Over the coming years, the number of heat pump installations are expected to significantly grow, and the number of installers entering the market will also increase as the installation of fossil fuel appliances decline. 

Installing an air source heat pump is not the same as installing a gas or oil boiler. It is, therefore, crucial that all heat pump installers understand not just how to install, but why they should install a heat pump system in a specific way. Grant, like all manufacturers, needs to equip installers with this knowledge and provide the products to help achieve this success in the field.

Just as there are many types of system to consider (old or new, underfloor or traditional radiators, micro or mini bore pipe) there are many solutions available to the installer, each one with a different feature or benefit to assist the system operation. 

Some installers may prefer using a large 250l buffer, if they have the space (or a small 30l one if they don’t), some may prefer complete hydraulic separation by using a plate heat exchanger, and some that see the benefits of a traditional low loss header.

This leads me onto the use of a combined volumiser/low loss header. There are many factors that can affect the performance of a heat pump – incorrect flow rate, high pressure drop in the pipework or heat emitters, lack of control to balance the flow rate in each zone, to name but a few. Failure to address one or all of these could affect the performance of the heat pump and could be expensive to remedy after the event. 

While I am not discounting the benefits of utilising a buffer or plate heat exchanger (although the latter would still need a buffer on the heat pump side to provide the minimum water volume required for the heat pump) I have seen, first hand, the benefits (not to mention the ease of installation) of using a volumiser/low loss header.

As an example, the Grant combined unit is larger than a standard low loss header because it holds 11.5 litres of system volume and accommodates a 3kW back-up heater. The unit, which is manufactured using 3mm mild steel, incorporates 50mm insulation. It is also supplied with a 16A relay, two 28mm isolating valves, a ½” drain cock, a ¼” manual air vent, a reducing bush, and four blanking plugs. The heater can be controlled by the heat pump, the system controls, or by a separate air thermostat.

This unit has multiple functions but principally it serves as a volumiser and hydraulic separator – installers can enable their preferred set up, using the unit either as a volumiser or hydraulic separator. It provides an extra 11.5 litres to the system volume connected to the heat pump and it also gives hydraulic separation of the primary circuit of the heat pump from the secondary system circuit. 

This means that the flow rate/differential through the heat pump can be maintained, irrespective of the flow rate/differential required on the system side. 

The size of the unit also helps to minimise the internal turbulence that can occur when the system mass flow of water exceeds that for the primary heat pump circuit.

Furthermore, its factory-fitted 3kW electric immersion element provides a backup or supplementary heat source if required.

The combined volumiser/low loss header enables installers to separate the heat pump from the rest of the system and this is beneficial in many ways. First and foremost, the performance of the heat pump will be protected because the volumiser/low loss header is allowing the heat pump to maintain the target flow temperature while the system side can achieve whatever flow rate/differential is required to deliver the heat to the emitters. 

Secondly, the header can be used to pair two heat pumps together for larger systems, or even a heat pump with an oil or gas boiler. This works for even larger systems where the heat pump could only be expected to satisfy a portion of the overall heat loss.

This is not the only way to install a heat pump and there are experienced engineers who have their own methodologies which work extremely well too. 

The low loss header is just one way, but hopefully it provides engineers with an installer-friendly solution to futureproof their heat pump installation.

Heating Ventilating & Plumbing (HVP) magazine is the leading plumbing and heating magazine for installers, getting the news to you first and crafting unbeatable journalism to give you the professional edge over your competitors.

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