Category Archives: heat pump
We seem to be on a bit of a roll with the ground source heat pump. Last week we finally sorted out the leak in the ground loops that had been plaguing us for the last 6 months. Today our application for the Renewable Heat Incentive got approved. We applied for it at the end of July and it looks as if our first payment will be at the end of October. The incentive is paid on a quarterly basis, so this means that the approval today means that our first payment is exactly 3 months from when we first applied.
The current tariff is 18.8p for every kWh generated. According to our EPC, it has been estimated that we will be generating 35,405kWh per year. A quick bit of mathematics will show that this generates a payment of around £1,660 per quarter. These payments are for 7 years and by the time we reach the end of this period, it should have re-couped the capital that we invested in the ground source heat pump.
We have installed our own electricity monitor (Owl Intuition) so we know exactly how much electricity that we are using. While we are going to have to wait to see how the heat pump, and the house, performs over the winter, current indications are that we are using between 150kWh per week in the summer to around 1,000kWh in the winter (this includes all of our heating, hot water, lighting and cooking). We will have to see how it all pans out…..
This time last year we were installing the ground loops in the top field. And it looks as if we have finally located and fixed the leak. It was only a slightly leak, but over a two week period we would lose all of the pressure in the ground loops.
The ground loops themselves were put under pressure once they were installed and while the ground was being back filled. This would have enabled us to detect if there were any problems. In the end, the ground loops were under pressure for a few months without losing any pressure. So we knew this wasn’t going to be the problem. We had checked (and rechecked) all of the manifolds in the manholes. Again no problems. This only left the large pipes that feed the manifolds.
The leak was on one of the compression elbows on the large 63mm pipes. Unfortunately, the leaking elbow was not in one of the manholes and this meant digging a hole – a big hole. Once the joint was exposed, it was cleaned and tightened up. We haven’t lost any pressure since Tuesday (4 days ago). We will give it a few more days before gently backfilling the holes. It is a great relief all round that we have finally located and fixed the leak.
We have had our fair share of problems with the ground source heat pump. At first, it kept tripping out with low pressure alerts. The ground loops were flushed 3 or 4 times and eventually the alerts abated – we have only had one in the past 3 months.
However, there seems to be a leak on the ground loops and the end result is that we lose pressure in the system. This is a bit surprising since we had the ground loops on a pressure test for a few weeks after the ground was back filled – we didn’t lose a drop during this period. However, the larger pipes that connect the manifolds were back filled later and we believe that the joints on these larger (653mm) pipes may have worked loose. In hindsight, we should have made sure that all the joints in the system were accessible from inside the manhole, however, we now have no choice other than to dig them up.
RHI (renewable heat incentive) is an incentive paid by the government to encourage people to install renewable forms of heating. This covers ground source heat pumps (like the one that we have installed) and the incentives are intended to enable users to recoup the upfront investment involved in installing the systems. The incentives are calculated on a 7 year repayment period.
RHI is covered in depth elsewhere on this blog, but today we managed to submit our application. The process is all online and administered by Ofgem. You will need to have your MCS registration number (your installer should provide you with this), your EPC reference number and your GDA (Green Deal Assessment) number. Other than that, you just have to answer a few simple questions. It didn’t take more than 30 minutes to fill in the online form. Now it is just a matter of waiting for the application to be reviewed.
Although the application process opened in April, it has taken us a few weeks to sort out the EPC. The RHI payments are based on the heating requirements calculated as part of the EPC. I haven’t really paid that much attention to EPCs before (you need one if buying or selling a house), but when a payment depends on it, it gets a lot more attention.
We had a problem that the first couple of EPCs that were done bore little resemblance to the original calculations before by the system installer. The original estimates were that the annual heating and hot water demand would be in the region of 50,000kWh. The first two EPCs were in the region of 30,000kWh. The current RHI payment is 18.9p for every kWh generated, so a 20,000kWh difference equates to around £3,780 per year, or £26,460 over the 7 year payback period!
The main problem with the first two EPCs seem to be the unique nature of our property – some areas are double height, some parts of internal insulation on the original solid stone walls, even the heat pump itself seem to cause some head scratching. The first assessor failed to produce an EPC at all! He did the initial visit, asked lots of questions and then we never heard from him again. The second assessor did his best, but our property didn’t neatly fall into many of the boxes that needed to be ticked.
