Keeping hot water hot in a large domestic hot water system can use a lot of energy. Today’s market is calling out for more cost efficient and environmentally friendly solutions, to the point that current building regulations now require architects and building services engineers to actively seek opportunities to reduce energy consumption.
Not surprisingly, the energy required to temperature maintain the domestic hot water system represents a higher proportion of the current energy needs of a building. Therefore any energy saving that can be achieved on the hot water distribution will have a larger percentage impact on the total energy reduction over most other services.
Re-circulating hot water system
The conventional way of distributing hot water throughout a building is a flow a return system (re-circulating hot water system) that constantly circulates hot water fed by a storage tank around the building, returning to the water heater for re-heating after it has cooled within the distribution pipework.
The main design principle of the re-circulating hot water system is simply the temperature of the water at the tap outlet, with no consideration for energy efficiency or water wastage.
This is in complete contrast to electric trace heated single feed distribution systems.
Trace heated single feed system
Hot water temperature maintenance trace heating solutions addresses the key need of hot water at the point of use, whilst also reducing power consumption and water wastage, as well as offering the option to disinfect periodically against Legionella.
Hot water temperature maintenance is achieved by fixing your selected self regulating heating cable along the hot water pipes to compensate for any heat loss. By installing trace heating, under thermal insulation, the hot water in the pipework can be maintained above its minimum required temperature (usually +55°C or +65°C) in a predetermined minimum ambient temperature (usually +18°C).
Our H2OWAT hot water heating cable continually adjusts its heat output to equal the heat loss from the pipework. As the pipe temperatures falls under no-flow conditions output increases. As the pipe temperature increases under hot water flow conditions, output from H2OWAT decreases.
Trace heated single feed hot water systems offer particular benefits in large buildings such as hospitals, school, hotels and commercial premises where a significant proportion of the overall energy consumed is by the hot water services across many tapping points. In addition to energy efficiency a trace heating system also provides space, material and installation time/cost savings and reduces water wastage.
Due to the trace heating system reducing the amount of waste water this satisfies the requirement of Part G of Building Regulations in regards to waste or undue consumption of water.
The use of insulation is required on all systems as insulating distribution pipework can improve the efficiency of the hot water system by around 70% (Stephen and Mason, 1987) this data is based on a domestic system, so for larger commercial buildings the potential heat losses that the pipework would experience are unacceptable.
Estimating the energy and water wastage is very difficult as it depends on the frequency of use, amount of water which needs to be run off (dead leg), and the behaviour of the users.
A well insulated re-circulating system is only about 55-60% efficient compared to that of an insulated trace heating system which improves the system efficiency to 75% and effectively doubles the volume of useful hot water available.
As with any heating system it is more economical to maintain a temperature than it is to continually re-heat a material.
Heat loss from a re-circulatory system would be twice that of a trace heated system (double length of pipework) plus the cost of reheating water. Running costs would be dependant upon the rate of water circulation but with losses and reheating, would certainly exceed those of a trace heated system.
The combination of hot water maintenance trace heating and the correct thermal insulation will:
- Reduce the amount of pipework (as much as 50% less) required to supply the hot water by removing the need for the ‘return’ part of a flow and return system
- Remove the need to ‘heat’ and then ‘re-heat’ the water as required by a flow and return system. Reducing the power needed to heat raise the water
- Reduce the amount of water wasted whilst waiting for the hot water to reach the outlet
- Allow for periodic purging of the hot water pipework system to protect against Legionella
Trace heated systems are simple to install and very reliable, with low maintenance requirements, are efficient in reducing the need for water re-heating and eliminate return pipework, pumps and control valves.
Capital costs are reduced, water is saved by eliminating ‘dead leg’ waste and system efficiency is increased.
* For more information, please contact ESH Trace Heating Ltd *