Preliminary items

To specify the correct size of heat pump, full room by room heat loss calculations were undertaken using the U-values of the old and historic building elements.

From the calculations the peak heating demand of the areas to be heated at the external design temperature were established as well as the annual heating and hot requirement for heating and hot water.

The thermal conductivity of the ground a metre below the surface was also obtained by excavating a number of trial pits in the area proposed for the ground loops. This, coupled with the results of the heat loss calculations enabled the size of the ground loop to be accurately calculated ensuring that the brine temperature entering the heat pump is always above zero degrees.

Site survey

Prior to commencing work a site survey was undertaken to agree the proposed layout of the ground loops, entry points into the building and plant locations.

It was agreed that the best location for the ground loops was in a field to the rear of the property as it was of flat topography. The only access route to the field was through the landscaped gardens for the property which the customers were concerned about. Worcester Renewable Energy ensured them that it would carry out the excavation with care and minimum distribution and return it to a condition ready for re seeding.

The location of the plant and ground loops along with trenching route were then formally communicated in a layout plans.

Topography

The landscaped gardens rise up to the field containing the ground loops resulting them being higher than the ground source heat pump in the plant room. The ground loops were therefore pressurised and an appropriately sized brine pump selected with the sufficient power to pump the ground loop fluid up to the field and back again.

Access

Access to the field was through a small gate at the top of the garden. This was chose as the perfect route for the ground loop interconnecting pipework to pass through avoiding any hedgerows being disturbed.

Geothermal manifold location

It was decided that the geothermal manifold chamber serving the five ground loops would be best sited near the hedge row of the field where it could be located.

Ground loop location

A clear area of the field between some mature trees was selected for the location of the ground loops keeping them away from the canopies of the trees where roots may have been present.

Arrival of groundwork team on-site

On arrival to site, the Worcester Renewable Energy ground work team carried out a final inspection and cat scan of the proposed area for the ground loops to check for the presence of any underground service before excavation commenced.

Seting out

Each of the ground loops was set out and the ground marked to ensure trenches were excavated exactly where required and with the required separation.

Manifold pit

A 3m square by 1m deep pit was also excavated to accommodate the external geothermal manifold chamber allowing for ease of access and working.

Plant & machinery

All of the groundwork was carried out using the appropriate plant and machinery for the respective tasks involved.

Excavation of ground loop trenches

Excavation of the five trenches as set out commenced which confirmed the ground conditions previous established for the design of the ground loops.

Delivery of sand

Sand for bedding and backfilling the trenches was delivered to a holding area from where it was transported to the trenches.

Sand bedding

Each trench was bedded with 100m of sand prior to the installation of the ground loops, the sand serving to both protect the ground loop pipework from any sharps in the bottom of the trenches and also to ensure good thermal contact between the ground loop pipework and surrounding ground.

Delivery of ground loop pipework

The ground loop and armoured interconnection pipework were again delivered to a holding area from where they were transported to the trenches.

Ground loop installation

Each of the 5 ground loops was laid in  ensuring that the pipes were against the walls of trenches, correctly spaced and free of any stress.

Ground loop return

The return ground loop pipework was cable tied at the head of each slinky whilst keeping it straight and against the side of the trench to maximise the amount of thermal gain.

Completed ground loops

Once the five ground loops had been installed, the installation team then moved on to installing the armoured interconnecting pipework back to the plant room containing the ground source heat pump.

Excavation of interconnecting trench

The trench from the plant room through the garden was carefully excavated, avoiding an number of services that cross over it.

Interconnecting trench route

The route the interconnecting trench through the landscaped gardens was kept outside of the canopies of the established trees to ensure their routes were not damaged in the process.

Access to ground loop field

The interconnecting trench passed through the gate to the field containing the ground loops as previously planned to avoid disturbance to the hedgerow.

Service ducts

Service ducts from into the plant room containing the ground source heat pump were formed for the interconnecting pipework to pass through.

Entry of ground loops

The interconnecting pipework was installed through the service ducts protecting it from any damage from the wall material.

Interconnecting pipework installation

The interconnecting pipework was laid into the interconnecting trench. The armoured pipework specified did not require the trench to be bedded or backfilled with sand, speeding up installation time.

Interconnecting pipework route

The interconnecting pipework travelled up the interconnecting trench through the landscaped gardens.

Interconnecting pipework route

The interconnecting pipework was installed in the trench through the gate into the ground loop field.

Geothermal manifold chamber

The geothermal manifold chamber which contains flow setters allowing for the flow rate for each ground loop to be balanced on commissioning was installed in the previously excavated pit. A heavy duty manifold lid was specified so that chamber could be driven across by machinery when cutting the grass in the field.

