Category: heat pump (Page 4 of 4)

Digging to install the ground loops

August 20, 2013 / stephen

There is 1533m of plastic pipe to be buried in the top field for the ground source heat pump. Spaced 0.75m apart, this means we require around 1100 sqm of ground.

Rather than digging trenches, we are removing all of the top soil and sub-soil to a depth of 1m. This should be quick. The top soil and subsoil is put into different piles so that when the ground is reinstated the top soil is on (yer) top.

We haven’t got enough space to store all of the soil in one go, so we are installing the ground loops in sections – digging a section, installing the pipework and the back filling the section, before moving on and digging the next section.

While this is a lot of work, it is quicker than trying to dig 1m deep trenches.

We were a dumper driver down on Monday afternoon, so I stood in for a couple of hours.

This is a big dumper and takes 10 tonnes of soil at a time!

The view from a 10 tonne dumper as the topsoil is being removed.

How much does it hold? mmm……

We were a labourer short on Monday afternoon and I got the (dubious) honour of standing in – 3 hours driving a 10 tonne dumper! I am the Stig!

Preparing for the ground loops

August 17, 2013 / stephen

Now that all the pipework has been installed, the screed is going to be laid next Tuesday. Until this point, the house is out-of-bounds otherwise the pipeworks may get damaged.

So we are going to take the opportunity to install the ground loops in the top field. There is around 1533m of plastic pipe to bury in the ground – about 1 meter deep. If we have got our calculations right, this means digging up about 1,100 sq m of the top field. The ground loops are a fundamental part of the ground source heat pump. This will extract the heat out of the ground and provide all of the heating and hot water for the property.

The pipes need to be installed as loops where the pipes are around one meter deep and one metre apart. Rather than digging trenches we are going to remove all of the topsoil and subsoil from the field. We will then install the ground loops and replace the subsoil and topsoil. We will do it in sections. By installing the ground loops at this time of the year, there is half a chance that the grass will re-establish before the winter sets in.

We order a 30 ton excavator, but unfortunately we couldn’t get it up the road to the farm. Our plan B is this 8 ton ecavator. It is smaller and will take longer to move the soil, but at least we can get started on Monday.

This carries a 10 tonne load and should make quick work of moving the soil for the ground loops.

Progress on the underfloor heating

August 17, 2013 / stephen

The underfloor heating is now installed upstairs together with the first fix plumbing for the bathrooms. The insulation has been installed downstairs. The insulation consists of large slabs of expanded high density polystyrene that is foil backed. It is 50mm thick and is cut to size using a wood saw. Once it is down, it can be walked on.

A strip of expanded plastic is put all around the edge of the room. This forms a gap between the edge of the screed and the wall. This allows the screed floor to expand and contract as it heats up and cools down. Without this, there is a possibility that the screed would expand with the heat, push against the walls and crack.

The screeders are booked for Tuesday morning. By then all of the pipework needs to be clipped to the insulation, so that 70mm of screed can be laid on the floor. It will take a day or so for the screed to go hard. During this time, no one will be allowed inside the house.

While the house is out of bounds, we will install the ground loops for the ground source heat pump in the field.

The underfloor heating has been installed upstairs together with the “first fix” plumbing. This means that all the hot and cold water pipes have been run to each of the bathrooms as well as all the drainage. We have used the same installer for the underfloor heating and the first fix plumbing to make life easier.

The insulation is down and we have put a damproof membrane on the inside of the walls. This end of the building has had some damp problems in the past so we want to be a 100% sure these problems are fixed moving forward. The white pipe is the main water supply for the property and we have temporarily located it to a tap outside while this work is going on.

Just the pipes to be installed downstairs before the screed can go down on Tuesday.

The insulation is down on the floor. The damproof membrane has been fixed to the walls. There will be two large doors here that open on to the courtyard, but for now we have boarded one up and put a temporary door on the other. If we put the “real” doors on now, they would only get damaged during the building work.

Underfloor heating upstairs

August 13, 2013 / stephen

We made a start today on installing the underfloor heating. We are installing this throughout the building – both upstairs and downstairs.

The upstairs heating works via a system of metal plates that are fixed to the underside of the floorboards and heated by a set of water pipes. We left a 25mm gap between the large oak beams and the floor joists to make installing the plates a little easier. We have also cut out notches in the joists before the floors went down to make it easier to run the pipework.

All in all, it only took a day to install all of the underfloor metal plates.

This shows the ceiling from below and shows the metal plates that have been fixed to the underside of the floorboards. The flow and return pipes will be installed later.

This shows the metal plate screwed to the underneath of the floorboards. The flow and return pipes get clipped into each side later. After the first fix electrics and plumbing have been installed, insulation will be put between the joists and the ceiling will then be plasterboarded. You can see the 25mm gap we left over the top of the big oak beams to allow the plates to be installed.

The cost of moving utilities: Electricity

July 21, 2013 / stephen

One of the things that I missed when budgeting was the cost of moving some of the utilities. While none of the amounts are showstoppers, they do start to add up. And the fact that they haven’t been showstoppers is more down to luck than judgement.

So first electricity…….