Eventually, on the third attempt, we got an EPC assessment that was close to the original heat calculations. The annual heat demand is still below the original calculations, but it is close enough. The RHI application was submitted this morning and with any luck we should hear in the next week or so.
After a number of months of anticipation, the Department of Energy and Climate Change (DECC) has announced that the domestic RHI scheme is now live and ready for applications. You can see the press release here: https://www.gov.uk/government/news/new-scheme-offers-cash-incentive-to-households-using-renewable-heating-systems-in-their-homes
The application process on the Ofgem website is also live and it seems ready to receive applications. You will find out more here: https://www.ofgem.gov.uk/environmental-programmes/domestic-renewable-heat-incentive/about-domestic-renewable-heat-incentive
From what I can see, the policy or process has not changed from what has been disclosed previously. The rate (18.8p per kWH generated for ground source heat pumps) remains as discussed previously.
I am just waiting on our green deal assessment and EPC before completing our application. It will be interesting to see how long it takes to process. Watch this space!
We have just installed a Network Owl to monitor our energy usage. This monitors the power being used on our incoming electricity supply and uploads the data to the internet. We can then monitor power usage from anywhere and (pretty much) in real time.
We have a 3 phase supply and are using a Network Owl and Owl Intuition-lc. This solution is intended for home and light commercial premises that are on a three phase supply. The hardware is under £100 and it took less than 30 minutes to set it up.
Creating an online account to view the data is a little quirky, but if you follow the instructions carefully it doesn’t take long.
Having installed a ground source heat pump, all of our heating and domestic hot water is essentially electric albeit aided by extracting heat out of the ground. So we thought it would be important to having an understanding of the amount of power that we are using. This solution looks promising and I am somewhat intrigued by the numbers. By combining the data from the Network Owl with data from our weather station and internal temperature sensors, we should be able to get a reasonable understanding of the heat performance of the house.
We are getting quite a bit of condensation off the pipe work for the ground loops. Often the anti-freeze in the ground loops is below freezing, so this isn’t too surprising. The main issue is that the drips fall onto the electrics for the ground source heat pump, particularly the switch for the 3 phase supply. Although the switch is IP65 rated, I wouldn’t want to see it get wet over a prolonged period.
The answer has been to install 4ft of plastic guttering underneath the pipework. This catches the drips and prevents the electrics getting wet. I suspect that these drips will just evaporate once in the gutter.
I went to three seminars today at Ecobuild 2014 on RHI. A lot of the information that was presented in these session has been seen before. However, there were some new snippets:
- The launch date for domestic RHI has still to be confirmed, however, it is expected to be Spring 2014. A number of the speakers referred to the date being finalised in the “next few weeks”;
- The domestic RHI payments will be “deemed” (i.e. estimated) rather reliant on using installed meters. The estimation will be based on the calculations completed as part of the MCS installation;
- There are a couple of situations were meters will be required. This is where the property is either a second home or there is an additional form of heating (e.g. gas boiler). The metered payments will only be able to adjust the payment upto the deemed value, i.e. the metering will only be used to adjust the deemed payment downwards;
- Applications for RHI will be administered by Ofgem. Applications will be made on online and it is expected that applications should take 20-30 minutes to make. In many cases, the decision of the online application will be instanteous;
- The applications will require details from your MCS certification as well as your green deal assessment. Hopefully, this will speed up the application process as details will be pulled in from these documents;
- The government reserved the right to reduce the tariff by up to 20% should the RHI be over subscribed.
You will find more information on the Renewable Energy Association website.
It is Ecobuild this week in London. On Thursday, there are a couple of sessions on RHI (Renewable Heat Incentive). This is a government scheme that provides funds for those people installing renewable forms of heating. This applies to ground source heat pumps (as well as air source heat pumps).
You will find more information on RHI in previous blogs entries.
While the incentive has been in place for non-domestic use, the domestic scheme is due to launch next month. While the overall framework for the incentive is well understood, there are a number of details still to be clarified. I am hoping that the sessions at Ecobuild this week will help provide some answers.
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).