Heating and hot water system

  • Background information

    The heating and hot water system at The Exchange is made up of several components, which need to work in sync with each other to deliver a reliable supply to your home.

    In simple terms, there are three boiler units, each with three individual boilers in the plant room for the estate.

    Those boilers generate heat and hot water that is delivered through a network of pipes to each home via a heat interface unit (HIU). There are also strainers at various points in the system, including in each HIU, to ensure debris from the water that drives the system doesn’t get into the mechanics.

    At the moment, six boilers across two of the units are operation, and can provide in excess of 100% of peak demand. This means that should we have unexpected failures of one or two boilers, the system will still be able to deliver all the heating and hot water you need.

  • Outages during October and November 2021

    The boiler units were automatically switched off on seven separate occasions between 28 October and 9 November. The first incident was caused by the main strainers in the plant room being blocked. Once those were cleared, heating and hot water were restored.

    The other six incidents since 29 October were due to the pressurisation unit in the plant room sounding a low pressure alarm which causes the boilers to shut down automatically. Normally, low pressure is caused by leaks. Although we identified and immediately fixed leaks following three of the outages, the pressurisation unit continued to sound the alarm and trigger the automatic shut-down of the boilers.

    On 9 November, we disabled the pressurisation unit and put in a temporary work-around to ensure the system continued to be topped up with water should the pressure drop. Between 8pm and 8am, an engineer was in the plant room to check that the work-around did what it needed to in the absence of the pressurisation unit and to check whether water was being drawn into the system as would be expected should the water pressure drop. None was.

    That suggested that there was a problem with the pressurisation unit, although it wasn’t displaying any faults. A series of diagnostic checks by the manufacturer didn’t identify any faults, but we decided to replace the unit anyway as we didn’t want to risk reinstating the old unit and having another outage. The pressurisation unit was replaced on Tuesday 14 December and BSW were on site to make sure it was working properly and in sync with the rest of the system. So far, there have been no further problems or false alarms.


  • Heat interface units (HIUs)

    We’ve completed a series of strainer cleans to the HIUs in your homes, which has resolved problems with heating and hot water in most cases. Please contact Orka if you still need your HIU strainer to be cleaned.

    We’d also reviewed 17 especially poorly performing HIUs and are reviewing the latest data to see if there’s more we can do.

  • Frequency of leaks

    There shouldn’t be this number of leaks and outages on a system of this age. The components on the heat network require oxygen levels to be carefully maintained, to prevent the lifespan of those components from being compromised. The volume of leaks has compromised some components, resulting in further leaks. The short-term remedial works (see below) should have resolved this issue.

  • Short-term remedial works

    In mid-September, before the October/November outages, we commissioned Fairheat to review the known issues at The Exchange. Their findings resulted in a short-term action plan to ensure you have a stable and functioning heat and hot water system over the colder winter months.

    We completed most of the short-term actions as planned before Christmas 2021.

    We’ve brought back into service three additional boiler modules, which will double the number of available boiler modules and ensure peak demand can be fully met. We’ve also adjusted the boiler temperatures and the pumps so that they operate to maintain a constant differential pressure rather than continuously at maximum. That will improve efficiency and the life of the system.

    We’ve also installed a new water treatment unit and have scheduled regular sampling of the water so that water in the system remains clean and doesn’t interfere with the mechanics.

    In addition, we’ve removed debris from the system both in the plant room by increasing cleaning of the main strainers to fortnightly, and also by carrying out HIU strainer cleans in your homes.

    A report from a pipework and anchoring expert who visited The Exchange in early November didn’t identify any excessive strain on the pipework, so we didn’t need to have a rolling programme of planned downtime to install additional supports to the pipework as we’d initially thought we might.

    We've replaced the valves at the top of the risers. Previously, even though we’d checked that they were closed, they were sometimes letting air in to the system which was causing air locks, which in turn was resulting in localised outages. The replacement work should have rectified this.

