How to Install a Condensing Combi Boiler

Updated March 23, 2017

With adequate insulation, a Combi or combination boiler can heat a home, particularly a small home, sufficiently. The boiler requires less space in a home than do orthodox boilers. Central and localised heating boilers are available for use. Other benefits of using a condensing Combi boiler are that the equipment does not require a hot water storage cylinder or a feed and expansion tank. It is important that you follow the specific guidelines that accompany your boiler when you install the equipment.

Locate the boiler in your home so that exhaust gases can safely emit out of the boiler into the air while fresh air remains available for combustion. Make sure the terminal is not obstructed by combustible materials or low hanging ceilings. A minimum of 1300 millimetres height, 465 millimetres width and 325 millimetres of open depth space are required around the boiler. Use chalk to map out the best location for the boiler. This will ensure that you have the correct parameters identified before you install the Condensing Combi boiler.

Position the radiators below a pair of windows. Hang the radiators no less than 100 millimetres above the floor and 150 millimetres below windowsills to allow for heightened comfort levels in the room while the boiler is working. Measure off 75 millimetres of open space on each end of the radiators to allow valve clearance. Fit double glazing to allow for increased radiator placement freedom.

Select pipe sizes and routes. Position pipes away from doorways and other obstructions. Try to fit your pipes beneath first floor floorboards. Route the pipes down to the ground floor radiators. Map out a route for the pipes to branch outward to the upstairs radiators. Run main flow and return pipes parallel to one another. Map out the pipe routes before installing the pipes. Make sure that pipes are fitted to go from the flow pipe to the side of each radiator. Leave room for air vent elbows above each vertical rise. Use 22-millimeter pipes to create the main circuits and 15-millimeter pipes to tee off each radiator.

Install pipes and routes. Fit the radiator tail valves into the radiator tapings. Use thread seal Poly Tetra Fluoro Ethylene tape to seal the threads. Place the on/off and thermostatic radiator valves on the flow into the radiator. Use chalk or a pen to mark the flow on the radiator. Insert the air vent plug above the lock shield valve and the blanking off plug above the radiator valves. Attach the radiator values and lock shield valve bodies to the radiator tails. Avoid securing the bodies to the tails too tightly. Connect the cold water inlet from the rising main to the boiler. Use a 15 millimetre copper pipe to loop the boiler to your house's cold water supply pipe.

Add gas supply. Contact a registered fitter to run gas to the boiler. Search the yellow pages for a utility company to request the service of a registered fitter so you can add a gas supply to your boiler. You should not run gas to the equipment yourself.

Things You'll Need

  • Tube cutter
  • Pipe bending spring
  • Blow torch


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About the Author

Rhonda Campbell is an entrepreneur, radio host and author. She has more than 17 years of business, human resources and project management experience and decades of book, newspaper, magazine, radio and business writing experience. Her works have appeared in leading periodicals like "Madame Noire," "Halogen TV," "The Network Journal," "Essence," "Your Church Magazine," "The Trenton Times," "Pittsburgh Quarterly" and "New Citizens Press."