Dual full Bivalent Heating Systems

A bivalent heating system is a way of combining the high efficiency, low running cost and low carbon foot print of a heat pump with your existing boiler (Oil, LPG or gas) without the need to change your existing radiators.

This system is particularly advantageous for older or larger properties with a higher heat loss where a heat pump alone would not be capable of providing enough heat during cold weather or where a multiple heat pump installation is not possible due to the lack of electric power supply to the site.

It is also worth considering if you don’t wish to disturb your whole house due to the fact radiators and pipe work may need upgrading to accommodate a heat pump.

Why is the running cost of a heat pump more economical?

A heat pump is on average 320% efficient compare to the latest condensing oil boiler 95%.

However the cost of electricity is higher than oil (for example). But due to its high efficiency the running cost is still on average 30% cheaper to run.

Please visit our heat pump page for more details.

Bivalent heat pump oil boiler North Devon

How does it work?

An ECODAN heat pump is fitted alongside your existing heating system.

The heat pump will take care of most of the heating needed during a large part of the year.

All ECODAN heat pumps are capable of modulating and come with a weather compensator!

The modulation is there to only produce the heat required when working.

The modulation allows the system to vary the temperature in the radiators themselves. The colder it gets outside the warmer the radiators will be and vice versa.

However from time to time cold snaps may come and (due to different factors related to your house) the heat pump may not be able to cope alone. This is why you will need to go back to your existing boiler to get over these cold periods.

The water temperature coming from the heat pump to your radiators can vary from 35ÌŠC to 50ÌŠC depending on outside temperature, where a typical oil boiler water temperature will be between 60ÌŠC and 80ÌŠC

The switch over point will be tuned specifically to your house requirement. On average the switch point between heat pump and oil boiler is around -3ÌŠC.  

Bivalent heat pump oil boiler Barnstaple South Molton


The water in your heating system flows either though the heat pump, or through your existing boiler before flowing to your radiators and hot water tank.

This is controlled via the control box with the help of a programmable room stat, a conventional heating clock and an outside stat. This system will then decide whether to switch on either the heat pump or your boiler depending on which will provide the most efficient heating for your needs.

Useful information sheets & brochures (downloadable PDF)

» Ecodan brochure 2013 FTC4
» 5 Bed Country House bi-valiant Heat pump Oil boiler