There were two electric meters on the property. One in each of the properties. The meters belong to the electricity supplier (e.g. EDF, E.on, British Gas) and it is usually free to get a meter removed. We removed the meter from number 8 and continue to use the meter in number 10 to power the cement mixer etc.

There was third – there was a meter in one of the outbuildings, but we have never had a bill for this one and we had it removed before knocking down the building. I talked to the electricity board and no one seems to know who owns it. So now it languishes in the long grass in the back field.

The existing meter in number 10 needs to move to the new utility room, but unfortunately that will have to wait as it isn’t built yet. I reckon we can move it around October/November time. When it does move, we would like the cables put underground rather than being attached to the front of the property (which they are at the moment).

In addition to the changes to the single phase supply above, we also need to install a 3 phase supply. This is to power the ground source heat pump. We are fortunate that there is a three-phase supply on the pole right outside the property. Again this needs to go to the new utility room (still not built) with a three-phase meter. This should go in the same trench as single phase supply.

On the basis that we dig the trench and laying the duct to the utility room, the cost is £2,600 plus 5% VAT. All of the work that relates to the change of supply is completed by Northern Power Grid. Plus, of course, there is the cost of digging the trench. Once the order has been accepted, you are given an MPAN number that can then be given to the electricity provider of your choice who will install the meters (one for the single phase supply and one for the three-phase supply). I am currently shopping around for the best electricity provider. More updates on this later.

The existing electricity supply comes in via overhead cables. The cables are then attached to the front of the house. The plan is that there will be put underground and brought round into the new extension. The yellow sheaths are to protect the guys working on the scaffolding.

RHI – Update

July 12, 2013 / stephen

The update that we have all been waiting for on RHI (Renewable Heat Incentive) has just been published. You will find the information here: https://www.gov.uk/government/news/the-heat-is-on-for-householders

Specific detail on RHI is here: https://www.gov.uk/government/consultations/renewable-heat-incentive-proposals-for-a-domestic-scheme

The good news for us is that the scheme appears to be open to all householders, even those who previously had a gas boiler installed.

RHI eligibility for current gas users

July 5, 2013 / stephen

I have been concerned that we would not be eligible for RHI (Renewable Heat Incentive) for our ground source heat pump based on the criteria for RHPP (Renewable Heat Premium Payment). RHPP is the current scheme in place and RHI does not come into effect until Spring 2014. RHPP is a one-off payment, whereas RHI is based on a tariff (with different tariffs for different sorts of heat generation). Information on RHI is still fairly sparse although it is due to be updated “during summer 2013”.

With the current proposed tariffs for RHI, the incentive could be around £2,000 per year for 7 years. So a significant sum.

While the information on RHI is sparse, the information on RHPP is very clear about existing gas users on this page. Here is the relevant text….

if you have recently removed a mains gas heating system or currently heat your home with mains gas, you are only eligible to apply for solar thermal

On the basis that we aren’t eligible for RHPP, I began to wonder if we would be eligible for RHI.

However, you will find a factsheet on RHIon the Government’s DEC website here, but here is the relevant text regarding existing gas users.

If my current main fuel use is gas, can I still get RHI if I install a renewable heat technology?

Yes, we propose that the scheme be open to any home in Great Britain wishing to take part, even if they are currently using gas as their main fuel. However, almost 3 million homes in the UK do not have gas as an option. These off gas grid homes typically face higher bills and produce more carbon than the equivalent on grid home. For this reason, we are proposing that the tariff levels are set to be more financially advantageous to those homes off the gas grid, compared with those that are.

So this all sounds good for current gas users who want to move to a ground source heat pump.

UPDATE: 12th July 2013 The Government has released the latest information on RHI and the links to it will be found here. It is good news for current gas users as it appears the scheme is open to all households.

Ground source heat pump update

July 4, 2013 / stephen

I think we might have finally got there with the ground source heat pump. It has taken some time to sort this out and I am glad that not all of the decisions on the renovation have been quite as tortuous as this one!

So why has this been so difficult?

First of all, we had the debate over air source vs ground source. We thought that the difference in price between the two would have favoured an air source heat pump. However, having looked into it became clear the difference was not as big as first thought. Given that we have a one acre field adjoining the property, it seemed a shame not to use a ground source heat pump.
The next issue related to the provision of a 3 phase electricity supply. It turned out once the initially estimates had been done that we needed a 24Kw unit. Unfortunately, this is too big for a normal single phase supply and we needed a 3 phase supply. We had heard stories of it costing thousands to get a 3 phase supply installed, so we thought that we ought to get this sorted out BEFORE ordering a ground source heat pump. This took a while to get the quote from Northern Power Grid. More information here. To be fair to them, it took me a while to fathom out the form! Lots of questions that I didn’t know the answers to! Anyway, the cost for installing a 3 phase supply (and modifying the existing single phase supply) is £2,600. So not cheap, but not a showstopper.
Almost there…..but now there are questions over the depth of the soil in the field. We need at least 100cms of soil to go on top of the ground loops. We thought that there might be a problem because of the amount of soil in the others that we had dug. So there was nothing for it, but to dig a number of test holes. We did this last weekend and found that there is between 700-900mm of soil before you reach the bed rock. It has taken until today to establish that around 800mm will be sufficient, so once the sand is added to the bottom of the trench to hold the pipes, we won’t be that far off. We also have soil to come out of the garden when the footings and foundations are dug for the extension. This soil could be put on top of the existing soil to raise the overall ground level.
Then the last concern is over whether we are going to quailify for RHI. I have covered this elsewhere on the blog, so I won’t bore you again here. To qualify for RHPP, there must never have been gas on site. Since we do have gas onsite (even though the boilers have been removed), we don’t qualify for RHPP. RHI is due to in next be introduced next Spring, but earlier indications seem to be that we WILL qualify for RHI. We can’t say definitely, but we have decided to take a punt. RHI is likely to be worth around £2,500 per year to us for 7 years. So well worth having! This document on the Government’s DECC website is the closest that I have seen to confirming that we are eligible even though the property has had a gas supply in the past.

