues after the flow of hot water has ceased. These units can be designed either to store and supply hot water at mains pressure, or to store water at atmospheric pressure and distribute it by means of gravity. Again, these water heaters can be single point water heaters (e.g. sink water heaters) or multipoint water heaters. These are also known as "direct storage" units.
Heat Exchange - Coil Heaters
This type of unit consists of a heat exchanger, usually in the form of a coil of copper tubing immersed in a thermally insulated container of static heated water. Cold potable water, at mains pressure, passes through the heat exchanger and picks up heat from the stored water. The stored water is then reheated to bring it back to its original temperature. These are sometimes referred to as "indirect storage" units.
Heat Exchange - Calorifiers
Similar to coil heaters, except the location of the heating water and potable water are reversed. Hot water, generated by some remote appliance, passes through a heat exchanger immersed in a container of stored potable water. The stored water, heated by the heat exchanger, is drawn off when a hot tap is opened. The remote supply of hot water (which is often circulated through the heat exchanger by a pump) can be provided by a water-heating appliance (i.e. a boiler), or can be waste heat recovered from some other process. This type of hot water production is usually confined to commercial or industrial uses. These units are also "indirect storage" units.
Commercial Water Heaters (Boilers)
This method of heating water is similar to the instantaneous method. Water is heated as it passes through the water heater and may then go directly to the point of use or pass into an insulated storage tank. Circulation may be by natural convection but is more frequently pumped. Commercial water heaters are used where large quantities of hot water are required and are often connected to calorifiers to provide an indirect storage system.
The term "boiler" is commonly used to describe these appliances. The term "boiler" does not apply to appliances, which heat water or other liquids to a temperature lower than the normal atmospheric boiling temperature of the liquid.
Classifying By Storage Pressure
- Mains pressure units: Water is stored and delivered at mains pressure so hot and cold water is at the same pressure.
- Reduced pressure units (medium pressure): Pressure limiting valves, reduction valves, ratio valves or overhead feed tanks connected to the cold water connection of the water heater reduce the pressure of the delivered hot water to below that of full mains pressure.
- Gravity units (low pressure): A cold water cistern fitted to the storage tank ensures the water is stored at atmospheric pressure and gravity is used to distribute the hot water to the points of use. This system relies on the storage tank being located well above the draw off points.
Classification By Distribution Method
- Single point units: These are designed to supply water to one tap only. The water heater may be of the instantaneous or storage type.
- Multipoint units: These units have sufficient water flow capacity and thermal input to provide consistent supplies of hot water to several taps simultaneously. Again, these units may be of the storage or instantaneous design.
- Push through units: Also known as "free outlet" water heaters, these units store water at atmospheric pressure, but when the tap is opened mains pressure water is delivered. This is achieved by controlling the cold water supply to the water heater by what appears to be the hot tap at the point of use. On opening this tap, cold mains pressure water is allowed to enter the storage tank and push the hot water out of an uninhibited outlet at the point of use. When the tap is closed, the water in the storage tank returns to atmospheric pressure.
Simon Totterdell - Owner
Call Now - 99043074