Want to connect your solar heating system to your central heating system? Of course you can!
The longer answer is – it’s complicated, and there are some things to take into consideration.
Let’s say you have a solar hot water heater. You’re also considering installing an underfloor central heating system to keep your house warm in winter. Makes sense that the heat from the solar could also be used to heat the floor, right?
There are a few considerations. First, the solar will generally produce hot (almost boiling!) water. The heat pump will produce water around 40°C. If we put the water from the solar panel into the floor, the floor will get too hot to walk on. So we need a mixing circuit to mix in cold water to get an appropriate temperature. All the extra equipment costs money.
We also have to consider the working fluid. The water flowing through the solar panel will probably have a glycol dose, so that it doesn’t freeze when it’s on the roof at night. The underfloor heating system uses a different fluid. So we can’t easily mix the two.
The easiest way to combine the two systems is to use the solar to heat your domestic hot water, and use the heat pump to heat the floor.
All solar systems need a ‘boost’, to heat the water when there’s not enough sun. Normally this is either electric or gas. We can use the heat pump for this, although it requires the right control system.
The main thing to keep in mind is that the solar system will provide most benefit during summer, and the heating system will only be turned on during winter. So often, there’s minimal benefit to trying to combine the systems together.
So in summary, before you commit to combining your solar and central heating systems, have a look into the additional costs of doing so and make sure that the extra savings are really worth the effort.