Domestic hot water
Domestic Hot Water
Application guide
Intelligent solutions with lasting effect
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Table of content
1. Application overview |
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2. System Description |
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3. System design |
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3.1 Heat loss calculation |
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3.2 Product selection |
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3.2.1 Heating cable selection |
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3.2.2 Thermostat/Controller |
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selection |
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3.2.3 Accessories selection |
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4. Safety instruction |
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4.1 DO's |
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4.2 DON'Ts |
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5. Case stories |
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6. Technical support |
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Our quality management system 
and compliances
ISO 9001 |
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TS 16949 |
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ISO 14001 |
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PED |
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Along with full compliance with EU directives and product approvals
Let DEVI do the work
DEVI - an abbreviation of Dansk El-Varme Industri - was established in Copenhagen, Denmark, in 1942. As from January 1st 2003 DEVI has become a part of the Danfoss Group - Denmark's largest industrial Group. Danfoss is one of the world's leading companies within heating, cooling and airconditioning. The Danfoss Group has more than 23.000 employees and serves customers in more than 100 countries.
DEVI is Europe’s leading brand of electric cable heating systems and electric pipe heating systems with over 70 years of experience. The development of electric floor heating system takes place in Denmark, where the head office is situated while heating elements (cables and mats) are manufactured by Danfoss in EU.
Domestic Hot Water temperature maintenance system
This design guide presents DEVI’s recommendations for design and installation of Domestic Hot Water system. It provides guidance for a heating cable layout, electric data and system configurations.
Following DEVI’s recommendations will ensure energy efficient, reliable and maintenance free solution for constant wattage heating cables with 20 year warranty, self-limiting heating cables with 5 years of warranty.
1. Application overview
Modern living requires buildings to have hot water available whenever and wherever needed – and preferably immediately. The building regulations demand domestic hot water systems to ensure best comfort and efficiency as well as the Legionella control measures.
DEVIhotwatt™ systems ensure continuous and reliable supply of with the possibility to disinfect Domestic Hot Water (DHW). DEVIhotwatt™ is a self-limiting heating cable that is
used for temperature maintenance of hot water supply.
DEVIhotwatt™ systems compliments domestic hot water systems and enables the unique possibility to temperature control and disinfect, both for circulation systems and uniquely also for single pipe systems from source to tap.
DEVIhotwatt™ systems complies with IEC 62395-2:2013.
Benefits
•Unique opportunity - allows the installation of a single pipe hot-water system, that includes thermally controlled and disinfected hot water at the tap.
•Lower initial investment the electric pipe tracing in DHW system without
circulation requires less pipes and insulation (approximately 50%), less valves, less pumps and installation labor compared to the recirculating system.
•DEVI pipe tracing systems ensure hot water in all taps and savings when a circulating pipe system is unnecessary.
•DEVI heating cable reduces water waste as you can get hot water immediately.
•Protection against Legionella – DEVI system maintains water supply at the required temperature level and provides disinfection to combat the bacteria.
•DEVIhotwatt™ system is the Perfect solution to be used in domestic hot water systems. Including systems supplied by low temperature district heating.
•Energy efficient - Self limiting heating cables provide power where needed, adapting their output according to the ambient temperature. Less pipes and smaller boilers will in term mean lower heat losses.
•The heating cable is flexible and easy to install as it can be cut to length, right on site and installed directly on the pipe system.
4 Application guide · Domestic hot water · ©DEVI
2. System Description
Since 1998 the EU Drinking Water Directive (98/83/EG) in EN 806-2 has established standards for hot water in pipes that should not drop below 50 °C. The building regulations as well as global trends are demanding DHW systems to provide the best comfort, energy efficiency and the Legionella mitigation measures.
General design principles aim to provide uniform water temperature, which should also enable temperatures to combat Legionella growth.
The general recommendation for DHW is to maintain the heat source temperature between 50-60 °C (IEC 62395-2:2013).
