Design Review
FairHeat have encountered several developments with heat networks where the efficiency performance of those heat networks has been below expectations. This has resulted in £/kWh heat costs that have been significantly in excess of expectations. In addition to elevated heat costs, heat losses have had other negative flow on impacts, such as overheating in corridors.
The historical performance issues have been a product of several different factors, including over-conservative design decisions from design consultants, non-optimum equipment selection and insufficiently rigorous commissioning processes.
FairHeat carries out a review of the consultant’s design and identifies potential modifications to the design that will:
- Reduce capital costs
- Have a positive impact on performance (e.g. heat network losses)
- Comply with good practice with regards to current industry standards, particularly with regards to the minimum requirements set out within CP1, the FairHeat Heat Networks Design Supplement and other industry guidelines.
During Stage 3 design the focus will be on ensuring that correct design assumptions are used and, that the design approach is in line with FairHeat’s Design Supplement (as per 1) and industry best practice. More specifically, FairHeat will:
— Review design documents to ensure key evidence has been provided:
- Network Options Appraisal
- Heating System Options Appraisal
- Pipe Size and Insulation Calculations
- Heat Demand Calculations
- Main Heat Plant Design Review
— Evaluate the design documents that have been provided and assess: (a) any areas of risk with respect to meeting Key Objectives & Targets; and (b) compliance with the overarching objectives
— Provide recommendations / suggestions for how to improve likely performance / minimise risks
— Check the peak heat load calculations for the sitewide space heating and hot water demand (including commercial connections)
— Review the LTHW plantroom hydraulic arrangement and sizing of plantroom equipment
– Carry out a sample of LTHW pipe sizing calculations (corridor, riser and distribution pipework) and check the calculation methodology for pipe sizing is in line with the Design Supplement requirements.
— Carry out sample pipe sizing calculations for the DHW pipework (up to 3 flat types)
— Provide recommendations / suggestions for how to improve likely performance / minimise risks
During the detailed design phase (Stage 4), FairHeat will:
- Carry out a review and comment on design
- Carry out heat load and pipe sizing calculations and provide marked-up schematics for risers, laterals and terminal runs
- Carry out pipe sizing calculations and provide marked-up schematics for the DHW circuit for different flat types
- Produce report outlining additional potential performance and value engineering opportunities for the heat network, along with a risk register
- Review the LTHW Stage 4 equipment schedules and comment on plant selection
- Review the Stage 4 M&E specification (heat network elements only) including commissioning and pre-commissioning (water treatment) specifications
- Review DesOps to ensure appropriate Stage 4 DesOps produced for control philosophy capturing response of system to demand including sequencing of all plant items, alarms and BMS points list (also categorisation of which sensors are to be remotely changeable e.g. boiler set points)
- Produce high level report outlining any recommended changes for review
Contractor Design Review
To protect the performance specification achieved at design, is important to monitor any variance between the contractor’s design and the M&E design, particularly with respect to any proposed value engineering. Furthermore, there have been instances in the industry of inappropriate equipment selection that has led to:
- Significant additional capital costs
- Delays to programme
- Long term performance impact and/or O&M costs
- Design/performance specification not being met due to altered design
To avoid such issues, FairHeat reviews the contractor’s technical submittals for key equipment, with FairHeat providing feedback to the design team in the review process. FairHeat Carries out review and comments on contractor design to ensure the approved consultant design has been met by the contractor drawings.
Technical Submissions
FairHeat reviews the contractor’s technical submittals for key equipment and provides feedback to the design team in the review process. This includes:
- Plant room and network: boilers, heat pumps, CHP, thermal storage, plate heat exchangers, pumps, water treatment equipment, pressurisation and expansion units, control valves, general valves/fittings/ancillaries, commercial/communal space heating equipment, BMS, pipework (above and below ground), insulation
- Dwelling: HIUs, pipework, insulation, space heating equipment/ancillaries
- Metering and billing: heat meters (plant room/network/dwelling), pre-payment/AMR system
Descriptions of Operations
A simple and effective Descriptions of Operations (DesOps) needs to be produced by a controls specialist, outlining how the Low Temperature Hot Water (LTHW) plant is to be controlled and operated through all plant room modes of operation.
The DesOps can have a significant effect on the efficiency (and operability) of the plant room. Thus, considerable thought is expected to ensure that the DesOps achieves the design intent and that the control strategy maximises efficiency through all modes of operation.
FairHeat will review the LTHW DesOps to ensure appropriate level of detail has been produced for control philosophy capturing response of system to changing demand.
Site Inspections
Several developers have had experience of heat network installation not being to the required standard. This could be down to installation not meeting design, specification or manufacturer’s recommendations, not meeting industry best practice or where there has been poor workmanship. These shortfalls in the mechanical installation of heat networks could significantly impact performance and/or equipment lifetime. This issue doesn’t just manifest in the installation of the pipework, but the equipment, ancillaries and insulation, all of which have standards of installation that should be met. FairHeat reviews the installation against specification to ensure that any issues are picked up early, with a consequent minimisation of impact on performance and/or programme.
