The future of residential controls in commercial buildings is very exciting and has great potential for growth in the building controls industry, according to Ash Goyal
The use of controls in domestic gas central heating systems has been standard practice since the introduction of the 'Guaranteed Warmth' campaign of the 1970s. For over 40 years control manufacturers have been working to provide effective domestic control systems that are straight forward to install, understand and operate.

The original design of pumped central heating and gravity fed domestic hot water storage has been replaced by sealed systems, condensing combination and system boilers and mains fed hot water cylinders.

Designers and installers are very familiar with programmers, thermostats, sensors, motorised valves and thermostatic radiator valves that are now a widely accepted part of the domestic controls 'culture'.

Innovation has also kept pace with the latest central heating designs. Digital touch screen programmers are available to provide wireless communication with boilers, zones and if required individual radiators.

However the demand for high density housing located on expensive land, combined with legislation on carbon release and fuel economy are changing the way we design residential buildings. The once clear differentiation between a domestic and commercial heating systems is becoming blurred and more complex.

Heating used electricity


Conventionally, domestic central heating has been considered to be a system where consumption of fuel was contained within the individual property i.e. a gas, oil or solid fuel boiler.

The heating of multi-residential flats has, until comparatively recently, been addressed primarily by electricity i.e. underfloor, panel and storage. In general this has been driven by installation cost, engineering complexity and in the case of gas central heating, safety aspects related to high rise buildings.

Legislation and climate change awareness are now ensuring that a new approach has to be made when supplying heating to multiple houses and apartments.

A bigger picture view has to be taken of the usage and efficiency of fuel use in the design of heating systems.

For example, the consumption of carbon based fuel has to be minimised by maximising the release of heat energy and generation of electricity i.e. combined heat and power. This also has to be supplemented by renewable energy carbon sources such as burning wood pellets (bio mass boilers).

This approach transforms a housing development from a multitude of domestic gas boilers and electric heaters to a centralised 'Energy Centre' which provides all the heating, and often a proportion of electricity, for the complete site.

The heating is now supplied by hot water via a distribution network to individual houses or apartment blocks; this is often referred to as a Community Heating Scheme.

The Energy Centre is the core of the community heating scheme. A typical installation would include gas boilers, combined heat and power units, bio mass boilers, thermal storage, buffer tanks, heat pumps and chillers if cooling is required.

The individual pieces of equipment would be mechanically and hydraulically integrated to ensure that energy was supplied to the houses and apartment blocks in the most fuel and emission efficient combination.

For example if there was a high call for domestic hot water in the mornings for showers, the Combined Heat and Power (CHP) plant would be utilised to provide electricity from the generators and thermal energy from the exhaust gases. If the hot water demand was higher than the supply, gas boilers could be brought on line to supplement the CHPs.

During the winter when there is a predictable high demand for heating, the bio gas boilers would be utilised to provide the base load with CHP and gas boilers on standby.

Control of the Energy Centre is complex and is provided by a building management system which supervises the plant and equipment to ensure safe and efficient operation.

Graphical displays inform the facility managers and maintenance staff of the status of the installation, which is also monitored and alarmed to ensure awareness of any exceptional occurrence or situation.

But what is happening in the individual houses and apartments? How is the thermal energy utilised and how is it controlled in each home?

Quite simply the individual gas central heating boiler is replaced by a heat exchanger that supplies heating and domestic hot water. These heat exchangers are called Hydraulic Interface Units (HIU) and act as the connection between the mains supply distributed from the Energy Centre and the hot water and space heating in the domestic dwelling.

A distribution network pumps the hot water service utility from the Energy Centre to each building in the local area. In the example of a block of flats, a satellite unit controls the supply to each individual apartment.

There are a number of options available when designing the heating system. Taking the example of an apartment and the type of HIU required; the main factor is the utilisation of the domestic hot water supply. Although centralised storage for the whole building is an option, the main focus in the UK has been on individual domestic hot water supply for each apartment.

As in the gas central heating system described earlier, domestic hot water is supplied instantaneously or by a hot water tank located in the apartment. The HIU consists of plate heat exchangers, pumps, valves and thermostatic controls and can be considered to be the equivalent to the domestic gas boiler. Instead of a gas meter to measure consumption a heat meter is supplied that measure the amount of thermal energy supplied to the apartment.

The hot water arrangement is dependent on the size of apartment or house in the community heating scheme and is aligned with the occupant's lifestyle. The single business professional is likely to have early morning demands for hot water; whilst the central heating load during the day can be quite low. Conversely a retired person could have a later demand for hot water but an almost constant demand for heating.

In both these scenarios the design would suggest HIU arrangement providing instantaneous hot water supply.

A large family would have a higher hot water requirement and may be better served with the HIU plate heat exchanger serving a hot water cylinder.

Wireless programmers


Controls for these systems are very similar to those seen in a typical domestic gas central heating.

Wireless time and temperature programmers would be ideally suited for a panel radiator system, switching on the HIU pump for the heating, with thermostatic radiators for individual rooms.

Where instantaneous domestic hot water is specified the pressure and temperature controls would be integral with the HIU, and in the case of thermal storage included in the Domestic Hot Water (DHW) cylinder unit.

The major difference in Community Heating Schemes is the higher incidence of underfloor heating. This is particularly true in more expensive, residential complexes where cooling is sometimes included as an option.

Zone control of under floor heating is an essential requirement with the option of wireless or wired time and temperature programmers. The HIU would have mixing valves and appropriate limiters to ensure lower temperatures to the underfloor circuits.

Often community heating schemes are a combination of social housing and private residential. This necessitates a wide spectrum of controls, from basic programmers to internet based systems accessed via PC's, smart phones and tablets.

Interestingly, although primarily a domestic system, often the most sophisticated controls are seen in expensive residential property. In these situations building services and lighting are often integrated with state of the art communication and audio visual packages. These give the home owner total control of their environment through touch screen and voice commands.

//The author is Ash Goyal, technical sales specialist at Honeywell //