Electrofusion welding

With all the ground loops and header pipework laid, the end of each pipe was then electrofusion welded to the appropriate connection of the geothermal manifold chamber.

This involved a strict procedure of pipe cutting, marking, scrapping, cleaning, clamping and welding to ensure dependable welds.

The end of each pipe was cut square and even using a special pipe cutter, and any burrs or shaving were removed as failure to do so can leave the heating wire uncovered leading to short circuit, overheating uncontrolled melting and even sudden ignition.

The insertion depth of each pipe into the fitting was also measured and the outer oxidized surface of each pipe removed to the required depth using a mechanical rotational peeling tool. The surface of each pipe then wiped with an alcohol wipe to remove any dust residue and other contaminants, a critical step to avoid any poorly welded joints.

To prevent pipe movement during the welding and cooling cycles which would adversely affect the welding process, the pipes and fittings were all clamped in place. Once these steps had all been completed the joints were then welded using an electrofusion welding machine for a specific amount of time relative to fitting being welded.

Welds were then allowed to cool for a defined period of time to allow the unified melted pipe and fitting to cool down and solidify in a way that the material will regain the same flexibility and strength as it had prior to welding.

Ground loop pressure test

A full pressure test of the completed ground loops was carried out prior to backfilling of the trenches taking place to confirm the absence of any leaks. The test was completed in accordance with British Standards over a predefined period of time to allow for initial expansion of the pipework, the results of the satisfactory test recorded on a pressure test certificate.

Backfilling of ground loop trenches

With the installation of the ground loops complete and pressure tested a further 100mm of sand was laid over the top of the pipework along with geothermal warning tap before backfilling with the previously excavated soil. The sand acting to both protect the ground loop pipework from any sharps present in the backfilling soil and also ensuring that there is good thermal contact between the ground loop pipework and backfilled substrata.

Backfilling of interconnecting trenches

With the installation of the interconnecting pipework complete and pressure tested geothermal warning tap was laid within the backfilling previously excavated soil.

Topsoil

Once trenches had been backfilled with the previously excavated material, the top soil was then laid back over ready for re-seeding.

Finished garden surface

The finished surface where interconnecting pipework had been installed was left neat and tidy to the customers satisfaction.

Finished field surface

The finished surface where the ground loops had been installed was also left neat and tidy to the customers satisfaction.

Plant room

Prior to renovation works the plant room was a disused cellar.

Plant room concrete floor

A new concrete floor was installed to the plant room in preparation to receive the plant room equipment.

Tanking

The walls were tanked to prevent the ingress of water and the interconnecting pipework from the ground loops converted to copper ready for the plant room installation to take place.

Concrete floors

Concrete floors were installed to the cellar rooms in preparation to receive the underfloor heating installation.

Insulation

The floor was insulated to prevent the heat from the underfloor heating system transmitting downwards into the concrete slab.

Underfloor heating

Rather than tacking or clipping the pipework directly to the insulation, castellation plates were installed. These ensured accurate and uniform pipe spacing as well as suspending the pipes to allow complete screed coverage around their full diameter. Because a manual screed was being used, the plates also protected the pipes from foot traffic reducing the possibility of damage whilst the screed was being laid.

Underfloor heating manifold

Once all the underfloor pipework circuits were installed the tails were connected to the underfloor heating manifold using pre-formed bends to neatly form the 90° radius required on each pipe to transition it from a horizontal to vertical direction.

Underfloor heating pressure test

Before allowing the underfloor heating system to be screeded, it was pressure tested above its working pressure for any leaks. The results of the satisfactory tests recorded on pressure test certificates.

Heat pump installation

 Buffer tank installation

Plant room installation complete

Commissioning

With the system fully installed the final stage of the installation was to commission it. The ground loops were flushed and filled with water and glycol to ensure they are protected down to -10°C, checked using a refractometer and the flow rates through each of the slinky’s balanced using the flow setters in the geothermal manifold chamber. The underfloor heating system was then filled with water and inhibited to protect it from corrosion and fungal growth. Like the ground loops the flow rates through each circuit were balanced using the flow setters on the underfloor manifolds. The operating parameters, such as the weather compensation heat curve and hot water temperature were then set within the ground source heat pump controller and a commissioning certificate completed with all the commissioning readings and settings recorded.

Tile floor finish

Tiles have been installed throughout the hall which are one of the best floor coverings for use with an underfloor heating system as they offer very little heat resistance to rising heat generated from the system pipework beneath.

Tile floor finish

Tiles have been also been installed in the games alley.