Why fit chrono-proportional controls?

Why fit chrono-proportional controls?

Replacing an older boiler with a high-efficiency condensing model won’t necessarily optimise potential energy savings, says Gareth Ash, Marketing Services Manager at Danfoss. He explains how installing chrono-proportional control, also known as TPI (Time Proportional and Integral) can unlock this potential.

Domestic heating systems with a simple mechanical thermostat can’t achieve the full energy-saving benefits of a condensing boiler because the boiler will rarely be running in high efficiency condensing mode with this type of control. Switching to a basic on/off electronic room thermostat can produce a reduction of over 2% in both energy and carbon emissions. However, using an electronic thermostat with chrono-proportional capability provides much closer temperature control and maximises energy savings. In fact, ‘real world’ tests conducted by Danfoss showed reductions of 10% are achievable compared with a mechanical thermostat.

So what is chrono-proportional control and why is it more efficient? Chrono-proportional is the technical term for time-based on/off control. Instead of standard on/off control it introduces a fixed cycle rate on the system and then uses an advanced control algorithm to determine the duration of the on and off periods within each cycle in proportion to load, increasing both comfort and economy.

Chrono-proportional has clear advantages over the other main control types. For example, products with mechanical bellows are slow to react in ‘natural convection’, making them less effective in maintaining the boiler in high efficiency condensing mode. Although faster than bellows, an electronic on/off thermostat is slow-reacting and is still reliant on natural convection rate. Chrono-proportional control works by ensuring the boiler ‘on’ time is reduced to a minimum and matching the heat output with the heat loss. This not only maintains the set comfort temperature but also maintains a lower return temperature, keeping the boiler in condensing mode for longer.

All Danfoss electronic room thermostats come with the comfort and energy-saving benefits of chrono-proportional control, from entry-level options to fully programmable products. Additionally, the all-new Danfoss TPOne programmable room thermostat offers the extra savings of a selectable Delayed or Optimised start. Both adjust dynamically to the difference between the ambient and set temperature, either delaying startup or calculating the optimum time to start heating to hit setpoint at the scheduled time. For more information visit