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Don’t get into hot water with the wrong approach


One size doesn’t fi t all – and correct specifi cation is key when it comes to the right approach for each household’s hot water demand. Darran Smith, technical manager for Alpha, discusses the considerations for heating engineers when tackling a hybrid installation


T


he domestic heating sector will be going through a revolution over the coming years. With the new Future Homes Standard looming,


the government is regulating a shift away from traditional gas boilers and further towards a low- carbon future.


One option that we’ve been discussing with our


installers is a hybrid approach to heating and hot water provision. A heat pump is installed to provide space heating, with a boiler retained (or updated) for hot water. The hybrid system works equally well with a heat pump and combi, LPG or oil-boiler, so it’s a good option for off -gas grid homes too. But with hybrid and hot water provision, it’s not


necessarily one size fi ts all. The main consideration with all hybrid systems is to establish the overall heating demand and hot water requirement. Installers will need to understand the household’s demands and the constraints of the property to specify the best solution. Armed with this, you can look to one of two common layouts for a hybrid heat pump with boiler: 1. Combi boiler + heat pump The simplest and most compact layout is pairing a combination boiler with a heat pump. The boiler takes care of the hot water and backs up the heating in colder conditions, whilst the heat pump is dedicated to the main heating load. 2. Conventional system boiler + heat pump + cylinder The second option is to use a conventional system boiler combined with a heat pump and a hot water storage cylinder. With this layout, either the heat pump or boiler is drawn upon to provide the heat when required.


With many homes having limited space and a


combination boiler already fi tted, the fi rst solution is generally proving to be more popular and is arguably the best choice. Homeowners don’t suff er any losses in terms of a) needing to carve out additional space for a new cylinder, or b) factoring in recovery time whilst the cylinder recovers its hot water reserve. Plus, it


Renewables


costs less to install. However, for homes with large families who will have greater water requirements, the second option is the best choice as it has the benefi t of the larger cylinder. The fl ow rate is therefore not impacted by the size of the boiler and a higher hot water demand can be catered for. Either of these two layouts off ers a practical solution


for homeowners looking to not only reduce their monthly outgoings, but to also incorporate renewable technology and run a warm but more environmentally friendly household, with hot water readily available. Regarding effi ciency, a hybrid system chooses the best heat source depending on energy prices and temperature. It also has the advantage of being able to work in both higher demand situations and systems where design or heat losses are not at their optimum. This is because you always have the back-up of a boiler to top up the shortfall. A commonly raised topic with hot water, especially


with heat pumps and renewable input, is the need to raise the water temperature to at least 60ºC on a regular basis to remove any risks of legionella bacteria. Regardless of which layout is used, your customers needn’t worry. With a combi, there is zero risk as no hot water is


stored at any point. And with a conventional set-up, the boiler is used to heat the cylinder to the necessary level to eradicate any risk. Regardless of which hybrid boiler/heat pump


approach is taken, it’s vital to understand the requirements of this sort of system and you’ll need to ensure that it’s set up correctly for optimum heating and hot water performance. Diverting away from the familiar scope of a pure gas boiler installation may feel a challenge. However, it also provides an opportunity to extend your business into new areas; and support and training is available out there in the industry to help you on this journey.


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