Groundworks and Headerworks

These terms describe the joining together of the boreholes to provide circulatory system for the thermal fluid, including a main feed to, and from, the heat pump.

Correct installation of the headerworks is important for any borehole installation, but particularly so for multiple boreholes where the flow balancing between boreholes is essential to reaching the design efficiency of the borehole array.

We have long experience in providing headerworks for both large commercial and small domestic projects.


COP stands for the Coefficient Of Performance and is the figure given to express the efficiency of the heat pump.  The higher the number, the better the efficiency.

Geological Survey / Thermal Response Tests

A geological survey will give a strong indication of the thermal characteristics at the site where the boreholes are to be drilled, but for large scale projects, or for complicated geology, a Thermal Response Test might be of value.

Thermal Response Tests measure the thermal characteristics of one or more boreholes at a specific site. Test data is used to predict the performance of more boreholes, within an array.

For multiple boreholes, it is essential to correctly dimension the borehole number, depth and spacing.

Header Pipe Installation

Header Pipes are the pipes running between the manifold and the heat pump. These pipes are in most cases 63mm in diameter for domestic but can be 250-350mm diameter for larger installations. For single boreholes the 40 or 32mm borehole probe diameter will suffice.

Synergy Boreholes can, if requested, install these pipes directly to the GSHP within the building.


Commissioning is the ‘go live’ for the borehole and GSHP system.  Before commissioning every system, we ensure each of the following.

  • All the boreholes are pressure tested
  • A Loop Test Certificate made available to the client
  • The pipe network will be cleaned, sanitised and flushed, before being refilled with thermal fluid (glycol) which contains a long-term bacterial growth inhibitor.

ISO 9001

ISO stands for ‘International Organisation for Standardisation’

The most widely recognised standard is ISO 9001, a basic quality management system that can be used in industries of any size, anywhere in the world. Registration to ISO 9001 certifies that an organisation has an effective quality management system, satisfying the requirements of the governing body.

32 or 40mm Loops

The liquid flowing through the geothermal probes must pick up the heat energy from the surrounding ground as efficiently as possible in order that the heat pump may more easily harvest as much heat as it can.

Several factors can influence the efficiency of the transfer of heat from the ground into the circulating fluid, some of these are,

  • Geology – the physical thermogeological characteristics of the strata surrounding the borehole
  • Presence or absence of groundwater and groundwater movement.
  • Thermal conductivity of the material (grout) in the borehole surrounding the probes
  • The overall dimensions of the borehole array and depth of the individual boreholes
  • The type of liquid flow within the geothermal pipe or probe.

In short

  • Borehole depths below 100m may operate more efficiently at 32mm
  • Borehole depths above 100m will operate more efficiently at 40mm
  • 50mm for boreholes deeper than 200m may be more efficient

Thermal Pipe Material

Geothermal loops should be made of PE100+ material, not PE80

PE100+ material is a superior grade material with a higher purity and durability than ordinary PE100. Geothermal loops should be SDR 11 and crack resistant.


Requirement Calculations

These must be conducted by an experienced professional and not a high pressure salesman. If not done correctly, the result can all too often be a heat pump sale with an underestimation of the borehole requirement, leading to a negation of the reason for going for the technology in the first place i.e. lower energy costs.

Heat Pump Installer

What To Expect From A Heat Pump Installer

Householders should check that the installer is a member of the two industry led and government approved schemes: the Microgeneration Certification Scheme (MCS) and Renewable Energy Consumer Code (RECC). The MCS scheme will cover any technical related issues while the REAL Assurance Scheme (which manages RECC) covers all contractual related disputes, including deposit protection and workmanship guarantees.

Installers should:

  • Be MCS certified and comply with the latest standards
  • Visit in person and complete a technical survey before quotation.
  • Explain how the heat demand of the property was calculated.
  • Explain how the system will be installed and if there will be any disruption to the property.
  • Explain the efficiency of the installation based upon the star rating
  • Supply clear, easy to understand and detailed information and advice on how best to use the system and operating   instructions.
  • Provide clear, easy to understand information on product and workmanship warranties including information on insurance backed schemes.
  • Provide a full breakdown of costs in their quote and include the terms and conditions.
  • Not ask for more than a 25% deposit.
  • Householders have the right to cancel the contract within seven days with no penalty.