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A smooth transition to a greener future

Heat pumps are already playing a big part in decarbonising commercial buildings, a role that is only set to increase as the UK heads towards Net Zero. Stewart McGillivray, from Guardian Water Treatment, looks at the steps M&E contractors and building managers need to take, to ensure successful heat pump retrofit in existing applications.

The electrification of heat is a crucial part of the Net Zero roadmap, with heat pumps leading the charge when it comes to ending our reliance on fossil fuels. Apart from having the potential to offer carbon neutral heating (and cooling), heat pumps provide a host of long-term benefits, future-proofing buildings and providing a single solution for all temperature control, including zoning options for complex commercial sites.

Generally, heat pumps require less maintenance and last longer compared with gas boilers and associated HVAC. And, while the price of electricity may be high at the moment, it will come down in the future, with our transition towards a totally renewable grid further enhancing the carbon saving benefits of all electricity-based heating.

Heat pump upgrade checklist

Initial assessment: The first step in a heat upgrade is an energy audit and assessment of your current heating system. Determine your property's heat load, insulation, and the type of heat pump system that best suits your building’s needs. Consider the layout of your commercial space and the environmental factors that might affect the heat pump's performance.

Selecting the right heat pump: Based on your assessment, choose the appropriate type of heat pump. Air Source Heat Pumps are often more cost-effective for smaller commercial spaces, while Ground or Water Source Heat Pumps may be more suitable for larger properties.

One of the big benefits of upgrading to a heat pump is that it can potentially provide heating and cooling – at different times of the year or simultaneously, depending on the varying demand of indoor zones. This streamlining of functionality makes the cost implications in a commercial upgrade less stark. For example, where a building had ‘traditional’ heating and cooling, using gas boilers, air handling units, fan coil units and electric chiller cooling, the upfront expense of replacing these systems can make a reversible heat pump more economical.

Site preparation: Installing a heat pump may require some modifications to your building. For ASHPs, an outdoor unit needs to be installed, which should be situated in a well-ventilated location. GSHPs require digging trenches or drilling boreholes for ground loops. Ensure the site has the necessary space and access for these installations.

Heat pumps are not like for like replacements for gas boilers or conventional electric heating which is why system design is so important. One of the main changes is flow temperature, heat pumps operate best at low temperatures, so it’s important than any existing heat emitters – radiators, underfloor heating – have been sized correctly.

Performance must also be optimised with adequate heat loss prevention, such as suitable insulation. While a heat pump can work in pretty-much any application, the benefits are magnified considerably where efficiency levels are high. A key part of a heat pump upgrade should be a holistic approach to energy performance, which extends to every part of the system, including the pipework.

Pipework performance: Where possible, we advocate retaining as much of the existing pipework as possible, but in doing so the design should be reviewed to ensure that the new capital plant will be protected from the ingress of debris, and can easily be cleaned and commissioned. Debris and excess dissolved oxygen within a system can lead to corrosion and leaks, compromising system efficiency and therefore negating the benefits of choosing a heat pump in the first place.

Works should be phased, with a pre-works validation of the existing system’s water quality and hydraulic performance. Retained pipe work surfaces must be inspected and sent for surface microscopy to determine if there are potential problems but also to give peace of mind; this pipework must also be passivated correctly - any corrosion present will attack the new, un-passivated pipe work.

Based on survey and existing records, a bespoke cleaning strategy can then be implemented - for the new pipe work and conditioning of the existing pipe work.

Monitoring: The best way to have a true picture of system condition throughout all phases of the upgrade and, ideally, beyond, is real-time monitoring, recognised as the most effective way of ensuring corrosion is prevented before it even starts.

24/7 remote monitoring provides an accurate picture of what is going on inside the pipework continuously, with results recorded every 15 minutes to determine peaks and troughs in corrosion rates throughout the build.

In the interest of sustainability, which any building owner/manager choosing a heat pump will be focussed on, real-time monitoring also saves water by potentially avoiding the overuse of flushing and chemical dosing. Rather than a knee-jerk reaction to a sample, monitored systems can be maintained in a more measured fashion. If unstable readings return to normal quickly, then in most cases no further action is required.

Post works, monitoring provides validation of hydraulics and water quality. We recommend monitoring corrosion indices for a period of time, say one year, to align with seasonal commissioning, essential to proving the performance of the new heat pump system.

21 December 2023

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