    We still need to flush through the pipework, but we won’t do that until we’ve seen the new pressurisation unit work effectively for a few weeks. We now plan to carry out the flushing as part of our longer-term plan.

    We haven’t yet undertaken an extra check of the water quality by a third party as the various issues appear to have been resolved without having to do that at this point. We’ll now do that piece of work before we start the longer-term programme to provide extra assurance.

  • Long-term remedial works action plan

    In addition to the below we've also agreed a planned shutdown every Wednesday between 12 noon and 3pm to allow Orka to do work without needing to communicate at short notice.

    Reference Action Time frame Downtime implication Update
    1 Replacement of boilers, with new configuration of pipework in plant room and installation of buffer vessels and control valves to improve generation efficiency and improve stability of network temperatures 30 July – 15 August 2022 One day in total

    Removal of header has been completed w/c 4 April

    Remaining plant and boiler work on hold pending installation of a new flue to the boiler.

    2 Implement new controls to improve plant operation and reduce operating costs

    30 July – 15 August 2022

    None On hold pending replacement of flue.
    3 Install additional water treatment equipment, in order to improve long term water quality and consequent system reliability and equipment longevity 18 April - 18 July 2022 None Install complete w/c 18 April. Awaiting commissioning -  by mid-July.
    4 Reduction of operating temperatures to extend pipework lifespan (beyond initial design lifespan) 13-14 April 2022 None Complete. Further reductions will be delivered once pipework modifications have been completed.
    5 Re-insulation of riser pipework 30 July - 15 August 2022 None To be carried out at the same time as the re-insulation to plant room pipework.
    6 Removal of top of riser bypasses where possible or, where not possible, replacement of bypass valves where these are identified to be faulty

    16 -20 May 2022

    Works will not take place over the weekend

    Block by block - one day maximum Complete.
    7 Replacement of a limited number of faulty HIUs to reduce network flow rates and increase differential pressure across the system 23 March - 29 June 2022 For individual properties as per appointment. No site wide downtime Complete. One HIU needs to be swapped due to issue of vibrating pipework.
    8 Improve insulation coverage on pipework within dwellings where HIUs are replaced, to reduce heat network losses 23 March - 29 June 2022 None Complete.
    9 Install plantroom monitoring equipment to provide better performance information, with implementation of additional alarms and remote access for diagnosis 18 April - 18 July 2022 None

    BMS remote monitoring is complete (w/c 18th April)

    Guru installation 50% complete. Remaining works to be completed by mid-July.

    10 Removal of existing flues to the boiler and fitting of a new flue.
    • Temporary flue connection to existing boilers
    • Existing flue removal
    • Main flue installation

    11 July – 29 July 2022


    11 July


    11 – 13 July


    27 – 29 July




  • Services from Fairheat and Orka

    We’ve now instructed a new contractor, Fairheat, to deal with repairs to your heating and hot water system. The technology was relatively new when it was first installed at The Exchange, which means that previous contractors have often struggled to resolve problems in full.
    Since then, the entire heating and hot water industry has learnt far more about how these systems work and why problems arise, and there are now new contractors in the market, like Fairheat, with greater expertise of managing communal networks like the one that serves your home.

    Fairheat will carry out the work required for the long-term remediation plan on the estate. They are experts in this field, and we shared a summary of their report with you in February to explain what needs to be done. You can see an overview of the work and any heating and hot water shut down days that will be needed in the long-term remedial works action plan drop down above.

    Fairheat have also taken responsibility for repairs and maintenance to the heat interface unit (HIU) in your home, as well as delivering the longer term planned improvement works to the plant room and heat network.
    Fairheat have sub-contracted Orka heating engineers to provide a responsive repair call-out service. From now on if you require a heating operative to attend to a problem with your HIU, or to restore a loss of heating or hot water, you should report this to Orka’s repairs call centre on 020 8261 7321, which is available 24 hours-a-day. You can also reach them via email at reactive@orkabs.com.
    Orka will also respond to maintenance faults or service issues within the main heat plant room that may affect the stability and efficiency of your heating and hot water supply.