HeatpumpMonitor.org One-Year Data Anniversary

11th December 2023 marks the one-year anniversary of publishing Marsh Flatts Farm’s heat pump performance data to HeatpumpMonitor.org.

For those not familiar with HeatpumpMonitor.org, it’s an online dashboard showing real-world performance metrics for a range of different heat pump installations – mostly in the UK but with a few in other countries.

Main page of HeatpumpMonitor.org, filtered to only show systems with a full year of data

Almost all the installations are Air Source systems and most are Retrofits, replacing gas- or oil-fired boilers. I thought it would be good to contribute a Ground Source system, in a New Build property, for comparison purposes. The main motivation for adding my system was the cold snap forecast for mid-December 2022, with a period of below-freezing temperatures.

From the main page, the Blue icon on each row takes you to a page containing static summary information about each installation, and the Grey icon takes you to the ‘My Heatpump’ App page showing the operational data in a graphical format.

‘My Heatpump’ App View, showing data for the past Month (as of 2023-12-11)

The blue bars are the daily total Electricity Consumption and the yellow bars are the daily total Heat Output. The purple line shows the outdoor temperature (rather more relevant for Air Source systems) and the blue spots are the daily CoP values.

Clicking on one of the daily bars brings up a more detailed view, shown below:

‘My Heatpump’ App View, showing 24 hours of temperature and energy data up to 19:45 on 2023-12-10

The summary information below the graph is a recent addition, breaking out the different Coefficients of Performance for Hot Water (requiring a higher temperature so rather less efficient) and Central Heating – in both cases excluding the power consumption in ‘standby’.

Key Take-Aways

  • In the past year, my system has used 1242 kWh of Electricity to generate 4495 kWh of Heat, giving a Seasonal Coefficient of Performance (SCoP) of 3.62
    • I typically pay about 20 pence per kWh of electricity (on the Intelligent Octopus Go tariff, which is 7.5p for 6 hours overnight then 29.78p for the remaining 18 hours)
    • That means the annual cost for central heating and hot water is about £250, or less than £1 per square metre of floor space
      • Note that about three-quarters of the domestic hot water heating is done by diverting excess solar power generation to the immersion heater, not using the heat pump
  • My system’s SCoP is better-than-average but not great
    • It is significantly more efficient when it’s moving more heat – and it’s more efficient at the start of the heating season (i.e. November and December) when the ground is still relatively warm
      • When switched on without the compressor running (i.e. ‘standby’ mode) it’s consistently drawing 60W, roughly 20W for the circulation pump and 40W for the control system, with no heat output registered on the heat meters (although that heat is still going into the house)
      • Because of this, I switch it off completely over the summer months (end of April to end of September) – and these consumption figures reflect that

HeatpumpMonitor.org is thoroughly successful in meeting its stated aim of demonstrating that heat pumps work very successfully in UK properties and in the UK climate. This is real data from real installations, uploaded by real customers without any vested interests.

The associated Open Energy Monitor community forum (that pre-dates HeatpumpMonitor.org, which is a spin-off from the forum rather than the other way around) is full of knowledgeable and helpful people and is well worth a visit.

Paul Novus MVHR Fan Bearing Replacement

Woke up to a vague, persistent ‘mechanical’ noise somewhere in the house. After opening the door to the Plant Room it was immediately apparent the fan bearings on the Paul Novus 450 MVHR unit had failed – slightly surprising after only 6 years, but then they are running 24×7. The fans were still working and there were no errors on the control panel, but the noise wasn’t good – and I have enough experience with bearings to know they only ever get worse, not better. What was good was the sound attenuation on the MVHR ducts – the noise was only really obvious in the Plant Room and in Bedroom 2 immediately beneath it, so the noise was not being transmitted to other rooms via the ducting.

A quick Google search turned up the service manual for the Paul Novus with guidance on getting to the fans and the advice to replace the complete fan units: centrifugal housing, fan rotor, motor, electronics etc. (Estimated cost of £280 per fan.) I was hopeful it would be possible to just replace the bearings instead and proceeded with some dismantling.

I was very pleasantly surprised by the specification of the fans: embpapst units with part number G3G160-AD54-22. Really good build quality and the prospect of not being too difficult to repair. YouTube turned up an excellent video showing the dismantling and bearing replacement procedure.

Bearings are generally standard and pretty cheap and one of the great things about living in Derby, with its rich heritage of railway and aerospace engineering, is that there are some excellent suppliers of these sorts of spare parts located within a few miles. Derby Bearings Ltd don’t win any prizes for inventive business naming but they do offer an excellent service and carry good stocks – they had a couple of options in the correct size for only £4 each (£8 per fan).

The fans are now running quietly again and peace is restored. I’ve written a Technical Article with some hints and tips to make the job easier next time – or for other people attempting it for the first time.

I do wonder if the exceptionally hot summer weather contributed to the premature failure – could the heat have softened the lubricating grease in the bearings, causing it to leak out, making them more prone to rusting when the cold and damp weather returned?