The increasing use of HIUs

Heat Interface Units (HIUs) are increasingly being used to deliver heating and hot water to individual properties within multi dwelling developments with a centralised plant room. Jon Cockburn, head of marketing at Heatrae Sadia, explains the reasons behind this trend.

HIUs, sometimes referred to as 'heat boxes', are used in conjunction with centralised plant and are designed to serve individual flats and apartments. They can be used to provide heating or heating with domestic hot water.

Historically, each individual property in a multi dwelling scheme would have its own separate heating system - typically comprising a combi boiler or electric heaters. However, this approach has presented issues for developers and installation and maintenance teams, many of which can be resolved by using centralised plant and HIUs instead.

For example, it was becoming increasingly challenging for developers to meet their CO2 compliance targets by using individual heating appliances. In contrast, centralised heating plant offers increased efficiencies, and can help developers to meet their targets, whether using traditional fuels or low carbon and renewable technologies.

With centralised plant, using technologies such as biomass, solar thermal water heating and CHP actually becomes simpler and more achievable, as it can be difficult to incorporate these technologies into individual properties in a multi occupancy scheme. The diverse thermal loads offered by multi occupancy accommodation also presents an attractive demand profile against which such technologies can be operated to maximise the benefits.

Using centralised plant also reduces the problems associated with supplying gas to multi dwelling buildings. It decreases the risks linked to gas distribution pipework, and eliminates the need to fit numerous flue terminals and condensate drainage systems. The capital installation and whole life costs are therefore reduced.

The time and costs involved with boiler installation, servicing and maintenance are also significantly reduced. Furthermore, using centralised boiler plant in rented accommodation schemes eliminates the need for landlords to carry out legally required gas appliance checks in individual properties, for which gaining access is often an issue.

It is possible for a developer to opt for centralised plant without installing HIUs in each property, but without them there will be no way to control the heating or monitor usage. As well as delivering heat, HIUs provide temperature control and also record the heat consumed by an individual dwelling, so can therefore assist with the metering/billing of an individual household's energy use.

If a HIU is used, meter reading and energy billing can be carried out remotely from a central location, which could be very attractive for councils and those operating a large portfolio of buildings. Metering can also be a positive incentive for occupants trying to lower their energy consumption and can help to reduce fuel poverty among vulnerable groups.

HIUs can be installed within each individual dwelling, or in the dividing wall between each dwelling and the 'landlord' space - the latter providing easy access for inspection and maintenance.

The Hi-Max Instant ID from Heatrae Sadia has a compact design and comprises two generously sized plate heat exchangers - one for the hot water, and one for the heating system - and is designed to ensure that the primary return temperatures going back to the centralised heating system are very low to maximise the operating efficiency of the system. A controller monitors and regulates the heating and hot water system in order to optimise performance, working with the room thermostat.

It features a low energy pump and fully modulating pressure independent flow control technology for automatic balancing and fine temperature control, and its compact design means that it can fit in a standard kitchen cupboard. In addition the scale reduction feature keeps the appliance low maintenance.

Suitable for single and dual zone heating systems, the HIU can be specified in new build properties where Building Regulations require a minimum of two space heating zones.

The Hi-Max Instant ID is KIWA approved, and also carries the NEMKO N mark, which demonstrates that the product has been assessed for conformity to electrical safety legislation by a competent body.

In recent times there has been a trend towards centralised plant being used alongside HIUs to deliver heating and hot water to individual properties in multi dwelling developments. In comparison to the traditional approach of fitting individual heating systems in each flat or apartment, this offers many benefits for developers and installation, servicing and maintenance teams.

For further information please call 01603 420 220

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