Month: August 2013 (Page 2 of 5)

We have laid the first 3 ground loops and are now in a position to cover them back over.  Each loop is 50m and there is a layer of sand below and above the pipework.  The subsoil is then carefully reinstated avoiding any very large stones.

There is a flow and return for each of the loops. Each loop has a tap that controls the flow to and from each ground loop. This allows the flow to be controlled to each loop compensating for the fact that some of the loops are further away from the pump.

Each pipe is 100m long, so each loop is 50m. Each of the manholes has a 6 port manifold so that is 600m of pipe connected to each manhole. There are 3 manholes making a total of 1800m of pipework.

The first 300m of ground loops are being covered using some of the subsoil that we removed earlier in the week.

There is around 100mm of sand on the bottom, then 100mm of sand on top of the ground loops. Then the subsoil is carefully reinstated.

The first 300m of ground loop disappearing under the subsoil.

Installing the loops for the ground source heat pump is turning out to be a lot more labour intensive that we were expecting.

Rather than digging trenches, we have decided to take up all of the top soil and sub soil to a depth of about 1m.  Digging 1 m deep trenches 1m wide and 1 meter apart is just to hard.  It is easier to remove all fo the soil in one go rather than digging trenches.  However, this approach has generated a lot of soil – and I mean a LOT!  We have mountains of the stuff.  We have even flattened the top of one of these mountains and are piling the soil on top.

The other problem that we have is that subsoil contains a lot of fractured stone.  It doesn’t contain any clay.  This means that we need to scrape the bottom and pack the subsoil down so that there is little chance of the pipework being damaged when they are laid.  The ground is then “tracked” in. This means going backwards and forwards and using the tracks on the excavator to flatten the bottom.  This also crushes a lot of the bigger stones.  Since we have upgraded to a 14 tonne excavator, it really does crush the stones in the bottom.

All of this means that it is taking longer (and costing more) to install the ground loops.  I am not sure that there is anything we could have done differently.  But we probably could have plan and estimated the ground work a little more accurately.  Clearly, the amount of effort involved in installing the ground loops will vary according to the quality of the ground.  It would be wise to check this out before starting on work like this.

The other issue to consider is access – can you get machinery of the right size onto the site.  Doing ground works on this scale requires big machines and getting them on site (or even to site) can be a challenge.  If your contractor is hiring machinery, make sure that the hire company has looked at the routes to the site and agreed that the machine can be delivered.  Then if there is an issue, this is down to the hire company and not you.

We have stripped the one half of the field and piled all the soil on the other half! We are now out of space!

We are starting to run out of space.

This is a 14 tonne excavator. We had to trade up from our 8 tonne excavator to try and speed things up. There is a lot of soil to move.

We are now starting to run out of space and are piling up the spoil.

We need to remove around 1100 sq m of soil to a depth of around 1m.  This is a lot of soil and we intend to install the ground loops in three sections.  We will dig each section, lay the pipes and then refill the hole.  We simply don’t have enough space to take all of the soil off in one go.

It took  the whole of the first day to remove the top soil (at a depth of around 100-200mm) on 1100 sq qm.  The top soil will not be put back until all three sections have been installed and the sub soil put back.  If we were to put the top soil back section by section, we would end up with a mess if it rains.

By the end of day 2, we have removed around 250 sq m of subsoil.  The mountains of soil are starting to build up and we are running out of space. 

We are using an 8 tonne excavator.  We tried to get a 30 tonne excavator on site, but it was too big to get up the road.  The 8 tonne excavator was the biggest we could fire at the time.  We have a 14 tonne excavator turning up in an attempt to speed up the ground work.

Start of day 2 of removing the soil for the ground loops. It took all of the first day to remove the top soil. Now we are starting on the sub soil.

We have started removing the soil for the ground loops. You can see the 150mm of topsoil and then the 700-800mm of subsoil. The piles of soil are starting to build up in the top field. We need to get the ground loops installed in this section so that we put the sub-soil back (making a bit more space!).

Each of the ground loops starts and finishes in a manpower. These are 750mm x 1200mm manholes that are going to be 1000mm deep. The bottom of the manholes are propped up on concrete block to allow for the pipework to be installed.

These are the manholes for the ground loops. You can see the drain pipes in the background. These are installed into the foundations of the extension before the concrete slab can be laid.

We have separated out the top soil and sub soil to make reinstating the field that bit easier.

All of this subsoil and topsoil has been removed to install the ground loops. The pole in the background is in the next field.

Not exactly treasure, but this is the only thing that we have found while digging up the field. It is an old electric bench saw.