The Greenstar system boiler range can be used with the following controls, provided the boiler is fitted with the Optional Integral Diverter Valve. I System boilers DT20 Twin Channel Digital programmer (with 240v room thermostat) DT20 RF DT10RF The hot water temperature control on the I System boilers is achieved using a volt free cylinder thermostat. CDi System boilers DT20 Twin Channel Digital programmer (with 240v room thermostat) DT20 RF DT10 RF DT10 RF Optimiser Intelligent System Package FR10 FR110 FW100 ISM1 The hot water temperature control on the CDi System boiler is achieved using the cylinder sensor supplied.