Bivalent: ASHP + OIL
Bivalent Systems by Heatology.
"This system is most advantageous for older / larger properties with a higher heat loss...."
A bivalent heating system is a clever way of combining the high-efficiency with the low running costs and low carbon footprint of a heat pump with your existing boiler (Oil Boiler) without the need to swap your existing radiators.
This system is most advantageous for older / larger properties with a higher heat loss and where an air source heat pump alone would not be capable of emitting enough heat during our cold weather or where a multiple air source heat pump installation is not possible due to the overloading of electric power supply.
If your maximum electrical loading is currently 100amp single phase and therefore fits this criteria.
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%. Let's say your existing standard boiler is approx. 80% efficient.
A 16kW output heat pump has an ‘input’ rating of 5kW. This would be the maximum loading from your supply. The heat pump compressor and fan are inverter driven giving modulation on temperature demand.
The cost of electricity is higher than oil (at the moment 5/12/16), but due to its high efficiency the running cost it is still on average 30% cheaper to run. The heat pump will take care of most of the heating needed during a large part of the year.
Modern air source heat pumps are capable of modulating and come supplied with a weather compensators.
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 entirely on its own. This is why you will need to go back to your existing boiler to specifially for these cold periods.
The water temperature coming from the heat pump to your radiators will vary from 35C to 50C depending on the temperature outside, where a typical oil boiler water temperature will be between 60C and 80C.
The switch-over point between these installed systems will be tuned specifically to your house requirements. On average the switch point between heat pump and oil boiler is around -2 water flow 45C.
The water in your heating system flows either though the air source 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, with a conventional heating clock and an outside stat. The system will then decide whether to turn on either the air source heat pump or your boiler depending on which will provide the most efficient heating.
"The aim of the Bivalent system is to minimise the use of your existing oil boiler whilst adding comfort to your property by keeping a continual heat throughout the house, instead of going from hot to cold all the time with the added benefit of reducing your running costs. The best of both worlds."