So after all that I think we are just about ready to place the order for the underfloor heating and the ground source heat pump. At last!

And now for some gratuitous photos of digging holes in a field!!

Only 700mm of soil covering the bedrock

Another skill to add to my CV!

In total, I dug 9 holes across the back of the field. The depth of the soil ranged from 600mm to 1300mm – it averaged 700-800mm in most of the locations.

Renewable Heat Incentive

May 13, 2013 / stephen

The situation with the Renewable Heat Incentive (RHI) is a little confusing. Mainly because the details will not be finalised until this Summer (when exactly, who knows!). If you are interested, you can sign up for email alerts on the Dept of Energy and Climate Change here for details once they are released.

The principle is pretty straightforward – for ground source heat pumps the incentive is between 12.5-17.3p/kWh for each kWh of energy produced by the heat pump. The incentives are different for other forms of heat pumps. The rates will be confirmed when the RHI is finalised later on this year. The incentive is payable over a 7 year period.

There are some criteria attached to receiving the payments, so do make sure that you have a good look at the material that is currently available. You will also need to ensure that your installation is fully certified. Most reputable heat pump suppliers/installers will handle the certification for you.

So what is the bottom line for us? Well, we know the annual kWh as this was calculated when the suppliers worked out the sizing of the heat pump. From the calculations, it looks as if our installation will produced around 15,000kWh per year. At the higher rate, the RHI would be around £2,500 per year. So over a 7 year period, this is equivalent of £17,500. This almost covers the cost of the installation in the first place.

You will find more information here…….

UK Government website
https://www.gov.uk/government/policies/increasing-the-use-of-low-carbon-technologies/supporting-pages/renewable-heat-incentive-rhi

Energy savings trust
http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Renewable-Heat-Incentive-RHI
I rang them to get some more information on RHI and they couldn’t tell me anything more that what was on their website. Maybe things will improve once the details are finalised.

Ground source heat pump

May 13, 2013 / stephen

Heat pumps work on the same principle as fridges and freezers – but in reverse. They cool a refrigerator to a low temperature and then circulate it through a set of coils that are either buried in the ground (ground source heat pump) or have a fan that circulates air over them (air source heat pump). The refrigerant warms up, picking up the heat from either the ground or the air. The heat is then extracted from the refrigerant and the cycle starts again. The heat from the refrigerant is used to drive a central heating system as well as domestic hot water.

Ground source heat pumps tend to be more effective (as the ground temperature does not vary as much as the air temperature), but they tend to be more expensive as they need coils to be buried in the ground.

Because of the way these pumps work, you need to put energy in (to reduce the temperature of the refrigerant), but you get energy back from the ground/air. For every unit of energy put in, ground source heat pumps will generate 3-5 units of energy. This ratio is called “Coefficient of performance” (COP) and you will find it quoted on most of the ground source heat pumps on the market. For example, for the NIBE F1345 unit that we are considering has a COP of 4.79.

To calculate the size of heat pump required, you need to provide the size of the rooms, the use of the rooms (bedrooms tend to be cooler than other rooms) and insulation levels. Where you live in the UK will also affect the amount of energy that these pumps will be able to extract. You don’t need to worry about all of this as the ground source heat pump suppliers will do the calculations for you.

The calculations for our property indicate that we need a pump capable of generating around 22Kw. The nearest size heat pump is 24Kw. This is fairly large heat pump and unfortunately this requires a 3 phase electricity supply as the load is too great for a single phase supply (which is the “normal” electricity supply in most domestic properties). I have had to get a quote from our electricity power supplier (Northern Power Grid) for installing a 3 phase supply. I will cover this elsewhere on the blog.

Heat pumps are not cheap. A ground source heat pump tends to be more expensive that air source, if only because of the coils that need to be buried into the ground. A 24Kw unit is going to be around £10K and all the additional bits and pieces will roughly double that cost. However, there is some good news as there is a Renewable Heat Incentive (RHI) available from the Government. RHI is intended to encourage people to install renewable heat sources and from the calculations that I have done, I suspect that the RHI will cover the cost of the ground source heat pump over a 7 year period. I will cover RHI in more detail elsewhere on this blog.