Intelligent boiler systems

Intelligent boiler systems

Published: 01-03-2006

The Greenstar CDi boiler

The Greenstar CDi is Worcester's top of the range gas-fired condensing boiler series, available in four combi outputs - 25kW, 30kW, 35kW and 40kW and two regular - 30kW and 40kW and one 30kW system boiler. The combi versions condense in CH and DHW modes making it more efficient than its SEDBUK A rating.

All CDi's contain Worcester's WB Aluminium Silicon heat cells, a purpose built component for SEDBUK A rated appliances. As the flue gases pass through the heat cell, the extra surface area cools the flue gases to around 55 degrees centigrade whereupon the latent heat, normally lost to the atmosphere, is released and applied to the system. It is this ability to extract as much heat as possible from the gas it burns that gives the Greenstar range an exceptionally high level of operating efficiency.

Hydraulic Block

The hydraulic block holds 10 water components in the combi boiler in one place and reduces pipework, and because there are fewer connections in the boiler it minimises the risk of leaking.

It contains:

  • Circulating pump
  • Diverting valve
  • Hot water heat exchanger
  • Flow turbine
  • Pressure release valve
  • Hot water temperature sensor
  • Automatic bypass valve
  • Drain off point
  • Inhibitor introduction point
  • Automatic air release

The Heatronic Printed Circuit Board

The advanced heatronic PCB is built into the boiler, so the installer does not have to purchase any additional features usually associated with boiler controls. It features a precise temperature control, frost protection control and anti-cycle timer - managing the boiler's output. It also includes a fault-finding diagnosis which lists specific problems. Service engineers can gain access to the history of the boiler operation, including information on how many times a DHW outlet has been operated and how many hours of CH has been demanded.


The RT10 room thermostat is a wall mounted unit installed traditionally in the hall or landing of the home. Its optimum start means that prior to the boiler firing up for a heating demand the actual room temperature is checked and depending on the temperature, the boiler may be prevented from firing up, thus saving fuel.

Unlike conventional room thermostats, which simply turn the boiler on and off when the room temperature has been reached, the TD200, in conjunction with the RT10, uses a system called load compensation. The RT10 operates as an NTC sensor (negative temperature coefficient). In short, as the room temperature changes, the resistance over the sensor changes. It then signals to TD200, which then tells the boiler to reduce the flow temperature downwards whilst maintaining the required room temperature. The boiler is then forced to condense more, maximising its fuel efficiency.

TD200 Control

The TD200 control, fitted to the boiler fascia or wired externally, is Worcester's most sophisticated, giving more control of heating and hot water.

The TD200 and the RT10 are, in partnership, a heat compensation system which is perhaps more convenient to install than weather compensation systems, which require an external sensor to be sited on a north facing wall. Because it records the operating time of the boiler, installers can easily access the historical information on the running time in hours of CH and DHW.

In the unlikely event of a breakdown the TD200 can display the boiler's 10 most recent faults which saves installer diagnosis time. It also allows the installer to input a service reminder plus their company name and contact details. This means that once the boiler has been operational for a pre-determined number of hours the text display will alert the homeowner of the need for a service, displaying the installers contact details.

As well as the service reminder it gives the homeowner three on/off periods per day, seven day programming, dedicated advance buttons, 12 and 24 hour clock and a holiday function. It also automatically sets the date and time and changes between BST and GMT.

Installing a system such as this gives extra savings compared with a more basic control system. Estimates do vary, but if the appliance can stay in a condensing mode all of the time then the efficiency increases by around 10% over a partial condensing system.

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