Controlling the ground source heat

Or rather why we aren’t controlling the ground source heat pump!

A ground source heat pump extracts heat out of the ground to heat the house.  It works most effectively once the house has reached it’s target temperature.  At this point, the heat pump just trickles heat into the building to ensure that it stays at the set temperature.  In fact, it will often use additional energy from an immersion heater to get the house to it’s set temperature.

It can take a long time for the fabric of the house to warm up – in our case, it took a couple of weeks from a standing start.  However, I still suspect that the fabric of the house is warming up and drying out.  Let’s not forget that only a few months ago this building was open to the elements.

With this in mind, the NIBE engineer has told me to set the heat pump going and not to change it according to a schedule, or even when we go away on holidays.  If we were away for a few days, there would be little point in turning the heating off – it would take 3-4 days to cool down and then 3-4 days to warm up.  And we would probably use more energy in the process than we would if we just left it on all the time.  Let’s not forget with no one here, the windows and doors stay shut and the house is well insulated.  So heat loss would be a minimum.

It does, however, make sense to turn the hot water off.  It only takes around an hour to generate a full tank of hot water and that is from a standing start.  If the tank was full of hot water when it was turned off, it might only take 30 minutes to warm up depending on how long it had been turned off for.  I need to investigate how we can achieve this.  More updates later.

In terms of the other controls, we may control the secondary hot water pump (this pumps the hot water around the property to ensure that you get hot water out of the tap within a couple of seconds) and the valves for the towel rail circuits (there are two – one of the old part of the property and one for the new).  It will be very straightforward to control these using the Loxone kit.  We can set up schedules, over ride buttons as well as being able to access the controls remotely.

But other than that, there is little to control on the heat pump.  We have installed the latest software on the heat pump and this is automatically control the flow rates of the pumps to the underfloor heating and ground loops.  There are thermostats in all of the rooms that control the zone heating.  It would be straightforward to replace these with temperature sensors and actuators controlled by the Loxone kit, but it would have little benefit over what is already installed (re-badged Heat Miser units from NuHeat).