Print out and keep these step-by-step instructions on how to install a Thermaflow electric combi boiler.

Print out and keep these step-by-step instructions on how to install a Thermaflow electric combi boiler.


The boiler is the home appliance we all take for granted, usually due to the fact that it is tucked away in a cupboard somewhere, yet it is vital for our daily comfort and well being. Replacing old, inefficient boilers or electric storage heaters with more advanced and higher efficiency models is key in the fight to reduce rising fuel bills. The new Thermaflow TH Mrk 2 range of electric combi boilers give the customer four different ways to help reduce their fuel costs and carbon footprint, as they can choose from standard, solar, wood burner and solar-wood burner models. Ease of installation and operation are key features of the design, so reducing installation time.


1. Check the packaging is free from damage, then remove the boiler from the box. The primary expansion vessel is in a separate box. Carefully read the manufacturer’s instructions and familiarise yourself with the boiler, connections and installation requirements


2. After confirming that the proposed location for the boiler is adequate to support the weight when full, place the boiler in position with all components facing forward to allow necessary access for future maintenance


3. There are six pipework connections on the boiler - five 22mm, and one 15mm compression. These are: central heating flow; central heating return; cold water inlet; hot water outlet; primary expansion vessel connection; and safety relief valve. If a solar, wood burner or solar-wood burner model is being installed, there will be an additional two or four 22mm connections, depending on the model.


Connections must be made using compression joints, not soldered, to prevent the seals from being damaged. Screw the automatic air eliminator provided into the connection on the pipework at the top of the insulated plate heat exchanger. All connections are marked with a label. Ensure pipework conforms to current building regulations.


4. Make all necessary electrical connections in accordance with the manufacturer’s instructions, chosen electricity tariff and current electrical regulations. For external controls we recommend a Danfoss TP5000si or similar for ease of installation and use. Other external controls can be used.


5. After checking that all pipe connections are tight, fill the system via the filling loop fitted on the boiler. Flush the system with cleanser in accordance with the manufacturer’s instructions. When the flush is finished, completely refill the system and purge of all air via the cap on the automatic air eliminator. Leave the grey cap on the air eliminator in the open position and the black quick fill cap on the top in the closed position. Set the fill pressure to between 1.5 and 2.0 bar


6. Commission the boiler in accordance with the manufacturer’s instructions. Adjust the hot water flow rates and preset any pressure reducing valves fitted to a maximum of 3 bar. Balance the heating circuit and flow and return temperatures. Fill out the log book provided and explain the operation of the appliance and external heating controls to the customer.


This feature ran in the November/December issue of HVP.