The closer you look at Air Source Heat Pumps, the more you see their similarities to boilers.
Pump House compared the installation guidance and standards for air source heat pumps and boilers. We looked at the MIS 3005 incorporating the ASHP side and the BS 6798 covering the installation of boilers not exceeding 70kW.
Both technologies produce condensate, although the composition of the condensate is different. Boiler condensate is acidic with pH levels of between 3.6 and 4.2. The condensate from the outdoor unit on an ASHP is pure water condensing on the cold coil from the surrounding atmosphere.
Pump House has deep experience in the disposal of condensate from air conditioning systems and boilers. We train and educate installers in how to dispose of condensate too. Furthermore, we produce guidance document covering the key influencing factors and routing solutions.
Basic factors to consider:
- Domestic boilers can produce around 2 to 3 litres of condensate per hour
- Annual volumes of 600 to 1000 litres per year
- Boiler produce condensate inside the building envelope and tends to be between 20oC and 40 oC
- Boiler condensate is acidic and can only go into the waste water system. You must neutralise it before it goes straight to ground, into a rain water pipe, or sceptic tanks.
- The use of a soak away must incorporate lime chipping as a form of neutraliser and to provide void spaces to allow adequate drainage.
Air Source Heat Pumps
- Units upto 14kW can produce between 10 and 15 litres of condensate per defrost cycle
- Annual volumes of 2000 to 3000 litres per year
- ASHP produce condensate outside the property and can be between 3oC and 5oC
- ASHP condensate is pH neutral and can go into any suitable drain
- The use of a soak away is also acceptable. This does not need to incorporate lime chipping, but the material must have some form of void space to allow for adequate drainage
What the regulations say:
The regulation helps avoid the risk of standing water. This can pool and freeze causing a slip hazard on paths and walk ways around the heat pump.
The boiler standard BS 6798 covers a range of routing options. The options reflect the differences between ASHP and boilers.
Heat pump condensate has a lower temperature than condensate from a boiler. It is important to have a large diameter pipe (The minimum is 32mm) and as steep a fall on any pipework as possible to avoid the risk of the pipe becoming frozen.
The following diagrams show some specific routing options to assist installers.
For those super Eco installations, the condensate could also be directed into rainwater harvesting.
The definition of a soakaway and the design and sizing are covered in BRE 365. However, this is not specific enough on the smaller volumes we are looking at from boilers and ASHP’s. It does, however, define the requirement of a geotextile liner. This is designed to eliminate the ingress of the surrounding soil and plant roots into the soakaway.
Installers can refer to boiler installation standard BS 6798 to avoid constant referral to BRE365. BS 6798 incorporates installation guidance on the soakaway design to cover boilers upto the 70kW rating. The routing option takes into consideration the difference in volumes between boiler and ASHP. The soakaway needs to be slightly larger than that for a boiler.
Pump House has designed an ASHP specific soakaway which comes complete with a Geotextile liner and 32mm pipe connector.
Pump House are a specialist in heat pump mounting. We support installers with installation best practice. Contact Pump House on 0115 900 5858 or email firstname.lastname@example.org