What is district heating?
District heating has been designed to heat many homes or properties from just one boiler. This can be two buildings, a block of flats, a housing estate or any variety of buildings either linked or spread over a large distance. Substantial annual savings can be made by only having one boiler to service annually, and with new build developments, the saving will be even greater because individual boilers will not need to be installed.
How does it work?
District heating works by having one main plant boiler room. The size of the boiler will depend upon the entire heat load of the buildings that are going to be connected to it.
From the plant room, we install something called a heat main which carries hot water to every building that it is connected to. It has a flow and return pipe exactly the same as you would find in the building heating system. The hot flow goes to the building connection and the colder return water travels back to the plant room which is constantly re-heated via the boiler and sent back to the properties.
Building connections are the point where the heat main connects to the building and the downstream heating system. These will vary depending on the system currently in place. In most circumstances we would replace the current boiler with a plate heat exchanger (PHE). This gives an indirect heat transfer between the water in the heat main and in your heating system. The PHE is much smaller than most domestic boilers and will normally fit in exactly the same spot meaning there is very little need to alter the pipework inside.
In the building, we either install a full control system to replace the existing system, for example the Honeywell time clock, or the existing controls can be left in place. This all depends on your preference.
To act as a backup when the biomass boiler is being serviced annually, you can also add a fossil fuel boiler, which will heat the site during any down time and so give you extra peace of mind.
Design and installation
It is very important that our design team examine all elements involved with district heating. We look at the best way to run the heat main from the plant room to the properties and measure all the lengths, connections and any junctions we have to put in. Pipe size is determined by quite a few factors such as pressure loss, load and flow rate.
There are many different ways to connect each building. Generally, we either bring the heat main up inside the building underneath the wall and foundation, or to the outside edge and use special elbows to connect through the wall above the damp proof membrane.
The heat main is normally set in a trench at a depth of 900mm. At the bottom we use an aggregate like pea gravel for drainage. We then lay a bed of sand on top. The heat main is laid, along with any additional ducting for control cabling. It is then covered with more sand until it is no longer visible. Once this is done, we refill with the spoil that came out of the trench. Any leftover spoil is removed from site.
Technology we use
We use some of the most thermally-insulated underground heat mains available. The pipe has one of the lowest heat loss percentages. All joints we install underground, whether they are tees or elbows, are fusion welded. This ensures they will never leak and all connections are pressure tested before any trenches are reinstated.
Fair Energy has fitted many district heating schemes, click here to read what our customers say about them.