Specialists in Low Energy and Heat Pump Heating Technology

Pipework and Pipe Components

Important - Pipe Sizes

It is very important not to undersize the water pipes in a heating system. This is doubly the case in a heat pump system because it uses much higher flow rates than a conventional heating system.

The above table shows both the ideal water flow rates and the amount of heat that can be carried in a copper pipe attached to a heat pump system.

If we take a 15mm pipe then the table above shows that this will ideally take 8.0 litres per minute of water which equates to 2.8KW but can take up to 12.0 litres per minute which equates to 4.2KW but with a higher pressure drop. At this higher figure though the pressure drop is 1.5 KPa per metre so over a ten metre flow and ten metre return with 30% allowance for fitting losses then we have a total resistance of 40KPa which is really quite large!

We saw a heating system recently which was trying to push the entire 12KW capacity down a single 15mm pipe and not surprisingly it did not work.

This becomes even more important with plastic pipe where the pipe size is the outer dimension. Typically a 28mm plastic pipe is the same as a 22mm copper pipe.

Golden Rules

  • Use 22mm pipe for connecting the cylinder, thermal break and heat pump for models up to 7KW
  • Use 28mm pipe for connecting the cylinder, thermal break and heat pump for models from 9 to 12KW
  • Use 35mm pipe for connecting the cylinder, thermal break and heat pump for 14 and 16KW models
  • If you are using plastic pipe, go up one pipe size from the figures above
  • You must use a 30 mesh (600 micron) or better strainer in the return pipe to the heat pump
  • You should fit flow and return thermostats on each individual heating circuit
  • You cannot fit enough isolating valves
  • Fit a drain point at the lowest level and an automatic air vent at the highest point in the system
  • Make sure all water pipes are well insulated
  • The minimum insulation thickness for externally mounted pipes is 19mm, but ideally use 25mm to avoid heat loss
  • When connecting the heat pump OUT means FLOW and IN means RETURN
  • Ensure that any components used for a heating and cooling system are suitable for water at 6C

Strainers / Filters

As a bare minimum a Panasonic Aquarea should have a 30 mesh (600 micron) strainer installed in the return pipe to protect the heat exchanger. This should be installed correctly, in accordance with the strainer manufacturers instructions and have shut off valves either side to allow for easy cleaning. In addition it is advisable to consider the use of a magnetic filter.

We strongly recommend combining the two requirements and using a BoilerMag combined strainer and filter.

Boiler Mag Combined strainer and magnetic filter

The Boiler Mag in 28mm combines a powerful magnetic filter with a 35 mesh (500 micron) strainer to give significantly enhanced protection at minimal extra cost. We stock these and strongly recommend their use in place of a simple strainer.

Dosing Pots and chemicals

A new heating system will require, as a minimum, the addition of a chemical Inhibitor to protect against corrosion and lime scale and maintain system efficiency. An existing system will require the use of a cleaner or sludge remover and power flushing before the system is filled with water and inhibitor is added.

We supply System Cleaner and Sludge Guard for flushing your system out. We also supply System Guard Inhibitor to protect your system.

Monobloc systems because they use water outside will require anti freeze. We supply food safe mono propylene glycol anti freeze with inhibitor in 25 litre tubs.

We also supply system Dosing Pots in sizes from 3.6 up to 25 litres as an easy method of introducing these chemicals into a system.

Ensure that your pipe sizes are large enough and that you have the correct quantity of pipe components then click here to go to the next section