Andy Green, technical director at Baxi Heating, has offered advice on how to protect the heating system through a building lockdown, avoiding the risk of legionella.
As the UK lockdown continues, it’s important that building owners are vigilant about implementing preventative maintenance to protect heating systems in their empty buildings. Heating engineers and facilities managers have a key role to play in ensuring that the heating system operates efficiently and safely once a property is reactivated.
Where a short-term building shutdown period is anticipated, our advice is to leave wet heating systems in operation at a reduced temperature, at around 14ºC. This will avoid the possibility of damp entering the building, reduce the risk of microbial contamination which can cause corrosion, and help building operators or facilities managers keep energy bills down.
Introducing a weekly low usage maintenance schedule will ensure that the system remains in top condition and avoid any risk of a legionella outbreak. We recommend implementing the following programme:
- Carry out a visual inspection of the plant once a week, even where there is remote monitoring capability of both the building and heating system, to ensure that there is nothing untoward.
- Keep moving parts like pumps operating for ten minutes once a week to help prevent them seizing and failing when the building is reactivated. Most control systems will build this into their strategy.
- Allow the domestic hot water to reach pasteurisation temperature (60ºC) for one hour once a week to prevent bacteria forming and avoid the risk of legionella. Legionella bacteria are dormant below 20ºC and do not survive above 60ºC.
- Some water heaters, like our Andrews Water Heaters MAXXflo Evo unit, will have onboard controls that operate a legionella cycle to ensure that the whole system is brought up to pasteurisation temperature by monitoring the secondary return temperatures.
LONG TERM CLOSURE
In the event of a long-term building closure, there is the option to drain down the heating and hot water service.
The system should be isolated completely, ensuring frost protection from the system to prevent freezing. The building will need to be decommissioned completely and ventilation run through the building to prevent the build-up of microbial contamination.
REACTIVATING A BUILDING
When reactivating a site, we advise implementing the following 24-hour maintenance regime prior to reopening the building:
- Twenty-four hours before bringing the building back into operation, fill the system, remove the air, and bring the hot water system back up to 60ºC.
- Open all of the outlets until they reach at least 55ºC to make sure that all stagnant water is removed before shutting them. Flush the outlets and pipes through thoroughly and carry out operational checks.
- Carry out microbiological sampling to ensure that there is no contamination of the hot water supply. Depending on the outcome of the sampling, there could be a requirement to chlorinate the hot water system.
- Insurance inspections will also need to take place to ensure that the property is functional and compliant.
FOLLOW BEST PRACTICE
Ensuring good quality water and eliminating the risk of contamination through best practice maintenance programmes is the safest way to enable the system to be reactivated quickly when required. And as heating and hot water is a vital service, this in turn will allow buildings, and the businesses and organisations they house, to bounce back rapidly once we re-emerge from lockdown.