Water heating is provided by centralized or decentralized sources, Centralized water heating systems (district heating) often have large distribution network that might contribute to temperature inconsistencies. According to IEC 62395-2:2013 guidelines: ”For disinfection purposes min 55 °C is typically required for hot water installations fitted with mixing valves”.
In the case that the water temperature of DHW systems cannot achieve the recommended level, risks of possible water waste and Legionella will arise, therefore a supplementary electrical tracing system is recommended.
The Legionella bacteria which is commonly found in many types of water worldwide. The bacteria can create a potentially fatal type of pneumonia commonly by inhalation.
The Legionella bacteria multiply best where temperatures are between 20-45 °C and nutrients are available. A method used to reduce the risk from the Legionella bacteria, is to control the water temperature, which is easy to do with help of DEVI pipe heating system .
The DEVI pipe heating system for DHW, maintains the water at the desired nominal temperatures or heats (disinfects) it when needed.
1800 |
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1600 |
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1535 |
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1389 |
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1400 |
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1200 |
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1018 |
1000 |
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800 |
664 |
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600 |
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400 |
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393 |
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200 |
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0 |
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France |
Germany |
Italy |
Netherlands |
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Source: ECDC Annual Epidemiological Report for 2017
DEVI Pipe tracing systems will be required in the following cases:
•Low-temperature, heat source is supplying DHW at lower than 50 °C
•The ambient temperature variation is significant
•Tap is located so far away that the hot water temperature is not properly maintained
Source: ECDC Annual Epidemiological Report for 2017
Temperature and disinfection time
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Time settings for thermal |
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70°C |
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disinfection |
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ture of |
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60°C |
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disinfec- |
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Recomended |
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tion [°C] |
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50°C |
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55 |
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2 h 00 minute |
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40°C |
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30°C |
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60 |
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0 h 40 minute |
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20°C |
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65 |
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0 h 26 minute |
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70 |
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0 h 20 minute |
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75 |
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0 h 10 minute |
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At 70°C pasteurization process takes 20 min
At 58°C pasteurization process takes 50 min
At 50°C Legionella will no longer multiply
Ideal growth range |
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35-46 °C |
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Application guide · Domestic hot water · ©DEVI 5
Heat tracing in DHW (Domestic Hot Water) systems
DHW system, single pipe system
(without circulation) - the cable modifies its output and thereby temperature according to the conditions along the installation. This means that the DHW system is heated corresponding to heat losses, thus maintaining and/or controlling the temperature.
The more often the hot water tap is turned on, the less the hot water temperature maintenance system needs to be activated assuming a water supply with a higher or equal temperature to the respective requirement.
DHW system with circulation - continuous circulation of hot water to ensure that hot water is available at any of the taps.
In case of DHW with circulation - pipe tracing can be installed to ensure loop temperature. Thereby aiding the system to maintain temperatures at the required level.
DHW systems can also be installed to secure pipes where circulation can't be provided to ensure the wanted/ needed temperature.
Self-limiting heating cable
Self-limiting heating cable
The DEVIhotwatt™ pipe tracing in DHW system without circulation requires less pipes, less valves, less pumps and installation labor compared to the Recirculating system.
•Approximately 50% less pipes – less water volume in the pipes, thus smaller boiler can be used.
•Energy consumption reduction, as heat losses from the pipes will be reduced by a significant amount.
•Less maintenance cost, as less mechanical parts and pumps.
•Saving water – DEVI pipe heating system attached to the pipes keeps water at the desired temperature along the pipe system, so hot water is immediately provided, when demanded, and with minimum water loss.
The DEVI pipe heating system insures that DHW is supplied, independent of
the pipes length, and reduces the risk of localized temperature fluctuations by heating only where needed.
DEVI pipe heating system is insuring automatic maintenance of the required temperature 24/7.
6 Application guide · Domestic hot water · ©DEVI
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