Commissioning Monitoring
Commissioning method statements for key plant are often generic, not detailed enough and/or not site specific with regards to particular hydraulic arrangement or set point requirements. If these are not site specific, manufacturers can arrive onsite and carry out commissioning not appropriate to the system, or not to the design requirements. This can also occur onsite when the commissioning engineer hasn’t digested the method statement fully and just commissions how they have done in the past, not taking into account the system specifics.
Several developers have experienced significant issues with poor pre-commissioning activities on the heat network systems. These issues have primarily been associated with:
- Inappropriate filling processes and a lack of attention paid to avoiding system stagnation: This has led to corrosion taking place prior to handover and major intervention measures to arrest the corrosion, causing programme delays and permanent corrosion damage.
- Insufficient levels of sampling in accordance with BG 29: This has led to issues not being detected before they escalate. This had led to undetected corrosion and significant remedial measures (e.g. installation of additional side stream filtration).
- A lack of record keeping and trend analysis: Corrosion management and prevention should focus on analysing trends in KPIs (inhibitor levels, dissolved iron etc.). Without regular samples and graphical trend analysis, corrosion issues are difficult to diagnose.
Several developers have experienced significant issues with poor system control, stable temperatures and boiler sequencing post-handover. FairHeat have developed a process for a system load test that is proving successful at diagnosing such issues and ensuring remedial measures are carried out prior to the system being handed over, which is now a minimum requirement in CP1 2020.
Acceptance Testing
Historically, heat network commissioning has had a main focus on the centralised plant room with the dwelling commissioning not given the attention it requires, often left until the end of a project and rushed to meet handover deadlines.
Witnessing of dwelling level commissioning has typically only been required on a small number of end points, or only very high-level inspections/tests. This has resulted in installation and commissioning issues being missed, and not picked up until the resident has moved in, when it is often much more costly and time intensive to rectify. Poor performance of end points is often associated with elevated flow rates and return temperatures, where a few poorly performing units can have a detrimental effect on the heat network’s performance and efficiency.
Even with the main focus on the centralised plant room, there has been a tendency during commissioning to solely focus on achieving stable operation during peak load, despite part load conditions being more common during operation. This hindsight leads to unstable flow temperatures, risking the reliability of the heat network.
Acceptance Testing allows FairHeat to independently validate installation, commissioning and operation of all end points through a rigorous testing procedure, as per CP1 2020 minimum requirements and best practice, ensuring that the client and end user are delivered an efficient and reliable service. This process can be applied across all development end points, including dwellings, commercial connections and communal areas.
CP1 2020 Minimum Requirements outline an initial set of tests on a small number of dwellings to establish systemic issues that can be rectified before commissioning and testing the rest of the development, then taking a graduated risk-based approach to the rest of the development, testing the first 10% of dwellings points and then a randomized 10% sample of the remainder. If any fail to meet requirements, then a further 10% should be tested, which can introduce quite a lot of unknowns into project planning and budgeting.
CP1 Best Practice outlines that Acceptance Testing should be carried out over 100% of dwellings and end points to ensure that correct service levels and design return temperatures have been achieved across the network. This way, the client has complete confidence that all installation and commissioning issues are addressed and rectified pre-occupation.
Acceptance Testing provides performance verification of the energy centre and all end points. After each testing process, feedback is provided to contractors for rectification. This process ensures installation, commissioning and operation are all as per design and performance specification and prevents issues and faults emerging during the early years of operation, where their rectification would be more expensive and intrusive.
Acceptance Testing
Historically, heat network commissioning has had a main focus on the centralised plant room with the dwelling commissioning not given the attention it requires, often left until the end of a project and rushed to meet handover deadlines.
In addition to this, witnessing of dwelling level commissioning has typically only been required on a small number of end points, or only very high-level inspections/tests. This has resulted in installation and commissioning issues being missed, and not picked up until the resident has moved in, when it is often much more costly and time intensive to rectify.
Acceptance Testing allows FairHeat to independently validate installation, commissioning and operation of all end points (as per CP1 best practice) through a rigorous testing procedure, ensuring that the client and end user are delivered an efficient and reliable service.
Carrying out initial checks prior to a full rollout prevents the implementation of poor or incorrect commissioning practices being applied across the development.
This process can be applied across all development end points, including dwellings, commercial connections and communal areas.
Testing
Close-out Project Management
A developer experiences a significant amount of cost and management time dedicated to resolving issues that should be resolved prior to practical completion of their M&E services related to their heat networks, associated hot water and space heating systems. Due to competing pressures, the developer’s developments normally have a number of outstanding commissioning issues outstanding post-practical completion (PC). These vary from the Contractor not providing the required handover documentation (e.g., water quality records and commissioning documents) to operational concerns such as equipment commissioning not meeting performance requirements and a diverse range of other issues. Unfortunately, the experience to date has been that these issues are simply not resolved by the Contractor after practical completion, as the project team is demobilised, with the developer often being left with outstanding risks relating to performance and operability of their systems.
FairHeat supports the developer in project managing the process to ensure that outstanding issues at practical completion are closed out in a timely manner and that any costs are recovered from contractor retentions.
