She's electric

Electric heating is becoming more and more popular, and offers excellent business opportunities for the electrical contractor.

Some industry analysts are predicting that electric heating systems could even become more popular than gas boilers. It’s not hard to see the attraction for developers of smaller properties such as flats, and in particular landlords. With an electric heating system there’s no need to run a gas main to the property, or to find somewhere to put a flue or chimney. And for landlords, there’s no requirement for an annual gas safety inspection and certificate.

Increased levels of building insulation and double glazing have also meant that less energy is needed to heat modern homes, so electric heating has become a viable alternative to gas. Also, the government’s renewables obligation means a larger proportion of electricity now comes from greener sources such as wind turbines, making electric heating a more environmentally friendly choice.

For new-build properties, there are targets to be met in terms of the total carbon emissions of the building, and these are outlined in Part L of the Building Regulations. This is calculated by taking into account factors such as type of heating, room size, insulation, double glazing and the size of openings such as doors and windows. Further guidance on Part L is available from the Communities and Local Government department’s website, which can be found at www.communities.gov.uk.

In addition, good practical guidance is also available from many manufacturers and suppliers, showing the different products available as well as installation techniques. The majority of manufacturers also offer a design service and will tailor-make the heating equipment to a specific room size, shape and heating output required.

Compared with traditional wet systems, warm-air heating and off-peak storage heating, electric underfloor heating can usually be installed with minimal disruption, and often without the input of other trades or extensive building work.

Provided that a suitable power circuit can be made available, electric underfloor heating can be installed in a particular room or areas, without extensive work elsewhere in the property, which makes it ideal for retrofit or extensions.

Another advantage of electric underfloor heating systems is that they are easy to control locally, using time and thermostat control. Rooms can be separately controlled, so a different timer can be used for a bathroom area, which might only be used twice a day. This gives ease of use and convenience to end-users, as well as assisting in meeting Building Regulations obligations.

The Wiring Regulations 17th Edition (BS 7671:2008) now devotes a whole chapter to underfloor heating, treating it as a ‘special installation’. Chapter 753 gives clear, easy-to-follow requirements that are generally straightforward to implement in any installation.

Compared with traditional wet systems, warm-air heating and off-peak storage heating, electric underfloor heating can usually be installed with minimal disruption, and often without the input of other trades or extensive building work

BS 7671 requires automatic disconnection of underfloor heating systems, with residual-current device (RCD) protection not exceeding 30 mA. In a new installation this should be easy to implement, since this level of RCD coverage is required elsewhere in the regulations, notably to protect the majority of cables in walls and socket outlets.

Likewise, with a retrofit installation in an existing building, the RCD protection could be provided locally by use of an RCD spur, for example.

A maximum floor surface temperature of 35°C is stipulated where bare-skin contact is possible, for example in bathrooms. Maximum allowable temperature elsewhere is given as 80°C. Different systems are available from manufacturers that take these requirements into account, providing the manufacturer is made aware of where the system is going to be used.

There are also different types of electric underfloor system available, depending on the floor type. These include wood, tile and carpet.

BS 7671:2008 requires that floor-heating sheets be manufactured to BSEN 60335-2-96, and heating cables to BS 6351. Although these are manufacturing standards, the installer should take care to follow the manufacturer’s instructions so as not to damage the heating equipment during installation.

Chapter 753 of the 17th Edition gives clear guidance on identification and labelling of heating systems. Due to the concealed nature of the heating, it needs full labelling, and detailed records should be kept.

In particular the following is needed:

• Records of equipment installed
• Manufacturer information
• Location details, including measurements, if necessary
• Power loading details
• Instructions
• Level of cold-state resistance of elements.

When installed correctly, electric underfloor heating offers many benefits for householders, developers and landlords. The 17th Edition clearly identifies installation requirements, and manufacturers can also offer essential guidance on design and specifications.

And finally, once your electric underfloor heating system is installed, don’t forget that it requires notification under Part P of the Building Regulations.