Freezing condensate drains were very common last winter and the industry has been criticised for this Achilles’ heel of condensing boilers. However, it is only with the benefit of hindsight that we could be accused of failing to see this problem coming.
Many condensate drains are fitted on outside walls, leaving them exposed to the elements. Last winter’s cold weather was unprecedented and it was not surprising that condensates froze up, causing the automatic safety systems to shut the boilers down.
When condensing boilers were being developed in the 1980s, average winter temperatures were rising and the industry believed they would rise still further.
External pipework routes were, therefore, considered perfectly acceptable, as it made it possible to fit these high-efficiency appliances in the widest possible range of properties - particularly when refurbishing older buildings where access to suitable internal drainage points can be difficult.
Condensing boiler manufacturers are very specific about the requirements for the condensate drain, including what the pipework is made of, how it is routed and the location of the drainage outlet. All installation instructions include the option to route the condensate drainage pipework on the outside wall of the building. In some cases, there is no alternative.
The installer cannot then be blamed for carrying out the installation in a way recommended by the manufacturer, although they should also ensure condensate installations meet the requirements of BS6798.
In some countries where very cold winters are common, they have always run condensate pipework inside the property discharging into the internal household drainage system. If very cold winters also become the norm here, manufacturers may need to reconsider the use of external condensate pipework.
For now, to minimise the risk of freezing condensate this winter installers should look again at installations that might be vulnerable and consider the following:
- Re-routing the condensate pipework inside the building and connecting it to the internal drainage system where possible;
- Making sure all condensate pipes are insulated;
- Fitting trace heating to the external condensate pipework to keep it warm;
- Changing the condensate pipe for one of a larger diameter, as this may reduce the risk of freezing and pipe blockage.
John Hurst is chairman of the HVCA heating & plumbing services group