Gas suppliers require the temperature of the gas to be controlled at 0oC as it leaves the gas works. This prevents freezing of the ground around the pipe and avoids frost damage to the pipe as a consequence. There is often a considerable distance between the heat source and the perimeter of the gas works resulting in a sufficient lag to require a cascade control scheme.
The 2604 cascade controller offers many benefits over traditional cascade methods (two Controllers). Commissioning is much easier because the two loops are connected internally so there is no need to match the calibration of the master output to the remote input of the slave.
Improved control performance is achieved from the bumpless transfer into and out of the cascade and from integral wind-up protection on the master when the slave setpoint hits a limit, this in turn saves energy costs, and of course a single instrument solution saves both panel space and wiring.