Heat pump systems with radiators or underfloor heating can have vastly different efficiency ratings.
A poorly installed boiler will not always have much of an impact on gas bills.
However, compared to a good install a poorly installed heat pump can have a significant impact on running costs.
This is why it is important to hire an engineer who understands how to design and commission heating systems properly.
RHOST is a tool that can help you find a good engineer.
|BAD INSTALL||GOOD INSTALL|
|BOILER HEATING||75% Seasonal Efficiency||95% Seasonal Efficiency|
|HEAT PUMP HEATING||200% Seasonal Efficiency||500% Seasonal Efficiency|
People running heat pumps with low electric bills have these 3 things in order.
- Radiator sizes note, bullet points will be in-page links to the relevant sections of article
- Control strategy
- System design
What do radiators actually do?
Radiators are devices that transfer heat into a home. Ideally, they should transfer heat at different speeds to match the speed of heat leaving the building through the walls, roof, floor and windows. This can be done by constantly changing the temperature of the water flowing to the radiators.
Unfortunately, most boiler heating systems (and some heat pump systems) transfer heat into the home too quickly. This is because the system has been designed to deliver just one flow temperature to the radiators.
The water temperature is very high which is perfect on the very coldest days but not for most of winter. The speed of heat from the radiators is too quick and will overheat the home. A wall thermostat has to shut the boiler or heat pump off.
The thermostat then has to wait for the home to cool down slightly before turning the heating system on again. This is an inefficient way to control a heating system, but it is the most common way.
Wall thermostats and thermostatic radiator valves were actually introduced into homes in the early days of central heating to shut things off. They were not introduced as energy efficiency devices like many people think.
Note: A good installation engineer will install a boiler so that it can modulate the flow temperatures to the radiators. This is done with weather or load compensation controls.
The controls will need to communicate with the boiler. Some boilers use their own language while others use opentherm
Heat pumps come with their own compensation controls but they can be set up wrong which the next section discusses.